Full text of Safety Codes for the Prevention of Dust Explosions : Bulletin of the United States Bureau of Labor Statistics, No. 562

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UNITED STATES DEPARTMENT OF LABOR
W . N. DOAK, Secretary

BUREAU OF LABOR STATISTICS
ETHELBERT STEWART, Commissioner

BULLETIN OF THE UNITED STATES)
BUREAU O F LABOR ST A T IS T IC S / • • • •
SAFETY

CODE

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P-fiO

JftO# DDL

SERIES

SAFETY CODES FOR
THE PREVENTION OF
D U S T EXPLOSIONS
NATIONAL FIRE PROTECTION ASSOCIATION AND
UNITED STATES DEPARTMENT OF AGRICULTURE
SPONSORS

AMERICAN STANDARD
Approved by the

AMERICAN STANDARDS ASSOCIATION

DECEMBER, 1931

UNITED STATES
GOVERNMENT PRINTING OFFICE
W A SH ING T O N: 1932

For sale by the Superintendent of Documents, Washington, D. C.

Price 15 cents

CONTENTS
Page

Introduction_______________________________________________________
Committee on dust explosion hazards____________________________
National Fire Protection Association_____________________________
United States Bureau of Chemistry and Soils_____________________
Importance of dust explosions___________________________________

1
2
2
3
3

Safety Code for Starch Factories_____________________________________
Introduction___________________________________________________
Definitions_____________________________________________________
Construction and arrangement of buildings_______________________
Kilns__________________________________________________________
Dry starch grinding and grading_________________________________
Pearl and powdered starch bulk packing__________________________
Lump starch cooking, pressing, grading, and packing______________
Control and removal of suspended dust__________________________
Removal of static dust_________________________________________
Prevention of ignition___________________________________________
Mechanical precautions_________________________________________
Housekeeping__________________________________________________

5
5
5
5
6
7
7
7
8
8
8
9
9

Safety Code for Flour and Feed Mills_________________________________
Definitions_____________________________________________________
Construction of buildings________________________________________
Control and removal of suspended dust__________________________
Removal of static dust__________________________________________
Prevention of ignition__________________________________________

11
11
11
12
12
12

Safety Code for Terminal Grain Elevators_____________________________
Definitions_____________________________________________________
Introduction___________________________________________________
Structural features_____________________________________________
Construction_______________________________________________
Surfaces and ledges_________________________________________
Walls and roofs____________________________________________
Track shed________________________________________________
Locations__________________________________________________
Communications___________________________________________
Bins and tanks_____________________________________________
Basements, tunnels, and galleries____________________________
Shafts_____________________________________________________

15
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16
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17

Ventilation____________________________________________________
Windows__________________________________________________
Basements, etc_____________________________________________
Roofs_____________________________________________________
Venting of bins and tanks___________________________________

17
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18
18

CON-TEKTS

Safety Code for Terminal Grain Elevators—Continued.
Equipment____________________________________________________
Elevator legs______________________________________________
Power-------------------------------------------------------------------------------Back stops________________________________________________
Legs, etc., run idle--------------------------------------------------------------Cleaners___________________________________________________
Space under machines______________________________________
Electromagnetic or pneumatic self-cleaning separators_________
Friction clutches___________________________________________
Screw conveyors___________________________________________
Bearings___________________________________________________
Space under conveyors______________________________________
Nonchoking devices________________________________________
Spouts and throw of grain in the open_______________________
Spouting of grain into bins or tanks__________________________
Grain driers____________________________________________________
Location___________________________________________________
Separation_________________________________________________
Louvers___________________________________________________
Belt conveyors_____________________________________________
Garners and hoppers_______________________________________
Removal of refuse from grain________________________________
Top of drier_______________________________________________
Floors_____________________________________________________
Floor sweeps_______________________________________________
Fans______________________________________________________
Steam coils________________________________________________
Fire-heated driers__________________________________________
Removal of dust from grain-handling equipment__________________
Heads, boots, garners, and scales____________________________
Belt loaders________________________________________________
Belt discharges and trippers_________________________________
Machines__________________________________________________
Dust-collecting system______________________________________
Shipping galleries___________________________________________
Car unloading______________________________________________
Removal of static dust__________________________________________
Sweeping__________________________________________________
Floor sweeps_______________________________________________
Electrical equipment____________________________________________
Wiring and equipment______________________________________
Motors-------------------------------------------------------------------------------Switch room_______________________________________________
Light for bins______________________________________________
Lighting___________________________________________________
Miscellaneous__________________________________________________
Heating___________________________________________________
Sulphur bleacher___________________________________________
Protection against sparks___________________________________
Locomotives excluded_______________________________________
Railway cars_______________________________________________
Insect control______________________________________________
Shovels____________________________________________________

Page
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25

CONTENTS

Safety Code for Terminal Grain Elevators—Continued.
Miscellaneous—C ontinued.
Smoking___________________________________________________
Waste cans________________________________________________
Lockers___________________________________________________
Oils_______________________________________________________
Miscellaneous storage----------------------------------------------------------Lightning protection_______________________________________
Static electricity_______________________ ___________________
Fire protection_________________________________________________
First-aid appliances________________________________________
Watchman________________________________________________
Standpipe and hose________________________________________
Use of hose streams________________________________________
Fire in bin or tanks-------------------------------------------------------------Automatic sprinklers------------------------------------------------------------

Pag®

Safety Code for Pulverizing Systems for Sugar and Cocoa________________
Introduction___________________________________________________
Definitions_____________________________________________________
Location_______________________________________________________
Construction___________________________________________________
Communications_______________________________________________
Power_________________________________________________________
Lighting_______________________________________________________
Wiring________________________________________________________
Preventive measures____________________________________________
Housekeeping__________________________________________________
Fire protection_________________________________________________

27
27
27
27
27
28
31
31
31
32
33
34

Safety Code for Spice-Grinding Plants________________________________
Introduction___________________________________________________
Definitions_____________________________________________________
Location_______________________________________________________
Construction___________________________________________________
Communications_______________________________________________
Electric power, lighting, wiring__________________________________
Prevention of ignition__________________________________________
Housekeeping__________________________________________________
Fire protection_________________________________________________

35
35
35
35
35
36
36
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37
37

Safety Code for Wood-Flour Manufacturing Establishments________*___
Introduction___________________________________________________
Definitions_____________________________________________ _______
Location_______________________________________________________
Construction___________________________________________________
Communications_______________________________________________
Electric power, lighting, wiring__________________________________
Preventive measures____________ _______________________________
Housekeeping__________________________________________________
Fire protection_________________________________________________

39
39
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44

Safety Code for the Installation of Pulverized-Fuel Systems______________
Introduction___________________________________________________
Definitions_____________________________________________________

45
45
45

25
25
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25
25
25
25
25
26
26
26
26
26

CONTENTS

Safety Code for the Installation of Pulverized-Fuel Systems— Contd.
Types of systems_______________________________________________
Regulation for all classes of systems______________________________
Location__________________________________________________
Construction_______________________________________________
Ventilation and dust collection______________________________
Pulverizer_________________________________________________
Magnetic separator_________________________________________
Electricity for light and power_______________________________
Grounding of machinery____________________________________
Dust collectors_____________________________________________
Vents_____________________________________________________
Blowers handling fuel in suspension__________________________
Driers_____________________________________________________
Pipe lines—Specification No. 1______________________________
Pipelines— Specification No. 2______________ ______ _________
Pipe lines— Specification No. 3______________________________
Storage and furnace bins____________________________________
Ignition___________________________________________________
Class A systems— Specific regulations____________________________
Fire protection_____________________________________________
Transportation pipe lines___________________________________
Screw conveyors_________________________________________ _
Unit systems— Arrangement of system s__________________________
Instruction cards_______________________________________________
Appendix A-—Storage of co a l____________________________________
Appendix B—Recommended procedure for extinguishment of fires in
pulverized-fuel conveyors, pipes, ducts, collectors, and b in s_____
Fires in conveyors, pipes, ducts, or collectors--------------------------Fires in pulverized-fuel bins_________________________________

Page
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57

Safety Code for Coal Pneumatic Cleaning P lan ts______________________
Introduction___________________________________________________
Definitions__ ______________________________________________
Buildings, machines, and apparatus to be covered by these regulations.
Types of systems___________________________________________
Dust-making adjuncts_____________________ •________________
Installation requirements of pneumatic cleaning machinery and appa
ratus________________________________________________________
Location___________________________________________________
Construction of building______________________ _____________
Screen-room arrangement___________________________________
Jig or table room___________________________________________
Window arrangement and construction_______________________
Building construction_______________________________________
Ventilation and dust collection______________________________
Dust collectors____ - ________________________________________
Air vents__________________________________________________
Safety vents_______________________________________________
Coal driers_________________________________________________
Storage bins_______________________________________________
Electricity for light, heat, and power...........................................................

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62

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CONTENTS

V II

Safety Code for Coal Pneumatic Cleaning Plants— Continued.
Fire and explosion protection____________________________________ ____66
Open flames and torches____________________________________ ____66
Smoking_______________________________________________________67
Fire drills______________________________________________________67
Safety Code for the Use of Inert Gas for Fire and Explosion Prevention. _
69
Introduction------------------------- --------------------------------------------------- ------69
Definitions_________________________________________________________70
General____________________________________________________________70
Determining the amount of inert gas required____________________ ____71
Table I.— Permissible percentage of oxygen based on the addition of
carbon dioxide_______________________________________________ ____71
Sources of inert gas supply______________________________________ ____72
Gas conditioning equipment_____________________________________ ____73
Gas distributing system_________________________________________ ____74
Analyzing, indicating, and recording equipment___________________ ____75
Test for approval____________ ________ _______________________ ______75
ILLUSTRATIONS
(Furnished by the Chemical Engineering Division, Bureau of Chemistry and Soils, United
States Department of Agriculture)
Between
pages

Explosions of starch dust, three views______________________
Explosion of starch dust, effectively vented---------------------------Explosions of feed dust, three views_________________________
Explosion of flour dust, effectively vented___________________
Dust explosions in terminal grain elevators, three views_______
Explosion of sugar dust____________________________________
Dust explosion in spice plant_______________________________
Explosion of cocoa dust____________________________________
Explosion of wood-flour dust________________________________
Explosion of wood dust_____________________________________
Explosion of wood-flour dust, effectively vented_______________

4 and

10 and 11
26 and 27

38 and 39

BULLETIN OF THE

U.S.BUREAU OF LABOR STATISTICS
n o . 562

WASHINGTON

D e c e m b e r , 1931

SAFETY CODES FOR THE PREVENTION
OF DUST EXPLOSIONS
Introduction
Dust explosions have been responsible for a series of disasters in
volving large losses of life and property extending over a long period
of years. I t is only recently, however, th at the seriousness of this
hazard has been generally recognized and measures for its control
undertaken. Following extensive research into the phenomena of
dust explosions by the Bureau of Chemistry of the United States
Department of Agriculture, the National1 Fire Protection Associa
tion organized, in January, 1922, a committee on dust explosion
hazards charged with the preparation of recommended regulations
for the prevention of fires and dust explosions in occupancies sub
ject to this hazard. This committee was formed with the coopera
tion of the United States Department of Agriculture, the present
joint sponsors thus having been closely associated in this work
since the inception of the project. The committee of the National
Fire Protection Association on dust explosion hazards proceeded
with the preparation of the regulations which form the basis of this
pamphlet, the reports of the committee being adopted by the asso
ciation and published as the recommended regulations of the Na
tional Fire Protection Association. These standards as prepared
were also adopted by the National Board of Fire Underwriters.
In 1926 the dust explosion hazards committee of the National
Fire Protection Association was reorganized to qualify as a sectional
committee of the American Engineering Standards Committee.
This reorganization consisted merely in adding the representatives
of a few organizations which had not previously participated in
the work. Following this the codes adopted by the committee and
by the National Fire Protection Association and the United States
Department of Agriculture were officially approved as “ Tentative
American Standards ” by the American Engineering Standards Com
mittee and published in the Bulletin of the United States Bureau of
Labor Statistics No. 433. Subsequently the codes were advanced to
the status of “ American Standard ” by the American Standards
Association, additional codes were prepared, and original codes re
vised to keep pace with developments in industry. The present pub
lication includes all the codes developed by this committee to date.

S A F E T Y CODES F O B D U S T E X P L O S IO N S

Committee on Dust Explosion Hazards
{Personnel as of May, 1931, when last committee action was taken)
D avid J. P rice, Chairman, U. S. Bureau of Chemistry and Soils, Department of
Agriculture.
H ylton R. B rown, Secretary, U. S. Bureau of Chemistry and Soils, Department
of Agriculture.
L. F. Adams, National Electrical Man H. E. Newell, National Board of Fire
Underwriters.
ufacturers Association.
C. J. A lger, Associated Corn Products A. H. N uckolls, Underwriters’ Labo
ratories.
Manufacturers.
F. C. A l l e n , Jr., Dust Collection R obert P alm, Consulting Engineer,
Sugar Industry.
Equipment Manufacturing Group.
E. P hillips , Dust Collection Equip
E ugene Arms, Mutual Fire Preven S. ment
Manufacturing Group.
tion Bureau.
George S. R ice, U. S. Bureau of
E. G. B ailey, Pulverized Fuel Equip
Mines.
ment Association.
E dwin B. R icketts, National Electric
Logan J. B orland, Conference of
Light Association.
Special Risk Underwriters.
J ohn R oach, International Associa
tion of Industrial Accident Boards
N athan G. B urgster, Western Ac
and Commissions.
tuarial Bureau.
W. J. B urk, Association of Govern F. W. Sehl , National Bureau of Cas
ualty and Surety Underwriters.
mental Officials in Industry of
Peter Steinkellner, International
United States and Canada.
Association of Fire Chiefs and In
G. F. B utt, Grain Elevator Construc
ternational Association of Fire
tion.
Fighters.
P. J. Conlon, U. S. Department of N. J. T hompson, Associated Factory
Labor.
Mutual Fire Insurance Companies.
G. R. H urd, Railway Fire Protection Schuyler Van L oan, American Spice
Association.
Trade Association.
J. A. Mull, Terminal Elevator Grain C. E. Wood, Society of Grain Elevator
Merchants Association.
Superintendents of North America.

National Fire Protection Association
The National Fire Protection Association, with offices at 60 Batterymarch Street, Boston, Mass., was organized in 1896 “ to promote
the science and improve the methods of fire protection and preven
tion; to obtain and circulate information on these subjects; and to
secure the cooperation of its members in establishing proper safe
guards against loss of life and property by fire.” The association has
two classes of membership. There are some 140 organization mem
bers, including “ National institutes, societies, and associations inter
ested in the protection of life and property against loss by fire.” The
associate membership, which is open to anyone interested, includes
over 4,000 architects, builders, merchants, manufacturers, ware
housemen, engineers, fire marshals, fire wardens, fire chiefs, electri
cians, credit men, bankers, insurance agents, and inspectors, cham
bers of commerce, public libraries, and many other organizations,
individuals, firms, and corporations.
The National Fire Protection Association is the internationally
recognized standard-making body for regulations for the prevention
of fire and for its control and extinguishment. The association
operates through some 35 technical committees each having jurisdic
tion over one section of its standard-making activities. The regula
tions of the association are purely advisory in character, but after

IN T R O D U C T IO N

adoption by the association are largely promulgated by State and
municipal authorities as the basis of regulatory measures and are
used by the fire insurance organizations as the basis of their
requirements.
United States Bureau of Chemistry and Soils
The United States Bureau of Chemistry and Soils, Department of
Agriculture, conducts special engineering and chemical research
investigations relating to the determination of causes of dust
explosions in manufacturing establishments and in the development
of methods of control and prevention. The work is conducted in
cooperation with other Government departments, State industrial
commissions, fire prevention and insurance associations, and other
national and State bodies interested in dust explosion and fire pre
vention.
The Bureau of Chemistry and Soils cooperates with the National
Fire Protection Association in the work of the dust explosion hazards
committee, of which Dr. David J. Price, engineer in charge of the
chemical engineering division in the Bureau of Chemistry and Soils,
is chairman. The regulations prepared by this committee, and pub
lished in the bulletin, embody the control measures developed in the
Bureau of Chemistry and Soils as a result of research relating to dust
explosion prevention in industrial plants.
Importance of Dust Explosions
The research work of the United States Bureau of Chemistry and
Soils, Department of Agriculture, indicates that practically all types
of combustible dusts when mixed with air in proper proportions can
be readily ignited by external sources of heat or flame. We can more
nearly appreciate the importance of this industrial problem when it
is realized that a recent Census of Manufactures shows th at at least
28,000 industrial plants, employing over 1,324,000 persons and manu
facturing products of an annual value in excess of $10,000,000,000, are
subject to the hazard of dust explosions. I t has been only in recent
years that direct attention has been given to the determination of the
causes of industrial plant dust explosions and the development of
control measures. Large losses of life, property, and foodstuffs are
occurring annually from explosions of this character. Many of the
explosions are occurring in lines of industry in which dust explosions
have not previously taken place. The extension to larger operating
scale and the utilization of by-products and waste materials, result
ing in the accumulation of large quantities of explosive dusts, have
greatly increased the hazard. The introduction of new manufactur
ing processes, as well as new types of mechanical equipment, have
added to the importance of dust explosion prevention.
The regulations of the dust explosion hazards committee have been
prepared to assist in the adoption of proper control measures for the
prevention of these explosions and the reduction of losses resulting
therefrom.

R e s u l t o f e x p l o s i o n o f s t a r c h D u s t i n a P l a n t i n t h e M i d d l e W e s t . F o r t y -t h r e e
w e r e K i l l e d a n d 30 I n j u r e d ; p r o p e r t y D a m a g e o v e r $ 3 , 0 0 0 , 0 0 0

pe r so n s

Ex p l o s io n

o f

s t a r c h

Du st.

F o r t y -t w o

liv e s

w ere

l o s t

$ 7 5 0 ,0 0 0

an d

22 E m p l o y e e s

in j u r e d

; Property

Loss,

Ex p l o s io n o f s t a r c h D u s t .

F o u r W o r k m e n I n j u r e d ; p r o p e r t y D a m a g e , A p p r o x i m a t e l y $200,000

T h e Ex t e n t o f t h is Ex p l o s io n o f s t a r c h D u s t w a s L o c a l iz e d a s t h e
R e s u l t o f l a r g e w i n d o w -g l a s s A r e a , w h i c h p r o v e d E f f e c t i v e i n
V e n t in g t h e e x p l o s io n
4— 4

Safety Code for the Prevention of Dust Explosions in
Starch Factories
(American Standard, approved September 24, 1931, by American Standards Association)

This safety code applies only to buildings erected subsequent to the
adoption of this code.
Introduction.
1. Many factories make wet starch only for subsequent conversion
to sugar or sirup, others produce starch only, others produce sugar,
starch, and dextrine.
2. The explosion hazard appears in three places: F irst in the corn
receiving and storage departments in the form of grain-elevator d ust;
second, in the dust arising from the milling and storage of the
so-called gluten feed; third, from the presence of starch dust.
3. As to grain storage departments, arrangements shall conform to
the Code for the Prevention of Dust Explosions in Grain Elevators.
(See p. 15.)
4. As to gluten and feed departments, arrangements shall conform
to the Code for the Prevention of Dust Explosions in Flour and Feed
Mills. (See p. 11.)
5. These regulations relate specifically to the hazard involved in
the handling of dried starch.
6. This hazard is characteristically present first at the kilns, and
follows all processes involving the handling of the starch from the
kilns up to and including the packing operation.
7. I t is now generally accepted that any kind of starch dry enough
to float in air is dry enough to contribute to an explosion, even though
the department may be one in which the air is quite humid.
Definitions.
In this safety code the following words are used as defined below:
“ S h a ll55is intended to indicate requirements.
“ Should ” is intended to indicate recommendations, or that which
is advised but not required.
“A pproved” refers to approval by the authority having jurisdic
tion in the enforcement of regulations.
1. Construction and arrangement of buildings.
11.
The four operations of (a) starch drying, (b) dry starch
grinding and grading, (c) pearl and powdered starch bulk packing,
and (d) lump starch cooking, pressing, grading, and packing shall
be in four separate buildings, which shall be removed at least 50 feet
from any other, and not be a part of or standing within 50 feet of
buildings containing operations of manufacturing. I f there is a
dextrine department, it shall be separate and conform to the regula
tions hereinafter applying to lump starch pressing, grading, and
packing. Edible corn starch and package goods, other than bulk
packages, may be packed in the lump starch department ( d) .
5

SA FE T Y CODES FOR D U S T E X P L O S IO N S

12. The buildings housing the last three operations, (&), (<?), and
(d)^ shall be of daylight type construction, with large windows of
thin glass with at least 50 per cent of the wall area of windows, or
other light construction th at shall not offer greater resistance to ex
plosions than glass area. Door openings along loading platforms
shall be accepted as equivalent to glass or other light construction.
Buildings should not be more than three stories above the basement
in height.
N ote.—See Figures 1 to 6, inclusive (pp. 29-31), for illustrations of typical
applications of requirements for glass or equivalent area.

13. Construction shall be fire resistive.
14. Transfer of starch between buildings shall be only by cart over
a tram w ay; or by inclosed spiral conveyors, equipped with a positive
seal or choke, under wide shed roofs, or by inclosing galleries having
sides at least 50 per cent open; or by other approved means.
15. A ll walls shall be finished smooth and irregularities of con
tour brought flush with the surface, or filled to reduce lodgment of
dust to a minimum. I t is recommended th at these surfaces then be
finished with white enamel paint. The surfaces of all posts shall
be brought to conform to this regulation. All ceilings and beams
shall be smooth finished, without crevices or ledges or roughness, such
as would provide attachment for dust. All floors shall be surfaced
smooth with cement or composition, or shall be of wood finish without
crevices or pockets offering lodgment for starch dust.
16. There shall be no floor openings other than those necessary for
the spouts and bin openings. Crevices between floors and spouting
shall be tightly closed with either hard or plastic cement to prevent
drafts through the floor. Stairs and elevators shall be outside of the
walls of the buildings, with fire doors on communications at floor
levels, or may be within the building if inclosed by fire walls with fire
doors on any stair or elevator opening into the building. Door open
ings to uninclosed outside stairs shall be protected by standard fire
escape doors.
17. There shall be no locker or change rooms within these
departments.
2. Kilns.
21. Except where kilns extend solid from floor to roof the top of
kilns shall be finished smooth with cement, and the roof of the
building shall be not less than 6 feet above the surface of the top of
the kilns, so th at this surface may be easily accessible for cleaning. I t
is recommended that this space above the kilns and below the roof
be entirely walled off from the rest of the kiln house by a fire-re
sistive partition extending from the kiln structure to the roof about
the perimeter of the kiln structure, this space to be lighted and ven
tilated by skylight, and if possible by doorways and windows in one
or more exterior walls of the kiln house.
22. Operations in the kiln building shall be limited to charging,
discharging, dumping, and preliminary reeling of starch.
23. The starch dumps shall be under hoods of fire-resistive con
struction, ventilated by fans of sufficient power to prevent escape of
dust when dumping, exhausting to water spray type collector, or
cyclone o<r cloth dust collector, housed in fire-resistive shelters above

SA F E T Y CODE FOR STA R C H FACTORIES

the roof of the kiln house or in other locations safely isolated from
the building. (See Regulations of the National Fire Protection
Association for Blower and Exhaust Systems.1)
24. In hot air drying systems, the inlet and outlet to and from the
drying tunnels shall be entirely above the level of the tunnel floors.
3. Dry starch grinding and grading.
31. Dry dust-collecting systems for apparatus ahead of the mills
shall be separate from the collecting systems for apparatus after the
mills. The apparatus immediately after the mills should preferably
have its own collecting system, which should be independent for each
mill.
32. All hoppers for bulk starch shall be provided with an explosion
relief panel in one wall, or in the top, with area equal to at least onethird the horizontal cross section of the hopper. This panel shall be
built so as to give way to outside of the building. The separation
between hoppers shall be by partitions of at least twice the strength
of the explosion relief panels. All hoppers shall be so constructed as
to minimize arching of the stock. The slope of the walls of the bottom
of the hopper shall not be less than 60° from the horizontal. The
interior of hoppers shall be finished smooth, preferably with shel
lacked hardwood; if of steel, the seams shall be lap joints and shall
have the projecting edge faced downward.
33. All starch before milling shall pass a %-inch or smaller mesh
screen, and electromagnetized pulley-and-belt separator, or shall be
raised by air lift.
34. The grinding chambers and all parts within the grinding
chambers of the mills should be of brass, bronze, or other non
sparking metals.
35. Each mill shall be effectively isolated from the trunk line of
transfer of stock, such as by individual rotary valves, or by effective
choke conveyors, before and after the grinding device with the space
between the valves or chokes fitted with adequate pressure relief vent
to outside air.
4. Pearl and powdered starch bulk packing.
41. Hoppers in this department shall conform to section 32.
42. I f there are five or more barreling or bagging stands in one
assembly, the floor surrounding the stand shall be of grating so
arranged over a spiral conveyor as to receive and remove the fall of
starch to prevent its being trodden under foot.
5. Lump starch cooking, pressing, grading, and packing (including per
missible packing of edible starch and other so-called package
goods).
51.
The cooking room, the pressing and opening room, the cylinder
seasoning room, the grading room, and the packing room shall each
be separated from the additional space on the floor on which it is
located by draft-stopping partition of fire-resistive construction.
The cooking room and the pressing and opening room shall be venti
lated by draft fans exhausting outdoors, or if desirable, to water
spray type collector or cyclone or cloth dust collectors in fire-resistive
1 Obtainable from the National Fire Protection Association, 60 Batterymarch Street
Boston, Mass.

S A F E T Y CODES FOR D U S T E X P L O S IO N S

inclosures on the roof, or in other locations safely isolated from the
building. There shall be a separate system of fans, ducts, and col
lectors for each department, and the collector housings shall be
placed as remote from each other as the arrangements of the prem
ises will permit. The doorways in these partitions shall be provided
with self-closing doors, so as to prevent the dust in the department
from escaping into other departments, except when people or objects
are passing the doorway.
52. The floors about the presses shall be provided for as about bar
reling and bagging stands, section 42.
53. All hoppers for ground or powdered starch shall conform to
regulations under section 32.
6. Control and removal of suspended dust.
61. All elevator legs, spouting, screw conveyors, stock hoppers,
bins, and grading machines shall be dust tight, and shall be equipped
with mechanical exhaust to dust collectors so that dust will not escape
from the apparatus under conditions of use and inspection. Each
department shall have its own complete dust-collecting system.
62. When a water spray type collector is used it may be within
building. Collectors of cyclone type shall be vented directly out
doors or to a secondary system of similar collectors which are vented
to the outside air. I f cloth collectors are used they shall be located
in fire-resistive housings on the roof of the building or at other loca
tions safely isolated from the building. All wind trunking of such
systems shall be of metal.
63. Dust escaping from filling machines or in hand-filling opera
tions shall be controlled by properly arranged collecting hoods
connected with mechanical exhaust.
7. Removal of static dust.
71. All surfaces on which dust settles shall be cleaned off suffi
ciently often to prevent the accumulation of a coating of dust.
72. The cleaning of surfaces shall be by vacuum sweeping appa
ratus, if it can feasibly be applied, and if not, shall be by soft brushes
or wipers or mops of loose fabrics.
73. F or removal of dust from motors, building should be equipped
with a stationary compressed-air system, operating at from 80
pounds to 100 pounds pressure. Fixed compressor piping systems
shall be of extra heavy type, and the compressors and receivers shall
be stationary and shall not be located in dusty departments. This
apparatus shall not be used while department is operating.
74. Kiln-tray repairing department shall be separated from adja
cent occupancy by dust-tight fire-resistive partitions, and shall be
daily cleared of starch dust accumulations.
75. Starch bags shall not be cleaned in the open, but may be
cleaned by drawing over the nose of a draft spout, or by shaking
them within an open top inclosure under mechanical draft sufficient
to prevent the escape of the dust into the room, or by other com
pletely inclosed bag cleaning device.
8. Prevention of ignition.
81. Open flames or igniting surfaces shall not be permitted.
82. Smoking and the carrying of matches shall not be permitted.
83. Electrical equipment shall be installed according to the regu

SA F E T Y CODE FOR STARC H FACTORIES

lations of the National Electrical Code,1 article 32, which covers
electric wiring and apparatus in dusty locations.
84. Static electricity shall be removed from such machines as ac
cumulate a charge by permanent ground wires, and from belts by
grounded metal combs or other equally efficient systems.
85. Fans and blowers shall be so constructed that fan blades can
not come in contact with fan housing. Bearings shall set well away
from fan housing to prevent the forcing of grease to the inside of the
fan housing or air chamber. (See Regulations of the National Fire
Protection Association for Blower and Exhaust Systems.1)
86. Ball or roller bearings should be used whenever practical,
otherwise ring, chain, or roller oiler bearings should be used.
9. Mechanical precautions.
91. The speed of revolution of spiral conveyors shall not exceed
100 revolutions per minute, and graphite buttons or other suitable
material shall be inserted in the bearing surfaces of all inner bear
ings. When feasible the upper half of the bearing may be removed
to permit the stock; to move freely over the bearing surfaces.
92. All elevator legs should be equipped with an automatic over
load release, or a signal system which will register when the leg be
gins to slow down, thus indicating to the operator the possibility of
choke at the boot.
93. Attention is directed to the fact that warning of the overheat
ing of bearings, in dusty and inaccessible locations and where the
heating of the bearing may cause explosions, may be obtained by the
use of approved journal alarms.
10. Housekeeping'.
101. All of the departments devoted to the handling and packing
of dry starch shall be kept free of stored material of every sort, other
than starch which has just been packed and is about to be removed to
the warehouse. This requirement embraces new and discarded ma
chinery and parts not in use and pieces of apparatus.
102. Efficient help and methods shall be employed to prevent mis
cellaneous dust clouds and to keep the departments clean at all times,
and no accumulations of starch dust shall be permitted on any sur
faces, other than those immediately about places where starch is
being handled in the open. The word “ accumulation 55 as used here
is to be interpreted as th a t amount of dust which is sufficient to ob
scure the view of the surface. All spills of starch from apparatus
and accumulations gathered in cleaning of surfaces shall be shoveled
up and sacked as made, and removed from building or to a recovery
department, or else returned to the stream of starch in process where
trade practice permits.
1 Obtainable from the National Fire Protection Association, 60 Batterymarch Street,
Boston, Mass.

84589°—32------2

R e s u l t s o f Ex p l o s io n

o f

feed

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Da m a g e C o n f in e d l a r g e l y t o U p p e r F l o o r s

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10—4

Safety Code for the Prevention of Dust Explosions in
Flour and Feed Mills
(American Standard, approved January 12, 1928, by American Standards Association)

Definitions.
In this safety code the following words are used as defined below:
“ Shall ” is intended to indicate requirements.
“ Should55 is intended to indicate recommendations, or that which
is advised but not required.
“Approved ” refers to approval by the authority having jurisdic
tion in the enforcement of regulations.
Construction of buildings.
1. M ill.—The “ daylight ” type of mill building (with large win
dow area) is recommended. Wired glass should not be used unless
necessary as protection against exposure.
2. Fire-resistive construction or mill construction is recommended.
3. Cleaning department shall be cut off from other departments by
standard fire walls or cut off in other standard manner.
4. Elevator and storage bins.—All storage bins shall be covered,
the side walls extending solidly to the roof of the bins, there being
no connection between bins.
5. Tunnels and basements shall extend as much above natural
ground level, and shall be as large and roomy as is practicable. All
tunnels and basements shall be dry and shall have all the natural
light possible to obtain, either by means of windows, areaways, or
sidewalk glass.
6. Basements of all buildings shall be of such construction as to
perm it the free circulation of air to all parts and shall be vented by
air shafts exhausting above the roof or by other approved method.
7. Mill, elevator omd storage bins.—Construction shall generally be
such that all interior walls, including bin walls, shall be smooth and
free from pockets or ledges that will permit the accumulation of
dust. In special cases where it is not practicable to entirely eliminate
ledges, then such ledges shall be finished with smooth surface and
be made as steep as possible. All pipes, conduits, etc., that of
necessity are exposed, shall be fastened to walls or ceilings in such
manner as to present a minimum surface for the collection of dust.
8. Roofs and side walls of belt conveyor galleries and the side
walls of all cupolas above bins shall be constructed of light material
offering little or no resistance to explosive energy.
N ote .— The term “ light material ” contemplates corrugated galvanized iron,
corrugated zinc, corrugated asbestos, brick tile, or gunite, and for cupola con
struction is intended to apply only to curtain or panel walls between columns.
Concrete may also be used similarly, provided the window area is greater
than 40 per cent of the free wall area.

SA FE T Y CODES FOR D U S T E X P L O SIO N S

Control and removal of suspended dust.
9. All elevator legs, spouting, roll housings, screw conveyors, and
stock hoppers and bins shall be dust tight.
10. All roll housings, elevator heads, and elevator boots on large
stands of elevators shall be vented by mechanical exhaust to dust
collectors.
11. Dust collectors shall be of the metal cyclone type and each
shall be vented directly out of doors or to a secondary system of
similar collectors which are vented to outside air.
12. Wind trunking shall be of tight metal.
^ 13. Belt conveyors shall be provided with hooded air suctions at
either or both ends when practical.
14. All grain bins (except tempering bins) shall be vented to the
outside air with a 12-inch or larger metal pipe properly hooded to
prevent the entrance of excessive moisture.
Removal of static dust.
15. Good housekeeping is a requirement of the utmost importance.
Dust, either in large or small quantities, must not be permitted to
accumulate on floors, walls, ledges, or other interior surfaces, as the
presence of such dust represents a very positive dust explosion haz
ard. All surfaces on which dust tends to settle shall be cleaned
sufficiently often to prevent the accumulation of a coating of dust.
16. F or removal of dust from motors, drier coils, and other such
surfaces, mills shall generally be equipped with a compressed-air
system operating at from 80 pounds to 100 pounds pressure. Either
a fixed compressor with suitable piping and hose, or a portable com
pressed-air tank may be used. When the latter is used it shall be
provided with a tank of sufficient capacity to maintain pressure for a
considerable length of time, making it unnecessary to bring the tank
to pressure while in the mill.
17. The use of vacuum sweeping systems is recommended for the
removal of static dust in grain storage and elsewhere when practical.
Prevention of ignition.
18. Open-flame heating or lighting arrangements and other de
vices where dusty atmospheres may come in contact with direct fire
or flame are prohibited.
19. Open-flame heaters or electric heaters shall not be used except
in such locations as in a laboratory where not exposed to dust.
20. Smoking and the carrying of matches shall not be permitted.
21. Electrical equipment shall be installed according to the regu
lations of the National Electrical Code1 for electrical devices in
dusty locations.
22. Static electricity shall be removed from such machines as
would otherwise accumulate a charge by permanent ground wires
and from belts by grounded metal comb or by other equally efficient
methods.
23. Fans and blowers shall be so constructed th a t fan blades can
not come in contact with fan housing. Bearings shall set well away
from fan housing to prevent the forcing of grease to the inside of
the fan housing or air chamber. (See Regulations of the National
1 Obtainable from th e N ational F ire Protection Association, 60 Batterym arch Street,
Boston, Mass.

S A F E T Y CODE FOR F L O U R A N D FEED M IL L S

Fire Protection Association for the Installation of Blower and E x
haust Systems.1)
24. Ball or roller bearings should be used wherever practical,
otherwise ring, chain or collar oiler bearings shall be used.
N ote .—Attention is directed to the fact that warning of the overheating of
bearings, in dusty and inaccessible locations and where the heating of the
bearing may cause explosions, may be obtained by the use of approved journal
alarms.

25. Pneumatic or magnetic separators (preferably pneumatic)
shall be placed ahead of all grinding or pulverizing machines of the
roller, attrition, or beater type (except those grinders which further
reduce the ground stock in the same system and those machines grind
ing bulky stock on which separators can not be operated). In ad
dition to the above such separators shall be placed ahead of scourers
where used.
26. Stock from each attrition mill or beater type of grinder
should be lifted by air through a metal wind trunk to a cyclone dust
collector properly vented or be discharged into a metal screw con
veyor. The flights on the conveyor shall terminate 18 inches or
farther from the discharge and in such a way as to form a solid mass
of stock at that point. The cover of conveyor at the discharge end
shall be held in place by springs to give relief if the spout receiving
stock from the conveyor should choke.
1 Obtainable from the N ational Fire Protection Association, 60 Batterym arch Street,
Boston, Mass.

Safety Code for the Prevention of Dust Explosions in
Terminal Grain Elevators
(American Standard, approved September 24, 1931, by American Standards Association)

Definitions
In this safety code the following words are used as defined below:
“ S h a ll” is intended to indicate requirements.
“ Should55 is intended to indicate recommendations, or that which*
is advised but not required.
“ Approved ” refers to approval by the authority having jurisdic
tion in the enforcement of regulations.
Section 1.—Introduction
101. Object. These regulations have but two principal objects:
First, to prevent dust explosions and minimize the resulting damage,
should an explosion occur; and second, to provide regulations for
minimizing fire hazards.
102. These regulations are applicable to terminal grain elevators
erected subsequent to the date of these regulations. These rules are
offered as an advisory guide for owners and operators who may wish
to avail themselves of the information herein contained to improve
existing elevators.
103. Good housekeeping cmd clean premises are the first essentials
in the elrnmnatioru of explosion hazard, consequently these regulations
are not intended to lessen in any way the responsibility of the owner
or operator in this respect. I t should also be emphasized that every
potential fire cause may produce a dust explosion. All devices and
processes should be safeguarded in accordance with the regulations
applying.
Section 2.—Structural Features
Construction.
201. As all new elevators of large capacity will be of noncombus
tible construction, with probably no exceptions, these regulations will
assume and require such construction. Full fire-resistive construc
tion (all steelwork protected by approved fireproofing) is not
required if combustibles in or exposing building consist only of grain
and belts. Where combustible material (other than grain and belts),
in whatever form, is present in quantity sufficient to produce a
serious fire, all steelwork exposed thereby should be protected by
approved fireproofing. In situations where extension of automatic
sprinkler protection to such parts of buildings containing com
bustible materials is feasible, such protection is recommended, and if
so equipped the requirement for fireproofing is waived.
15

S A F E T Y CODES FOR D U S T E X P L O S IO N S

Surfaces and ledges.
202. All interior surfaces, including the inside of bins and garners,
shall be as smooth as practicable. Horizontal surfaces inaccessible to
cleaning and all pockets and ledges shall be minimized. Such as
must necessarily exist shall be inclined as steeply as possible.
Walls and roofs.
203. All exterior walls above or below the bins or tanks in the
fo rk in g house and storage annex sections of the elevator, also the
walls of belt conveyor galleries and track sheds and the roofs of
all buildings or sections shall be so designed and constructed as to
offer the least possible resistance to explosion. In so fa r as possible,
the roofs and walls of tunnels between buildings or sections shall
conform to the foregoing, although it is recognized that tunnels
generally must be of heavier construction. Reinforced concrete is
more generally used than all other materials for walls, floors, and
roofs, except th at steel is commonly used for track sheds and con
veyor galleries. The lighter the construction the less damage will
result from an explosion, but the type employed will be influenced
by considerations of cost, permanence, ease of obtaining smooth
interior finish, condensation of atmospheric moisture, etc., though
it is desirable th at a thoroughly satisfactory type of light construc
tion be developed. W ith concrete or other heavy wall construction
dependence for explosion venting must continue to be placed on large
window area, which is also desirable even with light construction,
as glass offers much less resistance than the lightest practicable wall
construction. Glass should be no thicker than necessary. Wired
glass should be used only where necessary as protection against
exposure.
Track shed.
204. Track shed for unloading and (or) loading of cars shall be
separated from the elevator by a tight noncombustible partition to
exclude dust from elevator, or by as much clear space as practicable.
Windows in partition should be stationary, and doors, if any, selfclosing.
Locations.
205. As great a space as is practicable shall be provided between
the various buildings or sections of the elevator, but in no case less
than required by the inspection department having jurisdiction.
Communications.
206. A t the points where belt conveyor galleries or tunnels are con
nected to mam buildings, tight incombustible partitions shall be
provided. When communicating with structures wholly or partly
of combustible construction, partitions shall be of fire resistance
equal to adjoining noncombustible'walls. Belt openings in the p ar
titions shall be as small as possible and equipped with a vertical
automatic fire door with roller at bottom, closing down on belt,
leaving smallest possible opening when closed. Door opening shall
be protected by self-closing fire door. A ll fire doors shall be of
approved class A type if partition is of masonry; if partition is of
metal approved class B or class C doors may be used. All other

S A F E T Y CODE FOR T E R M IN A L G RAIN ELEVATORS

openings toward or into the combustible structure shall be protected
by approved fire doors, shutters, or fire windows as required by in
spection department having jurisdiction. The requirement for selfclosing doors on communications is to prevent circulation of dust
laden air.
N ote.—F or the installation of fire doors and shutters see Regulations of the
National Fire Protection Association on the Protection of Openings in Walls
and Partitions.1

Bins and tanks.
207. All bins and tanks should be provided with dust-tight cover
or deck.
N ote.—If bins are covered, bin floor should be water-tight to prevent water
damage to grain in event of explosion or fire, and manholes should be curbed
at least 2 inches, with overlapping covers. Curbs may be sloped if desired.
Bin floor should be scuppered. For standards applying to scuppers see Reg
ulations for Mill Construction.1 Manholes should be large enough to admit
workmen wearing respiratory apparatus; 24 inch diameter is suggested.

Basements, tunnels, and galleries.
208. Exterior walls of basements and tunnels should have as much
natural light and ventilation as possible. Tunnels and galleries
should be of such width and height as to afford easy access for
sweeping on both sides and under each belt.
Shafts.
209. All stairways and passenger elevators shall be inclosed in tight
noncombustible shafts, with all doors noncombustible and self-clos
ing, or closed from within by elevator operator. Stairs from base
ment to working or first floor shall not be continuous with stairs from
working floor to floors above. Where elevator leg belts are in an
inclosed beltway between bins, such inclosures should be tightly
closed at top and bottom, and hoppered to prevent accumulation
of dust.
Section 3.—Ventilation
Windows.
301. All buildings and operating rooms shall be provided with the
largest practicable area of windows, or a combination of windows
and louvers. Windows shall be easily accessible for operation, shall
be arranged to provide maximum ventilation when open, and shall
preferably be of the hinged or tilting type.
Basements, etc.
302. All rooms and areas, including basements, tunnels, and galler
ies, and space around track hoppers, shall be well ventilated, by win
dows or otherwise. Basements more than 100 feet wide should be
ventilated by one or more noncombustible shafts extending above
roof, or by other suitable means to provide frequent change of air,
forced draft to be used if necessary. Permanent openings in base
ment for admission of air should be provided. During periods of
operation all windows and exterior doors should be open unless
weather conditions prevent.
1 Obtainable from th e National Fire Protection Association, 60 Batterym arch Street,
Boston, Mass.

S A FE T Y CODES FOR D U S T E X P L O S IO N S

Roofs.
303. Roofs of track shed, cupolas, galleries, and tunnels should be
provided with monitors or other ventilators which will, in conjunc
tion with windows, provide frequent change of air.
Venting of bins and tanks.
304. Each bin or tank, including interspaces, shall be provided
with adequate positive air aspiration, or shall be separately vented to
outside. I f the latter, each vent shall be equivalent in area to a
round opening 12 inches in diameter or larger. All vents, wherever
possible, should be vertical stacks, and should be equipped with a
weather hood of a type that will not permit wind to blow into vent.
Where there is a story above the bins, such vent may necessarily be
located in the side of bin immediately below its top, in which case the
terminal of vent shall be of special design which will not permit wind
to blow into vent. No portion of vent shall be other than vertical
if such arrangement is possible, on account of liability of choking
with accumulation of dust.
305. I f a vertical stack or air aspiration can not be installed on a
bin or tank on account of interference with operation of house, or
structural conditions, stack may be inclined not more than 45° from
vertical, and where necessary, two or more such stacks may be con
nected to a common header stack and thence to the outside. Such
stacks (including header) may be inclined not more than 45° from
vertical. There shall be no intercommunication of bins except
through stacks which may necessarily join in a common header stack
as above.
Section 4.—Equipment
Elevator legs.
401. Elevator leg belts shall be inclosed in separate casings for
both up and down legs, except where running through belt way be
tween bins. (See item 209.) Heads shall be hoppered to either the
down or up leg, but not to both. Leg casings and connecting spouts
shall be dust tight. All doors or other openings in same shall be
equipped with dust-tight covers. Wood or wood rim pulleys shall
not be used. Boots should be above floor, rather than in pits, but
if latter, should be afforded ample room for cleaning and oiling, be
accessible by permanent iron ladder, and well lighted without the
use of extension cords.
402. Elevator boots should be so constructed as to minimize the
possibility of chokes.
403. Where grain is delivered to boot by conveyor belt, the latter
should be equipped with an automatic mechanical or electrical de
vice that will stop the belt or notify operator when the leg chokes or
slows down.
Power.
404. Legs should be driven by individual motors. Motors shall be
large enough to elevate maximum amount of grain that can be
delivered by largest single tributary spout or conveyor. Motors shall
be equipped with approved overload protection and no-voltage pro
tection. All legs should be equipped with a tamper-proof safety de
vice to either call attention of operators to leg slowing down or to
stop leg automatically in event of choke.

S A F E T Y CODE FOR T E R M IN A L GRAIN ELEVATORS

Back stops.
405. Elevator legs should be equipped with special automatic back
stops.
Legs, etc., run idle.
406. All legs, conveyors, machines, car pullers, etc., shall have
individual connections to power source, and shall not be run idle.
Cleaners.
407. All cleaning, or other grain processing machinery should be of
noncombustible construction. When wooden machines are used, such
machines should be metal clad; i. e., metal sheathing is tightly secured
to all wooden surfaces that may feasibly be so covered. All clippers,
smutters, and scourers shall be equipped with a screen to exclude all
m atter of larger size than the grain treated by the machine.
Space under machines.
408. All cleaners and similar machines should be set at least 8
inches above floor to provide access for sweeping.
Electromagnetic or pneumatic self-cleaning separators.
409. Electromagnetic or pneumatic self-cleaning separators shall
be provided ahead of all shellers, crackers, crushers, and grinding
machinery.
Friction clutches.
410. I f friction clutches are used, they shall be constructed entirely
of noncombustible material.
Screw conveyors.
411. Screw conveyors shall be fully incl'osed in tight substantial
metal housings, with free-lifting covers at discharge and over each
shaft coupling.
Bearings.
412. Roller or ball bearings are recommended for all boot pulleys,
fans, cleaning, processing, or grinding machinery, trippers and belt
conveyors. Ordinary sleeve or flat bearings in old equipment should
be equipped with approved journal' alarms. All bearings should be
provided with dust caps or other tight closure of all lubrication inlets.
Space under conveyors.
413. There should be at least 6 inches clear space under all rollers
supporting conveyor belts, to provide access for sweeping.
Nonchoking devices.
414. All garners should be equipped with a reliable “ telltal'e ” or
other device which will guard against overfilling, with consequent
possibility of a choke in leg.
Spouts and throw of grain in the open.
415. Spouts shall be stationary wherever feasible. Portable and
movable spouts will be permitted in working floor, bin, or distribut
ing floor. There should be no throw of grain in the open for consid
erable distances not confined in spouts (not applying to discharge of
grain inside of bins). Grain chutes also permit large amounts of

S A FE T Y CODES FOR D U S T EXPLOSION'S

dust to escape and should not be used if their use may be dispensed
with.
Note.—Dropping grain from bin bottoms or conveying in open chutes releases
dust clouds dense enough to explode and scatters large amounts of dust which
must be swept up, producing a highly undesirable condition in an elevator in
which all other danger spots may be well safeguarded. Specially designed
aerators located on the exterior of elevator or separated from same by a space,
are now used to some extent and are recommended as removing a dust-creating
process from the working story to the open air.

Spouting of grain into bins or tanks.
416.
Spouts introducing grain into bins or tanks should be ar
ranged, where possible, to prevent grain stream striking side of bin,
on account of the possibility of tramp iron striking a spark on contact
with side.
Section 5.—Grain Driers
Location.
501. Driers should be placed in a separate fire division, separated
from elevator or tanks by as much space as practicable.
Separation.
502. D rier units should be separated from each other by dusttight partitions.
Louvers.
503. Louvers, or other permanent openings where air enters or is
exhausted from buildings, shall be protected by substantial corrosion
resistive wire screens, not exceeding one-third inch mesh, to exclude
sparks, birds, paper, etc.
Belt conveyors.
504. Belt discharge above drier and belt loader below cooler
(where belts are used) shall be equipped as required under items 602
and 603.
Garners and hoppers.
505. Garner, hopper, or bin over drier and same under cooling
section shall be dust-tight and provided with adequate positive air
aspiration or effective vents to outside. I f grain is brought to drier
by belt, the belt shall not enter garner but shall discharge into spout
or aperture in closed top of garner.
N ote.—No special ventilation is required for hopper open to cooler which is
under suction.

Removal of refuse from grain.
506. Where operating conditions permit, all grain should pass over
a coarse screen immediately ahead of drier to remove cobs, paper,
sticks, etc.
Top of drier.
507. Top of drier should be open, so th at there will be no surface
on which dust will lodge, also to provide access for cleaning out refuse
which may lodge on ducts. I f closed, the top should be inclined at
a steep angle, or hopper from garner should be same size and shape
as top of drier.

SA F E T Y CODE FOR T E R M IN A L G RAIN ELEVATORS

Floors.
508. Where floors or runways around drier and cooler are neces
sary, same shall be of gratings. Where air separation is necessary
(as between drier and cooler) it shall consist of dust hoppers under
the grating floor, such hoppers to be connected at bottom to dustcollecting system.
N ote.—Solid floors may be used if all air is drawn from drier and cooler
through continuous ducts to fan and blown to dust-settling chamber with
hopper bottom connected with dust-collecting system.

Floor sweeps.
509. A floor sweep (“ sweep-up ” pipe) shall be located on each
solid floor in building containing drier. The development and in
stallation of satisfactory permanent vacuum sweeping apparatus is
recommended.
Fans.
510. Fans and power for same shall conform to Regulations of
the National Fire Protection Association for Blower and Exhaust
Systems.1 The requirement for nonferrous parts (item 411 of blower
regulations) shall apply unless blowing only air taken from outside
building through continuous tight duct. Power and control shall
conform to section 140, and items 151, 152, and 153 of the blower
regulations.
Steam coils.
511. (a) Steam coils shall be so designed, installed, and arranged
that dust will not lodge on coils, headers, or elsewhere in casing con
taining same. Coil room shall be separated by dust-tight partitions
and floors from drying section and all other parts of drier house.
(b)
I f coils heat air which has passed through‘cooler there should
be baffles or other arrangement to remove husks, paper, etc., so that
same will not go through either fans or coils.
(0) Room containing coils shall have grating floor, and if system
requires separation from room below, same shall consist of dust hop
pers under the grating floor, such hoppers to be connected at bottom
to dust collecting system. This rule shall not apply if room contain
ing coils is segregated as recommended in items 512 (a) , or if all air
is drawn from drier and cooler through continuous ducts to fan and
blown to dust settling chamber with hopper bottom connected with
dust collector system, but floor of coil room shall be so arranged that
hand sweeping is not rendered difficult by obstructions.
Fire-heated driers.
512. (a) Furnace shall be located in a fire-resistive room or divi
sion separated from drier and elevator by masonry walls with no
communication to drier except duct for products of combustion.
(1) Driers shall be equipped with a reliable automatic means for
regulating temperature in drier, and a separate and independent
automatic device which will effectively and reliably prevent tempera
ture rising to a dangerous point.
1 Obtainable from the N ational Fire Protection Association, 60 Batterym arch Street,
Boston, Mass.

SA F E T Y CODES F O B D U S T E X P L O S IO N S

(<?) I t would be highly desirable to devise some effective means of
preventing the introduction of sparks (flakes of carbon, etc.) into the
drier along with the products of combustion.
Section 6.—Removal of Dust from Grain-Handling Equipment
Heads, boots, garners, and scales.
601. All heads, boots and garners, shall be dust-tight and provided
with adequate positive air aspiration or effective vents to outside.
Scale hoppers shall be inclosed around top, between scale and garner,
to effectively prevent the escape of dust, and shall be provided with
aspiration or vent as above, or may be vented into garner by means
of any effective special arrangement.
Belt loaders.
602. All places where grain is discharged onto belts shall be pro
vided with adequate positive air aspiration, except where equipped
with specially designed choke feed or other arrangement which is
effective in preventing the liberation of dust.
Belt discharges and trippers.
603. All places where belts discharge grain should be provided with
adequate positive air aspiration both above and below grain stream.
Trippers may be equipped with a self-contained fan unit mounted
on tripper carriage and driven by the belt, or by other effective
means. I t is recommended that air aspiration or other effective
means be applied to ends of belts where no grain is discharged, to
prevent tailings of chaff and dust accumulating on floor at end of
belt.
Machines.
604. All cleaning and similar machines which produce an appre
ciable amount of dust shall be provided with adequate positive air
aspiration.
Dust-collecting system.
605. The entire dust-collecting system shall conform to Regula
tions for Blower and Exhaust Systems. All collected dust shall be
stored in dust house or vault located outside and as far detached as
practicable. (Much valuable information is contained in Under
writers’ Laboratories Report of an Investigation of the Suction
Method of Control of Floating Dust in Terminal Grain Elevators,
dated February 26, 1924.2)
Shipping 'galleries.
606. Discharge from belt or transfer from one belt to another at a
distance of 100 feet or more from elevator may be exempted from re
quirement for air aspiration (items 602 and 603) at discretion of
inspection department having jurisdiction, if gallery is adequately
ventilated by windows at such points.
Car unloading.
607. The dust liberated by car unloading, and especially where car
dumpers are used, should be controlled by inclosing as much of the
2 Obtainable from the Underwriters’ Laboratories, 207 Elast Ohio Street, Chicago, 111.

SA F E T Y CODE FOR T E R M IN A L G RAIN ELEVATORS

top of the track hoppers as possible and by applying adequate posi
tive air aspiration to such inclosures, or by other effective means.
Section 7— Removal of Static Dust
Sweeping.
701. Dust on floors and other surfaces, including all galleries and
tunnels, shall be removed daily by sweeper. As many sweepers shall
be employed as are necessary to keep the building clean. Push
brooms of hair or soft fiber are recommended, as they will throw
less dust into suspension than ordinary brooms and are better
adapted to sweeping under belts and other machinery. Spills and
chokes shall be cleaned up daily. (See item 907, Shovels.) General
cleaning should not be done with compressed air (for use in cleaning
motors, see note under item 802 (&). The development and installa
tion of satisfactory permanent vacuum sweeping1 apparatus is
recommended.
Floor sweeps.
702. Floor sweeps (“ sweep-up ” pipes) shall be located at conveni
ent points throughout building to facilitate disposal of sweepings by
introducing them into dust collecting system. The development and
installation of satisfactory permanent vacuum sweeping apparatus
is recommended.
Section 8.—Electrical Equipment
Wiring and equipment.
801. All electric wiring and equipment shall conform to National
Electrical Code.1 All parts of grain elevators, tanks, and driers shall
be considered Class I I locations under article 32, except offices and
similar locations so occupied and segregated as to be reasonably free
from dust and so classed by inspection department having jurisdic
tion.
Motors.
802. (a) Individual motor direct connected (or through suitable
speed-reducing devices) to each head pulley, conveyor, cleaner, car
puller, fan, etc., shall be the standard hereunder.
(5)
Of the permitted types of motors for Class I I locations (Na
tional Electrical Code x), preference should be given motors listed by
Underwriters’ Laboratories as suitable for use in atmospheres con
taining grain dust.
N ote.—Uninclosed motors, such as are used in many elevators, gather dust in
the windings, which is blown out by compressed air. While objectionable be
cause it throws dust into suspension, periodic cleaning is necessary, and no
better method being known, it is recommended that such motors be blown fre
quently under supervision of plant electrician. Motors shall not be blown while
running.

Switch room.
803. In all large elevators it is recommended that service entrance
equipment, panel boards, and switchboards be located in a room as
described in National Electrical Code, item 3204 (Z>). I t is also
1 Obtainable from the National Fire Protection Association, 60 Batterym arch Street,
Boston, Mass.

SA F E T Y CODES FOR D U S T E X P L O S IO N S

recommended that such room be adequately vented to outside build
ing if large oil immersed switches are used.
Light for bins.
804. I t is recommended that portable spotlights of suitable design
and approved construction, to be directed into bin through manhole,
be used as temporary or occasional lights for bin examination, instead
of extension cords let down into bin. (See 3204 (j) of the National
Electrical Code.1)
Lighting.
805. Lighting shall be incandescent electric, conforming to provi
sions of National Electrical Code. Watchman shall use electric lan
tern or flash light, or a separate light circuit on each floor for use of
watchman shall be provided. Electric lanterns or flash lights shall
be used in elevators where electric current is not available.
Section 9.—Miscellaneous
Heating.
901. Heating should be steam from outside source. Radiators and
pipes shall be kept free of all combustible material. Approved
electric heaters will be permitted in offices and similar locations so
occupied and segregated as to be reasonably free from dust, and so
classed by inspection department having jurisdiction.
Sulphur bleacher.
902. Sulphur bleacher shall be of noncombustible construction and
located outside. Furnace shall be outside, not exposing any com
bustible material. Fumes shall pass through cooling chamber with
at least 25 feet travel through cooler and piping, or if no cooler,
through at least 40 feet of pipe before entering bleaching tower.
Protection against sparks.
903. All openings less than 50 feet above ground, in exterior walls
on track or dock side, should be protected against sparks by sub
stantial galvanized wire screens of one-third to one-quarter inch
mesh.
N ote.—This is especially necessary for wooden elevators.

Locomotives excluded.
904. Steam locomotives should not be permitted to enter elevator or
track shed, on account of the spark hazard, and possibility of live
coals dropping into track hoppers.
Railway cars.
905. Railway cars shall not be allowed to remain inside car shed or
elevator, nights, Sundays, holidays or when elevator is shut down
and not in operation.
Insect control.
906. (a) Processes and materials for extermination of weevil,
Mediterranean moth, etc., shall be without fire hazard, or with hazard
reduced to an acceptable degree. Materials used for this purpose, if
combustible, shall not be stored in building, and quantity in building
shall be limited to that needed for use on the day brought in.
1 Obtainable from, the N ational Fire Protection Association, 60 Batterym arch Street,
Boston, Mass.

SA FE T Y CODE FOR T E R M IN A L, GRAIN ELEVATORS

(&) Materials used for this purpose shall not be sufficiently irri
tating or toxic to human beings to prevent entry while process is
being used. Materials and methods of application shall be accepta
ble to the inspection department having jurisdiction.
N o t e . —Revision of paragraph 906 is under consideration by the committee
with a view to harmonizing with the Recommended Good Practice for Fumi
gation, prepared by the National Fire Protection Association Committee on
Fumigation Hazards.

Shovels.
907. In shoveling of grain, dust, and other refuse on concrete or
steel bin bottoms, floors, etc., the danger of igniting suspended dust
by sparks should be reduced by equipping the cutting edge of shovels
with a strip of nonferrous metal or by use of wooden shovels.
Smoking.
908. Smoking shall be prohibited, and conspicuous signs to that
effect posted throughout the elevator buildings.
Waste cans.
909. Approved containers shall be provided, all oily waste and
other rubbish deposited therein, and emptied daily.
Lockers.
910. Workmen’s clothing shall be kept in approved metal lockers,
preferably in a separate building.
Oils.
911. Main storage of lubricating oil and grease shall be outside.
Storage of lubricating oil and g re a s e in the building shall be limited
to a maximum of 5 barrels and shall be in an oil room of noncombus
tible construction.
Miscellaneous storage.
912. There should be no storage within the elevator of sacks,
sacked grain, or screenings, or other combustible merchandise, ma
terials, machinery, parts, and supplies.
lightning protection.
913. All combustible elevators should be equipped with approved
lightning protection, or if roof and walls are metal clad, same may
be accepted as constituting lightning protection if provided with
approved metallic contacts at eaves, and walls grounded in approved
manner.
Static electricity.
914. Static electricity shall be removed from such machines or
equipment as accumulate a charge, by permanent ground wires, and
from belts by grounded metal combsi or other effective’ means.
Grounds shall conform to provisions of article 9 of the National
Electrical Code.1
Section 10.—Fire Protection
First-aid appliances.
1001.
Casks and pails and other suitable first-aid protection shall
be provided in noncombustible buildings to protect all combustible
1 Obtainable from the National Fire Protection Association, 60 Batterym arch Street,
Boston, Mass.

84589°—32------3

S A FE T Y CODES FOR DTJST E X P L O S IO N S

parts, machines, materials, etc. (except grain and belts), and
throughout all combustible buildings. Suitable fire extinguishers
shall be maintained near all motors and other electrical apparatus
(other than lighting equipment). (See Regulations of the National
Fire Protection Association for F irst Aid Fire Appliances.1)
Watchman.
1002. All combustible elevators should be patrolled by watchman
reporting to approved time recording apparatus. Rounds, apparatus,
etc., shall conform to requirements of inspection department having
jurisdiction. The employment of watchman in noncombustible ele
vators, tanks, or driers, is desirable for reasons outside the scope
of these rules, but it is not considered especially necessary in relation
to fire and explosion hazard, except that if containing combustibles
in quantity sufficient to produce a serious fire, watchman service is
desirable. See item 805 for recommendation as to lights for use of
watchman. For further information on this subject see the National
Fire Protection Association pamphlet entitled “ The Watchman.” 1
Standpipe and hose.
1003. Standpipe systems should be installed to protect all parts of
combustible elevators and to protect noncombustible buildings con
taining combustible parts, machinery, etc., to any considerable extent
where required by the inspection department having jurisdiction.
(See Regulations of the National Fire Protection Association for
Standpipe and Hose Systems.1)
Use of hose streams.
1004. Fire department or standpipe hose stream should be used
with great care around an elevator. Their careless and unnecessary
use may cause dust explosions by throwing dust into suspension.
N ote .—Large fire-resistive elevators usually contain little combustible mate
rial other than grain. When the combustible material, such as a wooden
cleaner, is located above bins, the application of water by hose streams may
result in heavy water damage to grain in bins, unless bins are curbed and floor
scuppered. (See note under item 207.)

Fire in bin or tanks.
1005. I f fire occurs in a bin, no attempt to clear the bin should
be made until it is definitely known that the fire has been extin
guished, as there is possibility of a dust explosion in dropping grain
onto a belt if a trace of fire remains in the grain.
Automatic sprinklers.
1006. An approved system of automatic sprinklers is recommended
for any combustible elevator, and, where feasible, for the protection
of such parts of noncombustible elevators as contain combustibles,
other than grain and belts, in quantity sufficient to produce a
serious fire.
1 Obtainable from the National Fire Protection Association, 60 Batterymarcb. Street,
Boston, Mass.

Dust

Ex p l o s i o n in a L a r g e T e r m i n a l G r a i n E l e v a t o r in t h e m i d d l e W e s t . A l l t h e S ix W o r k m e n
in
E l e v a t o r a t T i m e o f E x p l o s i o n w e r e K i l l e d ; P r o p e r t y D a m a g e o v e r $3,000,0 00

D u s t Ex p l o s i o n in
M en
K il l e d a n d
$25 0,000

la r g e

e a s t e r n

In j u r e d ;

T e r m in a l

p r o p e r t y

G r a in El e v a t o r , s ix
, A p p r o x im a t e l y

d a m a g e

26—2

R e s u l t s o f Ex p l o s io n o f G r a in

D u s t in a T e r m i n a l G r a in

E l e v a t o r in

S o u t h w e s t . F o u r t e e n m e n w e r e K i l l e d a n d 10 I n j u r e d ; P r o p e r t y
D a m a g e , A p p r o x i m a t e l y $500,000

t h e

26—3

Result

o f

Ex p l o s i o n

o f

s u g a r

Du st.

T w elve

M en

w e r e

K il l e d

an d

24 I n j u r e d ; D a m a g e , $1,000,000

26—4

Safety Code for Pulverizing Systems for Sugar and
Cocoa
(American Standard, approved September 24, 1931, by American Standards Association)

Introduction.
This safety code is issued to eliminate or reduce the hazards inher
ent in the manufacture of pulverized sugar and cocoa, particularly
the hazard of their ignition and the propagation of a resulting fire.
I t is essential that there shall be no escape of dust into the atmos
phere of the room, a condition favorable to a dust explosion and to
the rapid propagation of fire.
F or this reason it is im portant that the apparatus be provided
with effective appliances to prevent ignition and confine fire; proper
venting of the apparatus and ventilation of the pulverizing depart
ment are important.
The term “ pulverizing department,” as used in this code, com
prises the portion of the plant in which the pulverizing processes
are carried on. The equipment consists of the mills or pulverizers,
in conjunction with which may be used scalpers, bolters or screens,
separators or dust collectors, spouts and conveying apparatus.
Definitions.
In this code the following words are used as defined below:
“ Shall ” is intended to indicate requirements.
“ Should ” is intended to indicate recommendations, or that which
is advised but not required.
“ Approved ” refers to approval by the authority having jurisdic
tion in the enforcement of regulations.
Location.
1. (a) The processes of pulverizing should preferably be carried
on in a detached building used for no other purpose and located at a
safe distance from other property, or if close by, have exposing
walls blank and parapeted; such structure, except the exposing walls,
to be of light noncombustible materials.
(&) I f the processes, owing to the layout of the plant, can not be
carried on in a location as recommended in section 1 (<z), the portion
of the plant devoted to them shall be segregated and be located, if
possible, in the upper stories, under the roof.
Construction.
2. (a) When the processes are carried on in locations as designated
in section 1 (&), the walls, partitions, floors and ceilings of such
section of the plant shall be not less than 4 inches reinforced concrete
or the equivalent in strength and fire resistance if the building is of
fire-resistive construction; in buildings of nonfire-resistive construc
tion, partitions, floors, and ceilings shall be of equivalent strength as
27

SA FE T Y CODES FOR D U S T E X P L O S IO N S

required for buildings of fire-resistive construction, and shall be able
to withstand a standard 1-hour fire test.
In buildings of nonfire-resistive construction the partitions, floors,
and ceilings of the pulverizing departments may be constructed of
not less than 2%-inch tongued and grooved or splined planking,
firmly secured, and protected throughout by at least 1 inch of cement
plaster on expanded metal. All openings in such partitions shall be
provided with approved structural iron frames or have the edges
otherwise protected in an approved manner. Communications shall
be protected as provided for under rule 3.
(&) A portion of the exterior walls equal to not less than 10 per
cent of the combined areas of the inclosing walls shall be of light
noncombustible material, preferably thin glass, so located and ar
ranged that it shall not be a greater distance from the opposite wall
or walls than the least horizontal dimension of the room; or where
confined to end walls the length of the room shall not exceed twice
the least horizontal dimension of the room. The width of the corner
jamb or wing wall formed by a wall thus pierced and the adjacent
wall shall not exceed 10 per cent of the length of the pierced wall,
and in no case shall the distance from the glass or equivalent area to
the corner formed by the adjacent wall beyond, or in L-shaped
rooms to the projected line of the adjacent wall, exceed the least
horizontal dimension of the room.
Thin glass skylights may be accepted in part or entirely in lieu of
the required glass or equivalent area, provided the area of such
skylights whether used entirely or in p art shall be based upon a
requirement for 10 per cent of the combined areas of the inclosing
walls. Such skylights shall be located not farther from the outer
walls of the room than a distance equal to 10 per cent of the length
of the adjacent walls, and shall have a free venting area to the room
not less than the glass area required.
When structural conditions prevent the close observance of this
rule a deviation of not over 10 per cent in the dimension and distances
given in the foregoing paragraphs may be permitted, provided the
minimum glass or equivalent area required is based upon the modified
room dimensions.
N ote.—See Figures 1 to 6, inclusive (pp. 29-31), for illustrations of typical
applications of the above requirement for glass or equivalent area.

(c) Wired glass should only be used when necessary as a protection
against exposure. I f used, it shall be in sash so hung th a t they will
readily swing out in case of an explosion; such sash shall not be
secured. When thin glass is used, this form of hanging is not
necessary. Glass areas in walls shall be so located as to vent the
force of an explosion in the direction or directions of least exposure.
(d) Window ledges, girders, beams and other projections shall
have the tops beveled or other provisions made to minimize the
deposit of dust thereon.
Communications.
3.
(a) Access to the pulverizing department should be from the
outside; this can be accomplished by means of balconies. Where
this is not feasible and direct communications are required, these

S A F E T Y CODE FOR P U L V E R IZ IN G SUG AR A N D COCOA

shall be protected by standard self-closing, hinged class B fire doors,1
swinging outward from the rooms in which the processes are con
ducted, unless safe egress is provided to the outer air, in which case
standard automatic sliding fire doors may be used to protect the.se
openings.
N ote.—Where extensive operations are carried on it is recommended that
the direct communications referred to in rule 3 be protected by double class B
fire doors, automatic sliding on the inner side and self-closing hinged, swinging
54*-—40* Windows ——'b5v

« ,0 -

80 *

-------------------------------

-------- ------------------------ +

10* ►

W in d o w s

ROOM OR BUILDING
50**50^12* HIGH

R O O M O R BUILDING
100'* 5 0 1 2 'HIGH

Required Glass or
Equivalent Area
240 6q. ft.

Required Glass or
Equivalent Area
360 sq.ft.

Figure 1

Figure 2

50*-

Q
C

-5 0 ’-

BUILDING DR ROOM
50 x 100’* 12’ HIGH
Required Glass or Equivalent

Area 360 sq.fi.

j*— -40‘Windows------- .

so*

BUILDING OR ROOM
50’x100’x 12' HIGH
Required Glass or Equivalent

^ li

%1
-8
1
C I
1

Area 360 sq.ft^

Figure 4
outward, on the outer sid e; where such communications constitute serious
exposures, vestibules, of noncombustible materials to divert the direction of
the force or flames, are also recommended.

(b)
Where power is transmitted to apparatus within the rooms
from any driving mechanism or unit outside of same by means of
shafts, these shall pass through close-fitting shaft holes in walls or
1 See Regulation for the Protection of Openings in W alls and Partitions, obtainable from
the National Fire Protection Association, 60 Batterym arch Street, Boston, Mass.

SA FE T Y CODES FOE D U S T E X P L O S IO N S

partitions; if the transmission is bj means of belts or chains these
shall’be incased both inside and outside of the pulverizing department
in dust-tight inclosures, substantially constructed of noncombustible
materials.
(c) All pipe openings through walls or partitions shall be tight.
(a)
Conveyors, spouts, chutes, and elevator inclosures shall be of
substantial metal construction and dust tight.
(e)
W ith the exception of spouts and conveyors for raw material
or finished product in bulk, no conveyors, spouts, chutes, etc., shall
pass through any of the walls or floors separating the pulverizing
department from other portions of the building. Conveyors of the
screw type only shall be permitted to pass through the walls, pro
vided a portion of the blade, equivalent to at least one diameter of
the screw, shall be omitted at a point immediately inside of the wall
150'
120’ Windows

•L* SHAPED

BUILDING
ROOM 1 2 'HIGH

Required Glass or E quivalent
Area 6 0 0 sq.ft.
Liiw of Wall

of the pulverizing department and pins substituted therefor; when
the finished product is delivered from the pulverizing department
through spouts it shall be conveyed from the apparatus within the
pulverizing department to the spouts by means of screw conveyors
from which a portion of the blade, equivalent to at least one diam
eter of the screw, has been omitted and pins substituted therefor,
or an equally effective means of producing a “ choke ” between the
delivery section of the apparatus and the spout shall be provided.
N ote .—

See also secs. 7 (a) and 7 (f).

(/) The use of air for the conveying of the material, either in its
raw or finished state, to or from the pulverizing department, shall
not be permitted, neither shall it be permitted within this depart
ment, except that air currents generated by the fans within the mills
or fans operated in conjunction with the mills may be used in con
nection with the processes of pulverizing. (See Kegulations of the

SA FE T Y CODE FOR P U L V E R IZ IN G SUGAR A N D COCOA

National Fire Protection Association for Blower and Exhaust Sys
tems,1 sec. 420.)
Note.—In this connection, see also secs. 7 (e) and 7 ( g) of this code.
Power.
4.
(a) I f electric motors are used, these should preferably be lo
cated outside of the pulverizing department and the power trans
mitted as noted under paragraph 3 (b). I f inside of this department,
they shall be of a type approved for dusty locations.
(b)
All controlling and circuit-breaking devices, if within the
pulverizing department, shall be of the approved inclosed safety
type; cabinets or inclosures shall be dust tight and kept fully closed
when apparatus is in operation.
150'

Lighting.
5. (a) Electric incandescent lights only shall be permitted in the
pulverizing department. Lamps shall be inclosed in dust-proof
globes provided with approved guards.
(b) When portable lights or drop lights are required they shall
be inclosed in dust-proof globes and shall be guarded, utilizing ap
proved flexible cord designed for hard usage. Special dust-proof
outlets shall be provided.
(c) Switches and cut-outs shall be approved and dust tight. These
should preferably be located outside of the rooms containing the
pulverizing department.
Wiring.
6. All wiring shall be in conduit, in accordance with the National
Electrical Code.1
N ote.—Electrical materials, appliances, and apparatus noted under rules 4
(power), 5 (lighting), and 6 (wiring), their location, installation and use, shall
1 Obtainable from, the National Fire Protection Association, 60 Batterym arch Street,
Bositon, Mass,

SA FE T Y CODES FOR D U S T E X P L O SIO N S

be in accordance with the National Electrical Code.
Class II locations.

See art. 32, particularly

Preventive measures.
7.
(a) All apparatus shall be properly and securely installed to
insure constant true alignment and to avoid hot bearings or friction,
and no moving parts shall be fitted close to or come in contact with
any part of the inclosures or the structure. On all pulverizing ap
paratus, 1-piece cast-iron driven pulleys shall be used. Bearings
shall be self-lubricating, if possible, and all bearings shall be so
designed as to be dust tight. The apparatus shall be equipped with
such devices as will prevent ignition, or confine the results of ignition,
and with devices which will minimize the amount of dust in the
atmosphere. The apparatus should be installed and arranged in unit
systems so that pulverizers will deliver to but one set of scalpers and
bolters; interconnections between sets of apparatus should not be
permitted.
Screw conveyors shall be fully inclosed in tight, substantial, metal
housings; if the tops of these housings are removable they shall be
well secured. (This should not be understood to prohibit the use of
pressure relief vents at the discharge end of the conveyor.)
N ote .—Attention is directed to the fact that warning of the overheating of
bearings in dusty or inaccessible locations and when the heating of bearings may
cause explosions, may be obtained by the use of approved journal alarms.

(5)
All mills and other apparatus, including dust collectors, in
connection with the pulverizing system, together with their pulleys,
shafting and belts shall be electrically grounded in an effective
manner.
(c) All of the material delivered to the mills or pulverizers shall
pass over self-cleaning magnetic separators and shall be protected
against the entry of foreign materials in its passage to the mills.
The separators shall be of sufficient size to expose and insure the
removal of all ferrous materials passing over them; one separator,
if of sufficient size and strength, may serve a group of mills. Sugar
shall be passed through %-inch wire mesh screens before entering the
mills or pulverizers, and if dumped into a delivery hopper from a
floor above the mill or pulverizer, such hopper shall have a curbing
at least 7 inches above the floor and be provided with a screen of %inch wire mesh.
(d) All inspection openings in the pulverizing apparatus shall be
provided with wire mesh screens of not less than four meshes to the
inch.
(e) The mills shall either discharge the pulverized product di
rectly through spouts or scroll conveyors into the screens, bins, or
bulk containers, or the product may be discharged from the mills by
air currents set up by the centrifugal force of the blades or beaters
and an inclosed fan, or the pulverized product may be removed by
means of an exhaust fan.
(/) Mills delivering directly through spouts should be provided
with devices in or underneath the discharges which retard the flow
of product in such a manner as to keep a small space immediately
underneath or near the discharge filled up with pulverized material,
thus smothering any spark that may originate in the mill. This
can be effected either by means of a revolving choke valve, or if

SA FE T Y CODE FOR P U L V E R IZ IN G SUGAR, A N D COCOA

the material is delivered directly into the scroll or screw conveyor,
by the omission of a small portion of the blade and substituting
therefor pins.
(g) Blowers or exhaust fans shall be installed on proper founda
tions and secured in a substantial manner and shall not be used for
any other purpose.
Where practicable the exhaust fan shall be located beyond the
collector. When located between the collector and the pulverizing
apparatus or any portion thereof from which the dust is to be re
moved, the blades and spider should be of bronze or similar com
position, or the casing consist of or be lined with similar material.
Ample clearance shall be provided between the blades and the casing.
The fan bearings shall not extend into the casings. (See Regulations
of the National Fire Protection Association for Blower and Exhaust
Systems.1)
(A) Screens (scalpers, bolters, etc.) shall have their reels or sieves
in dust-proof inclosures. When connected to dust collectors, the flues
shall be of metal, and the collectors shall be properly vented to the
outside of the building.
(i)
All dust collectors (except those of cloth type) shall be con
structed throughout of noncombustible materials; cloth type collec
tors shall be provided with dust-tight metal inclosures or their equiv
alent. The fabric of cloth type collectors should be electrically
grounded in an effective manner.
All dust collectors used in connection with the pulverizing system,
if not located outside of the building, shall be located within the pul
verizing department and shall be properly vented to a safe point
outside of the building. (See also Regulations of the National Fire
Protection Association for Blower and Exhaust Systems,1 class C.)
(j) Pressure relief vents shall be of ample size and properly
proportioned. These are especially required at certain types of
mills, screens, dust collectors, and elevator heads. The vent flues
must be substantially constructed of metal and be carried out of doors
as directly and as nearly vertically as possible and shall not deviate
more than 22%° from the direction of the pipe from which they lead.
They shall not pass through an adjoining building or room. H ori
zontal runs shall be avoided.
Yent outlets should be provided with cowls or hoods, and where
the nonescape of dust is essential, with counterbalanced relief valves
or covers provided with a soft felt gasket, at least three-fourths inch
thick. (For illustration of safety relief vent see p. 34.)
(k ) Open flames of any kind, or any operations or repairs result
ing in sparks or utilizing direct heat, shall not be permitted in the
pulverizing department while in operation or when the air is charged
with floating particles of dust.
Housekeeping.
8. Good housekeeping is one of the most important factors; appa
ratus which will not leak and permit the escape of dust or sifting
out of the material is essential. Accumulations of escaping dust
1 Obtainable from* the N ational Fire Protection Association, 60 Batterym arch Street,
Boston, Mass.

SA F E T Y CODES FOR D U S T E X P L O S IO N S

must not be tolerated in the building. I t is recommended that the
interior of the pulverizing department be painted a color which is
in contrast with that of the dust.
Cleaning that is liable to produce dust clouds shall not be done
while machinery is in operation because of the possibility of the dust
being ignited by sparks originating from electrical discharges or
from other causes.

Fire protection.
9.
The building or rooms in which the processes of pulverizing are
carried on shall be protected by approved first-aid fire appliances
together with approved small hose and should be protected by a
system of approved automatic sprinklers. (See Regulations of the
National Fire Protection Association for F irst Aid Fire Appliances,
Standpipe and Hose Systems, and Sprinkler Equipment.1)
1 Obtainable from, the N ational Fire Protection Association, 60 Batterym arch Street,
Boston, Mass.

Safety Code for the Prevention of Dust Ignitions in
Spice-Grinding Plants
(American Standard, approved September 24, 1931, by American Standards Association)

Introduction.
1. This safety code is issued to eliminate or reduce the hazards
inherent in the manufacture of ground or pulverized spices, particu
larly the ignition and the propagation of a resulting fire or
explosion.
N ote.—No serious dust explosions have occurred during the normal operation
of spice-grinding plants. However, some spice dusts will explode, and these
regulations have accordingly been prepared as a guide to safe practice in the
construction and operation of such plants.

Definitions.
2. In this code the following words are used as defined below:
The term “ grinding department ” as used in this code comprises
the portion of the plant in which the grinding processes are
carried on. The equipment generally consists of cutters, mills, rolls,
or pulverizers; scalpers, bolters, or screens; dust collectors; convey
ing and elevating apparatus; and may include packing equipment
where barrels, sacks, or similar large packages are filled from a bin
or hopper containing bulk material received directly from the grind
ing or bolting machinery.
“ Shall ” is intended to indicate requirements.
“ Should ” is intended to indicate recommendations or that which
is advised but not required.
uApproved ” refers to approval by the authority having jurisdic
tion in the enforcement of the regulations.
The terms 66adequately,” “ effective,” and “ securely ” shall be in
terpreted as conditions subject to the approval of the inspection
department having jurisdiction.
Location.
11.
The grinding department should be located in a detached or
segregated section of tne plant or along an outside wall or in the
upper stories under the roof where vents to the outside can con
veniently be provided for dust collectors and other equipment in
which dust clouds may exist.
Construction.
21. The “ daylight ” type of mill building (with large window
area) is recommended.
22. Fire-resistive construction or mill construction is recom
mended.
23. Where other processes are carried on on the same floor the
grinding department shall be separated by partitions of a type cor
responding to the building construction and designed to prevent the
forming of dust deposits outside the grinding department.
35

SA FE T Y CODES FOR D U S T E X P L O SIO N S

24. As much of the exterior walls of the grinding department as
practicable should be of light noncombustible material, preferably
thin glass designed and placed to give way at a pressure less than
that required to rupture the partition, floor, or ceiling separating
the grinding department from other sections of the plant.
N ote.—See Figures 1 to 6, inclusive (pp. 29-31), for illustrations of typical
applications of requirements for glass or equivalent area.

25. The grinding department should be arranged so that a mini
mum of 1 square foot of light exterior wall can be provided for
each 80 cubic feet of volume and so that no p art of the room is farther
from the venting area than 1.1 times the least horizontal dimension
of the room.
26. Construction should be such that all interior walls including
bin walls shall be smooth and free from pockets or ledges where dust
could accumulate.
27. Window ledges, girders, beams, and other projections within
the grinding department which are impractical to eliminate should
have the tops beveled or other provision made to prevent dust ac
cumulations thereon.
Communications.
31.
Self-closing doors shall be used on all direct communications
between the grinding department and other sections of the plant
provided such doors will not prevent ready egress from the depart
ment in case of fire.
Electric power, lighting, wiring.
41. Motors and other electrical power equipment if used within the
grinding department shall be in accordance with the standards of
article 32 of the National Electrical Code1 for dusty locations.
42. Electric incandescent lights only shall be permitted in the
grinding department and all lights and switches shall be of the type
required by, and installed in accordance with the standards of
article 32 of the National Electrical Code 1 for dusty locations.
43. All wiring shall be in accordance with the standards of article
32 of the National Electrical Code.1
Prevention of ignition.
51. All apparatus shall be properly and securely installed to insure
constant true alignment and prevent hot bearing or friction likely
to cause a fire.
52. Static electricity shall be removed from such machines or
equipment as accumulate a charge by permanent ground wires and
from belts by grounded metal combs or other equally efficient sys
tems. Grounds shall be attached to equipment and to the earth in
accordance with the National Electrical Code,1 article 9.
53. (a) All raw material delivered to the mills or pulverizer
shall pass over magnetic separators of sufficient size to expose and
insure the removal of all ferrous materials passing over them.
(&)
Coarsely ground or small size material should be passed
through a wire screen of a mesh suitable to the product before en
1 Obtainable from tbe National Fire Protection Association, 60 Batterym arch Street,
Boston, Mass,

SA F E T Y CODE FOR S P IC E -G R IN D IN G P L A N T S

tering a mill even though it was passed over a magnetic separator
previously.
54. (a) Mills delivering directly through spouts should be pro
vided with devices in or underneath the discharges which will re
tard the flow of the product in such a manner as to keep a small
space directly underneath or near the discharge filled up with the
product, thus smothering any fire which may start. This can be
accomplished by means of a revolving choke valve.
(6)
When mills discharge to screw conveyors a small portion of
the conveyor blade should be removed and pins substituted there
for, thus providing protection similar to th at obtained in the pre
vious rule.
55. All dust collectors used in connection with the grinding sys
tem if not located outside of the building shall be located within
the grinding department and properly vented to the outside.
56. Pressure relief vents should be provided at the mills where
ignitions are likely to occur. The vents should be of ample size,
substantially constructed of metal, and be carried out of doors as
directly as possible.
57. No open flames of any kind nor any operations or repairs result
ing in sparks or utilizing direct fire heat shall be permitted in the
grinding department until all equipment has ceased operating and
the room has been carefully cleaned, including the wiping down of
equipment near the point where it is necessary to use the open flame
or direct fire heat. Care shall be taken to see that the air in the room
is free of dust and that first-aid fire protection in the form of small
hose or extinguishers is close at hand during such periods.
58. Smoking and the carrying of matches shall not be permitted.
Housekeeping.
61.
Good housekeeping is one of the most important factors and
it is essential that apparatus be kept in such condition th at it will not
leak or permit the escape of dust into the room. Accumulations of
dust shall not be tolerated in the building. I t is desirable to have
the interior of the grinding department painted a color which will
show by contrast the presence of any dust accumulations.
Fire protection.
71. The building or rooms comprising the grinding department
shall be protected by approved first-aid fire appliances together with
approved small hose and should be protected by a system of approved
automatic sprinklers. (See National Fire Protection Association
Regulations for the Installation, Maintenance, and Use of First-Aid
Fire Appliances, Regulations for Standpipe and Hose Systems, and
Regulations for Installation of Sprinkler Equipment.1)
1 Obtainable from the N ational Fire Protection Association, 60 Batterym arch Street,
Bositon, Mass.

Dust

Ex p l o s io n

Fo l l o w in g

F ir e

s p ic e P l a n t .
Fo u r f ir e m e n
IN J U R E D ; D A M A G E , $150,000

L o s t t h e ir

L iv e s a n d

13 w e r e

Ex p l o s io n o f C o c o a D u s t a n d R e s u l t in g F ir e . T h r e e M e n w e r e K il l e d
a n d O n e w a s I n j u r e d ; P r o p e r t y D a m a g e , $ 7 5 0 ,0 0 0

Ef f e c t s o f Ex p l o s io n

o f W o o d -f l o u r d u s t ,
f o u r m e n
P r o p e r t y D a m a g e , $10,000

w e re

in j u r e d

3 8 -2

;

R e s u l t s o f Ex p l o s io n o f W o o d D u st a n d R e s u l t in g f ir e . O ne p e r s o n w a s In j u r e d ; Es t im a t e d
D a m a g e , $75,000

Property

Ex p l o s io n

o f

W o o d -f l o u r d u s t , w h i c h w a s E f f e c t i v e l y v e n t e d w i t h o u t
W H EREVER H IN G ED W IN D O W S W ERE P R O P E R L Y IN S T A L L E D

St r u c t u r a l

d a m a g e

Safety Code for the Prevention of Dust Explosions in
Wood-Flour Manufacturing Establishments
(American Standard, approved September 2 4 , 1931, by American Standards Association)

Introduction.
1. This safety code is issued as a guide to eliminate or reduce the
hazards inherent in the manufacture of wood flour, particularly the
hazard of its ignition and the propagation of a resultant fire. This
code is intended to apply to new construction and rebuilt or re
modeled plants. I t is advisable to remodel wherever possible any
present installations to conform with these regulations.
2. I t is essential that there shall be no escape of dust into the at
mosphere of the plant, this condition being favorable to a dust
explosion and to the rapid propagation of fire. I t is important that
the apparatus be provided with effective appliances to prevent igni
tion and confine fire; proper venting of the apparatus and ventilation
of the pulverizing department are important.
Definitions.
3. In this code the following Avords are used as defined below:
“ Pulverizing department ” refers to that portion of the plant in
which the pulverizing processes are carried on. The equipment
usually consists of mills or pulverizers, in conjunction with which
may be used bolters or screens, separators or dust collectors, spouts
and conveying apparatus.
66Shall ” is intended to indicate requirements.
“ Should ” is intended to indicate recommendations, or that which
is advised but not required.
“Approved ” refers to approval by the authority having jurisdic
tion in the enforcement of the regulations.
The terms “ adequately,” “ effective,” and “ securely ” shall be
interpreted as conditions subject to the approval of the inspection
department having jurisdiction.
Location.
11. (a) The processes of pulverizing should preferably be carried
on in detached building used for no other purpose and located at a
safe distance from other property.
(b)
I f conditions are such that it is necessary for the pulverizing
building to be located in such a way as to expose other buildings,
walls between pulverizing building and other buildings should be
blank, fire resisting, and parapeted. Walls of pulverizing building,
except as noted, shall be of light noncombustible materials.
12. I f the processes, owing to the layout of the plant, can not be
carried on in a location as recommended in section 11, the portion of
the plant devoted to them shall be segregated in such a manner as to
minimize the possibility of an explosion or fire reaching other
portions of the plant.
39

S A F E T Y CODES FOR D U S T E X P L O S IO N S

Construction.
21. In buildings of fire-resistive construction, when the processes
are carried on in locations as designated in section 12, the walls,
partitions, floors, and ceilings of such section of the plant shall be
not less than 4-inch reinforced concrete, or the equivalent in strength
and fire resistance.
22. In buildings of nonfire-resistive construction the partitions,
floors, and ceilings of the pulverizing departments shall be con
structed of not less than 2%-inch tongue and grooved or splined
planking, firmly secured, and protected throughout by at least 1 inch
of cement plaster on expanded metal, or shall be of equivalent
strength if constructed of noncombustible or fire-resistive material.
All openings in such partitions shall be provided with approved
structural iron frames or have the edges otherwise protected in an
approved manner. Communications shall be protected as provided
for under section 31.
23. (a) A portion of the exterior walls in the ratio of not less than
1 square foot of wall surface for each 80 cubic feet of volume in a
given room shall be composed either of light, noncombustible mate
rial, preferably %-inch thin glass, or of automatic venting
devices in the form of hinged windows or panels so balanced as to
open under a predetermined pressure. Hinged windows or panels
shall not be fastened in such a way as to prevent opening under pres
sure originating inside of the room. Venting areas shall be located
in such a manner that no part of the room shall be further away
from the venting area than a distance equal to 1.1 times the least
horizontal dimension of the room.
(&) I f other than %-inch thin glass is used as a protection against
exposure, it shall be in hinged sash as described above.
(c) One-eighth inch thin glass skylights may be accepted in part
or entirely in lieu of the required glass or equivalent venting area,
provided the area of such skylights, whether used entirely or in
part shall be based upon a requirement of 1 square foot of venting
area for each 80 cubic feet of volume of room to be vented. Such
skylights shall be located not farther from the outer walls of the
room than a distance equal to 10 per cent of the length of the adja
cent walls, and shall have a free venting area to the room not less
than the glass area required.
N ote.—See Figures 1 to 6, inclusive (pp. 29-31), for illustrations of typical
applications of requirements for glass or equivalent area.

(d) Glass or equivalent venting areas in walls shall be so located
as to vent the force of an explosion in the direction or directions
where least damage may be done to adjacent buildings.
24. Window ledges, girders, beams, and other horizontal projec
tions or surfaces shall have the tops beveled or other provision made
to minimize the deposit of dust thereon.
Communications.
31. In buildings of fire-resistive construction, access to the pulver
izing department should be from the outside. On floors above the
ground floor this can be accomplished by means of balconies. Where
this is not feasible and direct communications are required, these
shall be protected by standard self-closing hinged class A fire doors,

SA F E T Y CODE FOR W O O D -FLO U R E S T A B L IS H M E N T S

swinging outward from the room in which the processes are con
ducted, unless safe egress is provided to the outer a ir ; in which case
standard automatic sliding class A fire doors, normally kept closed,
shall be used to protect these openings. (See National Fire Protec
tion Association Regulations on Protection of Openings in Walls and
Partitions.1)
32. In buildings of nonfire-resistive construction, access to the
pulverizing department should be from the outside. On floors above
the ground floor this can be accomplished by means of balconies.
Where direct communications are required these shall be protected
by standard class B hinged self-closing doors, swinging outward
from the room in which the processes are conducted, unless safe egress
is provided to the outer air, in which case standard automatic sliding
class B fire doors, normally kept closed, shall be used to protect
these openings. (See National Fire Protection Association Regu
lations on Protection of Openings in Walls and Partitions.1)
33. Where power is transmitted to apparatus within the room
from any driving mechanism or unit, outside of the pulverizing de
partment, the transmission medium (belt or chain) shall be encased
both inside and outside of the pulverizing department in practically
dust-tight inclosures, constructed of substantial noncombustible
material. Where power is transmitted by means of shafts, these
shall pass through close-fitting shaft holes in walls or partitions.
Shaft transmission of power is preferable.
34. All pipe openings through walls or partitions shall be tight.
35. Conveyors, spouts, chutes, and elevator inclosures shall be of
substantial metal construction and practically dust tight.
36. (a) W ith the exception of spouts and conveyors for raw ma
terial or for finished product in bulk, no conveyors, spouts, chutes,
etc., shall pass through any of the walls or floors separating the pul
verizing department from other portions of the building. Con
veyors of the screw type only shall be permitted to pass through
the walls, provided a portion of the blade, equivalent to at least one
diameter of the screw, shall be omitted at a point immediately inside
of the wall of the pulverizing department and pins substituted there
for ; when the finished product is delivered from the pulverizing de
partment through spouts it shall be conveyed from the apparatus,
hoppers, or bins within the pulverizing department to the spouts by
means of screw conveyors from which a portion of the blade, equiva
lent to at least one diameter of the screw, has been omitted and pins
substituted therefor, or an equally effective means of producing a
“ choke ” between the delivery section of the apparatus and the spout
shall be provided. (See secs. 51 and 54.)
(&) A ir may be used for conveying raw material to supply bins in
pulverizing department, but it shall not be used for conveying ma
terial directly to the pulverizers nor for conveying the finished
product from the pulverizing department to other departments of
the plant, nor for conveying material within the pulverizing depart
ment except between the pulverizers and separators, where air cur
1 Obtainable from the National Fire Protection Association, 60 Batterym arch Street,
Bositon, Mass.

84589°—32-----------4

S A FE T Y CODES FOR D U S T EXPLO SIO N'S

rents generated within the mills or by fans operated in conjunction
with the mills are generally used.
N ote.—In this connection see section 55. See Regulations of the National
Fire Protection Association for Blower and Exhaust Systems, section l l . 1

Electric power, lighting, wiring.
41. Motors and other electrical equipment should preferably be
located outside of the pulverizing department. I f located within
the department they shall be in accordance with the standards of
article 32 of the National Electrical Code1 for dusty locations.
42. Electric incandescent lights only shall be permitted in the pul
verizing department, and all lights and switches shall be of the type
required by and installed in accordance with article 32 of the
National Electrical Code,1 for dusty locations.
43. All wiring shall be in accordance with article 32 of the
National Electrical Code.1
Preventive measures.
51. (a) All apparatus shall be properly and securely installed to
insure constant true alignment and to avoid hot bearings or friction,
and no moving parts such as belts, pulleys, drive chains, etc., shall
be fitted close to or come in contact with any p art of the inclosure or
the structure. On all pulverizing apparatus, one-piece cast-iron
driven pulleys should be used. Bearings should be of the ball or
roller type, if possible, and all bearings shall be so designed as to be
dust tight. The apparatus shall be equipped with such devices as
will prevent ignition, or confine the results of ignition, and with de
vices which will minimize the amount of dust in the atmosphere.
The apparatus should preferably be installed and arranged in unit
systems so that each pulverizer will deliver to but one set of scalpers
and bolters. Interconnections between sets of apparatus should not
be permitted, unless the material passing from one unit to another
is conveyed through screw conveyors containing positive chokes.
(See sec. 36.)
(b)
Screw conveyors shall be fully inclosed in tight, substantial
metal housings; if the tops of these housings are removable, they
shall be well secured. (This should not be understood to prohibit
the use of pressure relief vents at the discharge end of the conveyor.)
N ote.—Attention is directed to the fact that warning of the overheating of
bearings in dusty and inaccessible locations, and when the heating of bearings
may cause explosions, may be obtained by the use of approved journal alarms.

52. Static electricity shall be removed from such machines or
equipment as accumulate a charge by permanent ground wires, and
from belts by grounded metal combs or other equally efficient sys
tems. Grounds shall be attached to equipment and to the earth in
accordance with the National Electrical Code,1 article 9.
53. (a) All of the material delivered to the mills or pulverizers
shall pass over magnetic separators, preferably of the self-cleaning
type, and shall be protected against the entry of foreign materials in
its passage to the mills. The separators shall be of sufficient size to
expose and insure the removal of all ferrous materials passing over
1 Obtainable from the National Fire Protection Association, 60 Batterym arch Street,
Boston, Mass..

S A F E T Y CODE FOR W O O D -FLO U R E S T A B L IS H M E N T S

them; one separator, if of sufficient size and strength, may serve a
group of mills.
(&) I f the material is dumped into a delivery hopper from a floor
above the mill or pulverizer, such hopper shall have a curbing at least
6 inches above the floor.
(c)
All inspection openings in the pulverizing apparatus shall be
provided with wire mesh screens of not less than four meshes to the
inch.
54. Mills delivering directly through spouts should be provided
with devices in or underneath the discharges which retard the flow
of product in such a manner as to keep a small space immediately
underneath or near the discharge filled up with the pulverized prod
uct, thus smothering any spark th at may originate in the mill. This
can be effected either by means of a revolving choke valve, or, if mate
rial is delivered directly into the scroll or screw conveyor, by omitting
a small portion of the blade and substituting pins therefor.
55. Blowers or exhaust fans shall be installed on proper founda
tions and secured in a substantial manner. Where practicable the
exhaust fan shall be located beyond the collector. When located
between the collector and the pulverizing apparatus, 6r any portion
thereof from which the dust is to be removed, the blades and spider
should be of bronze or other nonsparking metal or the casing consist
of or be lined with similar material. Ample clearance shall be pro
vided between the blades and the casing. The fan bearings shall
not extend into the casings. (See Regulations of the National Fire
Protection Association for Blower and Exhaust Systems.1)
56. Screens (scalpers, bolters, etc.) shall have their reels or' sieves
in dust-tight inclosures. When connected to dust collectors, the flues
shall be of metal, and the collectors shall be properly vented to the
outside of the building.
57. (a) All dust collectors (except those of cloth type) shall be
constructed throughout of noncombustible materials. Cloth type
collectors should be provided with dust-tight metal inclosures or
their equivalent. The fabric of cloth type collectors should be elec
trically grounded in an effective manner. (See sec. 52.)
(b)
All dust collectors used in connection with the pulverizing
system should be located on the roof, in segregated sections of plant,
or in separate buildings. I f this is not possible they shall be located
within the pulverizing department and shall be properly vented to a
safe point outside of the building. (See also Regulations for Blower
and Exhaust Systems, class C.)
58. (a) Pressure relief vents shall be of ample size. These are
especially required at certain types of mills, screens, dust collectors,
and elevator’heads. The vent flues shall be substantially constructed
of metal and be carried out of doors as directly and as nearly verti
cally as possible, avoiding especially short turns—never through an
adjoining building or room—and be properly proportioned.
(&) Vent outlets should be provided with cowls or hoods, and
where the nonescape of dust i« essential, with counterbalanced relief
valves or' covers provided with a soft felt gasket, at least threefourths inch thick. (For illustration of safety relief vent see p. 34.)
1 Obtainable from the N aponal Fire Protection Association, 60 Batterym arch Street,
Boston, Mass.

SA FE T Y CODES FOR D U S T E X P L O S IO N S

59.
No open flames of any kind, nor any operations or repairs re
sulting in sparks or utilizing direct fire heat shall be permitted in the
pulverizing department until all equipment has ceased operating and
the room has been carefully cleaned, including the wiping down of
equipment near’ the point where it is necessary to use the open flame
or direct fire heat. Care shall be taken to see th at the air in the room
is free from dust and that the first-aid fire protection in the form of
small hose or extinguishers is close at hand during such periods.
Housekeeping.
61. (a) Good housekeeping is one of the most im portant factors;
apparatus which will not leak and permit the escape of dust or sift
ing out of the material is essential. Accumulations of dust shall not
be tolerated in the building. I t is recommended that the interior of
the pulverizing department be painted a color which is in contrast
to that of the dust.
(b) Interior surfaces shall be cleaned in such a manner as to mini
mize the scattering of dust to other places. To this end it is recom
mended that dust removal be accomplished by an adequate pneumatic
or vacuum-sweeping system.
(c) Cleaning th at is liable to result in production of dust clouds
shall not be done while machinery is in operation because of the pos
sibility of the dust being ignited.
62. (a) Portable vacuum cleaners and air compressors shall not be
used for cleaning. Suction-cleaning appliances should be connected
by hose to taps of permanent piping extending to a suction fan or
equivalent.
(b)
The fan or equivalent and the collector shall be located in a
separate room. The discharge from this dust collector may be to
the dust collector used for the discharge of air from the vacuum
system connected with the pulverizing and screening equipment.
Fire protection.
71. The buildings or rooms in which the processes of pulverizing
are carried on shall be protected by a system of approved automatic
sprinklers and shall be equipped with approved first aid fire appli
ances, together with approved small hose. (See Regulations of the
National Fire Protection Association for Automatic Sprinkler Sys
tems, Standpipe and Hose Systems, and F irst Aid Fire Appliances.1)
72. Wherever possible, pulverizing machinery, screens, bolters, con
veyors, bins, etc., should be protected against fires and explosions by
the use of inert gas. (See Regulations for the Use of Inert Gas for
Fire and Explosion Prevention, p. 69; also Technical Bulletin No.
74, U. S. Department of Agriculture.)
1 Obtainable from the National Fire Protection Association, 60 Batterym arch Street,
Bositon, Mass.

Safety Code for the Installation of Pulverized-Fuel
Systems
(American Standard, approved September 5, 1930, by American Standards Association)

Introduction
1. This safety code is designed for application to new installations
and when making alterations or extensions to existing equipment.
I t is not retroactive.
2. Installation of pulverized-fuel systems should be under the su
pervision of engineers qualified by experience in the design, construc
tion and operation of such equipment.
Definitions
3. In this code the following words are used as defined below:
“ Shall ” is intended to indicate requirements.
“ Should ” is intended to indicate recommendations, or that which
is advised but not required.
“Approved ” refers to approval by the authority having jurisdic
tion in the enforcement of regulations.
The terms “ adequately,” “ effective,” and “ securely ” shall be
interpreted as conditions subject to the approval of the inspection
department having jurisdiction.
Types of Systems
4. Pulverized-fuel systems are of various types; all involve the
hazard incident to the creation and possible liberation of combustible
dusts unless properly designed, constructed, and operated. In general
they may be arranged in three classes as fallows:
Class A systems.—Indirect or those in which the fuel is intimately
mixed with air at the point or points where used and involving
storage bins at points of consumption.
Class B systems.—Direct or those in which the pulverized fuel is
fed to a fan by which it is blown as a combustible mixture through
large pipes to furnaces or other points of consumption. In the case
of circulating systems of this class, the unused fuel is returned to
the initial point to again be blown through the line. In these sys
tems, the pulverizers are located remote from points of consumption.
TJnit systems.—Those in which the fuel is pulverized at or near the
point or points of use, and delivered directly from the pulverizer
into the furnace by means of fan or blower, which may be an integral
part of the apparatus ; the air being admitted in the apparatus or
in conjunction with the fuel. Systems of this type do not employ
bins.
Regulations for All Classes of Systems
location.
11.
(a) The building housing fuel-pulverizing equipment shall be
constructed of noncombustible material.
45

SA FE T Y CODES FOR D U S T E X P L O S IO N S

(b) The process of pulverizing fuel may be accomplished either:
1. In the room or section of the building where it is burned, or
2. In a room, building, or floor separated from the rest of the
building by masonry walls and floors and used for no other
purpose.
12. (a) Where the process of pulverizing fuel is carried on in the
room or section of building where it is burned and the volumetric
capacity of the mill housing, mixing, or separating chamber (if any)
and all of the piping conveying coal suspended in air does not exceed
100 cubic feet, all such piping shall be at least equal to the require
ments of paragraph 25, specification No. 1.
(b) Where the volumetric capacity of the mill housing, mixing,
or separating chamber (if any) and all piping conveying fuel in
suspension in air exceeds 100 cubic feet all such piping shall be at
least equal to the requirements of paragraph 26, specification No. 2,
and all mixing and separating chambers shall either be constructed
for a working pressure of 50 pounds per square inch with a factor
of safety of four based on the ultimate strength of the material, or
located in a separate room or floor cut off from the rest of the build
ing and constructed in accordance with section 13.
(c) Where an inert atmosphere containing not more than 13 per
cent of oxygen is maintained in an approved manner within the mill,
separator, and piping, the entire milling and separating system, re
gardless of cubic capacity, may be located within the room or section
of building where the fuel is burned. All piping conveying fuel in
suspension in gas shall be at least equal to the requirements of
section 25, specification No. 1, and the separator (if any) shall be
constructed in accordance with section 19.
Construction.
13. Where the process of pulverizing fuel is accomplished in a
room, building, or floor separated from the rest of the building by
masonry walls, such building or section of building shall be con
structed as follows:
(a) I t shall be constructed of noncombustible material and spe
cially designed (1) to secure minimum lodgment of dust; (2) so that
all interior parts of the building on which dust may lodge may be
cleaned readily; and (3) to relieve the force of an explosion through
skylight, window, or explosion doors.
(b) Depending on local conditions, either light or heavy type of
building construction may be used.
(c) A. portion of the exterior walls equal to not less than 10 per,
cent of the combined areas of the inclosing walls shall be of light
noncombustible material, preferably thin glass, so located and ar
ranged that it shall not be a greater distance from the opposite wall
or walls than the least horizontal dimension of the room; or where
confined to end walls the length of the room shall not exceed twice
the least horizontal dimension of the room. The width of the corner
jamb or wing wall formed by a wall thus pierced and the adjacent
wall shall not exceed 10 per cent of the length of the pierced wall,
and in no case shall the distance from the glass or equivalent area
to the corner formed by the adjacent wall beyond, or in L-shaped
rooms to the projected line of the adjacent wall, exceed the least
horizontal dimension of the room.

S A F E T Y CODE FOR P U L V E R IZ E D -F U E L S Y S T E M S

Thin glass skylights may be accepted in part or entirely in lieu
of the required glass or equivalent area, provided the area of such
skylights whether used entirely or in part shall be based upon a
requirement for 10 per cent of the combined areas of the inclosing
walls. Such skylights shall be located not farther from the outer
walls of the room than a distance equal to 10 per cent of the length
of the adjacent walls, and shall have a free venting area to the room
not less than the glass area required.
When structural conditions prevent the close observance of this
rule a deviation of not over ten per cent in the dimension and dis
tances given in the foregoing paragraphs may be permitted, provided
the minimum glass or equivalent area required is based upon the
modified room dimensions.
N0TE.—gee Figures 1 to 6, inclusive (pp. 29-31), for illustrations of typical
applications of the above requirement for glass or equivalent area.

(d ) Wired glass should only be used when necessary as a protec
tion against exposure. I f used, it shall be in sash so hung that they
will readily swing out in case of an explosion; such sash shall not
be secured. When thin glass is used, this form of hanging is not
necessary. Glass areas in walls shall be so located as to vent the
force of an explosion in the direction or directions of least exposure.
(e) In buildings of light construction, the frame should be pre
ferably of steel with light nonbearing walls (except fire walls), con
structed of such materials as stucco on metal lath, tile, metal or
equivalent noncombustible materials and with roof of monitor otf
gable type, and all secured in such manner as to give way readily
under pressure of explosion.
(/) In order to prevent accumulations of dust the design of the
buildings shall be such and the structural members so shaped and
assembled or protected as to present the least possible extent of
surface on which dust can lodge. Access must be provided for
cleaning all parts of building on which dust may accumulate.
(g) Except for the passage of shafts, pipes, and closed conveyors,
these walls and/or floors separating the pulverizing plant from other
portions of the building shall, where practicable, be unpierced.
Where feasible all communication between the pulverizing plant
and the rest of the building shall be from the outside or by means
of fire-resistive stairways inclosed by masonry walls. In cases where
this method of access to pulverizing plant is not feasible indirect
communication through separating walls by means of vestibules may
be permitted, provided the wall opening is protected by an auto
matic sliding fire door approved for class A situations and the ves
tibule opening by a heavy closed hinged fire door approved for class
B situations at right angles to the sliding door, or other suitable
protected indirect communication approved by the inspection depart
ment having jurisdiction. (See Regulations of the National Fire
Protection Association for the Protection of Openings in Walls and
Partitions.1)
(h) All piping conveying fuel in suspension in air shall be at
least equal to the requirements of section 25, specification No. 1, and
1 Obtainable from the National Fire Protection Association, 60 Batterym arch Street.
Bositon, Mass.

SA F E T Y CODES FOR D U S T E X P L O S IO N S

the separators (if any) shall be constructed in accordance with
section 19.
Ventilation and dust collection.
14. (a) All buildings or parts of buildings in which the processes
of pulverizing are carried on shall be well ventilated to the outer air.
(b) The atmosphere of the room shall be kept as free as possible
from suspended or floating dust by maintaining all apparatus in a
dust-tight condition.
(c) Good housekeeping is a factor of the utmost importance. To
this end every coal drying and pulverizing plant shall be kept free
from even small accumulations of coal dust. All interior surfaces
shall be smooth and of a color, preferably white, which contrasts
with the dust. They shall be cleaned at sufficiently frequent inter
vals to prevent accumulations of dust.
Interior surfaces shall be cleaned in such manner th a t no dust
will be scattered or distributed. To this end it is recommended that
dust removal be accomplished by an adequate pneumatic or vacuum
cleaning system. The use of compressed air for blowing dust from
motors or other equally inaccessible places is permissible, but the
general use of compressed air (except in connection with water
spray) for blowing dust from walls and other interior surfaces is
prohibited.
(d) Because of the hazard attending the use of flexible electric
cable in coal pulverizing plants, the use of portable vacuum cleaners
or air compressors should be avoided. Portable tanks containing
compressed air may be used providing no electrical equipment is
operated inside of the pulverizing room in connection therewith.
(e) Vacuum cleaning systems, if installed, shall comply with the
following general requirements:
1. Systems shall be of sufficient power and capacity to ac
complish effective results.
2. Nozzles and handles shall be constructed of nonferrous
metal, fiber or other nonsparking material.
3. Hose, nozzles, handles and other metal parts shall be elec
trically grounded to the piping system and the piping system
effectively grounded to the earth.
4. Dust separation shall take place before the dust reaches
the exhauster. The discharge of separators shall be carried
outside buildings. The dust shall enter the receiving end of
the separator in a direction tangential to the metallic surface.
5. The motor and separator should preferably be located
outside of the pulverizer room.
Pulverizer.
15. All pulverizer mills shall be safeguarded against the hazard
of fire and explosion and be operated under competent supervision.
Means for interrupting power supply to pulverizing equipment shall
be provided near the equipment and at a readily accessible location
separated from the equipment by noncombustible partitions.
Magnetic separator.
16. (a) A magnetic separator of the self-cleaning type shall be
provided for each system employing pulverizing mills of other

SA F E T Y CODE FOR P U L V E R IZ E D -F U E L S Y S T E M S

than ball and tube type. In each case the magnetic separator shall
be installed ahead of the pulverizers.
Coal that has passed the magnetic separator shall be located or
protected in such a manner as to prevent the entry of foreign
materials.
Every magnetic separator shall be safeguarded against the passage
of coal when it is not magnetized, either by an interlock which will
stop the flow of coal or by a suitable alarm system which will notify
the operator that the separator is not functioning.
(b) The magnetic separator shall be of such size as to expose and
insure the removal of tram p iron or other magnetic substances.
(c) One separator, if of sufficient size and strength, may serve a
group of mills.
Electricity for light and power.
17. (a) All electrical equipment for light and power in pulverizer
house shall conform with the National Electrical Code.1 Provision
shall be made for remote control in order that current for light and
power may be cut off in an emergency without entering pulverizer
house.
(&) In no plant shall coal storage bins, conveying machinery or
fuel pipe lines be used as supports for electric lighting or power lines
other than those installed in conduit.
Grounding of machinery.
18. Static electricity shall be removed from such machines or
equipment as accumulate a charge by permanent ground wires and
from belts by grounded metal combs or other equally effective meth
ods. Grounds shall be attached to equipment and to the earth in
accordance with the National Electrical Code,1 article 9.
Dust collectors.
19. (a) All dust collectors (except those of cloth type) shall be
constructed throughout of noncombustible materials; cloth type col
lectors should be provided with dust-tight metal inclosures or their
equivalent. The fabric of cloth type collectors shall be electrically
grounded as required by paragraph 18. All dust collectors used in
connection with the pulverizing systems, unless located in the depart
ment devoted to the pulverizing, drying or storing of coal, or in con
nection with transport systems on class A bins, shall be located in
a separate room unless the proportion of oxygen within the separator
is maintained at less than 13 per cent. Dust collectors, and rooms in
which they are located shall be properly vented to a safe point outside
of the building.
(b)
Cyclone separators shall meet the following minimum require
ments :
1. The shell and thimble shall be made of iVinch steel
plate.
2. All seams shall be welded or riveted and welded.
3. All flanges shall conform to the flanges used on connecting
piping.
1 Obtainable from the National Fire Protection Association, 60 Batterymarch Street,
Boston, Mass.

SA FE T Y CODES FOR D U S T E X P L O S IO N S

Vents.
20. (a) Safety relief vents shall be liberally provided on all pul
verizing equipments, particularly in the discharge of the mill in class
A and B systems, or in the case of air separating systems, at the top
of the return duct to the m ill; at elevator heads, at every storage bin
for pulverized fuel and at dust collectors. Storage bin vents shall
have a cross-sectional area sufficiently large to permit the separation
of air from fuel without building up an abnormal pressure within
the bin. Safety relief vents taken off pipes and flues shall be of at
least the same area as the pipes or flues vented; they shall lead by the
most direct practicable route to the outside air in as nearly a vertical
direction as practicable; and shall not deviate more than 22y2 degrees
from the direction of the pipe or flue from which they lead. H ori
zontal runs shall be avoided. (For illustration of safety relief vent
see p. 34.)
N ote.—This rule does not apply to operating vents, meaning thereby such
vents as may be required for efficient means of operation. Such vents may be
connected into natural draft boiler stacks or breechings into same, or into an
induced draft suction near the fan, or into the furnace, provided they are
equipped with automatic balanced, noncorrodible dampers opening in the
direction of the normal draft.
In no case shall operating vents be permitted to deliver into the open room.

(b)
Where operating bin and mill vents are discharged into the
furnace, each pipe to the furnace shall be provided with a f a n ; fan
and discharge pipe shall be so proportioned th a t the velocity in the
discharge pipe from the fan is not less than 70 feet per second.
Each fan shall be provided with tight inlet and outlet dampers,
arranged to open only when the flow is toward the furnace, to close
automatically on interruption of flow and be positively held closed
when the fan is not in operation. The pipe from the fan to furnace
shall be laid out at such an angle as to provide no place for dust
to accumulate and from the outlet damper to the furnace shall be at
least equal to the requirements of section 26, specification No. 2.
Blowers handling fuel in suspension.
21. (a) Blowers shall be installed on proper foundations and
secured m a substantial manner. They shall not be used for any
other purpose, but this shall not be construed as prohibiting the
use of a blower as a means of supplying secondary air also.
(b)
Bearings of blowers handling fuel in suspension shall not
extend inside of blower casings or ducts.
(<?) All connections between discharge end of blower and main
duct shall be made so as to prevent leakage of fine dust. (See Regu
lations of the National Fire Protection Association for Blower and
Exhaust Systems.1)
N ote.—Nonferrous metals need not be used in the construction of fan blades
or lining of fan casings.

Driers.
22. Fuel may be dried either in the raw state or during the process
of pulverizing, in the mill and separating system.
(a)
Raw-fuel driers may consist of three types, the direct and
semi-indirect types which are fired by special furnaces, and the
1 Obtainable from the National Fire Protection Association, 60 B&tterymar<ch Street,
Bositon, Mass.

S A F E T Y CODE FOR PTJLV E R IZ ED -FU E L S Y S T E M S

indirect type in which coal is dried by means of inert gas from
boiler breechings or by means of steam or hot air before entering
the mill.
(i ) Driers of the direct and semi-indirect types shall be so de
signed and constructed that the products of combustion of the heating
unit shall not come in contact with the fuel being dried, except at
a distance of at least one-half of the length of the drier, and in no
case within 12 feet of the fuel bed.
Such driers shall be designed to prevent gases of combustion from
entering its shell when not in operation.
On account of the danger of spontaneous ignition due to over
heating coal, the use of this type of drier should be confined to fuels
having a high ignition temperature.
(c) Driers may be installed in boiler rooms of fire-resistive con
struction, cut off in a standard manner from the rest of the plant.
When drier is located in a boiler house, construction of latter shall
be of noncombustible material.
(d) Direct and semi-indirect driers if not located in boiler room
as noted in 22 (c) or in a separate building shall be separated from
the pulverizing department or any other section of the plant (except
as noted under 22 (c) or in similar occupancies) by means of non
combustible partitions or walls constructed of materials having a
fire resistance of not less than one hour in accordance with standard
specifications for fire tests of materials for construction.
Indirect driers, unless in a separate building, or in boiler room,
shall be similarly segregated or be provided with a protective cover
ing or insulation which will afford protection equivalent to materials
capable of withstanding a 1-hour fire test as noted in the foregoing.
(e) Mill driers.—In the process of drying coal in the mill, heated
air is injected into the air duct where it enters the mill and an equal
quantity of moisture laden air removed at some point beyond the
mill. The danger of fire and explosion from such a system is pri
marily due to overheating the coal in the mill or piping system. Such
overheating may occur either when the mill is shut down or when it is
in operation. This overheating can be prevented as follows:
M ill shut dowm. —So interlock the mechanism supplying heated air
to the mill with the power supply to the mill that heated air can not
enter the mill when it is not in operation. Dampers are seldom tight,
and if used must be supplemented by other more positive means.
Mill in operation.—I f the quantity and temperature of air supplied
remains constant with a varying coal feed or a varying moisture con
tent in coal, overheating may occur. Such overheating can be pre
vented by so controlling the heat supplied to the mill that a safe
temperature will be maintained in the mill discharge pipe. (The
safe temperature varies with different coal, under most conditions
satisfactory drying and safe operation can be obtained with a dis
charge temperature of 90° to 125° F .) H eat control may be accom
plished either manually or automatically. I f manual, install a
thermometer with a high-temperature alarm in the mill discharge
pipe for the guidance of the operator ; if automatic, use a thermo
stat in the same location. Whether manual or automatic control is
used the necessary reduction in mill discharge temperature should be

SA FE T Y CODES FOR D U S T E X P L O S IO N S

accomplished by reducing the heat input to the drying air and not
by reducing the quantity of air.
N ote.—A table of safe temperatures for drying coal is given in the Appendix.

(/) A ir heaters for mill driers.—Two types of air heaters are com
monly used with mill drying, i. e., steam air heaters and flue-gas air
heaters.
Steam air heaters.—Fires occur in this type of heater due to the
accumulation of dust on steam coils and other parts of heater; these
fires shall be prevented by the following precautions:
1. Keep the heater free from dust accumulations.
2. In starting up, start air flow through heater before turning
on steam.
3. In shutting down, maintain the air flow after steam is shut
off long enough to cool down the heater.
Flue-gas air heaters.—W ith this type of heater the temperature of
air entering the heater is not usually controllable within narrow
limits and adjustment of air temperature entering the mill is ob
tained by tempering with cold air.
For the safe operation of this type of system the following
provisions shall be m ade:
1. Heated air must be positively prevented from entering the
mill when it is not in operation.
2. Dampers, fans, and other auxiliary equipment must be so
arranged and interlocked that under no conditions will an open
path be provided for the flow of gas from the furnace to the mill.
N ote—Design practice varies so widely that detailed rules can not be given
for accomplishing the above requirements. Some typical examples of good
practice are given in Appendix B.

(g)
Goals (other than anthracite and coke).—On leaving the drier
the coal is hot and dry and in this state is particularly subject to
spontaneous ignition. The quantity of dried coal, either unground
or pulverized, stored in any plant should be kept as small as possible
without interfering with the continuity of plant operations. In all
cases operating schedules should be so arranged as to leave no dried
unground coal in the plant when the mills are shut down for a period
of 24 hours or more.
Pulverized coal exceeding a temperature of 150° F. shall not be
stored in any bin in connection with a class B system.
In order to draw attention to excessive rise in temperature of the
coal in the raw-coal driers, a temperature-indicating alarm device
shall be installed in the discharge end of the drier with its sensitive
member as close to the coal within the drier as practicable.
23. Dried coal elevator shall be of noncombustible construction,
dust tight, and provided with a safety relief vent to the outer
air.
24. All pulverizing mills and driers shall be constructed as dust
tight as practicable, and so operated as to avoid leakage of dust.
Pipe lines—Specification No. 1.
25. (a) All pipe lines conveying fuel in suspension shall be con
structed of lap-welded steel pipe, seamless steel tubing, butt-welded
sheet steel or their equivalent. Where butt-welded sheet steel is used
it should be No. 10 gage or thicker.

SA F E T Y CODE FOR P U L V E R IZ E D -F U E L S Y S T E M S

(b)
Fittings shall be constructed either of cast iron or butt-welded
sheet steel not less than No. 10 gage.
(o)
Where cast-iron flanged fittings are used, flanges shall con
form to the 125-pound American standard in diameter and number
of bolts.
(d) Where welded sheet steel fittings involving a change in di
rection are used they shall be provided with removable wearing
plates at all bends subject to abrasion. When such plates are used
the size of the fittings should be increased accordingly so as not to
decrease their effective diameter.
(e) All joints shall be made either by means of standard pipe
fittings or by steel angle flanges welded to pipes. Where welded
steel flanges are used, they shall be not less than one-fourth inch
thick, held together by bolts not less than five-eighths inch diameter,
number of bolts to conform to the 125-pound American standard,
center line of bolt holes to be not less than l 1/^ inches from outside
edge of flange. All pipe joints, control, switching, and shut-off
valves shall be of dust-tight construction.
Pipe lines—Specification Ko. 2.
26. The wall thicknesses given are the minimum requirement
with 1 2 per cent added to cover the usual mill tolerances.
Flat ring steel flanges 50-pound W. P.
Nominal pipe size (inches)

4____________________
5____________________
6 ____________________
8 ____________________
10 ___________________
12 ___________________
14 O. D _____________
16 O. D _____________
18 O. D _____________
20 O. D _____________
24 O. D _____________
30 0 . D _____________
36 0 . D _____________
42 0 . D _____________
48 0 . D _____________

Bolt circle Number of
(inches)
bolts

7H
8/2

9K
11 %

14K
17

18%
21 %
22%
25
29 ft

36
42%
49}i

Size of
bolts
(inches)

0 . D . of
flange
(inches)

Size of
holes
(inches)

4
4
4

8
8
8
8
8
12
12

%
%
%

%
%
%
%
%

16
24
24
32
44

%
%
%
%

%
%
%

%
7/s
%
Vs

1
1
1

Flange
thickness
(inches)

9
10
11

13 %
16
19
21

23^
25
27^
32
38%
46
53
59)4

P ipe dim ensions 50-pound W . P.
W all thickness

Nominal pipe size (inches) :
(inches)
4__________________________________________________0.133
5
_______________________________________ _. 135
________________________________________. 138
6
________________________________________. 147
8______
10_____
_______________________________________ _. 154
12 ______
_______________________________________ _. 162
________________________________________. 169
14 O. D_
________________________________________. 177
16 O. D_
18 O. D _______________________________:____________ _. 186
20 O. D _____________________________________________.194
24 O. D _____________________________________________.210
30 O. D_____________________________________________.234
36 O. D_____________________________________________.258
42 O. D_____________________________________________.282
48 O. D_____________________________________________.306

0. 391
. 437
. 478
. 568
. 710
. 914
. 917
1. 063
1. 090
1. 170
1. 214
1. 685
1. 987
2. 298
2. 612

S A FE T Y CODES FOR D U S T E X P L O S IO N S

Pipe lines—Specification No. 3.
27. Pipe shall be standard full-weight steel. Flanges and fittings
shall be A. S. A. standard B (16a) (125-pound standard).
Storage and furnace bins.
28. (a) Storage and furnace bins for pulverized fuel shall be
located as far as consistent with operating requirements from fu r
naces, and away from open flames or open lights of any kind. Bins
shall be so located and constructed that no radiation from furnaces,
boilers, steam pipes or flues, or other heating appliances, can m ateri
ally raise the temperature of the contents of the bin.
(&) All bins shall be of noncombustible material so constructed
as to present a smooth surface on the interior, and so shaped th at a
minimum of material will be left in the corners under normal empty
ing operation of the bin. Material used in construction of metal bins
shall be steel of sufficient thickness to secure ample mechanical
strength. Joints shall be riveted and caulked or welded; size and
spacing of rivets shall be such as to secure a dust-tight joint. Dust
tightness shall also be secured in cases where metal bins are lined
with concrete or where bins are constructed of concrete.
(d)
Except for vent openings, all storage and furnace bins shall
be normally tightly closed. When bins are filled by transferring
pulverized coal by means of air, either under pressure or by a fan,
the arrangement should be such as to assure a minimum dust cloud
within the bin. Such vent openings shall be equipped with tightfitting dampers or checks to prevent entrance of air from the outside.
(d )
All bins should be equipped with a reliable indicating device
to warn the operator before the bin is in danger of overflowing with
out exposing the contents. A t no time shall there be any pressure
other than that caused by the weight of the fuel in any pulverized
fuel storage bin.
Ignition.
29. For purposes of fuel ignition or supplementary use, fuel oil,
natural gas or artificial gas may be used if installed in an approved
manner.
30. Every coal conveying line shall be located away from all open
flames or open lights of any kind and at a safe distance from sources
of radiated heat such as furnaces, ovens, boilers, boiler settings, etc.
Class A Systems—Specific R egulations
Fire protection.
31. Every building or room containing the foregoing processes
shall be provided with approved fire extinguishers in such quantity
and of such type as outlined in the Eegulations of the National Fire
Protection Association for F irst Aid Fire Appliances.1 Wherever
the introduction of combustible material into the pulverizing room
makes automatic sprinklers necessary for' fire protection, their
arrangement and control shall be approved by the inspection depart
ment having jurisdiction.
1 Obtainable from the National Fire Protection Association, 60 Batterym arch Street,
Boston, Mass.

SA F E T Y CODE FO B P U L V E R IZ E D -F U E L S Y S T E M S

All raw-coal driers shall be provided with means of introducing
live steam or inert gases controlled by readily accessible, quick acting
valves.
Means should be provided to divert the contents of these driers to
the outside of the building in case of emergency. (See sec. 51 (&).)
N ote.—Attention is directed to the fact that warning of the overheating of
bearings in dusty and inaccessible locations, and when the heating of bearings
may cause explosions, may be obtained by the use of approved journal alarms.

Transportation pipe lines.
32. All pipe lines for transporting pulverized coal between mill
bins and points of consumption or storage shall be at least equal to
the requirements of section 27, specification No. 3.
Screw conveyors.
33. Systems using screw conveyors for handling pulverized fuel
shall be normally arranged with the driving power applied at the
end toward which the fuel is being conveyed. Where the length of
transfer is too great for a single screw so driven, any additional units
shall be similarly driven and so interconnected th a t the stopping of
the last screw in the series will automatically stop the others, or as
an alternative for such interlocking the junction point between the
two screw conveyors shall be placed outside of the building, and be
provided with a normally closed spillway or relief valve.
When it is necessary to transport fuel in different directions, and
this is to be accomplished by the reversal of motors, the motors oper
ating the screw conveyors shall be provided with overload releases
and screw conveyor drives should be provided with shearing pins.
All motors driving screw conveyors shall be provided with overload
releases.
A solid flooring shall be placed immediately under all screw con
veyors to retain any spilled material.
Unit Systems—Arrangement of Systems
41. No pulverizer shall be connected to supply more than one fu r
nace at a time. This shall not be construed as preventing the in
stallation of spare pulverizers which may be connected to any of
several furnaces if the regular pulverizer is disconnected; i. e., a
section of the discharge pipe between the pulverizer and the furnace
removed.
42. Piping from mill to burners shall be so arranged th at when
a mill is in use all burners which that mill can supply shall be in
operation.
43. Two discharge pipes from separate mills shall not be connected
to the same burner nozzle.
Instruction Cards
51. An instruction card, including the following precautions re
lating to safe operation, shall be conspicuously posted in the pulver
izing plant, boiler plant, and in buildings where pulverized fuel is
used.
(a)
The use of shavings or other similar light combustible ma
terials for starting fire in drier furnace is prohibited.

SA FE T Y CODES FOR D U S T E X P L O S IO N S

(&) The rotation of a revolving drier shall not be stopped while
it contains a charge of fuel.
Indirect driers delivering directly to the mills shall be run empty
before cutting out the mills, and coal gates, gas gates, or steam heat
ing valves shall be shut tightly. I f it becomes necessary to shut
down the mills for any reason for more than 24 hours, the driers
should be emptied.
In cases of indirect drier fires, shut off coal inlet and outlet gates,
gas inlet and outlet gates, and steam heating valves, if steam heated,
and turn on steam or inert gas extinguishing lines.
N ote.—When opening up a drier, transport line, or other apparatus which
has been sealed to extinguish a fire in the coal, or any place where live steam
has been injected for the same purpose, precautions must be taken to prevent
ignition of any gas which may have been generated during the period of
the fire.
After the fire has been extinguished and the coal has been cooled below
ignition temperature, the drier should be ventilated with a vigorous current
of fresh air for 10 minutes or more to remove poisonous gases before persons
are allowed to enter.

(<?) Whenever a plant has been idle for a period of two days or
more, all storage bins shall be thoroughly inspected before resuming
operation.
(d) Manhole or inspection openings of furnace bins shall not be
open while fuel is being discharged into the bins.
(e) Operators are cautioned against causing leaks in pipe lines
or bins by hammering.
(/) Damper in drier chimney uptake shall be wide open when fire
is started.
{g) In class B systems, if fuel supply line becomes clogged, the
furnace shall be immediately cut off and the secondary air stopped.
When obstruction has been cleared and before starting fan, a
thorough examination shall be made to ensure the removal of
smoldering particles of fuel.
(h) All fuel supply lines (of class B and unit system types) shall
be blown clear of fuel when shutting down at end of day.
(i) All conveyors and elevators shall be tightly and securely
inclosed and never opened while running. All conveying and dis
tributing piping shall be inspected daily and any leaks promptly
repaired. Previous to opening, machinery shall be stopped and
dust allowed to settle for a period of 20 minutes.
(j) Only daylight or hand flashlights shall be used when in
specting the interior of coal storage bins and pulverizing and coal
conveying apparatus when in operation. When apparatus is not
in operation guarded droplights with dust-proof globes utilizing
cord approved for hard usage such as type S or PA may be used.
Portable cord shall be used only from approved convenience outlets
provided for this purpose.
(k) Smoking and the use of open lights or torches shall be pro
hibited in the crushing, drying, and pulverizing plant.
(I)
Lighting pulverized fuel furnaces.—Before injecting pulver
ized fuel into a furnace:
1. See that there is sufficient draft on the furnace to ade
quately remove the products of combustion.
2. Provide lighted torches, adequate in number and volume
of flame, so disposed as to ignite all burners to be started.

SA F E T Y CODE FOR P U L V E R IZ E D -F U E L SY S T E M S

Keep the torches in operation until all danger of losing ignition
has passed.
N ote.—Many explosions resulting in loss of life and property have occurred
due to improper lighting-off practice. The requirements of a safe lighting-off
system vary so widely with' coals and equipment having different characteristics
that universally applicable detailed rules can not be written. The following
suggestions are offered as representing good ignition practice.
1. Permanent oil torches should be installed according to the National Fire
Protection Association Regulations for the Installation of Oil Burning Equip
ments.
2. Low-viscosity, high-flash-point oils such as kerosene or gas oil are
recommended.
3. Torches should have a supply of air under pressure independent of furnace
draft.
4. Portable torches, with which the tank .and piping are not in accordance
with codes for oil fired plants, should be withdrawn from the furnace
completely when not in use.
5. No gas having less than 400 B. t. u. per cubic foot is to be used for an
ignition torch, except that in furnaces fired primarily by blast furnace gas,
having coal burners only for use in emergencies, the gas may be used as a
lighting medium for the coal if the two types of burners are located according
to the best practice.
6. All gas torches should have a supply of air under pressure independent of
furnace draft or should be arranged like a Bunsen burner with the gas under
sufficient pressure to induce its own air supply.
7. The size of each torch should be proportioned according to the size of
the coal burner.
8. Bach torch should preferably be located so that its flame will approxi
mately parallel the coal stream to obtain contact for an appreciable length of
time with a given mass of coal.
9. The torch should be so located that the tip and ignition zone are outside
of the coal stream to avoid danger of having the torch snuffed out.

A ppendix A.—Storage of Coal
The observance of proper precautions in the storing of pulverized
or dried crushed coal is of pronounced importance in that failure in
this respect will probably result in fire due to spontaneous ignition.
In order to safeguard against this hazard it is urged that the follow
ing advisory requirements be complied w ith :
1. Semianthracite coal:
K S ? , i v S i Ze0a
Temperature of coal entering mills—
or dried crushed coal
200° F ______________________________________ 12 hours.
175° F ______________________________________ 16 hours.
150° F ______________________________________ 24 hours.
140° F ______________________________________ 36 hours.
130° F ______________________________________ 1 week.
2. B itum inous coal having less than 2 per cent sulphur:

Temperature of coal entering mills—
180° F ______________________________________ 12 hours.
150° F ______________________________________ 18 hours.
130° F ______________________________________ 24 hours.
120° F ______________________________________ 1 week.
3. L ign ite , subMtunvinous, ancl high sulphur coal:
Temperature of coal entering mills—
150° F ______________________________________ 12 hours.
130° F ______________________________________ 16 hours.
120° F ______________________________________24 hours.
110° F ______________________________________ 36 hours.
100° F __________________ — ________________ 1 week.

84589° — 32-

SA FE T Y CODES FOR D U S T E X P L O S IO N S

The last group of coals because of their higher inherent moisture
will drop in temperature in milling and will go to the pulverized
coal storage at considerably lower temperatures, provided the milling
system is properly vented to release the moisture given off in grind
ing. I f no water is evaporated, there will be only a small drop in
temperature. Whenever pulverized coal or crushed coal are stored
in thp plant, a regular daily inspection should be made to see that
there are no fires or overheating.
A pendix B.—Recom m ended P rocedure for the E xtinguishm ent
of F ires in Pulverized-Fuel Conveyors, Pipes, Ducts, Col
lectors, and Bins
The difficulty in extinguishing fires of the type noted above is
recognized by all persons who have had any material experience in
connection with the operation or maintenance of a pulverized-fuel
plant. Fires which otherwise would have been of slight extent
have spread beyond the incipient stage owing to the application of
improper extinguishing methods due to the lack of experience. F or
purposes of general information and guidance to those who may be
called upon to aid or direct such fire-extinguishing operations, the
following procedure governing such fire-fighting operations is given:
Fires in conveyors, pipes, ducts, or collectors.
In case fire is discovered in pulverized-fuel conveyors, pipes, ducts,
or collectors:
1. Stop coal supply as quickly as possible.
2. Stop air supply as quickly as possible.
3. Close all vents and gates and inspect all vents and gates which
should close automatically.
4. Introduce steam, carbon dioxide, or other inert gas. I t is sug
gested that pipe connections be provided on all such equipment for
the ready introduction of the extinguishing medium. Such connec
tions should not be less than 1 inch.
5. I f fire extinguisher can not be applied or is ineffective, water
may be introduced. Care should be taken not to use a high-pressure
stream which would create dust clouds which would be an explosion
hazard. W ater should be used only under supervision of responsible
authorities.
6. Procedure after fire is out will depend entirely on local con
ditions. In general, the equipment should not be put into operation
until it has been thoroughly cleaned.
Fires in pulverized-fuel bins.
In case fire occurs in a pulverized-fuel bin:
1. Stop coal supply to bin.
2. Stop carrier air to bin.
3. Close bin vent damper or, if it is automatic, make sure it is
tight.
4. Make sure that all other openings into bin, other than feeders,
are tight.
5. Notify foreman and fireman.
6. Foreman should sixe up situation to see if fire has been caught
quickly enough to be snuffed out by its own fumes.

S A F E T Y CODE F O B P TJLV E R IZ ED -FU E L S Y S T E M S

7. I f necessary introduce steam or inert gas. I t is suggested that
1-inch or 2-inch pipe connection or small hand hole be provided in
the top of bin for this purpose.
8. I f fire has made considerable headway before being discovered
so that vent damper has been damaged or seams have opened, it is
imperative that every effort be made to close these openings with
water-soaked bags or similar material. I f the material used is com
bustible it should be kept wet.
9. The use of large quantities of water inside the bin should be
avoided because it is of practically no value in putting out fire in
large quantities of pulverized fuel, and because it makes it almost
impossible to use the feeders.
10. The bin should be emptied as quickly as possible, even while
fire is in progress, by feeding coal to the furnace. This should be
done in spite of difficulties with feeders due to lumps of coke.
11. I f coal can not all be fed to furnace through feeders, the fire
should be completely extinguished before the bin is opened.
12. A fter the fire is out and the bin is opened as much coal as
possible should be scraped from the side walls with rods manipulated
through the manhole on top of the bunker. I f coke jams the feeders,
an attempt should be made to break it up with rods. I f this fails
men must enter the bin.
13. Before men enter the bin it shall be thoroughly aired for
several hours to eliminate fumes and to test whether fire is really out.
The bin should then be entered only on authority of responsible per
sons, and the men shall wear oxygen breathing apparatus and have
ropes around their waists held by men outside the bin. The men in
the bin shall be watched continuously unless the fire has been out
and the bin opened for at least 24 hours.
Practically all fires can be extinguished and coal can be fed
through the feeders without the emergency measures discussed
above in sections 6 to 13, unless there has been negligence in routine
inspection of bin. Routine inspection should consist in opening
such bin once a day. A man putting his head within the manhole
can determine whether there is any unusual increase in bin tem
perature or in fumes from smoldering fire, and if he temporarily
turns out his light he may be able to notice a dull red glow. Such
inspections, of course, should not be made while bin is being filled
nor until dust is settled after a filling period.
The following might be added to recommendation on bin fires:
14. The bin need not be emptied after a fire unless so much coke
has been formed that it jeopardizes safe feeder and burner operation.
I t is not safe operation if intermittent feeding and burning results
in deposits of unburned fuel in the furnace.
In this case the bunker should be emptied without burning the
coal, either by disconnecting feed pipe and discharging to buckets,
or by filling buckets in bunker and taking them out through the
manhole dn the top. Under no circumstances should the coal be
freely discharged to floor or sluiceway through openings in bottom
of bunker.

Safety Code for the Prevention of Dust Explosions in
Coal Pneumatic Cleaning Plants
(American Standard, approved December 31, 1930, by American Standards A ssociation)

A rticle I.—Introduction
11. This safety code is designed for application to new installa
tions and when making alterations or extensions to existing equip
ment. I t is not retroactive.
12. Installation of pneumatic cleaning systems should be under the
supervision of engineers qualified by experience in the design, con
struction, and operation of such equipment.
Definitions.
13. In this code the following words are used as defined below:
“ Shall ” is intended to indicate requirements.
“ Should ” is intended to indicate recommendations, or that which
is advised but not required.
“Approved ” refers to approval by the authority having jurisdic
tion in the enforcement of the regulations.
The terms 66adequately,” “ effective,” and “ securely 55 shall be
interpreted as conditions subject to the approval of the inspection
department having jurisdiction.
A rticle II.—Buildings, Machines, and A pparatus to be Covered
by these R egulations
Types of systems.
21.
Coal pneumatic cleaning systems as covered in these regula
tions employ air pressure and evacuation and are subject to the
hazard incident to the creation and distribution of dust, explosive
in air when ignited, also means of its ignition unless the system is
properly designed, constructed and operated. There are two prin
cipal dust-making mechanisms, and which may also be the means,
unless properly designed and operated, of distributing the d u st:
(а) Screens, shaking and/or vibrating screens, and revolving
screens.
(б) Pneumatic jigs or tables for separating the pure coal from the
refuse.
(c)
Other machines which may produce and distribute dust are as
follows: Conveyors, which may be of rubber or canvas, and inclosed
elevators used for several purposes, such as for carrying or conveying
the raw coal into the top of the building, conveying the clean coal
of the several sizes to bins or to the outside of the building, reelevating middling products, and conveyors or elevators for discharging
the refuse outside.
61

SA FE T Y CODES FOR D U S T E X P L O SIO N S

Dust-making adjuncts.
22. Potential dust hazards, either in dust making or in ignition of
dust already made, are found in :
(a) Dust collectors for collecting dust from air discharged by
evacuating hoods, separable into three general types:
(1) Cyclone collectors.
(2) Stocking or bag collectors for the finest dust.
(3) Screen-cloth collectors.
(b) Coal bins, such as bins for raw coal and for the cleaned prod
ucts. In some plants, however, some or all of these bins are not with
in the plant itself excepting there would be almost always within the
building raw coal bins which may be small in size for equalizing
the feed to the pneumatic jigs or tables.
(c) Dryers, which may be required if the coal to be cleaned
is wet or damp.
Article III.—Installation R equirem ents of P neum atic Cleaning
M achinery and A pparatus
Location.
31. The process of pneumatic cleaning shall preferably be accom
plished in a separate detached building used for no other purpose.
If driers are requisite in the operation it is desirable these be located
in a separate fire-resistive building or isolated room.
Construction of building.
32. The building containing pneumatic screening and cleaning
equipment and driers shall be constructed of noncombustible ma
terials and be of such design:
(a) To have internal surfaces, other than floors, for a minimum
lodgment of dust.
(b) That all interior parts of the building on which dust may
lodge may be cleaned readily.
(c) That will relieve the force of an explosion through skylight,
window or explosion doors.
Screen-room arrangement.
33. Where the coal screening is not in a separate building but is
in a room or rooms above the pneumatic or air jigs or tables, the
floor material should be of concrete or steel plate with openings
only for the passage of inclosed chutes, conveyors and pipes, and
inclosed stairways. Also, where the screen room is very large,
with outside walls having windows in at least one wall, it is desir
able to subdivide, so far as is practicable, by erection of partitions of
substantial fire-resistive construction, with self-closing fire doors,
extending across the room from side wall to side wall, to limit the
extent and violence of an inflammation in any one subdivision. I t
is preferable that the communication between rooms be indirect,
such as by doors .opening outward on an outside balcony or else use
double doors.
Jig or table room.
34. The room or rooms in which the pneumatic jigs or tables are
located should be arranged as provided in the preceding paragraph
for screen rooms.

SA F E T Y CODE FOR COAL P N E U M A T IC C L E A N IN G P L A N T S

Window arrangement and construction.
35. (a) A portion of the exterior walls of each of the several
floors or separate rooms shall have windows of an area in square
feet not less than one-fiftieth of the number of cubic feet in volume
of the respective room and there shall be a window or windows not
over 10 feet from each end of the room. The windows shall be so
constructed that they will rupture under an internal pressure of 1
ounce per square inch (9 pounds per square foot), or else they shall
be so hinged and not bolted or otherwise fastened, as to open out
ward under this pressure. Skylights of similar strength or hinged
may be accepted in lieu of equal area.
N ote.—See Figures 1 to 6, inclusive (pp. 29-81), for illustrations of typical
applications of requirements for glass or equivalent area.

(i)
Wired glass should only be used when necessary as a pro
tection against exposure. I f used, it shall be in sash so hung that
they will readily swing out in case of an explosion; such sash shall
not be fastened by bolt or lock. Windows and skylights shall be so
located as to vent the force of an explosion in the direction or direc
tions of least hazard to adjacent buildings or constructions.
Building construction.
36. (a) In buildings of light construction, the frame should be
of steel with light nonbearing walls (except fire walls), constructed
of such materials as stucco on metal lath, tile, metal or equivalent
noncombustible materials and with roof of monitor or gable type, and
all secured in such a manner as to give way readily under pressure
of explosion.
(6)
In order to prevent accumulation of dust, the design of the
buildings shall be such and the structural members so shaped and
assembled or protected as to present the least possible extent of sur
face other than the floor on which dust can lodge. No exposed sur
face, except the floor, stairs, steps and machinery, shall have an
inclination of less than 45 degrees, which condition may be met by
fastening securely a covering of iron sheeting or by using concrete
or hard plaster for filling up to the required angle to prevent dust
from accumulating thereon. Access must be provided for cleaning
all parts of building on which dust may accumulate.
Ventilation ^nd dust collection.
37. (a) All parts of the building in which the process of coal
pneumatic cleaning carried on shall be ventilated to the outer air
and where clouds of dust are given off, evacuating hoods at appropri
ate places and connected to an ample sized evacuating pipe, must be
installed to draw off dust as rapidly as made.
(&) The atmosphere of the room shall be kept as free as possible
from suspended or floating dust by maintaining all apparatus in
a dust-tight condition.
(c)
Good housekeeping is a factor of the utmost importance. To
this end every coal pneumatic cleaning plant shall be kept free from
even small accumulations of coal dust. All exposed surfaces other
than that of machinery shall be smooth and of a color, preferably
white, which contrasts with the dust. Floors and all other surfaces
shall be cleaned at sufficient frequent intervals to prevent dust from
accumulating.

SA FE T Y CODES FOR D U S T E X P L O SIO N S

(d) Interior surfaces shall be cleaned in such a manner as to
minimize the scattering of dust to other places. To this end it is
recommended that dust removal be accomplished by an adequate
pneumatic or vacuum-sweeping system. Compressed air should not
be used (except in connection with water spray) for blowing dust
from walls and other interior surfaces.
(e) Because of the hazard attending the operation of motors and
the use of flexible electric cable in coal pneumatic cleaning plants,
portable vacuum cleaners and air compressors shall not be used, but
instead the usual suction-cleaning appliances should be connected by
hose to taps of permanent piping extending to a suction fan or
equivalent.
(/) The fan or equivalent and the collector for the sweeping sys
tem shall be located in a separate room. The discharge from the
dust collector may or may not be the dust collector used for the
discharge of air from the vacuum system connected with the screens
and air jigs or tables.
Dust collectors.
38. All dust collectors (except those of cloth type) shall be con
structed throughout of noncombustible materials and be provided
with dust-tight metal inclosures. The fabric of cloth type collectors
should be electrically grounded as far as practicable in an effective
manner. All dust collectors shall be located in separate rooms; dust
collectors and rooms in which they are located shall be properly
vented to a safe point outside of the building and the discharge shall
be at sufficiently low velocity as to avoid fine dust being forced
through the bag or screen.
Air vents.
39. Safety relief vents shall be liberally provided in air separating
systems, at the top of the return duct to the respective machine; also
at elevator heads, at every coal-dust storage bin and at dust collectors.
Storage-bin vents shall have a cross-sectional area sufficiently large
to permit the separation of air from dust without building up an ab
normal pressure within the bin.
Safety vents.
40. To provide for relief of pressure of an internal dust explosion or
gas explosion there shall be vents taken off pipes and flues of at least
the same area as the pipes or flues vented; they shall lead by the most
direct practicable route to the outside air in as nearly a vertical direc
tion as practicable, and shall not deviate more than 22y2 degrees from
the direction of the pipe or flue from which they lead. Horizontal
runs to the point of venting shall be avoided. (For illustration of
safety relief vent see p. 34.)
Coal driers.
41. Driers if used may consist of three types, the direct and semiindirect types which are fired by special furnaces, and the indirect
type in which the coal is dried by means of inert gases from the boiler
breechings, or by means of steam or hot air.
(a)
Driers of the direct and semi-indirect types shall be so de
signed and constructed that the products of combustion of the

S A FE T Y CODE FOR COAL P N E U M A T IC C L E A N IN G P L A N T S

heating unit shall not come in contact with the fuel being1 dried,
except at a distance of at least one-half of the length of the drier,
and in no case within 12 feet of the fuel bed. Such driers shall be
designed to prevent gases of combustion from entering its shell
when not in operation. #
(b) Driers shall be installed in rooms of fire-resistive construc
tion, cut off in a standard manner from the rest of the plant.
(c) Direct or semi-indirect driers if not located in a separate
building shall be separated from the dust-making parts of the plant
by means of substantial noncombustible partitions or walls con
structed of materials having a fire resistance of not less than one
hour in accordance with standard specifications for fire tests of
materials for construction.
(d) Storage of dried coal: On leaving the drier the coal is hot and
dry and in this state, except for anthracite, is particularly subject to
spontaneous ignition. The quantity of dried coal, either coarse or
fine, stored within in any plant should be kept as small as possible
without interfering with the continuity of plant operation. Coal
exceeding a temperature of 150° F. shall not be stored in any bin.
In order to draw attention to excessive rise in temperature of the
coal in the driers a temperature-indicating alarm device shall be
installed in the discharge end of the drier with its sensitive member
as close to the coal within the drier as practicable.
Dried-coal elevator shall be of noncombustible construction, dust
tight and provided with & safety relief vent to the outer air.
All driers, conveyors and other dust making and transporting ma
chinery shall be constructed as dust tight as practicable, and so
operated to avoid leakage of dust.
Storage bins.
42.
(a) Storage bins for coal located in coal pneumatic cleaning
plants shall be so located and constructed th at no radiation from
furnaces, boilers, steam pipes or flues, or other heating appliances, can
materially raise the temperature of the contents of the bin.
(b) All coal bins in the coal pneumatic cleaning building shall be
of noncombustible material so constructed as to present a smooth
surface on the interior and so shaped that no material shall be left
in the corners under normal operation of emptying the bin. Ma
terial used in construction of bins shall be steel or reinforced con
crete of sufficient thickness to secure ample mechanical strength.
Dust tightness shall be secured in all cases.
(c) Except for vent openings all coal-dust bins shall be normally
tightly closed. The vent openings shall be equipped with tight fit
ting dampers or check valves to prevent circulation of air from the
outside.
Article IV.—Electricity fo r Light, Heat, and Pow er
51. Provision shall be made for remote control so that the current
for both light and power may be cut off when an emergency occurs,
without entering the coal pneumatic cleaning house.
52. All electrical equipment throughout the coal pneumatic clean
ing plant (except in sections so cut off as to be free from dust) shall

SA FE T Y CODES FOR D U S T EXPLO SIO N'S

conform to article 32 of the National Electrical Code 1 relating to
“Hazardous Locations, Class I I .”
N ote.—Article 32 of the National Electrical Code calls for totally inclosed or
other special types of motors specifically approved for use in hazardous at
mospheres. Fuses, circuit breakers, and similar devices are required to be in
dust-tight metal cabinets or cases, or to be of types which can not cause
exposed sparks. Lights are required to be in approved dust-tight globes—
which should be protected by substantial guards. Service entrance equipment
switchboards, etc., are required to be in separate dust-tight rooms or inclosure.
All wiring is required to be in rigid metal conduit.

53. Where, in the case of machinery, there are moving parts
electrically driven which require flexible cord, or in the case of
temporary machinery, or machinery under test, only approved cord
shall be used, such as special flexible trailing cables used in mining
machinery. Where this is used, care should be exercised in the
placing of cords or cables so that the insulation is not cut by move
ments of the machinery, and in no case shall conveying machinery
or pipe lines be used as supports except when the wires are placed
in rigid metal conduits.
54. When the fixed lights described above are not sufficient for
making inspections and repairs, especially within the inclosures of
machinery and bins, it may be necessary to employ portable lights.
I f these are used, the cord, the lights, and the attachment plugs must
be of approved design for use in a dusty atmosphere. However, it
is preferable, in place of portable cords and light attachments, to
employ “ permissible” flash lights and/or ^miners’ portable electric
storage battery lamps such as employed in gassy and dusty mines
which are termed “ permissible ” miners5 lamps.
N ote.—The term “ permissible,” used as a prefix to a motor, apparatus,
or device, means tested and approved by the United States Bureau of Mines
for use in gassy and dusty coal mines.

Article V.—F ire and Explosion Protection
61. Every building or room containing the foregoing processes
shall be provided with approved portable fire extinguishers in suf
ficient quantit}^ and of such types as outlined in the Regulations of
the National Fire Protection Association for F irst Aid Fire Ap
pliances.1 Other fire protection for fighting fires from within and
without the plant shall be in accordance with approved fire-fighting
regulations.
62. Driers and bins should be provided with a means of introduc
ing live steam, or inert gases controlled by readily accessible, quickacting valves. Means should be provided to divert the contents of
driers to the outside of the building in case of emergency.
Open flames and torches.
63. No stoves for heating the building, torches, or flames of any
sort shall be used under normal conditions. In case of repairs, when
it may be necessary to use electric, oxyhydrogen cutting or welding
torches, operation of the plant should cease and every precaution
1 Obtainable from the National Fire Protection Association, 60 Batterym arch Street,
Boston, Mass.

SA F E T Y CODE F O B COAL, P N E U M A T IC C L E A N IN G P L A N T S

shall be taken to clean np all dust in the vicinity prior to use of
the torches.
Smoking.
64. Smoking shall be prohibited in every part of the plant.
Fire drills.
65. Fire-fighting drills, embracing all employees of the plant,
including foremen, shall be held at least once a month.

Safety Code for the Use of Inert Gas for Fire and
Explosion Prevention
(American Standard, approved September 24, 1931, by American Standards Association)

Introduction.
This safety code, prepared in cooperation with the National Fire
Protection Association Committee on Manufacturing Risks and Spe
cial Hazards, is applicable to the prevention of fires and explosions
in industries and processes using flammable liquids and gases, as
well as to the prevention of dust explosions.
1. Carbon dioxide or other inert gases which when mixed with air
reduce the oxygen percentage of the atmosphere below the combus
tion limit can be used successfully in providing protection against
fires and explosions in certain hazards.
N ote.—These regulations cover only the use of inert gas for fire and explosion
prevention. For extinguishing fires by carbon dioxide see Regulations of the
National Fire Protection Association for Carbon Dioxide Fire Extinguishing
Systems.1

2. These rules indicate a standard method of using carbon dioxide
or other inert gases for the prevention of explosions and fires where
the hazards are of such a nature as to make this form of protection
necessary or desirable.
N ote.—Examples of where such protection may be called for are ovens,
driers, grinders, or pulverizers, special machinery and apparatus involving the
use or handling of flammable liquids, vapors, or dusts within an inclosure, tanks
used for storage of flammable liquids, and bins, vaults, or other such inclosures
containing material through which gas may permeate and where it is unneces
sary for anyone to enter the inclosure at frequent intervals.

3. Inert gas protection is not recommended for nitrocellulose or
other pyroxylin plastics in large quantities nor to prevent ignitions
or explosions of aluminum or magnesium powders, nor in cases where
decomposition or the release of combustion supporting agents may
occur and render ineffective inert gas protection.
4. Neither carbon dioxide nor nitrogen are poisonous, but in suffi
cient quantity they are suffocating, and it is not intended that inert
gas should be used in inclosures where employees are at work.
N ote.—Ordinarily no one would be overcome in an atmosphere of air and
carbon dioxide or nitrogen in the concentrations recommended within a time
amply sufficient for retirement from the room or inclosure.

5. Neither carbon dioxide nor nitrogen will injure metals, fabrics,
food products, or other perishable material. They do not freeze,
deteriorate, nor will they conduct electricity.
6. Where other inert gases such as flue gas, internal-combustion
engine exhaust, carbon tetrachloride, sulphur dioxide, di-chloro
methane, etc., are used special precautions are necessary to prevent
1 Obtainable from the National Fire Protection Association, 60 Batterym arch Street,
Boston, Mass.

SA FE T Y CODES FOR D U S T E X P L O S IO N S

possible injurious effects on employees or on the product being pro
tected.
N ote.—Flue gas is generally the most readily available and most frequently
used inert gas because it is economical and contains a relatively high per
centage of carbon dioxide. Injurious gases, particularly carbon monoxide, may
be present in flue gas or internal combustion engine exhaust and no one should
be permitted to enter any inclosure where poisonous gas is present or has been
used until the inclosure has been thoroughly ventilated and a test or an analysis
shows that no injurious gas remains.
In certain processes the use of steam is necessary or desirable, and in such
cases it may be used in combination with other inert gases provided it does
not introduce any additional fire hazards due to high temperatures.

7. Since the use of inert gas for fire and explosion prevention is a
comparatively new development it is recommended that these rules
be used with discretion. Only general essentials and the average
necessary specifications to make a workable code are given. Details
for each installation will necessarily vary according to the local
conditions and the hazard involved. Inspection departments having
jurisdiction should be consulted as to the application of these stand
ards and all details of installation, including the question of what
additional special hazard protection, if any, should be provided and
what other standards are applicable.
Definitions.
In this code the following words are used as defined below:
“ S h a ll55 is intended to indicate requirements.
“ Should ” is intended to indicate recommendations, or that which
is advised but not required.
“ Approved ” refers to approval by the authority having jurisdic
tion in the enforcement of regulations.
General.
8. The reduction of the oxygen content of air (normally 21 per
cent) necessary to prevent explosions and fires varies with the differ
ent materials being handled. Detailed information concerning the
oxygen reduction necessary is given under the section entitled
“ Determining the Amount of Inert Gas Required.”
9. Apparatus protected should be inclosed as tightly as possible
and arranged so that the supply of inert gas may mix with and dilute
the air entering the inclosure before any possible sources of ignition
are reached.
10. Inert gas should be injected into inclosures at the top or in
such a way that it will be distributed as uniformly as possible.
11. In tubes, spouts, conveyors, etc,, or where drafts are present
the gas should be injected into the inclosure so as to be carried along
with the draft or stock.
12. At spreaders, belt feeders, or other machines where hoods are
provided to carry away dust or fumes the gas should be introduced
at the point of hazard and distributed in such a way as to sufficiently
dilute the air entering the hood.
13. Before any inert-gas equipment is installed or remodeled com
plete working plans showing necessary details of the local conditions,
hazards, and of the proposed equipment shall be submitted for ap
proval to the inspection department having jurisdiction.
14. All apparatus and devices used shall be approved and standard
so far as such approvals and standards apply.

S A FE T Y CODE FOB U S E OF IN E R T GAS

Determining the amount of inert gas required.
15. Before the amount of inert gas required can be determined
it is necessary to know the volume of air entering the inclosure or
hood where the hazard exists and the reduction of the oxygen per
centage necessary to prevent ignition. In closed rooms or bins the
normal air leakage or rate of air change represents the volume to
be considered. This determination should be made by actual meas
urement if possible but may be computed if necessary.
16. Table I indicates the percentage to which the oxygen must be
reduced to prevent ignitions or explosions of the dusts and gases
listed when the required oxygen percentage is obtained by adding
to air pure carbon dioxide. Where gases other than pure carbon
dioxide are used lower oxygen percentages are required. The infor
mation at present available indicates that when nitrogen is used in
stead of carbon dioxide the oxygen percentage should be reduced
about 10 per cent below the figure given in the table. Both carbon
dioxide and nitrogen are present in different percentages in flue
gas, the medium most generally used in installations requiring ex
tremely large quantities of inert gas. When it is desired to provide
inert gas protection for a dust or vapor not listed or to use an inert
gas other than pure carbon dioxide, or where any unusual condition
exists the inspection department having jurisdiction should be con
sulted and if the information is not available arrangements should
be made for laboratory tests to determine the oxygen reduction
necessary under the existing conditions.
T a b le

I .—P erm issible P ercentage of Oxygen B ased on the A d d itio n of
Carbon D ioxide
Maximum permissible

Material
oxygen percentage
Pittsburgh coal dust_____________________________________ 16
Pyrethrum flower dust___________________________________ 15. 5
A cetone-------------------------------------------------------------------------- 15
Cotton lint or dust in suspension in air____________________ 15
Ethyl alcohol____________________________________________15
Gasoline vapor___________________________________________ 15
Kerosene vapor__________________________________________ 15
M ethan e________________________________________________ 14. 5
Cork dust_______________________________________________14.1
Wheat, corn, or oat elevator dust__________________________ 14
Ground oat hulls_________________________________________ 13. 7
E th er___________________________________________________ 13
Hard rubber dust________________________________________ 13
Wheat starch____________________________________________ 12
White dextrine___________________________________________ 12
E th ylen e________________________________________________ 10
Sulphur_________________________________________________ 8. 5
Carbon disulphide________________________________________ 8
Cotton in bulk—to prevent smoldering and reignition_______ 8
J u t e ____________________________________________________ 8
Carbon monoxide_________________________________________ 5.9
H ydrogen_______________________________________________ 5.9

17. I f a pure inert gas is to be used, i. e., a gas which contains no
oxygen or other combustible component, the amount required is cal
culated on the basis of the percentage of oxygen permitted by using
the form ula:
21 — 0 TT

S A FE T Y CODES FOR D U S T E X P L O SIO N S

in which x is the amount of inert gas required, O is the maximum per
centage of oxygen permitted and Y is the volume of fresh air con
taining 21 per cent oxygen within an inclosure and to be introduced
into a machine or inclosure.
For example, if 12 per cent is the maximum amount of oxygen per
mitted and the inclosure to be protected contains 1,000 cubic feet of
fresh air

£ =

750

Under such conditions it would be necessary to introduce 750 cubic
feet of pure inert gas into an inclosure to replace 750 cubic feet of
the 1,000 cubic feet of air or gas and air contained therein before it
would be safe to start the process creating the hazard. To maintain
this safe condition it would be necessary to add 750 cubic feet of
inert gas to each 1,000 cubic feet of fresh air admitted to the inclo
sure to replace leakage or as a part of the process.
18. When the inert gas to be used already contains a certain per
centage of oxygen as is the case when flue gas is the source of supply
the amount is calculated on the basis of the percentage of oxygen
permitted and the percentage of oxygen already present in the gas
by using the following form ula:

in which x is the amount of inert gas required, O is the maximum
percentage of oxygen permitted. O f is the percentage of oxygen in
the flue gas and V is the volume of fresh air containing 21 per cent
oxygen within an inclosure or to be introduced into a machine or
inclosure.
For example, if 12 per cent is the maximum amount of oxygen per
mitted and the flue gas contains 11 per cent of oxygen and the in
closure contains 1,000 cubic feet of fresh air

£ = 9000
Under such conditions it would be necessary to pass 9,000 cubic feet
of flue gas containing 11 per cent oxygen into and through an in
closure of 1,000 cubic feet capacity before it would be safe to start the
process creating the hazard. To maintain this safe condition it
would be necessary to mix 9,000 cubic feet of flue gas with each 1,000
cubic feet of fresh air admitted to the inclosure to replace leakage
or as a part of the process.
N ote.—In cases such as cited in the foregoing example where the proportion
of flue gas to fresh air is so large it is recommended that flue gas be used in
the full amount necessary to replace leakage or carry on the process without
making any attempt to combine or mix it with fresh air.

Sources of inert gas supply.
19. Inert gas for fire and explosion prevention shall be obtained
from a dependable source capable of supplying continuously the
amount required to dilute the oxygen within the inclosure protected

SA F E T Y CODE FOR U S E OF IN E R T GAB

to the predetermined point where ignitions will be impossible. Gas
may be obtained from storage tanks, gas producers, boiler settings,
special furnaces, internal combustion engines, or similar sources.
20. I f gas is obtained from storage tanks or gasometers provisions
shall be made to maintain the gas supply while recharging the tank
or tanks. A duplicate set of tanks may be necessary unless the
system is arranged so that a sufficient reserve supply can be main
tained to provide protection during the recharging period.
21. I f gas producers are used to furnish the inert gas they shall
have twice the gas producing capacity necessary to protect the hazard
unless they are used in connection with storage tanks or gasometers,
and can be operated to replenish the stored supply during periods
when no gas is needed for protection.
22. When inert gas is obtained from boiler settings or special
furnaces provision shall be made to maintain the supply at all times
while the hazard exists. Where the gas supply may fail and the
process protected is continuous a reserve supply in storage tanks
may be necessary. I f gas is obtained from the breeching of a battery
of boilers provision shall be made through the use of dampers or
valves to prevent dilution of the flue gas with fresh air drawn
through the grates or openings of any boilers which are idle or shut
down.
23. I f power is necessary to operate the equipment in which the
hazard exists, an internal combustion engine can often be used as a
source of power and the exhaust gases used to provide protection
against fire and explosion. The engine can also be used to operate a
compressor to compress the exhaust gases or force them through
pipes to the point where they are to be used.
24. When exhaust gases from an internal combustion engine are
used precaution shall be taken to keep the air-fuel ratio 12 to 1 or
higher, otherwise the exhaust gases themselves may contain sufficient
combustibles to form explosive mixtures with air.
Gas conditioning equipment.
25. When flue gas or any gas which may be injurious to the
product or plant equipment is used suitable cooling and conditioning
apparatus shall be installed. No conditioning equipment will be
necessary if clean, pure carbon dioxide or other commercially avail
able inert gas is obtained from an approved source.
26. Gas shall be cooled below the temperature at which it would
be a fire hazard to the product or equipment. Cooling of flue gas
may be accomplished by using it as the source of heat in preheaters,
economizers, or similar boiler-room equipment in which air or water
is heated, or by passing it through cooling towers consisting of long
runs of straight or spiral air or water cooled pipe.
27. Conditioning equipment may consist of a dust or soot separa
tor, a coke or wooden grid scrubber, a spray washer, one of the many
types of filters or air cleaners now on the market, a moisture trap or
a combination of these or similar equipment designed to remove the
objectionable impurities or render the gas suitable for use.
Note.—Special fans or filters can be used to remove a large percentage of
the dust, soot, and cinders generally present in flue gas.

84589°—32---------- 6

SA F E T Y CODES FOR D U S T E X P L O SIO N S

Spray washers can be used to remove very fine dust, soot, and certain other
impurities.
A good and low cost scrubber of the grid type may be constructed by group
ing inside a steel shell through which the gas passes a number of grids consist
ing of thin boards on edge and spaced a short distance apart. The boards of
one grid should cross the boards in the grid immediately below or above at a
slight angle to induce a spiral flow of gas and the entire interior of the scrubber
kept moist by a flow of water counter to the flow of gas.
Moisture traps may be provided to catch any excess moisture in the gas
leaving the cleaning equipment, where moisture would be injurious to the
product or material being protected or the gas distributing system.

Gas distributing system.
28. Equipment for distributing inert gas to the various machines,
inclosures, or points where an explosion and fire hazard exists will
consist of a fan, blower pump or compressor near the source of gas
supply with the necessary pipings and valves. Fans or blowers may
be unnecessary if sufficient suction is provided by the process creat

ing the hazard, but care should be taken in such installations to guard
against the dilution of the inert gas due to the entrance of fresh air
through leaky joints or fittings.
29. Fans, blowers or compressors shall be of ample capacity to
handle the required amount of gas and shall be installed in accord
ance with the National Fire Protection Association Regulations for
the Installation of Blower and Exhaust Systems.1
30. The distributing pipes where gas is to be used at more than
one point should be installed so that the cross sectional areas of the
various branch lines are proportional to the amount of gas they are
to carry.
31. Piping should be of ample size to deliver the required amount
of gas without unnecessary friction loss. High or low pressure sys
tems may be used.
1 Obtainable from the National Fire Protection Association, 60 Batterym arch Street,
Boston, Mass.

SA F E T Y CODE FOR U S E OF IN E R T GAS

32. Valves which can be sealed after the proper setting is de
termined shall be installed to control and regulate the flow of gas in
all branch lines.
33. Drains shall be provided in the pipe line where necessary for
the removal of condensed moisture.
34. Pipe connections to the inclosures to be supplied with inert gas
shall be arranged to distribute the gas uniformly, and when highpressure systems are used provision shall be made to reduce the pres
sure before it enters any inclosure so that the contents would not be
disturbed by the entering stream of high-pressure gas.
35. Where spray nozzles, discharge cones or horns are found neces
sary to distribute the gas uniformly, they should be designated to par
ticularly apply to the local conditions and shall be made of heat re
sisting material.
36. Noncorrosive pipe and fittings should be used where no condi
tioning equipment is used to remove from the gas sulphur or other
impurities which would attack ordinary iron piping.
Analyzing, indicating, and recording equipment.
37. Suitable analyzing, indicating or recording equipment shall be
provided to indicate the percentage of oxygen present within the
inclosure or at the point where the hazard exists, except that where
suitable equipment is not available the undiluted inert gas or flue gas
with the required C 0 2 content shall be used for protection.
38. The instruments may be arranged to draw their samples from
as many points within the inclosure as desired, but the point at
which the highest oxygen reading is obtained should be the one used
in controlling the hazard.
39. Where a process or equipment in which inert gas is used for
fire and explosion prevention is not under the direct control of an
operator who can observe regularly the instruments indicating the
amount of oxygen present, automatic apparatus shall be installed
and arranged to signal a dangerous increase in the oxygen per
centage.
40. When a dangerous increase in the oxygen percentage occurs
the equipment creating the hazard shall be shut down unless the
operator is able to promptly reduce the oxygen to the required
percentage.
Test for approval.
41. An operating test of the complete installation, including an
analytical check, shall be made before final approval. Inspection
departments having jurisdiction shall be consulted before such tests
are made. No changes shall be made in the rate of production in
machines using inert gas protecting systems which would affect the
quantities of air passing through without altering the inert gas
system to provide for the change and having another approval test
made.

Subject Index
Access:
B y means of balconies—
Page
Coal pneumatic cleaning plants________
62
Pulverizing systems for sugar and cocoa. 28
Wood-flour manufacturing establish
m ents_______•________ ____ _________
40
B y means of vestibules—
47
Pulverized-fuel systems_______________
Pulverizing systems for sugar and cocoa __
29
Air:
Use of, for lifting stock, flour and feed mills _
13
Use of, prohibited for conveying of material—
Pulverizing systems for sugar and cocoa. _
30
Wood-flour manufacturing establish
m ents_____________________________
41
Air aspiration:
Bins and tanks—grain elevators, terminal __
18
20
Garners and hoppers, grain driers------------Grain-handling equipment_____ _________
22
Air heaters, mill driers, pulverized-fuel sys
tems__________________________________
52
Air vents, where provided, coal pneumatic
cleaning plants_________________________
64
Apparatus, installation of:
Pulverizing systems for sugar and cocoa___ 32,33
Spice-grinding plants___________________ 36,37
Wood-flour manufacturing establishments. 42,43
Automatic heat control, coal driers. ( See
Coal driers.)
Automatic regulation of temperature. ( See
Temperature.)
Automatic
sprinklers. (See
Sprinklers,
automatic.)

Back

stops for elevator legs, terminal grain
elevators____________ __________________ . 19
Bags, starch, how cleaned____________ ____
8
Balconies, access by means of. (See Access.)
Barreling or bagging stands, starch factories. _
7
Basements:
11
Ventilation, flour and feed m ills__________
Ventilation, terminal grain elevators______
17
(See also Construction.)
Beams:
Finish, starch factories___ T...........................
6
(See also Construction.)
Bearings:
Blowers, pulverized-fuel systems, casings
50
for______________________________ ____
Fan, pulverized systems for sugar and cocoa
33
Fan, wood-flour manufacturing establish
ments_______________________________
43
Fans and blowers, flour and feed m ills------12
Fans and blowers, starch factories________
9
T ype recommended—
Flour and feed mills________ __________
13
Grain elevators, terminal______________
19
Pulverizing systems for sugar and cocoa. _
32
Starch factories.......................... ....................
9
Wood-flour manufacturing establish
m ents.................................. .......................... 42

B earings—C ontinued.
Warning against overheating—
Page
13
Flour and feed m ills___________________
Pulverized-fuel systems, class A ________
55
Pulverizing systems for sugar and cocoa. _
32
S tarch factories--------------------- ------------9
Wood-flour manufacturing establish
ments........ .......................................... .........
42
Belt-conveyor galleries, construction:
Flour and feed m ills.... ....................................
11
Grain elevators, terminal. ..............................
16
Belt conveyors. ( See Conveyors.)
Belts or chains:
Openings in walls, how equipped, terminal
grain elevators._______________________
16
Tiansmission medium, how inclosed—
Pulverizing systems for sugar and cocoa..
30
Wood-flour manufacturing establish
m e n ts.._......................................................
41
Bins:
Connections between, prohibited—
Flour and feed m ills_________________
11
Terminal grain elevators.____ _________
18
Leaks, caution to prevent, pulverized-fuel
systems______________________________
56
Load-indicating device, pulverized-fuel
systems.................................... ........................
54
Location—
Furnace, pulverized-fuel systems_______
54
S torage, coal pneumatic cleaning plants. .
65
Storage, pulverized-fuel systems________
54
Steam or inert gas for fire protection, coal
pneumatic cleaning plants_____________
66
Ventilation—
Grain bins, flour and feed m ills________
12
18
Grain elevators, terminal______________
Storage bins, coal pneumatic cleaning
plan ts..___ ________________________
64
Storage bins, pulverized-fuel system s___
50
( See also Air aspiration; Construction;
Fires; Inspection; Lights; Vent openings.)
Bleacher, sulphur, construction, grain eleva
tors......................................................... ..............
24
Blowers:
Construction—
Flour and feed m ills.....................................
12
Pulverizing systems for sugar and cocoa..
33
Starch factories.......................................... .
9
Wood-flour manufacturing establish
m e n t s .........................................................
43
Installation—
Pulverized-fuel systems_____ _________
50
Pulverizing systems for sugar and cocoa. _
33
Wood-flour manufacturing establish
43
m en ts........... ..............................................
( See also Bearings; Fans.)
Buildings:
Arrangement, starch factories______ _____
5
Ventilation—
Coal pneumatic cleaning plants________
63
Grain elevators, terminal------ --------------17

SUBJECT IN DEX

Buildings—C ontinued.
Ventilation—Continued.
Page
Pulverized-fuel systems_______________
48
(See also Communications; Construction;
Location.)
C arbon dioxide as inert gas for fire protec
tion, qualities of_______ ________________
Ceilings:
Finish, starch factories__________________
( See also Construction.)
Chemical engineering division, United States
Bureau of Chemistry and Soils__________
Choke valve on delivery spout:
Pulverizing systems for sugar and cocoa__
Spice-grinding plants.......................................
Wood-flour manufacturing establishments.
Chutes, type of construction:
Pulverizing systems for sugar and cocoa__
Wood-flour manufacturing establishments,
Cleaners, or grain-processing machinery, con
struction, terminal grain elevators----------Cleaning department, flour and feed m ills.. .
Cleaning systems. ( See Vacuum cleaning
systems.)
Cleaning, when permitted, pulverizing sys
tems for sugar and cocoa...... ..........................
Cloth type dust collectors. ( See D ust col
lectors, types.)
Clothing, metal lockers for, terminal grain
elevators_______________________________
Coal:
Dried—
Storage of. coal pneumatic cleaning plants.
Storage of, pulverized-fuel systems_____
Storage of—
Inspection, pulverized-fuel systems_____
Temperature for pulverized coal, pulver
ized-fuel systems, class B ____________
Time schedule, pulverized-fuel systems. _
Coal driers:
Coal pneumatic cleaning plants—
Construction, direct and semi-indirect
types______________________________
Dried-coal elevators, construction______
Fire-protection provisions_____________
Location, direct and semi-indirect driers.
Temperature, control of, in storage_____
Types defined...... ................ .........................
Pulverized-fuel systems—
Air heaters for mill driers_________ ____
Construction, direct and semi-indirect
driers__________ ____ ____ ____ ______
Damper regulations......................................
Dried-coal elevators, construction______
Emptying, indirect driers, when re
quired____________ ____ ___________56
Fire-protection provisions, class A sys
tems_______________________________
Fires in indirect driers, measures for ex
tinguishing_________________________
Flue-gas air heaters, operation practices..
Gas ignition after fire, prevention of____
Heat control, how accomplished, mill
driers______________________________
Location_____________________________
Overheating of coal, prevention of______
Revolving, when stopped............................

69
6

3
32
37
43
30
41
19
11

65
52
58
52
57

64
65
66
65
65
64
52
51
56
52

55
56
52
56
51
51
51
56

Coal driers—Continued.
Pulverized-fuel systems—Continued.
Page
Starting fires in furnaces, materials pro
hibited--------- ----------------- ---------------55
Steam air heaters, fire-prevention prac
tices----------------------------------------------52
Steam or inert gas for fire protection, class
A system s_________________ _____ _
55
Temperature, control of_______________ 51,52
Types defined________________________ 50, 51
Ventilation after fire__________________
56
Coal pneumatic cleaning plants, code for___ 61-67
(See also under specific subjects.)
Coal-conveying lines, location, pulverizedfuel system s.............................. ..........................
54
Cocoa. (See Pulverizing systems for sugar
and cocoa.)
Coil rooms, grain driers___________________
21
Combustible materials, storage. (See Storage
prohibited.)
Committee on dust explosion hazards, per
sonnel...... ............................................ ................
2
C ommunications:
Grain elevators, terminal, construction re
quirem ents..___________ _____________ 16,17
Pulverizing systems for sugar and cocoa,
general requirements____ _____________ 28-30
Spice-grinding plants, type of doors recom
mended______________________________
36
Starch factories, construction and arrange
m ent________________________________
6
Wood-flour manufacturing establishments,
construction and arrangement_________ 40-42
(See also Access.)
Compressed-air system:
Flour and feed m ills. ---------- ------------------12
Starch factories_________________________
8
Construction:
11
Basements, flour and feed mills__________
Basements, terminal grain elevators______
17
Beams—
Pulverizing systems for sugar and cocoa _
28
Spice-grinding plants__________________
36
Wood-flour manufacturing establish
ments______________ _______________
40
Bins—
Flour and feed mills___ ____ ___________
11
Furnace, pulverized-fuel system s_______
54
Grain elevators, terminal______________
17
Spice-grinding plants_________________
36
Storage, coal pneumatic cleaning plants .
65
Storage, pulverized-fuel system s_______
54
Buildings—
Coal pneumatic cleaning plants________ 62,63
Flour and feed mills__________________
11
Grain elevators, terminal-______ _______ 15,16
Pulverized-fuel systems_____________ 45,46-48
Pulverizing systems for sugar and cocoa _ 27, 28
Spice-grinding plants__________ _______ 35,36
Starch factories_______________________ 5,6
Wood-flour manufacturing establish
m ents_____________________________
40
Ceilings, pulverizing department, woodflour manufacturing establishments____
40
Ceilings, pulverizing systems for sugar and
cocoa__________________ ____ _________27,28
Communications, terminal grain elevators. 16,17

SUBJECT INDEX
C onstruction—C ontinued.
Floors—
Page
Coil room, grain driers________________
21
Grain driers, around drier and cooler___
21
Pulverized-fuel systems (class A); under
screw conveyors____________________
55
Pulverizing systems for sugar and cocoa.. 27,28
Screen room, coal pneumatic cleaning
62
plants_____________________________
Starch factories, surrounding barreling or
bagging stands_____________________
7
Starch factories, surrounding presses____
8
W ood-flour manufacturing establish
m ents_____________________________
40
Galleries, terminal grain elevators_______ 16,17
Girders—
Pulverizing systems for sugar and cocoa. _ 27,28
Spice-grinding plants_______ ____ _____
36
Wood-flour manufacturing establish-m e n t s ...____ ______________________
40
Kilns, starch factories___________________
6, 7
Ledges—
Flour and feed mills____________ ______
11
Pulverizing systems for sugar and cocoa-_ 27, 28
Spice-grinding plants________ _______ 36
Wood-flour manufacturing establish
m en ts._______________ _____ _______
40
N oncombustible—
Bins, coal pneumatic cleaning plants___
65
Bins, pulverized-fuel systems__________
54
Buildings, coal pneumatic cleaning plants
62
Buildings, fuel-pulverizing plants_____ 45,46
Buildings, terminal grain elevators_____
15
Dried-coal elevators, coal pneumatic
cleaning plants_____________________
65
Dried-coal elevators, pulverized-fuel sys
tems_______________________________
52
Friction clutches, terminal grain eleva
tors_________ ____ __________________
19
Sulphur bleachers, terminal grain eleva
tors................................................................
24
N onfire-resisti ve—
Buildings; pulverizing systems for sugar
and cocoa__________________________ 27, 28
Buildings; wood-flour manufacturing es
tablishments_______________________
40
Partitions—
Grain elevators, terminal______________
16
Kiln-tray repairing department, starch
factories___________________________
8
Pulverizing systems for sugar and cocoa. _ 27, 28
Wood-flour manufacturing establish
40
m ents_____________________________
Roofs—
Coal pneumatic cleaning plants________
63
Grain elevators, terminal______________
16
Pulverized-fuel systems_______________
47
Shafts, terminal grain elevators__________
17
Sulphur bleachers, terminal grain elevators.
24
Tunnels—
11
Flour and feed m ills.....................................
Grain elevators, terminal................. ...........16,17
Walls—
Coal pneumatic cleaning plants________
63
Flour and feed m ills_________ _________
11
Grain elevators, terminal______________
16
Pulverized-fuel systems................................46,47

Construction—Continued.
Walls—Continued.
Page
Pulverizing systems for sugar and cocoa. 27, 28
Spice-grinding plants.................. ................
36
Wood-flour manufacturing establish
m ents_____________________________
40
( See also Belt-conveyor galleries; Blowers;
Chutes; Conveyors; D ust collectors; Ele
vator inclosures; Fans; Grain driers;
Hoppers; Pipes and piping; Spouts; Vent
flues.)
Conveying of material. ( See Air.)
Conveyors:
Belt, grain driers.......... ............................... .
20
Coal pneumatic cleaning systems.................
61
Construction—
Pulverizing systems for sugar and cocoa.
30
Wood-flour manufacturing establish
m ents________________ ____ _________
41
Fires, procedure governing operations,
pulverized-fuel systems________________
58
19
Space under, terminal grain elevators_____
(See also Screw conveyors; Spiral convey
ors.)
Cooking, lump starch_______ ____ _________
7,8
Cyclone separators, pulverized-fuel systems,
49
minimum requirements_________________
D efin itio n s of terms used:
Coal pneumatic cleaning plants__________
61
Flour and feed m ills____________________
11
Grain elevators, terminal____________ _ ___
15
Inert gas, use of________________________
69
Pulverized-fuel systems, installation of___
45
Pulverizing systems for sugar and cocoa__27
Spice-grinding plants___________________
35
Starch factories_________________________
5
Wood-flour manufacturing establishments.
39
Delivery to or from mills:
Flour and feed m ills____________________
13
Pulverized-fuel unit systems_____________
55
Pulverizing systems for sugar and cocoa -. _ 32, 33
Spice-grinding plants___________________ 36,37
Starch factories_________________________
7
Wood-flour manufacturing establishments. 42,43
Delivery hoppers. (See Hoppers.)
Dextrine department, starch factories, con
5
struction______________________________
Door openings, starch factories, protection of.
6
Draft fans, lump-starch cooking and pressing.
7,8
Dried coal. (See Coal.)
Dried starch. (See Starch.)
Dried-coal elevators. (See Elevators.)
Driers, installation and construction:
Coal pneumatic cleaning plants__________64, 65
Grain elevators, terminal________________20-22
Pulverized-fuel systems____ ____________ 50-52
(See also Coal driers; Grain driers.)
Droplights. (See Electric lighting.)
Dry starch grinding and grading, construction
of equipment___________________________
7
Drying tunnels, starch factories, location of
outlets_________________________________
7
Dumps, starch, how constructed............... .......
6, 7
Dust:
Accumulations prohibited—
C oal pneumatic cleaning plan ts___ ____
63
Flour and feed mills......................................
12

SUBJECT INDEX

D ust—Continued.
Page
A ccumulations prohibited—C ontinued.
Pulverized-fuel systems.................... ...........
48
Pulverizing systems for sugar and cocoa. 33, 34
Spice-grinding plants_________________
37
Starch factories.......................... ....................
9
Wood-flour manufacturing establish
m e n t s .............................................. ...........
44
Collection—
Coal pneumatic cleaning plants________ 63,64
Flour and feed m ills__________________
12
Grain elevators, terminal______________21, 22
Pulverized-fuel systems_______________
48
Starch factories—_____________________
6,8
Explosions, hazards specified, starch fac
5
tories_________ ______________________
Explosions, importance of_____ _________
3
Grain elevators, terminal______________
15
Explosions, occurrence of spice-grinding
plants________ ______ ________________
35
Hoppers, grain driers, when required_____
21
Removal of, how accomplished—
Compressed air prohibited:
64
Coal pneumatic cleaning plants______
Grain elevators, terminal____________
23
Pulverized-fuel system ______________
48
Grain-handling equipment____________
22
Static dust—
Flour and feed mills________________
12
Grain elevators, terminal____________
23
8
Starch factories_____________________
Suspended dust—
Coal pneumatic cleaning plants______
63
Flour and feed mills________________
12
48
Pulverized-fuel systems_____________
Starch factories....................................... .
8
(See also Ignition.)
D ust collectors:
Construction—
Coal pneumatic cleaning plants________
64
Pulverized-fuel systems_______________
49
Pulverizing systems for sugar and cocoa_ _
33
Wood-flour manufacturing establish
m ents............................................................
43
Location—
Coal pneumatic cleaning plants________
64
49
Pulverized-fuel systems.................... ...........
Pulverizing systems for sugar and cocoa.
33
Spice-grinding plants................. ..................
37
Starch factories________ - ______ _______ 6,8,9
Wood-fiour manufacturing establish
m ents............................................. ..............
43
Types—
Coal pneumatic cleaning systems______
62
Flour and feed mills.....................................
12
Starch factories.............................................. 6, 7,8
Dust-making adjuncts, coal pneumatic clean
ing systems........................... ............................
62
Dust-making mechanisms, coal pneumatic
cleaning plants............................................... .
61
D ust explosion codes, development of______
1
D ust explosion hazards committee, personnel.
2
Electric heaters. ( See Heaters.)
Electric light and power control:
Coal pneumatic cleaning plants.................... 65,66
Grain elevators, terminal................................
23
Pulverized-fuel systems...................................
49

Electric light and power control—Contd.
Page
Pulverizing systems for sugar and cocoa___
31
Spice-grinding plants___________________
36
Wood-flour
manufacturing
establish
42
m en ts.. _............... ..........................................
( See also Electric switches.)
Electric lighting:
Drop lights, pulverized-fuel systems______
56
Drop lights, pulverizing systems for sugar
and cocoa____________________________
31
Fixed lights, coal pneumatic cleaning plants.
66
Grain elevators, terminal________________
24
Incandescent lights—
Pulverizing systems for sugar and cocoa _ _
31
36
Spice-grinding plants_________________
Wood-flour manufacturing establish
ments_____________________________
42
Lamps, protection—
Coal pneumatic cleaning plants________
66
Pulverizing systems for sugar and cocoa - _
31
Portable lights—
Coal pneumatic cleaning plants________
66
Pulverized-fuel systems_______________
56
Pulverizing sys tems for sugar and cocoa _ _
31
Electric motors. ( See Motors.)
Electric power. (See Electric light and power
control; Power.)
Electric switches:
Location, terminal grain elevators...... .........
23
Location, pulverizing systems for sugar and
cocoa.................... ................ ...........................
31
Type required, spice-grinding plants_____
36
Type required, wood-flour manufacturing
establishments_______________________
42
(See also Electric light and power control.)
Electric wiring:
Coal pneumatic cleaning plants_________
66
Grain elevators, terminal________________
23
Pulverized-fuel systems_________________
49
Pulverizing systems for sugar and cocoa. __ 31, 32
36
Spice-grinding plants___________________
Wood-flour manufacturing establishments _
42
Electrical equipment:
Coal pneumatic cleaning plants_________ 65,66
Flour and feed mills, installation_________
12
Grain elevators, terminal________________23, 24
Pulverized-fuel system s.________________
49
Spice-grinding plants___________________
36
Starch factories_________________________
8,9
Wood-floor manufacturing establishments.
42
Electricity for light, etc. (See Electric light
and power control.)
Electricity, static, removal of:
Flour and feed m ills.____________________
12
Grain elevators, terminal________________
25
Pulverized-fuel systems_____ ___________
49
Pulverizing systems for sugar and cocoa.. .
32
Spice-grinding plants___________________
36
Starch factories_________________________
9
Wood-flour manufacturing establishments.
42
Electromagnetic separators. (See Separa
tors.)
Elevator boots, construction, terminal grain
elevators_______________________________
18
Elevator inclosures, construction:
Pulverized-fuel system s_________________
56
Pulverizing systems for sugar and cocoa. _.
30
Wood-flour manufacturing establishments.
41

SUBJECT INDEX
Elevator legs:
Page
Back stops, terminal grain elevators.......... .
19
Equipment for, starch factories__________
8,9
Flour and feed mills, how equipped______
12
Grain elevators, terminal________________
18
Individual motors,terminal grain elevators.
18
Elevator shafts, construction, terminal grain
elevators____ __________________________
17
Elevators:
Dried-coal, coal pneumatic cleaning plants.
65
Dried-coal, pulverized-fuel system s______
52
Pulverized-fuel system s_________________
56
Starch factories, location________________
6
( See also Grain elevators, terminal.)
Equipment:
Construction, etc., terminal grain elevators- 18-20
Defined—
Pulverizing systems for sugar and cocoa.
27
Spice-grinding plants_________________
35
Wood-flour manufacturing establish
ments_____________________________
39
Dust-tight construction—
Coal pneumatic cleaning plants________
65
Flour and feed m ills__________________
12
Grain handling_______________________
22
Pulverized-fuel system s_______________
52
Pulverizings systems for sugar and cocoa.
33
Starch factories______________________
8
Wood-flour manufacturing establish
m ents_____________________________
41
• Individual power connections—terminal
grain elevators_________________ ____ 19
Run idle, prohibited, terminal grain ele
vators_______________________________
19
( See also Electrical equipment; Grainhandling equipment; Inert gas.)
Exhaust fans. ( See Blowers; Fans.)
Exhaust, mechanical. ( See Mechanical ex
haust.)
Explosion, prevention, use of inert gas for.
( See Inert gas.)
Explosion protection, coal pneumatic clean
ing plants_____________________________ 66,67
Explosion relief panels, hoppers, starch fac
tories, construction_____________________
7
Explosions, dust. ( See Dust.)

Factories, starch.

( See Starch factories.)
Fan bearings. ( See Bearings.)
Fans:
Construction, flour and feed mills............ 12,13
9
Construction, starch factories_____ ______
Draft, lump-starch cooking and pressing...
7,8
Grain driers___________________________
21
Installation and location—
Pulverizing systems for sugar and cocoa..
33
Wood-flour manufacturing establish
m ents_____________________________
43
Operating bin and mill vents, pulverizedfuel system s__________________________
50
Starch dumps__________________________
6
Suction, vacuum-sweeping systems—
Coal pneumatic cleaning plants................
64
Wood-flour manufacturing establish
m ents____________ ____ ____________
44
(See also Bearings; Blowers; Inert gas.)
Feed departments, starch factories, arrange
m ents__________ ____ ________ __________
5

Page
Feed mills. ( See Flour and feed mills.)
Fire doois, types required:
Grain elevators, terminal________________ 16,17
47
Pulverized-fuel systems_________________
Pulverizing systems for sugar and cocoa___ 28, 29
Wood-flour manufacturing establishments. 40, 41
Fire drills, coal pneumatic cleaning plants___
67
Fire extinguishers, type required:
Coal pneumatic cleaning plants__________
66
Grain elevators, terminal________________
26
Pulverized-fuel systems, class A _________
54
Fire-heated, grain driers, location of furnace.
21
Fire protection:
Air heaters for mill driers, pulverized-fuel
system s______________________________
52
Coal pneumatic cleaning plants__________66,67
Grain elevators, terminal________________25, 26
Pulverized-fuel systems, class A _________ 54, 55
Pulverizing systems for sugar and cocoa.. .
34
Spice-grinding plants___________________
37
Wood-flour manufacturing establishments.
44
(See also Inert gas.)
Fire-resistive construction of buildings. (See
Construction.)
Fires, procedure governing operations:
Bins or tanks, terminal grain elevators___
26
Coal driers, pulverized-fuel system s______
56
Conveyors, pipes, ducts, or collectors, pul58
verized-fuel system s__________________
Pulverized-fuel bins____________________ 58, 59
First-aid fire appliances:
Grain elevators, terminal________________25, 26
Pulverizing systems for sugar and cocoa. . .
34
Spice-grinding plants___________________
37
Wood-flour manufacturing establishments.
44
Floor sweeps:
Grain driers, where located. _____________
21
Grain elevators, terminal, where located...
23
Floors:
Finish, starch factories______________ 6
(See also Construction; Openings.)
Flour and feed mills, code for______________11-13
(See also under specific subjects.)
Flue gas. (See Inert gas.)
Friction clutches, terminal grain elevators.. .
19
Fuel:
Oil or gas for ignition, installation________
54
Supply lines—
Clearing of, class B and unit type, pul56
verized-fuel systems_____ ____ _______
Clogged, class B, pulverized-fuel systems,
instructions________________________
56
(See also Coal; Pulverized-fuel systems.)
Furnace bins. (See Bins.;
Furnaces:
Grain driers, lo ca tio n ....................................
21
Pulverized-fuel systems, lighting, proced
ure__________________________________ 56, 57
Pulverized-fuel systems, ignition practice,
suggestions__________________ _____ _
57
Sulphur bleachers, location.............................
24
(See also Grain driers.)

Galleries, construction.

(See Construction.)
Garners:
Grain driers, arrangement, e t c ...------------Grain elevators, terminal, how equipped- _

20
19

s u b je c t in d e x

Page
Gas. ( See Coal driers; Fuel; Inert gas.)
Girders, construction. ( See Construction.)
Glass or equivalent area:
Coal pneumatic cleaning plants__________
63
Pulverized-fuel systems_________________ 46, 47
Pulverizing systems for sugar and cocoa.._
28
Requirements, typical applications____ 29, 30, 31
Spice-grinding plants___________________
36
Starch factories_________________________
6
Wood-Hour manufacturing establishments.
40
( See also Wired glass.)
Gluten and feed departments, starch fac
5
tories, arrangements____________________
Grading, dry starch____________ ______ ___
7
Grain:
Spouting of, into bins or tanks___________
20
Storage departments for, starch factories—
5
Throw of, in open, prohibited___________
19
(See also Bins; Grain driers; Grain eleva
tors, terminal; Grain-handling equip
ment.)
Grain chutes, use not recommended, grain
elevators_______________________________
19
Giain driers:
Air aspiration, required for garner, hopper,
or bin_______________________________
20
20
Belt conveyors_________________________
Coil rooms, construction of______________
21
20
Construction o f . _______________________
Fans, requirements for__________________
21
Floor sweeps___________________________
21
Floors around driers, construction of_____
21
21
Furnace, location of____________________
Garners and hoppers___________________
20
Location in separate division....................... .
20
Louvers, how protected_________________
20
Refuse, removal of from grain____________
20
20
Separation of units_____________________
21
Steam coils, how designed and installed__
Temperature regulation, automatic equip
ment for_____________________________
21
Vacuum-sweeping
apparatus
recom
mended_____________________________
21
( See also Sparks.)
Grain elevators, terminal, code for_________ 15-26
( See also under specific subjects.)
Grain-handling equipment:
Belt discharges and trippers, provision for
air aspiration_________________________
22
Belt loaders, provision for air aspiration__
22
Car unloading_________________________
22
Dust-collecting system__________________
22
Heads, boots, garners, and scales, venting
of___________________________________
22
Shipping galleries______________________
22
19
Grain-processing machinery, construction___
Grain-storage department, starch factories,
5
arrangement___________________________
Grid scrubbers, inert gas-conditioning equip
ment, how constructed_________________
74
Grinding and grading, dry starch__________
7
Grinding department, spice-grinding plants,
construction and arrangement___________ 35, 36
Grounding of machinery, pulverized-fuel
system s.................................................................
49

Page
H eat control, how accomplished, coal driers,
51
pulverized-fuel systems_________________
Heaters:
Electric—
Flour and feed mills, where perm itted.__
12
Terminal grain elevators, where per
mitted_____________________________
24
Open-flame, flour and feed mills, pro
hibited______________________________
12
( See also Coal driers.)
Heating:
Open-flame, prohibited, coal pneumatic
cleaning plants_______________________
66
Steam, source of, terminal grain elevators.
24
Hoppers:
Construction, grain driers_______________
20
Construction, starch factories____________
7
Delivery, pulverizing systems for sugar and
32
cocoa________________________________
Delivery, wood-flour manufacturing estab
lishments____________________________
43
Dust, grain driers, when required________
21
Hose streams, use of in fire, terminal grain
elevators_______________________________
26
Housekeeping:
Coal pneumatic cleaning plants__________ 63, 64
Flour and feed mills____________________
12
Grain elevators, terminal________________
15
Pulverized-fuel systems_________________
48
Pulverizing systems for sugar and cocoa.. _ 33, 34
Spice-grinding plants_________ __________
37
Starch factories_________________________
9
Wood-flour manufacturing establishments.
44
I g n itio n :
Fuel, kind to be used, pulverized-fuel
systems___ ____________ _____________
54
Practice, pulverized-fuel furnaces________
57
Prevention of—
Cleaning prohibited, when, pulverizing
systems for sugar and cocoa__________
34
Coal driers, pulverized-fuel systems____
56
Coals, other than anthracite or coke, pul
52
verized-fuel system s_________________
Flour and feed mills__________________ 12,13
Pulverizing systems for sugar and cocoa.
32
Spice-grinding plants_________________ 36, 37
Starch factories_______________________
8,9
Wood-flour manufacturing establish
ments______________________________
42
( See also Fuel.)
Incandescent lights. ( See Electric lighting.)
Inert gas for fire and explosion prevention:
Amount required, how determined______ 71,72
Analyzing, indicating, and recording
equipment_________________________ 75
Apparatus and devices, approval of before
installation___________________________
70
Apparatus protected, how inclosed_______
70
Carbon dioxide, qualities________________
69
Conditioning equipment, when and how
installed_______________ ____ _________
73
Cooling of flue gas______________________
73
Distributing system, equipment for....... .
74, 75
Drains, pipe line, distributing system ____
75

SUBJECT INDEX
Inert gas for fire and explosion prevention— Page
Continued.
Driers and bins, coal pneumatic cleaning
plants_______________________________
66
Driers, raw-coal, pulverized-fuel systems,
class A ______________________________
55
Dust, soot, and cinders in flue gas, removal
of.___________________________________ 73,74
Equipment, working plans, approval re
quired_______________________________
70
69
Examples of where needed______________
Exceptions_____________________________
69
Exhaust gases, air-fuel ratio required_____
73
Fans, blowers, or compressors, distributing
system, installation of_________________
74
Fans or filters, conditioning equipment___
73
Flow of gas, distributing system, control of,
75
Flue gas, determining amount required___
72
Flue gas, etc., precautions as to use______ 69, 70
Formula for calculating amount—
Flue gas required_____________________
72
Pure inert gas required________________ 71, 72
Gas producers, capacity_________________
73
Grid scrubbers, conditioning equipment,
how constructed______________________
74
Injection into inclosures_________________
70
Injurious gases, where found_____________
70
Internal-combustion engine as source of
power_______________________________
73
Introduction at spreaders, belt feeders, or
70
other machines with hoods____________
Moisture traps, conditioning equipment—.
74
Nitrogen, qualities_____________________
69
Noncorrosive pipe and fittings, distributing
75
system ______________________________
N ot recommended, when___________ ____
69
Oxygen—
Percentage, increase in, regulation______
75
Permissible percentage based on addition
of carbon dioxide___________________
71
Reduction of, for use of nitrogen----------71
Piping, distributing system________ _____ 74, 75
Production rate in machines using inert
75
gas-protecting systems, changes in--------Pulverized-fuel bins, extinguishing fires. __
59
Pulverized-fuel systems—
Extinguishing fires in conveyors, pipes,
etc________________________________
58
56
Indirect driers________________________
Rules, general__________________________
70
Sources of gas supply___________________ 72, 73
Spray nozzles, discharge cones or horns,
distributing system ___________________
75
Spray washers, conditioning equipm ent-.74
Steam combined with gas, when permitted.
70
Supply, how maintained________________
73
Test for approval of gas equipment installa
tion__________ ______________________
75
Where necessary or desirable____________
69
Wood-flour manufacturing establishments.
44
Insect control, terminal grain elevators------- 24,25
Inspection:
Bins, pulverized-fuel systems, after shut
down________________________________
56
Coal storage, pulverized-fuel systems..........
58
Pipe lines, pulverized-fuel systems...............
56
(See also Lighting.)

Inspection openings:
Page
Furnace bins, pulverized-fuel system s____
56
( See also Screens.)
Installation requirements:
Coal pneumatic cleaning machinery and
apparatus____________________________ 62-65
Pulverized-fuel systems_________________
45
(See also Apparatus; Blowers; Pulverizing
apparatus.)
Instruction cards for safe operation, pulver
ized-fuel systems _ _________ _____________ 55-57
Interior surfaces, finish:
Coal pneumatic cleaning plants__________
Grain elevators, terminal________________
Pulverized-fuel systems_________________
Starch factories_________________________
Interior walls, construction. ( See Construc
tion, Walls.)
Jig or table rooms, coal pneumatic cleaning
plants, arrangement_____________ ____ _
K iln s, starch factories, construction of_____
Kiln-tray repairing department, starch fac
tories_________ ____ ____________________

63
16
48
6

62
6
8

L am ps, electric. (See Electric lighting.)
Leaks, pipe lines, pulverized-fuel systems,
caution to prevent______________________
56
Ledges, construction. ( See Construction.)
Light and power control. ( See Electric
light and power control.)
Lighting pulverized-fuel furnaces, practice. _ 56,57
Lightning, protection against, terminal grain
elevators______________ ________________
25
Lights, type required:
Examination of bins, terminal grain ele
vators _______________________________
24
Inspection and repairs—
66
Coal pneumatic cleaning plants-----------Pulverized-fuel systems_______________
56
(See also Electric lighting; Open-fiame
heating or lighting.)
Load-indicating device, bins, pulverized-fuel
54
systems_______________________________
Location:
Buildings—
Grain elevators, terminal______________
16
Pulverizing systems for sugar and cocoa..
27
Starch factories_______________________
5
Wood-flour manufacturing establish
ments___ _____ ____________________
39
Cleaning department, flour and feed m ills. _
11
Coal-conveying lines, pulverized-fuel sys
tems_________________________________
54
Grinding
department,
spice-grinding
plants_______________________________
35
Kiln-tray repairing department, starch
factories ___________________________
8
Pulverizing processes—
Pulverized-fuel systems_____ ____ _____ 45,46
Pulverizing systems for sugar and cocoa. _
27
Wood-flour manufacturing establish
m ents________ _____ _______________
39
Pulverizing plant, pulverized-fuel sys
tems__________________ ______ ______
45
Track shed, terminal grain elevators___
16

SUBJECT INDEX

Location—Continued.
Page
( See also Bins; Blowers; Coal driers; D ust
collectors; Fans; Grain driers; Motors;
Stairways; Sulphur bleachers.)
Locker rooms, starch factories, where pro
6
hibited________________________________
Lockers for clothing, terminal grain elevators.
25
Locomotives, terminal grain elevators, entry
24
forbidden______________________________
20
Louvers, grain driers, screen protection_____
Lump-starch cooking, pressing, grading, and
packing__ _______ _____ ________________
7,8

Machines:
Producing or distributing dust, coal pneu
matic cleaning plants_________________
61
Space under, terminal grain elevators-----19
Magnetic separators. ( See Separators.)
Manual heat control, coal driers. ( See Coal
driers.)
Matches, carrying prohibited:
Flour and feed m ills____________________
12
Spice-grinding plants___________________
37
Starch factories_______ _____ ___________
8
Mechanical exhaust:
Equipment; flour and feed mills_________ 12,13
Equipment; starch factories_____________
8
(See also Blowers; Fans.)
Mechanical precautions, starch factories-----9
M ill bins. (See Bins.)
Mill driers. (See Coal driers.)
Mills:
Construction of grinding chambers, dry
starch grinding_______________________
7
Pulverized-fuel systems, how safeguarded._
48
Pulverizing systems, cocoa and sugar, pre
ventive measures_____________________
32
(See Delivery to or from mills; Flour and
feed mills.)
Moisture traps, inert gas conditioning equip
m ent_____________ _______ ______ _______
74
Motors:
Coal pneumatic cleaning plants, type re
quired_________ ______________ _______
66
Dust removal—
12
Flour and feed mills------- -------------------Grain elevators, terminal______________
23
Starch factories_______________________
8
Elevator legs, terminal grain elevators.. .
18
Grain elevators, terminal, types preferred.
23
Location—
Pulverizing systems for sugar and cocoa..
31
Vacuum-cleaning systems, pulverizedfuel systems________________________
48
Wood-flour manufacturing establish
ments_____________________________
42
Overload protection, elevator legs, terminal
grain elevators_______________________
18
Overload release or signal, screw conveyors,
pulverized-fuel systems, class A ________
55
Spice-grinding plants........................................
36

National Fire Protection Association............
Nitrogen as inert gas for fire protection,
qualities of....................... .................................
Nonchoking devices. (See Overload release
or signal.)

2,3
69

Noncombustible construction. (See Con- P aSe
struction.)
Nonfire-resistive construction of buildings.
(See Construction.)

Oil and grease, storage limited, terminal grain
elevators________ ____ __________________
25
Open lights and torches, pulverized-fuel sys
56
tems, where prohibited_________________
Open-flame heating and lighting, when pro
hibited:
Coal pneumatic cleaning plants__________ 66,67
Flour and feed mills______ _____ ________
12
Pulverizing systems for sugar and cocoa.. 33
Spice-grinding plants___________________
37
Starch factories_________________________
8
Wood-flour manufacturing establishments.
44
Openings:
Floors—
Pulverized-fuel systems_______________
47
Screen rooms, coal pneumatic cleaning
plants_____________ ________________
62
Starch factories__ _____ ______________
6
Walls or partitions—
Grain elevators, terminal___ __________
16
Lump-starch cooking, pressing, grading,
and packing________________________
8
47
Pulverized-fuel systems_______________
Pulverizing systems for sugar and cocoa. _ 29, 30
Spice-grinding plants__________________
36
Starch factories_______________________
6
Wood-flour manufacturing establish
m ents______________________________
40
Operating bin or mill vents, pulverized-fuel
systems.............. ................ ................................
50
Operations:
Kiln building, starch factory, lim ited_____
6
Starch factories, arrangement of buildings.
5
Overheating. (See Bearings; Coal driers.)
Overload release or signal:
13
Conveyors, flour and feed m ills__________
Elevator legs, terminal grain elevators____
18
Elevator legs, starch factories____________
9
Garners, terminal grain elevators------------19
Motors, terminal grain elevators...................
18
Motors, screw conveyors, pulverized-fuel
system s______________________________
55
Oxygen, permissible percentage, inert gas
protecting system s............................................
71

Packing:
Lump starch, arrangement of premises___
Pearl and powdered bulk starch, arrange
ment of premises_____________________
Painting of interiors:
Coal pneumatic cleaning plants, color pre
ferred________________________________
Pulverized-fuel systems, color preferred.. .
Pulverizing systems for sugar and cocoa.. .
Spice-grinding plants____________________
Starch factories, color recommended--------Wood-flour manufacturing establishments,
pulverizing department_______________
Partitions. (See Construction; Openings.)
Pearl and powdered starch, bulk packing----Pipe openings in walls:
Pulverizing systems for sugar and cocoa.. .
Wood-flour manufacturing establishments.

7,8
7

63
48
34
37
6
44
7
30
41

SUBJECT INDEX
Page
Pipes and pipe lines, pulverized-fuel systems:
Class A systems, specifications__________
55
Conveying fuel suspended in air, construc
tion requirements------------------------------- 46, 47
Fires in, procedure, pulverized-fuel sys
tem s__________________________ ____ 58
Flanges, flat-ring steel, 50-pound W. P.,
specifications_________________________
53
Inspection and repair___________________
56
Leaks, caution to operator to prevent_____
56
52
Specification No. 1...........................................
53
Specification N o. 2---------------- ------------. . .
Specification No. 3-------------------- ------ ----54
U nit systems, arrangement______________
55
Wall thickness of pipes, specification No. 2.
53
(See also Inert gas.)
Pneumatic cleaning. (See Vacuum cleaning
systems.)
Pneumatic separators. (See Separators.)
Portable lights. (See Electric lighting.)
Portable vacuum cleaners. (See Vacuum
cleaners.)
Posting, instruction cards, pulverized-fuel
systems----------------------------------- ------ ----55
Power:
Elevator legs, terminal grain elevators, re
quirements__________________________
18
Fans, grain driers, requirements-------------21
Individual connection to source, terminal
19
grain elevators_______________________
Pulverizing systems for sugar and cocoa,
requirements_________________________
31
(See also Electric light and power control.)
Power-transmission apparatus, how installed:
Pulverizing systems, cocoa and sugar------30,31
Wood-flour manufacturing establishments.
41
Precautions for safe operation, pulverized-fuel
system s-------------------- -------------------- ------ 55-57
Pressing, lump starch, arrangement of prem
7,8
ises____________________ _______________
Pressure relief vents:
Construction of, and where required—
Pulverizing systems for sugar and cocoa.
33
Spice-grinding plants--------------------------37
Wood-flour manufacturing establishm e n ts ...------ -------------------- -----------43
Dry starch grinding mills........ ..................... .
7
Screw conveyors, pulverizing systems for
sugar and cocoa------------- -------------------32
Screw conveyors, wood-flour manufacturing
establishments..............................................42
(See also Safety relief vents.)
Preventive measures:
Pulverizing systems for sugar and cocoa.— 32,33
Wood-flour manufacturing establishments. 42-44
Protection against lightning, terminal grain
elevators-..-........ ................................................
25
Protection against sparks. (See Sparks.)
Protection for electric lamps. (See Electric
lighting.)
Pulverized or dried crushed coal. (See Coal.)
Pulverized-fuel furnaces. (See Furnaces.)
Pulverized-fuel pipe lines. (See Pipes and
pipe lines.)
Pulverized-fuel systems, code for.....................45-59
(See also under specific subjects.)
Pulverizers. (See Mills.)

Page
Pulverizing apparatus:
Inspection openings—
Pulverizing systems for sugar and cocoa.
32
Wood-flour manufacturing establish
m ents______________________________
43
Installation—
Pulverizing systems for sugar and cocoa_
32
Wood-flour manufacturing establish
ments______________________________
42
Pulverizing departments, defined:
Pulverizing systems for sugar and cocoa.
27
Wood-flour manufacturing establishments.
39
Pulverizing processes, location. (See Loca
tion.)
Pulverizing systems for sugar and cocoa, code
for_____________________________ _____ 27-34
(See also under specific subjects.)
R a ilw a y cars, terminal grain elevators, when
excluded_______________________________
Raw-fuel driers. (See Coal driers.)
Regulation of temperature, automatic. (See
Temperature.)
Repair work, when permitted:
Spice-grinding department______________
Wood-flour manufacturing establishments.
Revolving coal driers, pulverized-fuel sys
tems, when stopped____________________
Roofs:
Ventilation, galleries, etc., terminal grain
elevators_____________________________
(See also Construction.)

37
44
56

Safe operation, instruction cards listing pre
cautions for____________________________ 55-57
Safety relief vents:
Coal pneumatic cleaning plants, how ar
ranged_______________________________
64
Construction and arrangement, pulverizedfuel system s__________________________
50
Dried-coal elevators, coal pneumatic clean
ing plants____________________________
65
Dried-coal elevators, pulverized-fuel sys
tem s____________________________ ____
52
Suggested form of_____________________
34
(See also Pressure relief vents.)
Sash. (See Window sash.)
Screen-cloth dust collectors. (See D ust col
lectors.)
Screen rooms, coal pneumatic cleaning plants,
arrangement and construction.......................
62
Screens:
7
D ry starch, type required...............................
Grain driers, where required..........................
20
Inspection openings—
Sugar or cocoa pulverizing apparatus----32
Wood-pulverizing apparatus.......................
43
Louvers, grain driers, type req uired,.........
20
Pulverizing systems for sugar and cocoa,
construction.................................................. .
33
Sparks, protection against, terminal grain
elevators, where required............................
24
Spices, to be passed through, before enter
ing m ill.. _..................................................
36
Sugar, to be passed through, before enter
ing mill or pulverizer....................................
32
Wood-flour manufacturing establishments,
construction of...............................................
43

SUBJECT INDEX

Screw conveyors:
Arrangement—
Page
Flour and feed mills.....................................
13
Pulverized-fuel systems, class A _______
55
Pulverizing systems for sugar and cocoa. 30, 33
Spice-grinding plants_________________
37
Wood - flour manufacturing establish
41
m ents______________________________
Housings—
Grain elevators, terminal______________
19
Pulverized-fuel system s_______________
56
Pulverizing systems for sugar and cocoa.
32
W ood-flour manufacturing establish
m ents_____________________________
42
( See also Pressure relief vents; Spiral con
veyors.)
Scroll conveyors, pulverizing systems for sugar
and cocoa______________________________
33
Separators:
Cyclone, pulverized-fuel systems, minimum
requirements_________________________
49
Magnetic, where required—
Flour and feed mills__________________
13
Grain elevators, terminal______________
19
Pulverized-fuel system s_______________ 48, 49
Pulverizing systems for sugar and cocoa.
32
Spice-grinding plants_________________
36
Starch factories_______________________
7
Wood-flour manufacturing establish
m ents_____________________________
42
Shaft holes in walls:
Pulverizing systems for sugar and cocoa.__ 29, 30
Wood-flour manufacturing establishments.
41
Shafts, construction, terminal grain elevators _
17
Shovels, type permitted, terminal grain ele
vators_________________________________
25
Skylights; construction, location, etc.:
Coal pneumatic cleaning plants__________
63
Pulverized-fuel systems_________________
47
Pulverizing systems for sugar and cocoa__
23
Wood-flour manufacturing establishments.
40
Smoking prohibited:
Coal pneumatic cleaning plants__________
67
Flour and feed mills____________________
12
Grain elevators, terminal________________
25
56
Pulverized-fuel systems_________________
37
Spice-grinding plants___________________
Starch factories_________________________
8
Sparks, protection against:
Grain driers, fire-heated_________________
22
24
Grain elevators, terminal.......................... .
Specifications for pipe lines, pulverized-fuel
systems. ( See Pipes and pipe lines.)
Spice-grinding plants, code for_______ _____ 35-37
(See also under specific subjects.)
Spiral conveyors, starch factories:
Transfer of starch between buildings_____
6
9
Maximum speed___ ____ _______________
Spouts:
Arrangement, terminal grain elevators____19,20
Construction—
Pulverizing systems for sugar and cocoa. 30, 32
Wood-flour manufacturing establish
41
m e n ts.____________________________
Fitted to regulate flow of material—
Pulverizing systems for sugar and cocoa.
32
Spice-grinding plants....................................
37

Spouts—Continued.
Fitted to regulate flow of material—Con. Page
Wood-flour manufacturing establish
ments_____________________ ________
43
Spray washers, inert gas conditioning equip
m ent__________________________________
74
Sprinklers, automatic:
Grain elevators, terminal________________
26
Pulverized-fuel systems, class A _________
54
Pulverizing systems for sugar and cocoa__
34
Spice-grinding plants___________________
37
Wood-flour manufacturing establishments.
44
Stairways:
Grain elevators, terminal, construction___
17
Pulverized-fuel systems, how inclosed____
47
Starch factories, location________________
6
Standpipe and hose systems for fire protec
tion, terminal grain elevators____________
26
Starch:
Bags, method of cleaning________________
8
Dry, grinding and grading_______________
7
Drying of, arrangement of buildings______
5
Dumps, ventilating of___________________
6
Kilns, construction of___________________
6
Lump, cooking, pressing, grading, and
packing______________________________
7
Pearl and powdered, bulk packing_______
7
Transfer of, between buildings, equipment
for___________________________________
6
(See also Starch factories.)
5-9
Starch factories, code for__________________
(See also under specific subjects.)
Starch-kiln buildings, operations perm itted._
6
Static dust. (See Dust.)
Static electricity. (See Electricity.)
Steam, use of, for fire protection:
Coal pneumatic cleaning plants__________
66
Inert gases, combined w ith ______________
70
55
Pulverized-fuel systems_________________
Stocking or bag dust collectors. (See D ust
collectors.)
21
Steam coils, grain driers, design of_________
Steam heating, grain elevators, terminal____
24
Storage bins. (See Bins.)
Storage of coal. (See Coal.)
Storage prohibited:
Grain elevators, terminal, materials speci
fied__________________________________
25
Starch factories, materials specified______
9
Storage of oil and grease limited, terminal
grain elevators. _____ ____________________
25
Structural features, terminal grain elevators.. 15-17
Suction-cleaning appliances. (See Vacuum
cleaning.)
Suction fans. (See Fans.)
Sulphur bleachers, construction and location,
terminal grain elevators_________________
24
Surfaces and ledges, terminal grain elevators,
construction____________________________
16
Surfaces, interior. (See Interior surfaces.)
Suspended dust. (See D ust.)
Sweeping:
Grain elevators, terminal________ _______
23
(See also Vacuum cleaning.)
Switch room, terminal grain elevators, vent
ing of________ ______ ____ ____ __________23,24
Switches, electric. (See Electric switches.)

SUBJECT INDEX

Tanks.

( See Bins.)
Temperature:
Page
Grain driers, automatic regulation_______
21
Maximum, for storing dried coal, coal
pneumatic cleaning plants_____________
65
Maximum for storing dried coal, pulverizedfuel system s__________________________
52
Safe, coal driers, mill in operation_______
51
Temperature-indicating alarm device; coal
driers:
Coal pneumatic cleaning plants...................
65
Mill driers, pulverized-fuel systems______
51
Pulverized-fuel system s_________________
52
Terminal grain elevators. (See Grain eleva
tors, terminal.)
Track shed, construction, terminal grain
elevators_______________________________
16
Transportation pipe lines for pulverized fuel.
(See Pipes and pipe lines.)
Tunnels. (See Construction.)

United States Bureau of Chemistry and Soils.

U nit systems, pulverized fuel:
Arrangement and specific regulations_____
Definition_____________________________

55
45

Vacuum cleaning:
Portable cleaners prohibited—
Coal pneumatic cleaning plants________
Pulverized-fuel system s_______________
Wood-flour manufacturing establish
ments_____________________________
Sweeping apparatus or systems—
Grain driers, installation recommended __
Grain elevators, terminal, use recom
mended____________________________
Pulverized-fuel systems, installation re
quirements_________________________
Starch factories, removal of static dust___
C oal pneumatic cleaning plants ............ . _
Flour and feed mills, use recommended,
in grain storage, etc_________________
Wood-flour manufacturing establish
ments, use recommended____________
Vent flues, construction:
Pulverizing systems for sugar and cocoa__
Wood-flour manufacturing establishments,
Vent openings, bins:
Coal pneumatic cleaning plants, damper
equipment_____________ _____________
Pulverized-fuel systems, damper equip
m ent---------- ---------- --------- ------------------

64
48
44
21
23
48
8
64
12
44
33
43

65
54

Ventilation:
Coal driers, pulverized-fuel systems after Page
fire----------- --------- -----------------------------56
Coal pneumatic cleaning plants--------------- 63,64
Grain elevators, terminal________________17,18
Lump-starch cooking and pressing----------7,8
48
Pulverized-fuel system s------ ------------------Starch dumps.......................................... ........... 6, 7
(See also Basements.)
Vents:
Operating bin or mill, pulverized-fuel
systems____ _________________________
50
(See also Pressure relief vents; Safety relief
vents.)
Vestibules, access by means of. ( See Access.)

Walls:
Finish, flour and feed m ills--------------------11
Finish, starch factories__________________
6
(See also Construction; Glass or equivalent
area; Openings.)
Waste cans, provision of, terminal grain ele
vators_________________________________
25
Watchman for fire protection, terminal grain
elevators_______________________________
26
W’ater-spray-type dust collectors. (See Dust
collectors, types.)
WTindow ledges. (See Ledges.)
Window sash, swinging, when required:
Coal pneumatic cleaning systems________
63
Pulverized-fuel system s_________________
47
Pulverizing systems for sugar and cocoa. __
28
Windows, arrangement, and construction:
Coal pneumatic cleaning plants__________
63
Flour and feed m ills____________________
11
Grain elevators, terminal________________
17
Pulverized-fuel system s____ ____________ 46, 47
Pulverizing systems for sugar and cocoa-__
28
Spice-grinding plants___________________
35
Starch factories_________________________
6
Wood-flour manufacturing establishments40
Wired glass, use limited:
Coal pneumatic cleaning plants__________
63
Flour and feed mills____________________
11
16
Grain elevators, terminal________________
Pulverized-fuel systems_________________
47
Pulverizing systems for sugar and cocoa. __
28
Wiring, electric. (See Electric wiring.)
Wood-flour manufacturing establishments,
code for_______________________ ______ 39-44
(See also under specific subjects.)

Full text of Safety Codes for the Prevention of Dust Explosions : Bulletin of the United States Bureau of Labor Statistics, No. 562

FRASER