Proceedings of conference of men engaged in grain dust explosion and fire prevention campaign


Material Information

Proceedings of conference of men engaged in grain dust explosion and fire prevention campaign conducted by United States Grain Corporation in cooperation with Bureau of Chemistry, United States Department of Agriculture ... April 22-24, 1920
Grain dust explosion and fire prevention campaign
Physical Description:
ii, 159 p. : illus. ; 23 cm.
United States Grain Corporation
United States -- Bureau of Chemistry
Place of Publication:
New York
Publication Date:


Subjects / Keywords:
Dust explosions   ( lcsh )
Grain elevators -- Fires and fire prevention   ( lcsh )
non-fiction   ( marcgt )


Additional Physical Form:
Also issued online.
General Note:
Cover title.

Record Information

Source Institution:
University of Florida
Rights Management:
All applicable rights reserved by the source institution and holding location.
Resource Identifier:
aleph - 029786759
oclc - 00930933
lccn - agr20001757
lcc - QD516 .U3
ddc - 690.536 U55, 73-3364
System ID:

Full Text

D. J. PRICE, Presiding
Possible Lines of Extension of Dust Explosion Work in Commer-
cial Fields, by H. R. Brown ................................. 3-11
Changes in Elevator Construction Suggested by Recent Explosions,
by J. 0 Reed ................................................ 11-27
Latest Developments and Devices for Prevention of Chokes in
Elevator Legs, by P. E. Brady................................ 27-33
A Discussion of the Relation of Grain Dust Explosions as Ap-
plied to Flat-Warehouses and Elevators, by G. P. Bodnar...... 34-37
Experiences That Have Been Helpful in Making Inspections, by
G. A H ibbard ............................................... 37-42

DR. J. W. T. Duva, Presiding
Static Electricity in Attrition Mills and Methods of Removal, by
M E. M cCollam ............................................. 42-46
Recent Investigations of Static Conditions in Industrial Plants,
by H E. Roethe ............................................. 47-59
Relation of Electrical Equipment to Dust Explosions, by D. J.
P rice ....................................................... 60-66
Special Features in Lighting, by E. B. Fox, Commercial Engineer,
Edison Lamp Company ...................................... 66-74
Presentation of Dust Explosion Work Before High School Stu-
dents, by E. L. Riley ......................................... 74-77

DR. H. H. BROWN, Presiding.
Results of Work in Various Districts-
Review of Work in Eastern District, by H. R. Brown........ 78-80
Review of Work in Central and Northwestern D)istricts, by
P. E. Brady ........................................... 80-81
Review of Work in Pacific District, by M. E. McCollam..... 81-86
General Discussion of Experience in Making Inspections........ 86-91
Review of Explosions During Past Year........................ 91-92
Kansas City Explosion, by J. 0. Reed...................... 92-93
Effect of the Kansas City Explosion on Inspection Work
in the Southwest, by H. J. Helmkamp .................. 93-97

Review of Explosions During Past Year-Continued-
Port Colborne Explosion, by Dr. H. H. Brown............. 100-104
Denver, Colorado, Explosion, by D. J. Price .............. 104-109
Explosion, Aluminum Goods Manufacturing Company, Mani-
towoc, Wisconsin, by P. E. Brady ..................... 110-116
Explosion in Feed Mill and Elevator, Buffalo, New York, by
H. J. Helmkamp....................................... 116-119
"H-O" Mill Explosion at Buffalo, New York, by E. L. Riley.. 119-120
Newton Tea & Spice Company Fire, Cincinnati, Ohio, by
E. L. Riley ............................................ 120-121
Statement by Julius H. Barnes, U. S. Wheat Director, and Presi-
dent of U. S. Grain Corporation ....................... 98
Statement by Dr. C. L. Alsberg, Chief, Bureau of Chemistry, U. S.
Department of Agriculture............................ 98-100

E. N. BATES, Presiding.
Suction vs. Bucket Elevating in Handling of Grain, by G. D.
W itm er ..................................................... 122-127
Relation of Aspirating Systems in Grain Elevators to Dust Ex-
plosions, by W B. Lind...................................... 127-133
A System of Air Purification in Flour Mills, by H. J. Helmkamp. 133-138
Results and Impressions in Dust Explosion Meetings, by Dr. H. H.
B row n .............. ........................................ .. ........... 138-145
Statement by Watson S. Moore, Director and Second Vice-Presi-
dent, U. S. Grain Corporation ................................ 145-147
Interest of Grain Corporation in Dust Explosion Prevention, by
D r. J. W T. LD uveI ........................................... 148-151
Summary of Dust Explosion and Firc Prevention Campaign, by
D J. Price ................................................... 151-159

Conducted by


In Cooperation with
Bureau of Chemistry, U. S. Department of Agriculture
42 Broadway, New York, N. Y.
April 22-24, 1920

Alsberg, Dr. C. L., Chief, Bureau of Chemistry, U. S. Department of
Agriculture, Washington, D. C.
Bailey, Dr. C. H., University of Minnesota, St. Paul, Minnesota.
Barnes, J. H., United States Wheat Director, and President, U. S. Grain
Corporation, 42 Broadway, New York, N. Y.
Bates, E. N., Investigator, Bureau of Markets, U. S. Department of
Agriculture, Washington, D. C.
Bodnar, G. P., In Charge of Grain Dust Explosion Prevention Campaign
at Portland, Oregon.
Boerner, E. G., In Charge Grain Investigations, Bureau of Markets. U. S.
Department of Agriculture, Washington, D. C.
Brady, P. E., In Charge of Northwestern District, U. S. Grain Corpora.
tion, Minneapolis, Minnesota.
Brown, Dr. H. H., Organic and Physical Chemist, Bureau of Chemistry.
U. S. Department of Agriculture, Washington, I). C.
Brown, H. R., In Charge, Eastern District, Bureau of Chemistry, U. S.
Department of Agriculture, Washington, D. C.
Dedrick, B. W., Instructor in Milling Engineering. State College, Penn-
I)uvel, D)r. J. \V. T., In Charge, Grain Dust Explosion Prevention Cam-
paign, LT. S. Grain Corporation, New York, N. Y.
Fox, F. B., Commercial Engineering Department, E.dison Lamp workss .
Harris(on, New Jersey.
Fritz, C. M., Feflcral Grain Supervisor, Bureau otf Markets, I'. S. De-
partment of Agriculture, Chicago, Illinois.
Helmkamp, H. J., In Charge of Grain D)ust Explosion Preventiln tam-
paign at Kansas City, Missouri.
Hibbard, G. A., In Charge of Grain )Dust Explosion Prevention Cam-
paign at Chicago, Illinois.

Lind, W. B., Assistant, Grain Dust Explosion Prevention Campaign,
Minneapolis, Minnesota.
McCollam, M. E., In Charge, Pacific District, U. S. Grain Corporation,
San Francisco, California.
Moore, W. S., Director and Second Vice-President, U. S. Grain Corpora-
tion, 42 Broadway, New York, N. Y.
Price, D. J., Engineer in Charge, Grain Dust Explosion Investigations,
Bureau of Chemistry, U. S. Department of Agriculture, Wash-
ington, D. C.
Reed, J. 0., Assistant, Grain Dust Explosion Prevention Campaign, Bu-
reau of Chemistry, U. S. Department of Agriculture, Washington,
Riley, E. L., In Charge of Grain Dust Explosion Prevention Campaign
at Buffalo, New York
Roethe, H-. E., Assistant, Grain Dust Explosion Prevention Campaign,
Bureau of Chemistry, U. S. Department of Agriculture, Washing-
ton, D. C.
Waters, J. P., New York, N. Y.
Witmer, G. D., Assistant, Grain Dust Explosion Prevention Campaign,
Bureau of Chemistry, U. S. Department of Agriculture, Washing-
ton, D. C.

Kathryn M. Orr, Bureau of Chemistry, Washington, D. C.
Hilda A. Sternburgh, U. S. Grain Corporation, New York, N. Y.


April 22, 1920
Mr. PRICE-The dust explosion prevention campaign initi-
ated by the U. S. Department of Agriculture in October, 1917,
Shas been continued by the U. S. Grain Corporation since July
1, 1919. This conference of field men engaged in this work has
been called to consider and discuss certain important phases
of dust explosion and fire prevention work that have developed
during the progress of the campaign. In addition to the men
who are actually engaged in this work, we have in attendance
others who have been interested in its conduct. We are glad to
welcome them and invite them to assist in the consideration of the
various subjects.
The conference will be somewhat similar to the one held a
year ago in Chicago in connection with the war emergency canm-
paign. The program as outlined will include the more important
developments pertaining to this work.
In addition to the subjects listed in our program, we are to
have the honor of having Mr. Barnes, President of the U. S.
Grain Corporation, and Dr. Alsberg, Chief of the Bureau of
Chemistry, address us sometime during the afternoon session
on Friday. Mr. Mloore, Vice-President of the U. S. Grain Cor-
poration, has also very kindly consented to address us onl Satulir-
day morning.
The first subject presented will be "P'ossible lines of E-xten-
sion of Dust Explosion Work in C',ommercial Fields." bv 11. R.
Brown, in charge of the work ill the Eastern Dis)trict.

This is certainly a broad subject but I believe it covers tlie
keynote of the entire conference. that is: "I low can tih iust
explosion work be continued '" or raller. "I lowv can tihe results
of our investigation be lna i on a prat'ti:l wo' rkilg hi:si, '?"

Now we must admit that at present there are no funds avail-
able to continue the work in its present form after July 1. That
does not mean that the work is finished but rather that it has
been divided into a number of smaller working units. As we
go out into other fields we are going to carry the dust explosion
work with us. Some of us will go with milling or grain com-
panies, others with insurance companies or various kinds of
manufacturing concerns. Wherever we go we can carry the
story of dust explosion prevention and do our bit to keep the
good work moving.

Dust Explusiun D)emontraticn- produced by blowing dust into an open flame in a
miniature elevator.

I would like to suggest a few methods which might be fol-
lowed to accomplish this. If we cannot do the work ourselves
we must ask other organizations to take it up. For our general
inspection work in its present form the best results can probably
be obtained through three organizations, namely, fire depart-
ments, insurance companies and industrial commissions. These
organizations can insist on the plants in their districts being
clean. You remember our motto: "Diusl free mills and elevators

are explosion proof." Can we not impress this on these or-
ganizations in such a manner that they will take up this phase of
the work and see that the plants in their districts are properly
protected? Whenever you have an opportunity to present our
work before any of these organizations do so. The cheese-cloth
method of demonstrating is very effective and easy to give.
When an actual explosion is desired a packing case or heavy card-
board carton can be used in place of the miniature elevator.
At one place in the eastern district an explosion demonstra-
tion was desired and we did not have the miniature elevator
with us. A cardboard carton was obtained, an 8-inch piece of
pipe partially filled with starch inserted through a hole in one
end, a flame placed within the box and the cover closed. The
dust was blown into the box from the pipe and the explosion
which followed was all that could be desired. By giving demon-
strations of this kind to interested organizations and urging them
to do all in their power to protect the property in which they
are interested the good work can be continued. All this can be
done without interfering with your other work and I know
everyone will be willing to take a few minutes of their spare
time to keep the dust explosion prevention work alive.
During our conference a number of suggestions will be made
regarding changes in elevator construction, changes in equip-
ment, and methods of eliminating dangerous conditions. Thliese
suggestions should be given to the mill and elevator construction
companies so that they can make further tests and determine
the most satisfactory method to adopt. The effectiveness of the
revolving damper, vent pipe, and choke conveyor underneath
attrition mills, should be brought to the attention of machinery
manufacturers with the purpose of having them standardize this
equipment and supply it with their mills. Can we not impress
this matter on the manufacturers so that new installations will
be arranged to reduce the dust explosion hazard in this equip-
ment to the minimum?
The electrical companies have been doing some excellent
work along the line of dust explosion prevention. When ex-
plosions due to electrical equipment were reported they inmmne-
diately started tests to determine to what extent such equipment
might be responsible for the starting of an explosion. Tliwir
investigations have shown beyond a doubt that an explosion can
be started by the breaking of an electric lamp in a dusty atno-
sphere. Further tests are Ixbing made bV these companies to
determine the best method of protecting tlese kamlps from break-

age. In fact, a complete study is being made of the lighting
system used in mills and elevators. This is a form of co-
operation which amounts to something. These companies are
much better equipped than we are to carry on investigational
work of this kind and their co-operation represents the first step
in the extension of dust explosion work in commercial fields.
The results of their investigations can be taken to the mills and
elevators in the form of better and safer lighting equipment.
Can we not arrange other co-operative work with various
commercial concerns? We have started the ball rolling. Why
not have machinery companies, mill builders and dust collector
manufacturers take up the work and complete the investigations
which we have started?
The Public Health Service should also co-operate with us in
eliminating the dust condition in mills and elevators. In a num-
ber of plants the dust is so thick that it menaces the health of
the employees, yet the company is not allowed to install a dust-
collecting system because it might cause a difference of a few
pounds between the incoming and the outgoing weights of the
grain handled. Cannot the Public Health Service insist that the
health of the employee is worth more than the slight loss in
the weight of grain, and see that dust-collecting systems are in-
stalled? They would be helping the employee, the company, and,
indirectly, the dust explosion work, because dust-free mills and
elevators are explosion proof. I would suggest that we arrange,
if possible, to have this organization co-operate with us.
Another method of extending our work is by using moving
pictures and magazine articles to bring the subject before the
general public. I believe a very interesting moving picture could
be prepared for public showing. Our present pictures are
adapted more for use in lectures before technical societies.
If the magazines will publish an article occasionally on the
subject of dust explosions, or we can have a live story written
about the work for one of the popular magazines, the work will
be kept before the public and their interest in the subject main-
tained until we are able to put the work on a sound foundation
and resume our investigations.
I have endeavored to make a few suggestions for the ex-
tension of the dust explosion work. Perhaps you have other
suggestions along this line. If you have, I would suggest that
you give them at this time so that we can prepare a program of co-
operation and arrange for the continuation of the work in which
we have all become so interested.

Mr. PRICE-This subject was placed on the program first
because it was thought that there have been so many commercial
lines along which the work might be applied, that we could well
spend a brief time in discussing some of these phases. You re-
call the Department of Agriculture discontinued to a large extent
the research work relating to dust explosions and fires, at the
beginning of the war emergency campaign. Milling companies
and other industrial concerns in the meantime have taken up
parts of the work of interest to us. We will now devote a brief
time to discussion and I hope you will feel free to respond witlh-
out any hesitation.
Dr. DUVEL-I am very much interested in the health ques-
tion Mr. Brown referred to. I would like to know whether
you have run across anything to indicate the effect of dust in
mills and elevators on the health of employees. Is it probable
that rye dust and barley dust would be more objectionable than
dust from either wheat or corn?
Mr. BROWN-I have never run across anything definite
along this line. Rye, barley or some form of oat dust would
probably offer the greatest objection in the elevator line. I was
referring more especially to the smut millers inl flour mills. I
know of two cases where men engaged in this work have had
to give up the job. In another case the man seemed to enjoy
very good health and put on weight. Two out of three of the
men I knew did have trouble.
Dr. DUVEL-You find men complaining a great deal as to
the bad effects of working in a dusty atmosphere, vet there are
men who have been working under such conditions practically
all their lives and still apparently enjoy good health.
Mr. BR()OWN-Some claim it doesn't bother them in the
least, while in some cases new men go in there and are not abl:
to stand it. I think this question came up a year ago at tlhe Ci'"-
cago meeting. The question was raised lby l)r. I Iulctt of Prince-
ton regarding the health of people in 1Pittslmrgh. I recall it
was shown at that time that the tuberculosis deaitli rate iln P'itts-
burgh was lower than in any (other city. WVhctlier Siii)l'c lhMl
anything to do with it or not I don'tt know.
Dr. BROWN-From that side of the question, :a little arti-cle
which came across Mlr. 1'rice's desk and nile yVesterdcay recg;n l
ing a survey which had been made of tlhe ilndilustrties :t Nia.;ir;i,
Falls, published in a recent issue of the St. Louis NI edir.l Journ.l1

might be of interest. It was found that workmen throughout
various types of industrial plants there became diseased on ac-
count of the dust, even though apparently there was a very
small amount, at least as we see it from the mill and elevator
standpoint, in the atmosphere. When the dust was breathed
into the lungs it was not given out, but retained in the lungs and
eventually brought about congestion and disease. -In thinking
over that side of the question it seems possible that when grain
dust is taken into the lungs the starchy matter may be dissolved,
being soluble in water, and consequently would not have the
same effect but we might have that effect when certain dusts are
considered. Possibly it might be more true in the case of rice
dust, where the hull contains a very high percentage of silicate
which, of course, is not soluble.
Mr. McCOLLAM-It seems to me that most everybody on
this inspection work should have something to relate about the
health of the employees in the mills they have visited. I remem-
ber particularly two plants, a rice mill and a grain elevator. The
head miller in the rice mill had a very bad case of asthma which
he attributed to the dust he had been breathing all his life. The
man in the grain elevator also had asthma which he attributed to
the same cause.
Mr. PRICE-The Public Health Service has done quite a
little work in some other dusty industries and we hope this matter
may be brought to their attention in connection with our work
in the near future. In addition to this phase that has been sug-
gested, there may be some other lines that might be considered.
We would be glad to have the same presented.
Mr. BATES-I should like to ask you if there is at this time
any) plan relative to getting out a publication regarding grain
dust explosions in mills and elevators, summarizing and giving
results of this work?
Mr. PRICE-The Grain Corporation is planning that sort
of publication right now, containing sufficient information to
be of some value to the industry, as more or less of a report of
what the Grain Corporation has been doing in this campaign.
In addition, a manuscript is in course of preparation, which is
almost ready to go into publication channels, covering the work
from its origin in the Bureau of Mines in 1913 up to the present
time. This is a very complete treatise of the question as it relates
not only to grain dust but to other inflammable dusts as well.
Both publications should be available during the present year at

least. The Grain Corporation publication will undoubtedly be
ready soon.
Dr. BROWN-It seems to me that there are some things that
we ought to bring to the attention of the mill construction people.
For instance, we had a paper at our conference last year on the
question of prevention of chokes in elevator legs. We are ex-
pecting to have a further discussion of that question at this con-
ference. We had a paper last year on aspirating systems. VWe
are to have a further discussion of that this year. In these and
in many other cases, H. R. Brown referred to one-the case of
the revolving damper, the choke conveyor and the vent Pipe,
being standardized by the mill people-it seems to ille tllhaLt tllhee
and other ideas which have been brought out in the development
of the work should be brought to the attention of the mill con-
struction people but not, of course, given to them as finished
products. We are not able to do that today. I sometimes duubt
whether we shall ever be able to do that unless we can get into a
plant and develop these ideas on a commercial basis. Th'lese
people are able to do that, just as the electric lamp people witlh
whom we are co-operating are able to make direct tests and (do
practical work. It seems to me that these ideas which we have
should be given to these companies. Many of us probably llaV
go out into other lines of work but I don't think we will ever
forget the associations we have had, the ideas that have coine
to us. New ideas probably \%ill develop from time to time. \Ve
will go into other industries \:here we may find oilier iiiform:i-
tion on dust collecting systems that we feel would be more 0 t-Ci-
cient in a mill or elevator than ainy type we have seen there. It
will be worth while to keep iii mind tllhat the I)CeiiLrtenLiut 1and
thile trade is interested in this problcni aind we can send to the
Department and through them to tlhe tradc aUld to tile nill c&ol
struction people, some of these i(leas. lFor instance, I r;an acro.-,
the other day, a type of wliat is termeld a sino kCe JrUcilpittiLor.
It seems to me that it is something which could lie dlceveoi-Vedl.
along a different line possibly, lbuit to 1ie used as a sm iall typvle of
dust precipitator. Tle method of ope ration was iv cei.riftl-
ing, you might say. the smoke. Tle solid particles i1 SlI sPet.sionIl
were thrown to the outside and canie out as a thick liIliil. while.
the air. freed from smoke, passed on out. It seiiis i lilt' that
this idea might lhe d'eheloped ill son e sort of wav as a dust pre-
cipitator, especially where we have quantities of very (ime >Iiutq
in suspension which it doesn't seem pi)"ssilIle to cfillert uficlenltly
at the present time.

Mr. PRICE-One of the very gratifying things in this work
is that we have been able in the campaign to associate ourselves
with some of the most prominent milling and grain men in the
country. We are glad to have some of those men with us today.
Professor C. H. Bailey of the University of Minnesota, St. Paul,
came East primarily for this conference, which indicates the
extent of his interest. He was in charge of our work for the
first year in the Northwestern territory. We would like to have
him discuss this paper.
Dr. BAILEY-I don't know that I have anything to con-
tribute just at this point. I came to this conference primarily
to obtain rather than to give information. These men might,
however, be interested in the particular cause of my attending
this conference. We are contemplating erecting, this summer,
at Minneapolis, an experimental flour mill to include a rather
elaborate grain cleaning department. We want to incorporate
in that plant, as far as our finances make possible, the latest and
most useful of modern ideas with respect to dust-collecting. I
have little doubt that our grain cleaning department will be one
of the most valuable parts of this project. I will appreciate it if
you mnien keep this matter in mind during the course of my stay
with you, that you may give me results of your experience and
observation that will be of use to me. The plant which we ex-
pect to erect %vill not be large, but we hope to make it thoroughly
niodern. The mill is not being erected by the University or
Experiment Station, but by the State Railway and Warehouse
Commission. Our relations with them are very close and we
are co-operating with them.
Mr. PRICE-Professor Bailey wants to erect a dustless mill
and a dustless elevator in Minneapolis. He will appreciate the
ideas of you men. If there isn't anything further on this par-
ticular subject we will take up our next number on the program.
At the time of the explosion in Kansas City last September
(when the grain trade was wondering why this explosion occurred
and the circumstances surrounding its origin) many theories were
advanced as to how the explosion might have been prevented,
and numerous suggestions made as to how this plant might be
rebuilt to prevent another explosion from occurring. We, of
course, as you know, were very directly concerned in that ex-
jplosion. \Ve have been longing for a considerable time to see
an actual explosion occur. In connection with our thresher work
in tlhe Northliwest. although apl)proxinately 500 explosions oc-

curred in one season, yet to my knowledge no man engaged in
the work has actually seen an explosion. Men have reached the
scene soon after an explosion and have left shortly before an
explosion occurred. We have also wished we might be fortunate
enough to see a mill or elevator explosion without being near
enough to be in actual danger. We almost had that experience
last Fall.
The engineer who prepared the report of the investigation
of the Kansas City explosion advanced a number of ideas re-
lative to construction that at the time appeared to be, I feel free
to say, somewhat radical. When the report was sent to the Fed-
eral Grain Company we immediately received a request asking
permission of the Department to turn this report over to the
Burlington Railroad Company, who were rebuilding the eleva-
tor. Some of the ideas submitted by this engineer were not in-
corporated in our report as we did not feel sufficiently sure of
some of the proposed changes. We later learned, however, that
in the rebuilding of the plant the construction engineers were
carrying out some of the ideas that we delayed action on at
Washiington. At that time we told Mr. Reed, one of the in-
vestigators, that when we had a conference of this nature we
would give him an opportunity to prepare and discuss ideas
prepared by him or by other engineers through him. regarding
changes in elevator construction suggested by recent explosions.
Mr. Reed will now discuss this subject.

By J. 0. REED.
During the period from May 22 to September 13, 1919, fuur
months, there were five disastrous dust explosions in i odern
and so-called fireproof plants. These explosions occurred in
two feed grinding plants, two grain elevators and olne starch
factory. Seventy men were killed, 60 injured and thle proplertv
loss was estimated at $7,000,000. Due to the fact that such ai
large number of explosions occurred in such a short period (if
time in these plants of the most modern type of construction, it
seems quite appropriate that the subject, "Changes in Ilievatlr
Construction Suggested by Recent Egxplosions," be presented at
this meeting.
As stated before, sonicme of thle plants in which these explosions
occurred were constructed entirely of concrete and steel. I Ic.lvv

walls with very few windows were used in the building structure.
In fact, the building construction of all these plants was of such
a nature that excessive pressures were built up when the dust
became ignited. Long dust collecting and conveying systems
were used in some of these plants, a fact which tended to enable
rapid flame propagation. Because of these frequent and recent
disasters the opinion is beginning to prevail that a modern grain-
handling plant, constructed of fire-resistive materials, if not prop-
erly maintained, is more dangerous from a dust explosion stand-
point than the,old wooden type of plant. In L wooden house an
explosion occurs and blows out one side of the building. Fire

. ':. .....

.."r .. ..-
- ~ew -.wo

Extensive damage resulting from explosion of starch dust.

follows the exclusion, but in a large number of instances the
sprinkler system, if not damaged by the explosion, extinguishes
the resulting fire. In a concrete house, however, the explosion
is very violent because of the high pressures that are built up
within the building, clue to the solid walls. Concrete plants how-
ever, in my opinion, can be constructed in such a way as to
reduce the explosion hazard. The necessity for some change
(f construction is all the more emphasized by the loss of life and
the damage to property.
In the construction of a building to prevent disastrous dust

explosions, provision should be made to prevent high pressures
from being built up within the plant because of heavy wall con-
struction. For this reason the suggestion is offered that the plant
be constructed of very thin walls, a fact which could be made
possible by the use of some wire or sheet metal frame to which
is attached a very thin coat of cement, or, in other words, stucco
wall construction could be used. If an explosion should occur
in a plant built with walls of this nature very little resistance
would be offered to the increase of the volume of gases pro-
duced by the ignition of the dust. In a building designed in this
manner all the working stresses of the building, loads, etc., would
be placed upon the concrete columns and beams used in the
building structure. No stresses or weights would be placed upon
the walls. The walls would only serve as a filler between the
beams and the concrete columns.
As an additional means of preventing high pressures from
being formed within the plant it is also advised that large win-
dow areas be used in the construction of the plant, or, in other
words, the daylight type of building construction be used In
fact, it is suggested that at least one-third of the entire wall area
of the plant be covered with windows. These windows should
be of the steel sash type, should be self-supporting, and should
extend from the ceiling to the floor. Very small panes with the
thinnest possible glass which would not break by vibration should
also be used. Provision should be made for the ventilation of the
plant by having butterfly windows swing open horizontally from
the floor and from the ceiling. As an elevator is usually several
hundred feet high, there is usually a strong wind prevailing at
upper stories of the plant. With these windows open on a windy'
day, from the top and from the bottom, the best possible ventila-
tion would be afforded to the interior of the plant, especially
in the "texas" of the building. There is a strong possibility that
the wind at times would be so strong that a large amount of the
floating dust would be blown out of the elevator through these
windows. In speaking to a man who had worked in a plant in
which windows of somewhat this type were use, I was informed
that on certain days, when there was a high gust of wind blow-
ing, they almost cleaned out the "texas" simply by opening the
In order to prevent the accumulation of dust in a plant in
such a manner that a dust explosion could not become disastrous.
and also for the purpose of making it easier to keep a plant
clean, all ledges or surfaces in the plant where dust may ac-

cumulate should be placed at an angle greater than the angle of
repose of dust. In a plant of this nature no dust accumulations
can lodge overhead. All steel beams and girders should be
covered with cement. As it has been proven that concrete is a
good preservative of steel construction work, its use will serve
as a means to prevent the rusting of the metal framework of the
plant as well as to prevent the dust from accumulating overhead
on the steel beams.
The bin floor of a grain elevator sh uld be constructed flush
with the top of the storage tanks for the purpose of eliminating
thle explosion hazard produced by dust accumulating between
the top of the bins and the bin floor. Dust that accumulates in
such a place becomes very old, dry and inflammable. When an
explosion occurs in some other section of the plant this dust is
thrown into suspension and acts as a feeder to the initial explo-
sion. As the space is entirely open above all the bins an oppor-
tunity is given for the flame to propagate to all the bins and
produce a very disastrous explosion. If, however, the bins are
constructed flush with the bin floor, each bin is separate and an
explosion in one bin is not very likely to propagate to many other
The working floor should be very open with the entire weight
of the building supported by heavy concrete and steel columns.
Only a small percentage of the sides of the working floor should
be covered with walls, and in place of these walls some type of
rolling steel curtain doors should be used, which could be opened
during the day to permit the greater part of the working floor
to be open. Since there is no great amount of machinery on the
working floor, and since there are only a few workmen outside
of the unloaders in the working shed who ever remain on the
working floor, there would be no objection to that portion of
the plant remaining open. Large steel sash windows should be
placed at intervals between the curtain doors to provide light
when the curtain doors are closed.
The storage bins should be as small as is practical. As stated
before, all bins should b! covered and should have perfectly
smooth sides to prevent dust from accumulating, a fact which
was empnliszied by tle explosion in the plant at Port Colborne,
( )itaLrio.
Thle baslement should be constructed only partially under
tle, ground. If, for instance, an 8-foot basement is to be used,
(,oly 4 feet of the basement should be below the ground level.
The 4 feet of the basement above the ground level should be

covered with very thin walls and a large window area. Provi-
sion should be made that these windows could be opened to pro-
vide ventilation and air to the basement. Then if an explosion
were to result no great pressures and no rapid flame propagation
would occur. By placing the basement only partially under
ground, the working floor of the plant would be a slight distance
above the ground level, a fact which would require the cars that
run under the working shed to be run up a slight incline plane to
the working shed. This would have its distinct advantage, in
some cases, for by the use of an incline plane to the plant the
cars could be handled more readily due to the fact that the
engine would push the cars up the plane to the working shed and
the cars could then be easily handled by the workmen simply by
permitting the cars to run by gravity to the unloading pits. If
there are tunnels that run under the storage tanks, provision
should be made that portions of the tunnel be open or confined
only by means of very thin walls or windows. A vent at the
end of a .tunnel could even be suggested.
If by the action of the Boards of Trade and State Ware-
house Commissions suction is not permitted to be used on ele-
vator legs, it seems quite advisable that natural vents be placed
on all elevator legs, bins, garners and scale hoppers in the plant.
Scale hoppers and garners, especially should be vented to the
outside for the reason that when grain is run into a scale hopper
or garner the dust-laden air in the hopper and garner is forced
out into the building. By the installation of a vent the dust-
laden air, instead of being forced out into the building proper,
will be discharged to the outside. If an explosion should occur
in one of the places where there is a vent provided thile vent
would also serve to a considerable extent as a medium to relieve
the pressure created within the place where the explosion occurs.
In the installation of a vent for elevator heads, it would seem
advisable first of all to consider the construction of the elevator
legs. In most of the elevators today the trunking of the ele-
vator legs does not run direct from the boot to the head, but in-
stead, in that portion of the plant where the storage section is
placed, there is what is termed an "elevator well" through
which the elevator belts run instead of in the elevator trunking.
If the elevator building should at any tinime sag or vibrate there
is no guarantee in an installation of this nature that the elevator
head pulley shall remain in line with the pulley in the elevator
boot. At the same time there is a great amount of dust that
accumulates in this "elevator well" which is very difficult to

clean out. With some source of ignition, as for instance a
spark from a bucket or from friction due to an elevator choke
or legs becoming out of alignment, usually there is so much
dust that a disastrous explosion results. As a means of pre-
venting the possibility of the elevator head pulley becoming out
of line with the elevator boot pulley due to the installation as just
described, it seems quite advisable that the entire elevator leg or
trunking be built solid and in one piece from the boot up to the
elevator head. The elevator would then be self-supporting, would
rest upon the floor in the basement, and would not be put out
of alignment by the sag of the building. Heavy steel plate con-
struction would be used for the elevator trunking so that if an
explosion were to occur it would be confined until it reached the
vent at the head. It seems quite natural that the elevator heads,
due to the fact that they are so close to the roof of the building,
should run out through the roof and there be capped by means
of a ventilator of a special design which would serve to ventilate
the lofters and provide an escape for the gas in the event of an
ignition of dust. Natural vents on bins serve several purposes.
They remove one of the greatest objections to the use of the
closed bin, for the reason that they provide ventilation to the
grain contained in the bin while at the same time they provide
a relief for the air pressure developed as the grain is being run
either into or out of the bin. Ventilators of some special type
should be placed over these vents and should be so designed that
sparks from locomotives would be unable to get in. Vents would
probably be of some use in the tunnels underneath the storage
bins where there is always poor ventilation and heavy dust clouds.
It seems to be the tendency in modern elevator construction
to install extensive dust collecting systems which extend to all
sections of the plant. During a very recent explosion the fact
was brought out very conclusively that dust-collecting systems
of an extensive character are very dangerous to have in a plant
because by a lengthy installation an excellent chance is afforded
for the flame to propagate through the trunking of the dust-
collecting system to all sections of the plant. It seems quite
advisable, due to this fact, that instead of one large system being
used for the collection of all the dust in the plant, a series of
small systems should be used. For instance, a separate system
should be installed for the suction floor sweep in the "texas" and
a separate system for the working floor and basement. It also
seems advisable that the fans on all cleaning machines should
exhaust directly into a cyclone dust collector installed outside


of the plant instead of into a main trunking which leads to a sys-
tem of dust collectors. If suction is permitted to be used it seems
quite advisable that a separate system be installed for the aspira-
tion of the garners, a separate system for the scale hoppers, and
a separate system for the elevator heads, etc. If it is necessary
that a main suction trunk of any length be used it seems that
instead of running this trunking through the center of the plant
it should be run on the outside of the plant, for if then an explo-
sion propagates through the dust collecting system it will be car-
ried outside and probably do little damage. In this trunkinlg
outside of the plant some sort of a relief valve could be designed
and installed which would relieve the pressure in the dust-collect-
ing system and vent the explosion, thereby further reducing
danger of damage.
All the trunking of the dust collecting system should be con-
structed in sections so that it is possible to take down the trunk-
ing and clean it out. This trunking should be of such a size that
high air velocities shall prevail in the system for the reason that
no dust is then able to fall to the bottom of the steel tube. All
elbows of the trunking system should have a radius of at least
twice the diameter of the pipe. All trunking should be properly
grounded for static electricity.
Very recently there has been two explosions which originated
in the suction fans used in connection with dust-collecting sys-
tems. This fact would seem to indicate that either the fans were
not constructed properly to reduce to a minimum the possibility
of the formation of sparks within the fan casing, or the fans
were receiving poor care during their operation. To reduce to
a minimum the possibility of the fan blades striking the sides of
the outer sheet-iron fan casing, and to eliminate other fan
troubles, the following recommendations and suggestions regard-
ing the construction of fans arc made for your consideration at
this meeting:
1. The fan blades should be enclosed and fixed securely on
the sides to a sheet-iron casing. The fan hub to which the blades
arc attached should extend about one-half inch beyond this fan
blade casing. There should be a clearance of at least one and one-
half inches between the fan blade casing and the outer fan cas-
ing. By an installation of this nature it seems quite impossible
for a fan blade to become loose and strike the side (f the fan
casing and produce sparks.
2. The hub to which the fan blades are attached should he
fixed to the revolving overhanging shaft by means of two tapered

keys, one key at each end of the hub, the angle between the keys
to be 120 degrees. These keys should be held in place in the fan
hub by means of set-screws which should be screwed into a
small hole or seat in the key produced by the point of a drill bit
after the key is driven into the hub.
3. In regard to the proper maintenance of the fan it appears
quite essential that frequent inspections should be made of the
fan to determine the clearance between the fan blades and the
outer fan casing. For this purpose a door or some other open-
ing should be provided in the side of the outer fan casing to
facilitate inspection.
4. It seems quite necessary that some provision be made in
the construction of the fan to provide for the end thrust of the
fan and for the adjustment or clearance between the fan blades
and the casing by means of collars being placed on the fan shaft
next to the journals.
In making these suggestions regarding the construction of
grain elevators it will be noted I have considered only elevators
constructed entirely of fire-resistive materials, such as concrete,
tile and steel. You gentlemen, due to the fact that recent ex-
plosions have occurred only in plants constructed of fire-resistive
materials, may put forth the argument that elevators should
be constructed of wood, since explosions have not occurred of
late in plants of this type of construction. The following rea-
sons are given in advocating the construction of concrete ele-
1. The depreciation on an elevator built entirely of concrete
is small, while the 5 per cent. a year depreciation on wooden
elevators is a conservative figure. The depreciation and up-
keep of the machinery is much less in a concrete building, owing
to the solidity of the structural supports and the absence of
2. The safety afforded the elevator owner is a matter which
must be considered. The day is past when the elevator can be
replaced within 60 days. exceptional at the present time to
secure the delivery of lumber required for the wooden elevator
construction within that time. In past years almost immediate
shipments could he depended upon from the lumber mills of
northern Minnesota and Wisconsin. Now 90 per cent. of the
lumber must conice from the Pacific Coast.
3. It has been proven that reinforced concrete is the most
flexible of all material in the construction of grain elevators and

storage tanks. It is claimed that 99 per cent. of the larger grain
elevators and storage houses at the terminals, and possibly 90
per cent. of all the fireproof country elevators are now being
built of reinforced concrete. Where grain, earth and water pres-
sures are to be resisted, reinforced concrete is the logical ma-
4. In a recent fire in the concrete elevator of a cereal com-
pany at Minneapolis, the fire resisting qualities of concrete were
demonstrated. On the first floor of this elevator there were
several attrition mills with wooden feed legs, sacking spouts.
reels and conveyors. The fire burned out this installation but
the only damage done to the building structure was a slight
crumbling of the concrete over an area of a few square feet and
to a depth of less than one-half inch, resulting in no serious in-
jury to the strength of the bin bottom. If, however, the bin
bottom slab had been supported on exposed steel beams, which
I have stated before in this paper should be covered with con-
crete for the purpose of preventing dust accumulations from
forming, the heat developed would have been sufficient to cause
the steel to sag and possibly collapse under the load.
In my effort to present the subject of "Changes in Elevatoi
Construction Suggested by Recent Explosions," I have only con-
sidered some of the important changes which I thought necessary.
I have only touched the subject in a general way and have by no
means tried to draw up a code or a detailed plan on elevator
building construction. I desire a full discussion on some of thel
suggestions which I have made and for this reason I wish to
give you a summary of some of the changes I have advocated.
As you have noted, I have recommended that grain elevators
be constructed of fire-resistive materials with thin walls and
large window areas providing good ventilation. 1 lalf-basencents,
or no basements at all; comparatively open working floors, and
enclosed bins have been suggested. The question of vents ton
garners, weighing hoppers, bins, and elevator heads, together
with a change in the installation of the elevator trunking has
been considered. I have advised that the elevator heads be run
out through the roof of the building and vented, and also have
dwelled upon the subject of dust collecting systems only in a
general way by recommending that shorter and separate systems
be installed. I, however, have gone into detail on the lproler
construction and installation of exhaust fans. Lastly, I have
endeavored to show you the economic necessity of reinforceil
concrete elevator construction. It is these subjects which I de-

sire that you discuss and which I think demand some considera-
tion in the construction of grain elevators for the prevention of
disastrous dust explosions.
Mr. PRICE-Mr. Reed has covered this matter very thor-
oughly. Do you concur in everything that has been said about
changes in construction to prevent disastrous explosions from
Mr. BODNAR-In the Northwest I came across two con-
crete elevators, each with a capacity of about 90,000 bushels,
that had a peculiar construction which might help prevent dis-
astrous dust explosions. Each of the elevators had five or six
bins, the tops of which were open to the open air around the
entire upper periphery. The openings were anywhere from 12
to 2 feet high. When the elevator operates so that grain is
falling into the bins the wind or any breeze will clear out and
carry away most of the dust in the air. If there was an explo-
sion on the main floor there would probably be enough.relief of
pressure through the opening above mentioned that no serious
results would occur. One of these elevators is at Walla Walla.
Wash., and the other somewhere in Idaho.
Dr. BROWN-Are the bins all connected?
Mr. BODNAR-Yes. There was no floor on top of the bins.
All of the bins were open. The opening I mentioned might just
as well have been a window area with all of the windows
knocked out.
Mr. REED-In the elevator I have considered the windows
can be closed when it rains.
Mr. BODNAR-The operators of these elevators say they
were never bothered by weather conditions.
Dr. BROWN-Most of the wheat in the Northwest can stand
a little extra moisture.
Mr. PRICE-They leave a foot and a half or two feet be-
tween top of bins and floors?
Mr. REED-I advised that each bin be enclosed. Now in an
installation of that nature, as Mr. Bodnar states, there is no dust
that can accumulate between the bins and the bin floor.
Mr. BODNAR-There is no bin floor in this case, that is,
the bins are open entirely.

Mr. PRICE-There are a number of questions I would like to
bring up. In regard to the matter of thin walls, about how thick,
approximately, should these walls be?

Mr. REED-The walls at Kansas City on the working floor
were about six inches thick. In the construction of the shops
used in the army cantonments and the like, which were con-
structed of concrete, they just placed in between the steel or
concrete colums that were used a wire screen or something of
that nature upon which they squirted a spray of cement, I think
not over one-half inch or an inch thick. When I speak of a thin
wall I mean a wall not over 2 inches thick.
Mr. BRADY-Is there any objection to a brick wall?
Mr. REED-That would be a little too thick.
Mr. PRICE-In addition to this matter of construction, Mr.
Reed also suggested that the working floor be almost entirely
open, a very small percentage covered. His theory is to have
the working floor entirely open with a small part of it covered,
and instead of a basement have an inclined plane to handle the
cars. I would like to present that matter for discussion.
Mr. BRADY-I think there ought to be some work done
relative to fans in elevators. The explosion that recently took
place at Manitowoc shows that a steel fan is something to be
reckoned with in eliminating explosions. Here was a case where
a wire got into a steel fan, made a spark and caused the explo-
sion, a thing that is apt to occur in elevators or mills. Fans, it
seems to me, could be encased in some way so that you would
have a plate on the inside of those fans, and the blades made
of something other than steel, maybe bronze, aluminum or some-
thing of the sort that wouldn't strike a spark when it would hit
along the side of the fan casing. A while ago an explosion oc-
curred in Denver, supposed to have been caused by the fan
running loose and going up against the steel casing. It there
made a spark which ignited the dust in thle dust-collecting Sys-
tern. Nuw this question could be presented to some of the people
that make fans and have them make such provision.
Mr. PRICE-At what points in the elevator would the fans
be located?

Mr. REED-At any point where suction is applied and an
aspirating system used there should be a fan.

Mr. PRICE-The objection has been raised that some State
regulations prohibit suction of any kind between the receiving
point and the weighing of the grain.
Mr. BRADY-You can use indirect suction on the buckets or
elevator leg at any time.
Mr. PRICE-This is all beyond the weighing point, I take it.
Mr. BRADY-The point I want to raise is to change the con-
struction of fans.
Mr. REED-Why not constru t a fan that a piece of wire
can't get into very easily; one that can't work to the side and
produce a spark-one that will not permit the fan blades to
work to the sides? Aluminum is said to deteriorate in air where
there is a great quantity of air being handled. This fact almost
justifies that it be not considered.
Mr. BRADY-Other metals could be used, probably.
Mr. REED-Bronze would cost too much.
Mr. PRICE-The Manitowoc explosion was in an aluminum
manufacturing plant-an explosion of aluminum dust in which
the investigators assigned the cause to a metallic spark caused
by a wire getting into the fan. The cause of the Denver ex-
plosion is debatable. Late developments bring out more doubt
as to whether the explosion was caused by the fan slipping to
the side. It would seem just as probable that it may have
started in the rolls by sparks from foreign materials.
Mr. BRADY-On the subject of the fan, I am not quite clear
on the inner casing that is referred to.
Mr. REED-The fan hub is keyed to the overhanging shaft
by two keys, one at each end of the hub, the angle between the
keys to be 120 degrees. The fan blades are enclosed and are also
placed at an angle, a fact which I think is good construction.
Mr. PRICE-What is the objection to it? Is it a good idea?
Mr. BROWN-I understand that the blades of the fan are en-
closed by a plate at each side. How are you going to get the
dust out of the fan after it goes in?
Mr. REED-It comes out at the end that is not enclosed.
Fans are being constructed that way today.
Mr. BROWN-Where does the dust go in?
Mr. REED-Into the eye of the fan.

Dr. DUVEL-The ordinary fan has two bearings, doesn't it?
Mr. REED-Yes. They are at one side of the fan casing.
I am not speaking about an extra large fan. Almost all small
fans used today have the overhanging shaft and all the bearings
on one side of the fan casing.
Mr. ROETHE-Is that a multi-vane fan?
Mr. REED-No.
Mr. PRICE-We, generally, agree with the idea Mr. Reed
has brought out, if this fan is going to solve the trouble. We
have gotten just a little away, however, from some other feature.
relating directly to construction. Mr. Reed said that he knew
of an elevator in Baltimore where some of the ideas suggesteCd
were being carried out. What elevator is this, Mr. Reed?
Mr. REED-The Mount Clare Elevator operated by the B. &
0. Its capacity is about 500,000 bushels.
Dr. BROWN-I might state my views in connection with
some of the points that have been brought out, although slightly
divergent from the last two or three points of which Mr. Price
has spoken. The one with the basement largely above ground-
level appeals to me as something well wortli while. The Purt
Colborne elevator-Government elevator at Port Colborne-
was so constructed. In fact, there was only about two or three
feet below the surface and about ten or twelve feet above the
surface. There was a window surface of the wall of easily,
I should say, two-thirds of the portion of the wall above ground,
but the interesting fact, as I will try to bring out in the review
of that explosion tomorrow, was that the windows were drawn
in and not blown out. The explosion was nut in the basement, but
should it have been in the basement and propagated through the
basement, there certainly was enough window slace and w'uak
construction to have vented it and the remaining jprtiun of llthe
construction was probably sufficiently strong Ito have licd1 the
pressure that might have been built up back uf thi su-c;illcd
light construction. If we are going to advocate' light cUonstruc-
tion for side walls our super-structure would have to be of very
heavy structure to withstand the force. If we ihave a proper
mixture of dust andl air to give us thle most intlaniimable du-t
and air mixture, thle rate of Irmaigatiouln andi the presure de-
veloped in the expi',sion is g, ini to be so ins,,tantaLneous that we
are going to get a sudden destruction of everything unless a very

large area of the structure will give way easily and the smaller
portion will be of sufficient strength to withstand, for a short
time at least, that excess pressure.
In regard to the open structure and especially in the "texas"
that question was considered very seriously in connection with
the Port Colborne disaster and was brought up at the hearing
held in Port Colborne sometime after that. It seems to me,
although we probably do get a certain amount of ventilation and
a certain amount of the dust carried out, that if we have enough
dust present in suspension in the elevator so that seemingly a
large enough quantity must be carried out to reduce the hazard,
we certainly are going to get a sufficient quantity accumulated
to make a very dangerous condition. Unless the walls are light
and largely open we are going to have enough pressure developed
in case of an explosion to be very dangerous. In the elevator
at Weehawken the walls were of very light construction, might
say, above the bin floor. To the roof of the bin floor the walls
were of brick and about 8 to 10 inches thick. The "texas" walls
were of 4-inch hollow tile. The side walls of the bin floor with-
stood all pressure developed and were not pushed out to any
extent, but the walls of the "texas" were largely blown down.
I was in that elevator only a short time after the explosion hap-
pened. They had not cleaned up at all and there was only a
very small quantity of dust accumulated anywhere. It was in-
teresting to note the path of the explosion through the "texas."
On some of the girders the dust on three sides had been charred
while the dust on the other side 'was not charred. There was
some dust on this side but not much. There was a normal quan-
tity of dust on the sides of the elevator and the floors were quite
clean. This illustrated to me the ease with which an explosion
will propagate through a comparatively small quantity of dust,
seemingly, which may have accumulated on the side walls or on
the beams, etc. There was no evidence of dust on the beams in
this Weehawken elevator and the side walls were very clean.
I have never been in but one elevator which was cleaner.
Mr. BODNAR-In two elevators of about the type I have re-
ferred to, I have found Mr. Reed's idea carried out in so far as
the well or manlift shaft of the elevator is concerned. This well
was constructed of wire netting covered by concrete not over
one-half inch thick. These two elevators are in Idaho.
Mr. McCOLLAM-In regard to Mr. Reed's point' about
eliminating elaborate dust-collecting systems, in an Ogden ele-

vator of one-half million bushels capacity, the only dust-collect-
ing system is their battery of cyclone dust-collectors on the
cleaning machinery. This is located on the outside of the ele-
vator. No suction is applied anywhere in the elevator. They
have a very tight job of millwrighting throughout the elevator.
Every joint in the steel elevator legs is packed very tightly with
felt, and all other joints in the scale hoppers and garners are
likewise packed very tightly.
Mr. BATES-I would like to ask if this thin wall suggested
of stucco on metal lathing isn't supported between ihe spans as
is ordinary siding?
Mr. REED-If I remember correctly they put this wire up
with very little support at all. Immediately back of the wire
they put up heavy boarding and shot the concrete right up against
it with a cement gun.
Mr. BATES-Unless these spans are short, such a wall would
not sustain a very great pressure from the outside, as in the case
of a high wind, and in that kind of construction at any place
where there was weight or constantly changing pressure you
would expect it to crack and give trouble.
Mr..REED-I think there was some siding.
Mr. BATES-Would it not be well to recommend light con-
struction between the framework of the supports, nut attempting
to say what that light construction should be, in preference to
giving our ideas in regard to any particular structural design?
If we attempt to specify definitely shapes and thickness we are
bound to get into trouble.
In Mr. Reed's suggestions hlie brought out some very inter-
esting points in fan design. I believe whatever is given to the
industries in the way of specifications should be very general. In
fact, in that kind of fan there is no way you can hold the pro-
pellers from slipping to the outside, because if the fan bec(illles
loose on the shaft the shaft does not go through the fan hub.
The idea of making the blades narrow at the tip is to keep the
velocity of the air the same at all points, which is desirable,
especially in high-speed fans.
Mr. WAT'lERS-In regard to the stucco construction Mr.
Reed spoke about, it may be all right on upper stories, but in an
elevator it is just as necessary to try to eliminate fire from the
outside. If there is a fire nearby you wett thdown iie elevator

to keep the fire from coming in contact with the elevator. In
that case those stucco walls will under no condition stand any
pressure of water. They would therefore not be very appropriate
on the first floor.
Mr. REED-You are talking about fireproof construction.
\What we are considering is explosion proof, not fireproof con-
Mr. VWATERS-Stucco of that sort would not be fireproof.
Mr. HELMKAMP-I doubt if it would stand some of the
winds in Kansas.
Mir. REED-A wall could be designed to withstand the wind
pressures. Wind pressures are not as great as explosion pres-
Mr. BRADY-You could niake it of solid concrete, could
you not?
Mr. PRICE-I think a more practical construction would
probably be a medium between the very thick construction of
the present and what we are considering here.
Mr. HIELMKAMP-In connection with this thin construc-
tion on the working floor, the Murray elevator at Kansas City is
being constructed with that in view. They also have the tun-
nels equipped with five vents, one at each end and three be-
tween the bins.
Mr. FRITZ-I have taken quite an interest in your discus-
sion of the explosion at the Murray Elevator. Two years ago
this month I was working at the elevator, conducting investiga-
tions relative to the invisible loss occurring in dried corn. Part
of our work was to detect, if possible, the amount of loss that
occurred in handling corn in the house, that is, loss that could
be accounted for as dust. As a part of our work, we decided to
try to dleternmine the amount of dust that collected per square
yard on each floor for the duration of twenty-four hours. It
was deemed advisable to leave the customary number of doors
and windows open on each floor. A square yard of paper was
placed at different places on each floor and allowed to remain
there for twenty-four hours. At the end of the period the col-
lected dust was weighed and recorded. It was found that there
was a more or less regular increase from the scale floor to the
ground or working floor. The point I wish to emphasize is that
this substantiates the recommendations of the gentleman who

just talked to you concerning the advisability of having numerous
windows and doors in the future elevator construction. The scale
and garner floor of the Murray Elevator had many windows as
did sbme of the intermediate floors. When these were open
most of the dust was carried out by the air currents and only
slight effort was necessary to brush the sills and girders. On
the working floor the situation was entirely different. There
being fewer openings, the dust could not escape as freely be-
cause of the lack of openings to allow air currents to pass through
and consequently most of it settled on the beams, floors, etc.
Mr. PRICE-The explosion in the Murray plant started down
in the basement where the large quantity of dust was present.
Dr. BROWN-I would like to hear some discussion on the
question Mr. Reed brought out, of extending elevator casings
out through the roof. My reason for interest in that is that I
made that as a possible recommendation in the case of the re-
building of the Port Colborne elevator.
Mr. BRADY-A construction of that nature is now being.
used in some of the oat plants, as I understand it. A cereal
company in the Middle \Vest are capping the legs in their plant.
They have had some explosions in these legs since they capped
them. The cap would blow off and not do any damage to tihe
Mr. HIBBARD-The Milwaukee explosion took place on tlhe
main floor and the elevator was constructed of steel plates but the
explosion was so strong that it blew the plates out and tore tlhe
bolts out and they had another explosion at the top.
Dr. BROWN-That would be a question of pressure and ve-
locity developed. With the most inftlanmnable mixture (of dltt-t
and air probably the pressure exerted ulpward w" uld overcmtiic the
air pressure and the inertia in thle dead air w'uld be so tireat
that the side walls would blow out and not ovcrcroie the Ivizar-d.

By AMR. P. I". BRAD'Y.
Choke-ups in elevator legs occur frequently. The four coin-
mnon causes for such occurrence's are: (1) O)verhladiing; (2)
Bins becoming full; (3) Belt plugged by fior'-*in material; (4)
Power going off.

The over-loading feature is generally caused by a mechanical
defect in that the belt and cups used to carry the load away from
the boot are sometimes too small to take care of the incoming
grain. Conditions of this kind do not often take place, but in
some instances these facts have been brought out. One instance
of this developed during an investigation of a dust explosion
which occurred in a large starch factory in this country. It de-
veloped that this company was using a large conveyor which
emptied into an elevator boot and elevated through a leg. When
this conveyor was loaded to full capacity the boot or leg was
not of ample size to take the product away. Consequently a
man had to be employed to gauge the flow of the material in the
conveyor and it was his'business to see that this conveyor was
never loaded to a degree whereby it would choke the leg. Of
course, such conditions are most inefficient as well as dangerous.
At times it was known that this man had permitted the con-
veyor to be over-loaded and thus a choke occurred in the eleva-
tor leg. This kind of an occurrence could be remedied by putting
in the proper sized leg and cups to elevate the material which
might come from such a conveyor when the conveyor was run at
full capacity. Defects of this nature can be remedied by proper
mechanical installations. Such occurrences do not take place
frequently in the average mill or elevator, but mention is made
of this fact to show one of the causes of choke-ups.
At times a choke-up occurs when the bins become full, the
spout leading to the bin backs utip into the elevator head, causing
the grain to back-flow into the boot. This is one of the common
causes of elevator choke-ups, especially in country elevators. The
average country elevator is run by one man and he does not get
up to the top of his house as often as might be expected. Con-
seq(juently hlie is not always familiar with the amount of grain in
the bins. Ile invariably is very busy and sometimes these bins
become filled up. The spout leading to same fills up and event-
ually the grain starts to run down the elevator leg and a choke-
up occurs. There are two ways for eliminating these occurrences.
The first is by putting in a bin alarm system. This consists of
a device which is attached to the top of the bin. When the bin
becomes filled with grain this device automatically gives a signal
warning. It is operated by electricity and the warning is given
by the ringing of a hell on the work floor. Another way to
overcome a choke-up is by placing what is called a signaling
distribtutor on tile spout which leads to the bin. As the spout
fills utip it chokes back into the distributor, or, in other words, an

overflow device. This overflow may be emptied to a floor or any
suitable receptacle. The operator can easily see this falling
grain in most any part of the work floor, or hear it rattling down
the tube, when he immediately shuts off the grain and the flow-
age stops. He then shifts the spout to another bin. Various
turn-heads or overflow signaling devices are on the market, all
of which are working to a fairly satisfactory degree.
Sometimes the return spout, the non-chokable head, is run
into a relief chamber. When the bin is full the return spout dis-
charges into the relief chamber which fills to the point where the
downward pressure equals the sidewise pressure in the supply
spouts, thereby shutting off the supply of grain. This feed will
handle any kind of grain and prevent chokes from over-feeding.
Another automatic shut-off for an elevator leg is also in use.
When the spout at the head of the elevator has filled to an over-
flow, the grain then runs down into the balance cylinder. The
weight of the grain bears this cylinder down and automatically
closes the gate in the elevator boot, thus stopping the flow of ma-
terial into the elevator. An electric signaling device is sometimes
attached so that a bell rings when this cylinder becomes filled
and moves its normal position.
Sometimes sudden shut-downs in elevator legs occur. This
happens when the cups are full of grain. This results in a
choke-up, back-legging causing it, that is. the belt starts to drop
down instead of going up. Back-stop devices have been brought
out which operate automatically, immediately acting as a brake
on the head pulley when it starts to revolve opposite to the way
it is supposed to run. This is simply an automatic brake device.
Various kinds are used and arrangements of this kind should be
encouraged, as choke-ups are caused frequently, especially on
electrically-driven legs, by what is known as back-legging.
It appears that more research work should be done along the
lines of providing better equipment for the prevention of choke-
ups in elevator legs. The average house today takes no precau-
tion for such occurrences. The elevator contractors and con-
struction companies pay little heed to devices of this nature, and
it appears that some work could be done whereby these various
concerns and engineers could get together and form some kind
of a standard code with reference to equipment of this nature.
Mr. PRICE-This subject is a most important one since a
large number of explosions have occurred from "choke-ups" in
elevator legs.

Mr. DEDRICK-The point brought up by Mr. Brady in
regard to the choking of elevators is one in which I am very
much interested. An elevator can be choked down gradually as
the result of a poorly constructed or defective elevator head
discharge, or when by reason of too great a speed, the grain is
discharged or thrown with such force that it strikes the forward
end of the head, rebounds, and falls down the back leg.
A certain quantity of grain thus keeps returning over and
over all the time the elevator is in operation, and in the course
of an hour or two will become gradually overloaded and then
choke down, unless the grain from the intake spout is shut off
to relieve and allow the elevator to clear itself.
I have had elevators choked down simply by strings lodging
on the tongue (a projection above the throat or discharge and
between it and the back leg). They piled up so high that a stream
of grain or other stock, discharged from the cups, would not
wholly clear this obstruction and, meeting with this obstruction,
would fall down the back leg.
\When at such times grain or any other material falls down
the back leg it induces air pressure within the leg and causes
what is called "blowing," producing a great deal of dust which
is emitted from any opening in elevators, spouts, etc. This
"blowing" serves notice that something is wrong and that there
is danger of a possible choke and stoppage of the elevator belt.
The point of discharge, that is the throat, may be too high and
cause more or less trouble and choking down.
I have had a few cases where I was called in to rectify the
matter and found the throat was utip so high that the grain would
not discharge properly; that so much grain would go down the
back leg that perhaps in a half-hour's time or even less, the
elevator would be choked down. unless relieved in time to avoid
it. and then allowing the elevator to clear. The method of re-
lieving the elevator and preventing a choke down when the dis-
charge spout is filled or clogged up at the head, by allowing the
grain to flow down a spout the opening of which is above the
(logged point, and this relief spout led to a point into the intake
spout at boot and just ahead of it, so that the returning grain
will flow in ahead and cut off the original feed, thus allowing
the returned grain to make the round over and over until the clog
at lIcad is cleared, is very good indeed. However, I think the
best i ethod is to have an automatic arrangement in which the
fvcd is cut otT entirely, that is. the grain from the release spout at
the hl'ad flowing into a receptacle or pivoted box that under a

given load or weight will operate a lever or series of levers con-
nected to the slide of intake spout and close it, allowing the ele-
vator to clear itself of all grain, the box being large enough to
accommodate the excess grain. I think slides could be thus ar-
ranged to be closed automatically the same way, whether the
grain is led into the boot at front, back or side.
The choking down of an elevator is, I think, one of the most
dangerous features for causing fires and possible explosions in
a grain elevator, flour mill, or any cereal plant. I know of a
number of cases where the choking down of the elevator has
started fires.
Mr. PRICE-Now you men have been in many plants the
last few years, and I am very desirous to know if you have been
in plants where they have installed any of these devices, or some-
thing similar. If so, which is giving the best results that could
be obtained in connection with choke-up troubles.
Mr. WITMER-In the new Pennsylvania Railroad elevator
at Baltimore, which is under construction and not yet in com-
plete operation, they have a device installed which is supposed
to take care of the elevator going back, or a back stop. The
elevator has not as yet been tried out sufficiently to say whether
it will work successfully or not. They have only run about
100,000 bushels of grain in order to try out the machines. I have
been told that when this plant is completed it will not only be
the largest grain elevator on the eastern coast, but will have
the latest and best equipment obtainable. In other words, the last
word in elevator construction.
Mr. HIBBARD-In the new plants that are built in the west
they have separate motors, and when a choke occurs in the eleva-
tor it breaks a circuit and throws the motor off.
Mr. PRICE-We understand the Public Elevatir at New Or-
leans has been using a device of this nature.
Mr. BROWN-I do not recomnnuend this installation at this
time. I understand f'roim Mr. San ford, the superintendent, that it
is his own1 invention alMil lie is eIdel(avo'ring tot get a patent on it.
I can give you a lbritf des-riptiion oft the systeni. 'Thle elevator
is run by one itor andt tiCte t',iivLC i- carrying grain to the (leva-
tor is run by a separate imitior. .An idlcr pulle' on 0 the tIlcV'ator
belt is counected to a steim engine1 goetror. Ill case tf a chike,
the elevator lelt slows down; at the same time the governor
drops and breaks thlie circuit to the o1(itor running the cmonveYtr
which carries the grain to the l)oot tif the elevator. In tins way.

before the elevator belt has had a chance to stop or choke, the
grain being carried to the boot is stopped and prevents the boot
being filled. This elevator also has a stop at the top to prevent
the buckets running down and carrying grain back to the boot.
As soon as the trouble has been remedied, the elevator is started
again. In fact, it must be started before this automatic contact
is thrown in by the governor. As soon as the elevator is again
in operation, the belt conveyor can be started and the grain ele-
vation continued as before. I do not know whether I have made
myself clear on this matter. This installation, I believe, is the
only satisfactory installation that I know of in the country and
is fool-proof.
Mr. RILEY-In regard to the non-chokable leg mentioned by
Mr. Brady, I wish to state that I visited this plant and saw this
leg in operation and I understand that it has been in use for
some time and is giving satisfaction. Housed in at the back of
the leg, just below the spout leading from head of leg, is a metal
bucket held in position by a weight or counter-balance attached
to bucket by a short piece of bell-cord, this cord passing over a
small pulley placed at one side of leg. This weight or counter-
balance exceeds the weight of the bucket by fifteen pounds. The
bucket is attached by steel cable to tension pulley of belt drive,
driving screw conveyors that convey grain to leg. If the bin that
leg is discharging grain to becomes filled, and grain flows back
into leg from spout leading to bin, this bucket receives it and
as soon as weight of grain in bucket exceeds weight of counter-
balance, bucket drops down and automatically draws tension pul-
ley away from driving belt of screw conveyor that conveys grain
to leg, allowing driving belt to slack and thereby stopping con-
veyor. Stopping of conveyor automatically shuts off flow of
grain from spouts leading into conveyor, as these spouts lead
into the side of the conveyor instead of to the top as we usually
find them. The capacity of this bucket is approximately 600
pounds of grain and this grain passes out through a three-inch
hole in the bottom of bucket where it falls into leg and is carried
to head of leg where it again falls into bucket and this continues
until spout is set for another bin, when grain in bucket and leg
is discharged into it and bucket automatically resumes its normal
Mr. PRICE-Mr. Riley sent a report to Washington regard-
ing this installation and we felt that it was giving satisfactory

Dr. BROWN-Whenever we get a choke in an elevator, we
get friction at the head, and I should like the opinion of sonime
one as to the practicability or effectiveness of sprinkler heads in
elevator heads to extinguish the fire, or to prevent excess heat-
ing which may result from a choke.
Mr. HIBBARD-It takes about 170 degrees Fahrenheit to
open a sprinkler head, and by that time the whole plant would
be on fire. The sprinkler head, as a rule, is set out at a side
with an opening between. It is not directly over the pulley.
Dr. DUVEL-Would it not be possible to provide elevator
heads with a thermo-couple adjusted so that when the tempera-
ture resulting from friction approached the danger point, the
elevator would be stopped automatically. Such a device could
probably be used in connection with or as a supplement to sprink-
ler heads. I appreciate that elevator foremen, in case of a choke,
are frequently inclined to force the machinery in order to relieve
the choke, but I believe in most instances, if they can be nude to
fully appreciate the hazard surrounding such procedure, they
would prefer to stop the elevator and remove the cause of the
choke rather than to take the chance of an explosion. This. of
course, involves a long and tedious process of education.
Mr. HIBBARD-The sprinkler head has to be out of the
way because if it comes in contact with the buckets it is likely to
be broken open and flood the leg. That is why they set it )lit to
the side with an opening into the elevator head.
Dr. BROWVN-You can set it directly above the pulley, I
Mr. McCOLLAM-In this connection I might call yuir at-
tention to an installation in California. It seemed a very clean
installation when it came to put out a fire. You might call tlhein
gas heads; that is, carbon dioxide tanks were attached to tli,
elevator head. In case of fire the fusible heads were niclttl and
the carbon dioxide flowed into the elevators andl. of course, S.t-
tied, being heavier than air, and put out the fire.
Mr. PRICE-The P'acific Coast has evidently tried tILhe ut of
inert gases very effectively.

I will try to tell as briefly as possible the relation between
Flat-warehouses and Elevators with respect to Grain Dust Ex-
plosions as these types of grain handling houses appear to me
from personal observation.
In the Pacific Northwest I had occasion to visit many Flat-
warehouses that handled flour and grain stocks of the U. S. Grain
Corporation. Most of the warehouses had cleaning-houses
equipped with about the same type of cleaning machinery that is
found in the ordinary elevator so that similar conditions prevailed
in the former as were found in the latter kind of grain handling
In warehouses without any grain handling or cleaning ma-
chinery, which fact implies the creation of very little or no dust
as compared to the elevator, it seems to me that the chances of a
dust explosion are very slight or remote. In case of a serious fire,
a warehouse of the above type, handling flour, would have an
explosion risk where one handling grain alone would not. The
bursting of flour sacks piled as high as they are (have seen them
as high as 13 feet at least) could very easily cause heavy dust
clouds with the resultant explosion risk. The bursting of grain
sacks under similar fire conditions would be unlikely to create
enough dust for an explosion.
The cleaning section of the plants visited was usually found in
about the center of the warehouse. The machinery, elevator legs,
spouts, etc., are more or less exposed to the interior of the ware-
house so that in walking through the warehouse much of the
machinery is visible. It is the desire to consider these types of
warehouses with respect to the following feature, that is, the
amount of exposure of cleaning house above the top of the ware-
house proper. The cleaning section of the first type is so open
with respect to the interior of the warehouse that even though
there is a sufficient quantity of dust accumulated on the spouts
and other ledges to propagate an explosion, the explosion could
hardly do much damage in so far as the demolishing and hurling
of material by the force of the explosion is concerned, as would
be the case were thle machinery enclosed to the extent it is in an
The remarks made with reference to this cleaning house will

apply with equal force to the portions of the cleaning houses in
the other two types that are below the roof of the warehouse
proper and exposed to the interior of the warehouse. So far as
an explosion is concerned about the same thing-would happen in
the parts of the cleaning houses above the roof of the warehouses
as would happen in the ordinary wooden elevator that was dusty
or had dust accumulations to propagate an explosion.
The cleaning house in the first type is not equipped with bins
such as are found in the wooden or concrete elevator. The other
two cleaning houses are equipped to handle or store grain in
bulk on a small scale, (up to about 10,000 bu.) that is, grain
received in sacks, after being cleaned, is held in storage for
short periods. The arrangement for discharging the grain into
the bins is the same as that of the elevator. Ordinarily the grain
is resacked as fast as it is cleaned. When this is not the case the bins
are used and there is therefore the same danger of an explosion it.
the bins of the cleaning house as there is in the bins of the
With reSpect to the bins and choke-ups in the elevators the
same precautions therefore apply for prevention of dust ex-
plosions as apply to the elevator. With those we are familiar,
so there is no need mentioning them at this time.
The cleaning section of the warehouses visited was rarely as
high as the country wooden or concrete elevator of about forty or
fifty thousand bushels capacity, and no manlifts such as are com-
mon in elevators were found. Consequently they have nothing
that resembles that part of the elevator commonly termed the
"well." Any explosion occurring in the bottom of the cleaning
house could not travel up through a "well" as was apparently
the case in a recent explosion in the Middle \Vest. In my visits
to elevators it was not unusual to find the "wells" of elevators
pretty dusty compared to other parts of the plants. In case of the
cleaning-house of the flat-warehouse it is therefore an advantage
to have no "well" in which dust can accumulate to produce an
explosion hazard.
A fire originating from a dust explosion (or from any other
cause) in the vicinity of the elevator heads is more easily, or rather
more safely reached in the case of the cleaning house than in the
case of the grain elevator. The stairways of the former are
arranged in the order they are in a flour mill of about two or
three hundred barrels capacity. In quite a number of the elevators
visited I heard operators declare that if a fire ever started in the
cupola of their elevator, the fact that there was a sufficient fire

equipment in the top of the elevator, would not be an inducement
to go up the manlift to the top to extinguish the fire. The ob-
jection seems to be the fact that the manlift is ordinarily sup-
ported by means of a fibre rope. The flash of a dust explosion
could very easily ignite the rope and it would be consequently
quite hazardous to attempt to put a fire out in the top of the
elevator. A fire starting from a source other than a dust ex-
plosion would naturally create the same condition but probably
not as quickly, depending upon the circumstances.
From the standpoint considered the elevator is therefore not
as desirable as the cleaning house of the flat-warehouse. A
suggestion pertinent here is: Equip elevators with the manlifts
braced with metal and then supported by steel cables instead of
fibre rope.
With one exception the cleaning houses in the flat-warehouses
of the Northwest were much cleaner with respect to dust than
either the wooden or concrete elevators taken as a whole, and
consequently the explosion hazard was less, and will continue
so providing the above condition remains true.
The points brought out in the above discussion are about as
1. On account of the open style of construction of the
section of the cleaning houses beneath the roof of the ware-
house proper an explosion in the cleaning house at this floor would
not result in as much direct damage from the explosion as would
be the case in an elevator.
2. Flat-warehouses of the type found in the Northwest have
the same danger of dust explosions in elevator heads, bins, and
upper floors as the wooden or concrete elevator (when the clean-
ing houses are equipped with bins).
3. On account of the fact that the cleaning houses of ware-
houses have no "wells" common to elevators, explosions occurring
in the former on any floor have no easy access to other floors,
except through elevators and stairways if these are not closed by
4. On account of the use of manlifts supported by fibre
ropes the elevators present more danger when it comes to putting
out fires in the cupola of the elevator than do the cleaning houses
with fire at a similar point.
Mr. PRICE-Here is a chance to find out something about
the Pacific Northwest. Are there any questions you would like
to ask Mr. Bodnar?

Dr. DUVEL-If the elevator managers are aware of this
danger I would think they would use a wire cable on the manlift
or elevator instead of ordinary rope.
Mr. BODNAR-I have seen that arrangement in two ele-
avators in Idaho. In the elevator at Moscow, Idaho, the man-
lift is equipped with a wire cable about three-eighths of an inch
in diameter, which is quite flexible and serves the purpose I had
in mind.
Dr. DUVEL-It seems to me if they recognize they have
that risk it would be one of the first things they would take
care of.
Mr. BODNAR-I went into an elevator and found a fire ex-
tinguisher on the top floor only. It had not been in use for
years. The operator said if they had a fire in the basement he
wouldn't run up to the top floor to get the fire extinguisher, or
in case of a fire in the cupola he would not go up to attempt to
put the fire out.
Dr. DUVEL-I suppose that was for the benefit of the in-
surance company?
Mr. PRICE-Are there any further questions on the dis-
cussion of the flat-warehouse matter?
Mr. REED-I would like to ask a question. Are the cars
loaded by means of sacks or is the grain shipped in bulk?
Mr. BODNAR-The grain is shipped in bulk and sacks to
the mills on the coast and is ground there. The coast is learning
to handle grain in bulk more and more than it has been doing,
and it is just a question of time when they will not handle any
more in sacks. In my recent visits to the country I noticed many
new concrete elevators in the course of construction. These cer-
tainly are signs of the breaking away from sack handling of
grain in favor of the bulk method.

In making inspections of the mills and elevators in Wisconsin,
Illinois, Michigan, Indiana and parts of Kentucky it has been
my fortune to come in contact with varied types of managers
and superintendents. Some of these were very skeptical, espe-
cially the man who has been in the business for a great number

of years and having no accidents. The other class were those
who, having read about the dangers from dust explosions, were
anxious to co-operate in every way possible to prevent them.
It is with the first class of men, or the skeptical ones, where
I have received the most opposition, that I have been able to
accomplish the most good. The same has been true in my own
case, as I was keen to see any defects or conditions in the plant
to prove my argument and bring home to the operator the seri-
ous condition that existed.
I have in mind one superintendent of a large elevator in par-
ticular in Chicago, who has been in the business practically all
his life and was pensioned by the operator, but is still handling
one of their elevators. When I made my first visit to the plant,
while giving a demonstration of a small explosion and a short
talk to the men, the superintendent did not regard the dust situa-
tion as serious. He showed me every courtesy possible. It was
not until after the explosion at the Murray elevator in Kansas
City, when I returned to this same party and was giving him a
few details of the explosion and showing him a few photographs
of the destruction wrought by the explosion, that he finally
acknowledged the dangers existing from an accumulation of dust.
In order to withdraw gracefully from the argument, he wanted
me to understand that he had reference to an explosion caused
by spontaneous combustion in the dust, which we know is im-
The most helpful experience that I have had was that fol-
lowing the explosion at a feed plant and elevator in Milwaukee,
Wis., in Mlay of 1919. It was a disastrous explosion, killing
three men, injuring four, and causing a? property loss of about
one hundred and fifty thousand dollars.
The management thought that after erecting a concrete and
steel plant they had taken all precautions necessary for their
employees' safety as well as their own. They had overlooked
the explosion hazard and had no appliances or system to take
care of the removal of dust created in the handling of grain and
feed materials in their plant. It was while I was making the
investigation of this explosion that the management came to me
and made the request that when the plant was rebuilt they would
appreciate any help that we might be able to give them. Several
months later they notified me that they were about ready to re-
build and desired to have me make recommendations as to the
points at which suction should be applied and other explosion
preventive measures to be used. These requests were complied

with and suction was applied to the elevator boots, elevator
heads and to an expansion chamber on the screw conveyor which
received material from the attrition mill. The other safety mineas-
ures installed were a choke valve in the screw conveyor hold-
ing back a certain amount of material at all times to prevent the
spread of any explosion that might occur in the attrition mill or
other parts of the system, and a release pipe leading direct from
the screw conveyor to the outside to relieve any pressure that
might be created by an explosion in the system.
About thirty days after this equipment had been installed
an inspection of the plant was made and it was found in the
very best of condition; the suction system was collecting approxi-
mately eight grain sacks of dust and fine material per day, which,
without the suction system, would have been scattered through-
out the plant creating a dangerous condition and requiring con-
siderable labor. Where we find a dusty condition existing in a
plant it is usually laid to the scarcity of help.
One other experience noted in a Chicago elevator helps to
prove that a dust free elevator or plant is practically explosion
proof. It was in the evening just following the closing down of
the plant when fire was discovered on the distributing floor of
the elevator. An alarm was turned in and on the arrival of the
fire department the fire was quickly extinguished with a very
small fire damage. Upon investigation it was found that the
fire originated from an overheated bearing on one of the rollers
underneath the distributing belt. It was communicated to a
wooden frame work and from there to the cleaning machine,
which was mostly destroyed by fire. Previous inspections showed
this plant to be in very good condition and it is probably due
to this fact that there were no explosions causing heavy losses.
Mr. PRICE-It may be that the men who have made inspec-
tions have had experiences somewhat similar to those referred
to by Mr. Hibbard and we have sufficient time for discussion
of this subject, or any other subject taken up this afternoon.
Dr. BAILEY-I take it as the consensus of opinion that
when a series of bins occur in a plant it is advisable to cover the
bins and vent them through the roof with a steel or galvanized
iron vent suitably capped.
Dr. BROWN-I made that suggestion at Port Colborne.
Mr. McCOLLAM-May I add that it seems to be the gen-
eral tendency in modern elevator construction, as far as I have

observed, to use natural ventilation as far as possible? I will
call your attention again to the elevator in Ogden which has no
dust-collecting system to speak of at all. The garner and scale
hopper are both vented by means of a very large vent to the
open air. This is supposed to take care of the dust hazard.
Dr. BAILEY-Each one of these bins should have its own
distinct vent.
Mr. HELMKAMP-I have run across some elevators in
which the conveying belts seem to be pretty close to the floor.
It would seem that if they would raise these belts possibly six
inches it would be easier to sweep out and this change would
not incur much additional expense.
Mr. DEDRICK-The venting idea is good. I think the same
results could be accomplished by a suction system and dust kept
within certain limits and from getting out of machines, spouts,
elevators and other openings. The suction would pull the dust
out and away from bins, elevators, etc., at once, without allow-
ing it to float within the building. The fan drawing the dust
should exhaust into dust collectors, preferably outside the build-
There should be direct suction at every point where, in the
course of operation, dust is made, and liable to escape and to
spread throughout the plant. For instance, I would carry a suc-
tion trunk with a hood right up to the car door and over the
dump grating. This would take a great deal of dust right at that
point, and leave that much less to be contended with after the
grain entry in the elevator or mill. In the ordinary elevator
much of the dust made at the unloading chute blows into or
enters the building.
This can be accomplished by having just enough suction to
pull nothing but the light floating dust away and keep it mov-
ing toward the hood. The elevator heads might be built higher
beyond the circle described by the moving belt and cups, and
there at the top, at discharge end, instead of the ordinary suction
spout with its small opening, have the suction spout opening ex-
tend the full width of top and back a ways. This could be
accomplished by flaring the spout so as to cover this opening.
Tlhis would give more spread or surface to the drawing current,
at the same time weakening it so that it would be less liable to
draw good material with the dust, as happens with a small open-
ing with a concentrated current that draws more heavily at the
point where the grain is discharged as the belt and cups move

over the head pulley. To avoid any possibility of good grain
or material being drawn up, baffles may be placed inside the
elevator head below the suction spout opening and the discharged
grain thrown in a spray, thus preventing a direct current acting
on the grain.
At the trip is another source of much dust. This dust can
be taken care of by placing a suction hood over the point of
grain discharge. A suction trunk should extend the whole length
of the elevator bins and tanks. Stubs would allow of making
connection with a trunk attached to the trip that extends on both
sides of trip over the bins on each side of the gallery or belt
carrier. To the ends of the trunk, hoods (inverted cones) could
be attached, one on each side of trip. These hoods need be only
part size of the open bin, but placed somewhat above the open
bins. The suction current should be strong enough to draw the
dust as it arises from the bin when being filled, and thus keep
the dust within that zone or area until it reaches the hood.
This idea can be carried out on the working or unloading
floor, by having the unloading carriage movable like the trip,
with a hood over it to be attached to a main suction trunk over-
head, similar to the one at the top. A hood should be placed at
the discharge end of belt also. Suction should be applied at the
elevator boot, between the legs. The main thing, I think, is in
the first place to avoid, if possible, the making of dust. and,
secondly, to remove such dust as is made and liable to escape and
float about the building, as quickly as possible at the various
points. It does not make any difference as to the kind of build-
ing construction, whether wood, iron, steel or concrete-dust is
a menace to all alike. A concrete or steel constructed elevator
or plant may not burn down. but it can be wrecked by a dust
explosion in the twinkling of an eye. It seems like the height of
folly to erect costly steel or concrete elevator plants with the one
idea of preventing destruction by fire, and then to make no ade-
quate provision for preventing the making of dust or its escape
into and diffusion all through the plant, and thus having the
even-present possibility of a disastrous explosion.
Mr. BODNAR-In connection with Mr. Hibbard's paper,
I desire to refer to the general cleanliness of plants in the North-
west. They believe on the Pacific Coast that the climate has
something to do with preventing explosions, inasmuch as they
have never had any, but I have set off, in demonstrating ex-
plosions, much of their own dust. even on extremely wet days.

and I cannot see why they feel that they will never have an ex-
plosion. In some of the plants they seem to be taking modern
precautions, and still they feel that the climate is keeping them
from having explosions.
Mr. PRrCE-It would be advisable for them to adopt addi-
tional .precautions. The large number of thresher explosions
in that territory were due to unusual climatic conditions. This
would indicate the possibility of explosions in mills and elevators.
Is there is no further discussion, we will adjourn until to-
morrow morning.

April 23, 1920
DR. J. W. T. DUVEL, Presiding
Dr. DUVEL-A few years ago, if you talked with mill
operators as to disturbances or dafigers attributed to static elec-
tricity, they were of the opinion that your arguments were based
on some fanciful theory. Conditions have changed very largely
in recent years. I am sure I am not overstating the situation
when I say that this difference in viewpoint is due largely to the
work that has been done by the Department of Agriculture and
the Grain Corporation along dust explosion prevention lines.
The first paper this morning will give us some definite in-
formation on static electricity in attrition mills and methods of
removal, as based on observations and investigations by Mr.
McCollam, who has been in charge of our dust explosion work on
the Pacific Coast.

Mr. McCOLLAM-Mr. Chairman: I have been assigned the
subject "Static Electricity in Attrition Mills and Methods of
Charges of static electricity which may be built up in attrition
mills are of interest to us chiefly as a possible cause of grain
dust explosions. There has been much doubt as to the power of
static electrical discharges to ignite dust and cause fires or ex-
plosions. Some of the many interesting questions arising in this
connection are heat and duration of sparking, leakage, insulation
by some substances, such as oil films, and humidity conditions as


affecting a high potential in an attrition mill. Experimentation
has resulted in difficulties being experienced in igniting dust with
static discharges, and no fires or explosions resulting from static
could be obtained in an attrition mill. However, the experiences
of myself, as I will describe later on, have pointed to quite a real
possibility of danger from this type of electricity in attrition mills.
Of course, fires and explosions have taken place in many attrition
mills, but the cause has been assigned, generally, to foreign sub-
stances going through the mill and striking fire. Such materials
may be stones, nails, pieces of metal, etc. Static electricity as a
cause has been generally depreciated.
In treating this phase of the subject, we may say that the ex-
plosion is secondary in the case of an attrition mill. and it is
usually the fire originating in the mill which starts the trouble.
This fire spreads to dusty), spouts or bins which are connected with
the mill and an explosion occurs. Sometimes the fire spreads
rapidly and an explosion occurs almost instantly, and at other
times the fire smoulders for some little while, the explosions oc-
curring later on. There are three possible causes of fire starting
in an attrition mill. These are: First, hard metallic foreign sub-
stances going through the mill and striking sparks; Second,
frictional heat caused by grinding certain materials may cause
combustion to start, especially under conditions of over-feeding
if mill has no vents to complete the air circulation; Third, spark-
ing or discharge of static electricity over an appreciable period
may ignite the product being ground in an attrition mill. This
latter means is the one with which wve are concerned most at
this moment. Most of the static electricity in a direct connected
attrition mill is generated by the action between the grinding
plates. It is questionable whether there is any static generated
at all by the induction motors driving the mill. In case of :a
belt driven mill, there may be quite an appreciable charge on the
belt building up a potential in the mill.
For the most part. it is my intention to describe the details
surrounding a series of seven explosions which took place in an
attrition mill during the period of one week in the cereal mill of
the Sperry Flour Company, at Stockton, California. Some of
these explosions occurred on the same day'. The most violent
explosion of the seven was one which resulted in the elevator le.Z
to which the mill was spouted being ldanagedl. A wooden safety
vent at one side of the legi was hlo(\n oft. as was also the elevator
head. Opinion was expressed that an expllosion could easily
have been caused throughout tlic plant had it not been clean and

free from dust accumulations, and this is probably true. The
attrition mill in which the explosions occurred was ball-bearing
and directly connected to induction motors. It was used for
grinding oat hulls expressly. From a huller the groats and hulls
fell to an air blast which was used to separate these two products.
The hulls were blown over into a chamber which was spouted
to the attrition mill. The groats being heavy fell by gravity into
a separate bin. The significance of this is that any heavy foreign
substance would have fallen into the bin with the groats and
would not have been carried over to the attrition mill. As an
added protection, the mill had the usual magnetic separator before
it. The mill had no choke conveyor beneath it and was spouted
directly to an elevator. After the first few explosions, the miller
assumed that since it was practically impossible for any foreign
material to get into the mill, the cause could be traced to static
electricity. He took some pains to prove his assumptions, and
did it very conclusively in his own mind. First, a gold-leaf
electroscope was procured and various parts of the particular
mill were tested. Violent positive deflections were noticed when
parts of the frame were touched, and none at all, or what the
miller thought were negative deflections, when the shafting was
touched. What was probably more convincing and certainly
more spectacular, was the next step taken by the miller. He cut
a piece out of the plate housing of the mill and inserted a piece
of glass through which he could watch the inside of the mill.
At the instance of the most violent explosion, the miller was
watching sparks jumping from the grinding plates of the mill.
The sparking was intermittent at first and then continuous. The
sparks seemed to be streaming around the outside edges of the
grinding plates. Almost immediately after this last occurrence
the explosion took place in the elevator leg. The miller partic-
ularly noticed the color of the sparks or "fire." It was the light
blue, characteristic of static electricity. The miller was convinced
that the explosions were being caused by static sparking in the
mill, and immediately took steps to avoid future trouble. Not
only this mill buit all the attrition mills in the plant were grounded
as a result.
The miller, in doing this. fully believed that all the charge
could be led off wby simply attaching the ground wire to the frame
of the attrition tiill. This method was employed, and although
in my opinion it is not as desirable a wiring system as could be
installed, the fact stands that no more trouble has been forth-
coming in this plant since the grounding was done.

The reason for the effectiveness of this grounding method
was due no doubt to the fact that the mill was a ball-bearing one,
and it is here that we must turn to a consideration of the relation
of types of bearings on an attrition mill to the passage and stor-
ing up of static charges. Even though a ground wire is led from
one point of contact on the frame of a ball-bearing attrition mill,
it is possible that this may suffice to lead off all of the electricity.
The principle of lubrication of a ball-bearing machine is entirely
different from that of an ordinary box-bearing. There is always
a certain point on one of the balls which is in contact with both
the shaft and the housing, so that no insulation is offered to the
passage of static electricity. A lead from the frame of the
machine could therefore take off charges from all portions of the
mill. An ordinary box-bearing is lubricated differently, the ob-
ject being to establish a permanent film of lubricant between the
shaft and housing. This acts as an insulator and an electrical
charge will not pass if the lubrication is perfect and a complete
film established. So that a mill with this kind of bearings
would not be relieved of static simply by a lead from the frame,
since this lead would not be taking the charge from the shaft to
which the grinding plates are attached, and to which, in the case
of a belt drive, the pulley is attached. It would be necessary,
therefore, to take leads from contacts on both frame and shaft
to insure complete removal of static charges.
While the conditions under which static may be generated and
stored up in an attrition mill may be rather complex, arising
from kind of material being ground, rate of feeding, humidity
of atmosphere and possible leakage, and the kind of bearings and
drive on mill. the method for removal of this type of electricity
is very simple and effective. Nothing more will be said about
it other than describing one wiring method found to be quite ef-
fective and treasured in a large cereal mill in Oakland, Cali-
fornia. Two attrition mills in this plant had been the seat of
numerous fires, even though equipped with magnetic separators.
This trouble went on for months with regularity, and the installa-
tion was about to be removed, when the mechanical engineer
decided upon static electricity as the cause of the fires. IHe
placed a brush on the shaft of the mill and made a contact on
the frame of the mill. letting the wire from this brush make a
contact on the frame of the mill. lie laid a wire from this con-
tact to a contact on the choke conveyor. An insulated wire was
used in wiring the machinery, while the ground wire, or the wire
leading to the ground through a water pipe, was naked copper

wire, with, of course, no sharp angle turns in it. I think there
were two turns in the wire, both of which were very gentle turns
that led from the contact over to a copper band around the water
pipe, which was first well scraped to insure good contact. That
is all there was to it. After he made that installation the trouble
in the mill stopped. This may be a coincidence, but it points
strongly to the danger of static charges in mills of this type.
Some conclusions which I have drawn from the series of ex-
plosions in an attrition mill at the cereal plant of the Sperry
Flour Company at Stockton, California, which I have already
described and which, of course, are open to discussion, are as
follows: First, static electricity is generated in large quantities
at times in an attrition mill. Second, static electricity may ignite
ground oat hulls or oat hull dust, causing fires and resulting ex-
plosions, but to do this the discharge must extend over an ap-
preciable length of time. Third, effective methods of wiring
must involve a study of the possible paths of electricity and
insulating mediums, and leads should be taken from all parts
insulated from one another.
The film of oil between the shaft and housing of an ordinary
box-bearing is an insulator preventing the passage of static elec-
tricity, but such a condition does not exist in the case of a ball-
bearing mill.
The purpose that I have hoped to accomplish at this moment
is to draw attention to the occurrence and results of static elec-
tricity in the attrition process of milling. I wish to emphasize
my opinion that static electricity may cause fires and resulting
explosions, and that it is a sensible precaution to remove static
charges from all machinery in a plant, and especially from an
attrition mill.
Dr. DUVEL-We have this very interesting subject pre-
sented by Mr. McCollam for discussion. I am of the opinion,
however, that it will be desirable to have Mr. Roethe's paper
first and discuss them both at the same time. They are closely
associated, and if handled in this way will save time, and no
ldoul)t avoid repetition. There being no objections, I will ask
Mlr. Roethe to present his paper on "Recent Investigations of
Static Conditions in Industrial Plants."

46 .

SMr. ROETHE-Mr. Chairman: Upon the completion of the
threshing investigations in the Pacific Northwest in the summer
of 1919, an opportunity was afforded to make a study of static
electricity in representative mills and elevators. The electrical
equipment used in the case of grain mills and elevators con-
sisted of an Albrecht type voltmeter, a six-cell Murdock con-
denser, a spheregap, and a galvanometer taken from an ordinary
electrical resistance thermometer. The investigations continued
from August 22d to September 12th, which allowed only a lim-
ited time at each of the plants. The plants included were the
Sperry Flour Mill of Spokane, the Fisher Flour Mill of Seattle,
the Sperry Mill of Tacoma, the Albers Milling Company plant
at Portland, and also the Portland Flouring Mills and the Crown
Flour Mills of Portland, the Washburn-Crosby "A" Mill, the
Northwestern Consolidated "B" Mill, the Northwestern Con-
solidated "F" Mill, and the Northwestern Consolidated Elevator,
all at Minneapolis. Incidentally the last named elevator was the
only one in operation in the cities visited, so we could get no
results of tests conducted at this time in any other elevator. I
wish to emphasize the fact that the results obtained were not
extensive enough to establish any permanent or definite conclu-
sions regarding production of static charges in grain mills and
elevators. However, we hope that the results obtained were at
least of some value.
The general procedure was to start on the top floor of each
plant visited and take the different machines or series of ma-
chines in the order that they were reached. Leads from the
voltmeter, spheregap and galvanometer were run to the differ-
ent machines, and a study was made of static charges found on
each part of the individual machines, and on the machines as a
whole or as a unit. The ground wire in each case was run to a
water pipe, or similar pipe. to insure effective grounding. An
effort was also made to study the relation of the different parts
of the machine to one another. For instance, it seemed advisable
to secure information regarding the difference of potential be-
tween the roller on the roller mill and the frame of the machine
itself. I give that as an illustration to show that we desired to
obtain results showing the difference of potential between the
different parts of the machine itself as well as between the various
machinery and the ground.

Considerable rain was encountered in the Pacific Northwest,
in Seattle in particular, consequently the readings secured there
were not great, due to the high humidity. Generally the ther-
mometer readings in the Pacific Northwest ranged from 6552 to
75 degrees Fahrenheit, and the relative humidity from 22 to 60
per cent. While in Minneapolis the fore part of September, we
found the temperature ranging from 72 to 82 degrees Fahren-
heit, and the relative humidity ranging from 34 to 40 per cent.
This shows that the readings of humidity were higher and also
of a greater range in the Pacific Northwest than at Minneapolis.
I might just make a few statements regarding positive and
negative electrification, because in giving the results obtained
reference is continually made to these terms. The theory is gen-
erally accepted that all bodies have upon them a natural amount
of electricity which cannot be detected owing to the fact that all
bodies have a similar amount. However, it is possible to re-
distribute this natural electricity. Since it is always necessary
for two bodies to be electrified at the same time and with op-
posite electrifications, it is apparent that rubbing or friction
effects the redistribution of this electricity which existed upon
the bodies in its natural state. It is also evident that one body
acquires more than its normal amount of electrification, and the
other body loses some of its normal amount. There is, therefore,
only one kind of electricity, but two kinds of electrification:
one produced by an excess of electricity upon a body, and the
other by a deficit. The sign "positive" or "plus" indicates that
a body has more electricity upon it than is natural or normal,
and the sign, "minus" or "negative," that it has less than its
natural amount. When a positively charged body is brought
in contact with a negatively charged or neutral body, a flow of
electricity takes place, electricity passing from the positively
charged body to the other.
Rather than give the detailed results obtained at each plant
I will summarize the readings made at all the plants visited. We
found violent positive deflections on the suction pipes of un-
loading systems in which grain was being unloaded from cars.
We also found 100 volts on these pipes. Workmen informed
us that on hot dry days violent charges were found on these
pipes when smutty wheat was being unloaded. This is in line
with results obtained in similar tests on the discharge pipes of
suction fans on threshing machines, where very violent positive
deflections were recorded on the fan casing and discharge pipes.
This indicates very strongly that the passage of dust, particularly

smut dust, electrifies the metallic pipe. In the case of threshing
machines we have also found positive electrification on the grain
pan over which the threshed grain passes, positive electrification
on all parts of the elevator, and also on an aspirating system
which was installed on one separator. In other words, the pas-
sage of grain and dust over a dissimilar material, such as a metal-
lic surface, produced electrification. Generally, we found that
a metallic surface was positively charged, and the material pass-
ing over it was negatively charged.
In the case of drive belts, large charges were always found
on practically every belt, the charge depending upon climatic
and operating conditions, the size, speed, material and slippage
of the belts themselves. A maximum of 75,000 volts was found
on a leather drive belt in one mill on the Pacific Coast, running
from an electric motor to the main shaft in the basement. The
belt was 22 inches wide and moved at a high rate of speed.
Conveyor Belts-Tests were made both on troughing belt con-
veyor rolls and flat belt conveyor rolls. Conveyor belts do not
travel at what we would term great speed, generally moving at
the rate of 750 feet per minute, or approximately 8Y2 miles per
hour. The slippage and friction is not apparently great on such
belts. In a mill in the Pacific Northwest we found 45,000 volts
on a rubber conveyor carrying smutty grain from the elevator
head to the distributors on the top floor. A similar belt in the
basement of the same building gave a reading of only 200 volts.
Grain from the same car was being conveyed at the time tests
were made. It is very probable that the belt in the basement,
which was conveying the grain from the nearby car, was more
directly or effectively grounded than the belt on the seventh or
top floor, although the entire building was of concrete and steel
construction. There is a possibility that the grain, which was
smutty, was charged during the process of elevation with static
and transmitted a large part of it to the conveyor belt above the
bins. No voltage was found on canvass conveyor belts.
Elevator boots, legs, heads and spouts-We found no de-
flection or voltage on the boot in any mill or elevator inspected.
We found no voltage, but a strong positive deflection on the legs;
no voltage, but violent positive deflections on the heads; strong
negative deflection on the spouts.
Separators, scourers, etc.-Next, corning to tlhe receiving and
milling separators, we found no voltage or deflection in any case.
On the scourers a maximum of 1,500 volts was found on the

fan shaft, a maximum of 2,500 volts on the discharge pipe, and
a strong negative deflection on the fan shaft and discharge pipe.
No voltage was found on tempering mixers; strong negative
deflection was recorded on the horizontal spirals conveying wet
wheat; none on spiral conveyors moving dry wheat.
No voltage or deflection was found in the magnetic separa-
tors with the exception of the magnet.
In the roller mills, no voltage was found, but a strong nega-
tive deflection was found on the feed rollers and also on the
No voltage or deflection was found on the scalping and cen-
trifugal reels and flour dresser. The same can be said for sifters,
including plansifter and bolter.
No deflection or voltage was found on middlings purifiers.
No voltage, but violent negative deflection was found on bran
and shorts dusters.
In the case of the Williams grinders, every part was violently
charged with electricity. We found a negative deflection on every
part, and 1,500 volts on the shafting and casing.
On the blower fans no voltage was recorded, although on
one or two occasions we found a violent negative deflection on
the intakes and discharge pipes. On several occasions a positive
deflection was found on the fan casing, fan shaft, intake and
discharge pipes.
No voltage was found on the tubular dust collectors, although
at one time a violent negative deflection was recorded on the
discharge pipe.
On the Cyclone dust-collectors a maximum of 250 volts was
found on the drum and 500 volts on the intake.
The surprising thing in regard to the plants visited was that
no effort was being made in any of the mills or elevators to carry
off the charges of electricity produced. We feel that this should
be done in the case of the large driving belts, scouring machines,
grinders, elevator heads, blower fans, attrition mills and probably
roller mills. In the case of belts, the charge can be very readily
disposed of by means of belt dressing or a metallic comb. We
found that the main drive belts, and those driving scourers and
grinders, were always heavily charged regardless of existing con-
ditions. The scourers should be equipped with a dry brush on
the shaft, andl wires should be attached to the discharge pipe
and fan casing. It is surprising that more fires do not occur in
scourers, due to the high speed of the machine and to the smut
and grain dusts which are always present. We had no difficulty

in recording several thousand volts on every part of the scourers.
In grinding machines, it is thought a dry brush should be placed
on the #haft, and that wires be attached to the casing and dis-
charge pipe. Here again large charges were always present or.
every part of the machine. In the case of elevator legs and heads,
while no voltage was recorded, there was always a marked differ-
ence of potential existing between the elevator head and the
ground. It no doubt would be advisable to attach a dry brush
to the pulley shaft and a wire to the head itself. Static was
often found present on the blower fan, on the casing, intake and
discharge pipes. The dry brush should be attached to the shaft,
and wires to the casing, intakes and discharge pipes. Mr.
McCollam has made reference to the different types of bearings
-including ball and plain bearings used on different machines
operating at high speed. No doubt in case of machines using
ball or roller bearings, it would not be necessary to attach a dry
brush to the shaft, a wire connected to the journal itself probably
being sufficient. However, to insure effective removal of any
charges to the ground, it might be well to use the dry brush.
Wires can easily be attached to the pneumatic unloading systems.
In closing, it is not at all easy to draw or form any definite
conclusions regarding the study of static electricity in the ele-
vators and mills visited, but the results show that, at certain
times, dangerous conditions do exist on or in scouring machines,
grinders, blower fans, and possibly the elevator head. Here con-
ditions are most favorable for the generation of static charges,
and an accumulation of them, and in these machines and equip-
ment dusty conditions prevail. A hazard exists in the vicinity of
rapidly moving large belts highly charged with static. This danger
is all the greater in the case of arcs of static produced in a dusty
atmosphere. A state of electrification exists on metallic tubing
through which dust or grain is passing. The readings were
greater in the case of smutty wheat or smut dust than clean wheat
or grain dust.

Mr. McCollam has already discussed static electricity in attri-
tion mills most satisfactorily, hence nothing further need be said
regarding these machines.

Dr. DUVEL-We now have for discussion Mr. McCollam's
paper on static electritcy in attrition mills, and Mr. Roethe's
paper on static electricity in general, just finished. Some very
interesting points have been brought out.

Mr. PRICE-I can recall that early in this work when a
dust explosion occurred, and we could not find the cause readily,
that "spontaneous combustion" was usually assigned. In other
words, it meant that nobody knew, in the lack of something
definite, how these explosions did occur. A few months ago
someone came into our office, I have forgotten just who it was,
and said the insurance companies were no longer using "spon-
taneous combustion" but somebody had started the theory that
always led them to believe that static electricity was the cause of
these explosions. After the things we have heard in both of
these papers, we have been given information which has always
been looked for in connection with this subject.
Mr. McCollam states that in one of the mills in California,
after a series of seven explosions had occurred, in the case of
an attrition mill, that the superintendent actually observed large
sparks of static electricity jumping from the grinding discs im-
mediately before the explosion. I said yesterday we were trying
for a long time to see a threshing machine explosion in the north-
west and the difficulties encountered, but here the superintendent
actually saw this explosion. I think that is remarkable evidence.
Mr. McCollam sent that report to Washington a few months ago.
The results that Mr. Roethe has given us clear up the difficul-
ties we had in the early days when determinations made in ele-
vators and mills indicated the presence of static electrical charges.
To my mind both of these subjects have been presented in a most
gratifying manner, because they have given us facts, which have
cleared up, beyond a doubt, the dangers existing in that direction.
MR. McCOLLAM-In the Sperry Flour Mill, where the ex-
plosions occurred, the miller simply used the method whereby
contact was made with the frame of the machine and the ground
wire attached.
MiR. PRICE-It appears that an arrangement where the static
discharge had to pass through the oil film might not be as effective
as the dry brush contact.
MR. McCOLLAM-There were no explosions occurring after
the grounding in either case.
MR. BODNAR-I think it would be necessary to conduct
some tests to determine this, in order to prevent large maximum
charges from passing through a small film of oil. It seems that
a very small film would let a discharge go through. Of course I
do not know how large a charge it would be. If oil insulates the
shaft then use a dry brush on the shaft.

DR. BROWN-In that connection I might say it has been
determined by the Bureau of Standards that a film of oil has ten
times the resistance to the discharge of electrical current that
ordinary air has. In other words, the resistance of oil is ten
times stronger than that of air. It seems to me also
that it is quite probable that a dusty atmosphere would
have a tendency to aid in the passage of a discharge
through it rather than to increase the resistance of the
air. Now, going back to Mr. McCollam's paper. Mr. McCol-
lam made the statement that he felt that there would not be
an immediate ignition of the dust from a single discharge, but it
was rather a question of a series of discharges over a short period
of time through the same dust, and it took apparently a small
amount of time to ignite the dust by means of the static discharge.
That rather bears out one thing that I brought out at the last
conference last year in connection with the condition of cotton.
We found in making a series of tests at the Bureau of Standards
that we could ignite cotton very easily with a static discharge, but
that there were two or three controlling factors; that if we main-
tained a constant rate of discharge and started with a charge of
low intensity, we would have to gradually build up the amperage
before we could get any ignition; but then if we decreased the
amperage on the static discharge, we could cut down the fre-
quency of the discharge and still get an ignition, and so we ob-
tained a point at which we could get an ignition of cotton very
readily by simply one discharge, provided we had sufficient inten-
sity or sufficient amperage on the discharge.
I might refer to another study of the subject I am interested
in. As you probably know, we had no trouble in the northwest
in igniting some dust on the ordinary static machine. We have
not ignited any in the laboratoryI in Washington with a static
spark. We have not tried it, but I happen to know that the
Bureau of Mines have done a lot of work on that line. Of course,
we feel that the use of an induction coil spark from an induction
coil is slightly different from the static spark. On the other
hand, we could control the ignition of the cotton in the same
way by speeding up the action of the induction coil as we could
with the static machine, and so I feel that the discharge is largely
comparable. You may be interested to know that at the Bureau
of Mines they have had no trouble at all in igniting some of their
dusts by means of the induction coil spark which is comparable
to the static spark, I believe by blowing, particularly gilsonite dust,
against or over an induction coil spark. Gilsonite, some of you

may not know just what it is, but it is a mineral closely related
to our asphalt.

DR. ALSBERG-I do not know very much about lubrication,
but I have been wondering whether you can use graphite as a
lubricant. Would not graphite act as a good conductor for elec-
tricity? I do not know whether such a lubricant or modification
of it has ever been used, but I imagine it would act as a pretty
good conductor. Of course we get good results from the dry
MR. BATES-I have never heard of graphite being used in
that kind of a bearing in the box. Graphite is used where heavy
pressures occur, and where dust is apt to collect. A dry lubri-
cant is used sometimes in connection with oil to add body to the
oil. The theory of lubrication is that the adhesion of the lubricant
to the shaft is sufficient, so that the speed of the shaft will draw
the lubricant through under its weight and thus bear the shaft
on a film of oil. This condition exists only at a speed and at
pressures varying with the consistency of the oil. I believe that
would be a very hard thing to produce in graphite. However, we
are apt to think of perfect lubrication as providing a perfect film
of oil, and we are apt to think that we can make the shaft in the
bearing perfectly shaped. As a matter of fact, very few bearings
probably are run at precisely the right speed and with the proper
pressure to get perfect lubrication, even if you had a perfect
cylinder running on a perfect cylindrical surface. Still it depends
upon the speed and pressure, while as a matter of fact every
variation of weight that occurs on your shaft is apt to change
the angle of the shaft in the bearing, and you are very apt to find
the shaft itself imperfect, so that every revolution of the shaft is
not sufficient to draw in enough oil to give good lubricating
effects. That undoubtedly accounts for the fact, as Mr. Roethe
told us, that the voltage in many cases does not rise to an amount
sufficient to show a deflection on some of the shafts by voltmeter
of the static type; that is, the charge is similar on the moving part
to that on the stationary part. Oftentimes we could not get read-
ings. At the same time by using a galvanometer as a measuring
instrument a very small amount of current affected the needle,
making it spring. We were able to detect the presence of cur-
rent, although the voltage was very small, undoubtedly due to
the fact that the voltage was not allowed to build up, because at
a certain low voltage it was neutralized through the bearing.
That. by the way, was the meaning of the term that Mr. Roethe


a used, "no voltage but a strong deflection." You could not have
"no voltage and a strong deflection," because when taking the
readings there must have been actual voltage, because no current
could flow without voltage.
I wish to call your attention to a misunderstanding regarding
this static electricity, as shown by the fact that Mr. McCollam
said we must have as gradual curves as possible. The discharge
of electricity or the detecting of electricity through a direct cur-
rent is very well known, that is, it follows very direct laws, and
we can predict and conduct current of that kind with a great deal
of precision. As we get into the alternating current, the laws are
varying, and up to the frequency of the ordinary 60 cycles we can
predict what is going to happen. When we get to currents of
extremely high frequency, such as you have discharged on alter-
nating current, electricity violates all the laws. An alternating
current would readily jump an air-gap in preference to following
a coil wire, and for that reason you find electric light plants
putting conductors of heavy copper wire on the outside of their
buildings. We are taking the static as it is generated, and we
do not have that frequency because there is no discharge through
the air. When a spark jumps through the air it burns a hole
through the air and becomes a good conductor, until it finally dies
out, and we do not get that current as it is generated on these
machines. Therefore, the best practice would be to put your
wires where they are best protected, running them through any
holes, in corners or any place, but have them well protected,
and the angles will have no effect on the current. This is some-
thing we should understand, because if we attempt to make then
place their wires in long smooth curves, we might get away with
it all right so far as the millers are concerned, but some of the
electrical engineers might view it with some reflection on our
knowledge of electrical principles.

Mr. McCOLLAM-I might say in reply to that, with ref-
erence to the installation in the Oakland plant, that before making
that wiring installation they asked the General Electric Company
for any information they might have on the subject for wiring on
static electricity, and the diagram they gave was followed out.
and that was one of the special features in that plant-naked
copper wire and the precaution against angle turns.

Mr. BATES-I certainly will have to admit that the authority
is good, but I do not in the least alter my statement.

Dr. ALSBERG-I wonder whether I am correct in my under-
standing that you do not get any charges on canvas belts,
Mr. ROETHE-The only canvas belts available for tests were
on conveyors. No voltage was found on these belts and no deflec-
tion, as indicated by the galvanometer.
Dr. BROWN-It has been suggested that graphite is used to
a certain extent, and Mr. Price has some information on that.
Mr. PRICE-The information we have is more or less hear-
say. I understand that a company in New York has made con-
siderable progress along that line; just what it is I am not in
position to say.
Mr. HIBBARD-It is just plain belt dressing to prevent
slipping. Just what the composition is I do not know.
Dr. BROWN-What was the determination? Was the sign
of the charge on the different belts negative or positive?
Mr. ROETHE-Generally we found positive sign on belts
and negative on the metallic pulleys and idlers, although in some
cases just the reverse was true. We secured no readings on the
discharge pipes, although we did find that the pipes were ap-
parently electrified to a certain extent because the chaff would
adhere to the pipe in a vertical position. The chaff was blown
out by suction fans on threshing machines.
Mr. PRICE-This stands out prominently in connection with
what we have been trying to find out and have been doing. I
want to ask Mr. McCollam now regarding this superintendent
who observed this explosion. On what basis did he decide
whether those sparks were not caused by the plates rubbing or
by metallic substances passing through the machine? What sat-
isfied the superintendent in his mind that they were electrical
sparks, and not metallic sparks?
Mr. McCOLLAM-The miller made no electrical determina-
tions on the machine other than with the gold-leaf electroscope,
and with this instrument he found very violent charges every
time he touched the frame of the machine. He went throughout
the plant and found other machines that had static electricity on
them. This was the only method that he employed to base his
assumption that the explosions were being caused by static elec-
tricity. He had made a study of static electricity and knew just
what kind of a spark it made at the time of the most violent explo-
sion. Ile was able to observe, in the housing of the mill, the color

of these sparks, and he called my attention to that very forcibly
and said that proved in his mind it was caused by static electricity,
and as I say, he mentioned the fact that the sparks were of light
blue color, which is characteristic of the static spark, and I do
not believe grinding plates rubbing together would produce sparks
of that color at all.
Mr. BATES-I believe sparks which would be caused by
abrasion or by something hard striking the rotating plates, would
fly off at a tangent, while the electric spark would not be affected
by the motion of the plate but would jump across the air-gap
between the plates. Another way to identify the sparks is by the
color. I have had thresher men state that on occasions when
they threshed grain after dark, the cylinder of the machine was
a perfect glow of blue fire. This indicates that there is often
a continual discharge of static electricity at thresher cylinders,
but that it is only the hundred millionth spark that occurs in
just exactly the right condition to start a fire. Electrical dis-
charges in threshing machines are dangerous only when the other
conditions are favorable to make the explosion.
Dr. DUVEL-Is there any further discussion on this subject?
Mr. FOX, of the Edison Lamp Works-One point might
be of interest regarding electric lighting. When going through
a mill the ordinary electric light bulbs can be used to detect the
presence of static electricity. The filaments in bulbs when
burned near machinery charged with static electricity will be
bowed out, and in some instances, especially in the ordinary car-
bon lamp, the filaments may be drawn to the edge of the bulb
and cause it to crack or break. We found considerable diffi-
culty along this line with certain types of lamps.
Mr. BATES-Would it be safe to use electric light bulbs
next to a machine to detect a static charge?
Mr. FOX-I do not know just how sensitive this would be
or how small a static discharge could be detected.
Mr. BATES-I have seen that tried on carbon filaments.
You can take a carbon lamp and rub a rubber comb through your
hair and draw the filaments almost to the side of the bulb when
it is burning.
Mr. FOX-That was the trouble in carbon lamps, the fila-
ments being drawn to the side of the bulb and eventually crack-
ing the bulb.

Dr. DUVEL-There is one point which Mr. Roethe men-
tioned in his paper relative to tests for static on belts when
handling different kinds of grain. I would like to ask if any
of the men have made any tests of third character in the handling
of flax. I think it is generally conceded that flax, after it has
been handled, becomes electrified; at least, flax handlers find
after handling flax through an elevator that the test weight per
bushel is decreased sufficiently, frequently to cause the loss of a
grade. There are probably two causes which play an impor-
tant part: First, the roughening of the seed coat, which is
normally very smooth, and permits the seed to pack well in the
test kettle; Secondly, the question of electrification. In some
experiments conducted at the Department of Agriculture, we
took a test kettle filled with flaxseed and stroked, showing a test
weight of 52 pounds. This seed was then placed in an ordinary
Mason fruit jar and shaken slowly back and forth 500 times,
then reweighed. On the reweighing the flaxseed more than filled
the test kettle and there had been a loss in the test weight. This
was repeated for an additional 500 shakes, still an additional
500, and still an additional 500, making in all 2000, weighing
being made after each 500 shakes. In each instance there was
an additional quantity of seed which would not go into the test
kettle and also an additional decrease in the test weight. As I
trecoilect, the-final weight was 48 or 49 pounds, being a loss of
3 or 4 pounds. Whether or not this was due to electrification
or merely to a roughening of the seed coat, I am not able to
say positively, but it is probable that both factors had some
Dr. DUVEL-Any further discussion?
Mr. REED-Several weeks ago I had an interesting experi-
ence with static electricity that may be of interest to those pres-
ent. While at Winchester, Va., I met the president of the Vir-
ginia Woolen Mills and during my talk with this gentleman, I
was informed that they experienced considerable difficulty in
the carding of their wool. He stated that on certain dry or
windy days, in a certain portion of the plant which was
exposed to the wind, their carding machines would not operate
properly, due to the fact that the static electricity which had
accumulated on the carding machine would turn the wool and
make ;t stand on end. The wool, in being carded, runs over a
large cylinder and is taken up at certain points by another cylin-
der which has teeth on it, and in that way every strand is
straightened out. Finally this wool is combed off the side of

the large cylinder and is run through two large rubber belts
which slide back and forth and rub the wool together. The
most difficulty they had with static was in running the wool be-
tween those two belts. There was an equal amount of friction
between those two belts and the static, which would in some
manner straighten out this wool and make it stand out on the
side. As a result they would not get a perfect cord, or what-
ever it was they were trying to form (I am not familiar with the
terms they use). I went into the plant and looked over the
machinery. They were trying to keep the humidity in the plant
as high as possible. In one section of the plant where they had
carding machines installed above the dye room, from which
there was a large quantity of steam coming up, they had experi-
enced no such difficulty. That section of the plant is high and
not exposed to the wind, but on the west exposure they experi-
enced considerable difficulty. I recommended that a comb be
placed on this belt and at the same time some sort of a comb be
placed upon the rotating cylinders. There is considerable diffi-
culty in the grounding of these cylinders due to the fact that
the combs on the cylinder are imbedded in a cotton or woolen
fabric. The combs on the cylinder do not touch the cylinder
itself, which is made of steel, but each comb is separate, and is
imbedded into this woolen fabric. Once a month they are com-
pelled to grind these combs. One man told me that on one
occasion he grounded a carding machine to a spool frame and
said they had very good results.
Dr. DUVEL-That is a very interesting observation.
Dr. BROWN-In our work in cotton we made an experiment
whereby we pulled the cotton through a suction pipe and allowed
it to strike against an insulated screen. We found a charge on
the pipe and one on the screen and these were almost equal.
When we gathered these together we had no charge. On actual
determination we found an excess amount on the pipe over that
on the screen, and we found that the equal amount of the posi-
tive sign on the charge was still on the cotton. In reality we
might have had two different types of charges which were
Dr. DUVEL-..If there is no further discussion of the two
papers dealing with static electricity e will take the report of
Mr. Price on "Relation of Electrical Equipment to Dust Explo-

Mr. Geo. H. Rice, who was to present this paper, as you know,
went with the Hartford Fire Insurance Company the first of
the month. I am not going to attempt to discuss the entire
matter of electrical equipment in so far as it applies to mills and
elevators, but want to present to you in a brief way what we
have been doing with the electric lamp companies in connection
with that phase of our electrical problem. You are somewhat
familiar with the nature of that co-operation and have been in-
formed from time to time of what has been done.
At the time of the Kansas City explosion last September our
investigation was very difficult to conduct and definite evidence
was lacking in many ways. One of the survivors, in fact the
only one, said that he remembered noticing a blue flash, near the
ceiling just before the explosion. It developed that the part of
the basement where he had seen the flash was about the location
of one of the electric lamps. This suggested the possibility that
the lamp may have ignited the dust. We made renewed efforts
to ascertain if this was the cause of the explosion. At the time
the first poster was issued by the Department of Agriculture and
the Food Administration, in view of the large number of cases
brought to our attention where workmen had been lowering
electric bulbs into dusty bins and explosions had occurred, we
felt that a warning of some kind should be given to the men.
We made five or six simple recommendations along precautionary
lines and, as you recall, one of those measures suggested that
the men refrain from lowering unprotected electric lamp bulbs
into dusty atmospheres, or bins. That caused interest on the
part of the lamp companies. Considerable correspondence was
received in Washington from the Westinghouse Company.
They wanted to know what reason we had for making a
recommendation of that kind. They referred to the work that
had been done at Pennsylvania State College in connection with
our attrition mill experiments and raised the question as to
whether or not we actually had conducted experimental work
showing that the use of these electric lamps was dangerous.
We had not done so, but felt that in view of the cases in the
field some warning should be given.
The Kansas City explosion led to direct relations being opened
up between the Grain Corporation and the different lamp com-
panies. We have had a number of very satisfactory conferences.

S The three companies concerned are the National Lamp Works
S of Cleveland, the Westinghouse Company at Bloomfield, N. J.,
S and the Edison Company at Harrison, N. J. In these conferences
S we have tried to work out definite lines of experimental work
and further investigations.
The work handled divides itself into two simple classes: first,
the possibility of explosions being produced by the breaking of
S the bulbs in dust, and, second, the possibility of fire or explo-
sion from dust settling on the lamp. The first suggestion was
almost cleared up immediately, as you know, in the work at Cleve-
land. In the tests conducted there, within a short time after
the engineers began the work, they established very definitely
that any type of lamp broken in a dust cloud will cause an ex-
plosion. We covered that phase of the work largely in our meet-
ing in Cleveland in January. We have a number of cases in the
field reported where explosions have been assigned to that par-
ticular cause. The experimental work settles beyond any doubt
that the breaking of the lamp in the dusty atmosphere will cause
an explosion. However, at the time of issuing the poster we
thought that for some reason carbon lamps were more dangerous
than the tungsten type, and even went so far as to suggest re-
placing all carbon lamps with tungstens, in some of the elevators.
hoping that we were getting away from the danger. We found
in the experimental work that the breaking of the tungsten was
just as dangerous as the carbon type.
The second phase of the experimental work is giving us more
concern. At a conference held in New York a few weeks ago it
developed that difficulty had been experienced in determining
whether or not ignition actually occurred by dust settling on
the lamps. I understand from Mr. Dows and Mr. Hills that in
the work at Cleveland the dust would smolder or smoke but they
were not able to conduct any tests where the dust reached a point
of incandescence or glowing heat. In the last conference the
representatives of the lamp companies, after being furnished with
a number of specific cases, as you recall-the cases sent in from
the field-made a number of inquiries that had been suggested
by the cases submitted, that related to fires being caused in that
manner. To get the information in an authentic way we took
up with you, by correspondence, the cases that you had reported.
We sent the lamp companies, at their request. I think 17 or 18
cases of fires caused in that manner. Now, what we are trying
to find out is whether in these cases that have been reported the
men actually saw a glow or the dust reached incandescence or

whether it was just smoking. The engineers of the lamp com-
panies are not doubting these fact(- but desire to determine
whether the dust was actually seen to be on fire. Now, to cite a
case of what I have in mind, Mr. Court of New Orleans, as you
will recall, at the Chicago conference, related the following ex-
perience (No. 4):
A workman, in a southern elevator, related an experience he
had while using an electric light in a dusty atmosphere. He had
been sent down into a small and narrow bin to do some cleaning.
As he climbed down and brushed off the ladder which led down
into the bin, he lowered the light into the opening ahead of him.
During the cleaning-up process a great amount of the dust fell
on the lamp and in a short time dimmed the light. The workman
immediately climbed down to the suspended light and noticed
that the dust on the globe was on fire. He did not know whether
he should pick up this fire, put it into his pocket and run up the
ladder, or try to extinguish the flames down in the pit. He
climbed out of the bin and turned off the current to the light.
As he states, every minute he expected to be blown to pieces, but
he escaped because there was not enough dust in suspension to
propagate the flames. From that time on vapor-proof bulbs were
placed on the extension lights in that elevator.
Now, we recall very definitely, Mr. Court gave that experi-
ence almost word for word and so we took the matter up with
him by correspondence and have a letter from him here. This
was done after our last conference with the lamp companies.
Mr. Court states:
"Received your letter this afternoon and in reply to
my experience in elevator leg, when I was brushing down
the ladders I had put the portable light half-way down the
leg, and as I was going down, I was cleaning the steps
and never noticed anything until I got to the light. As
the globe was very dusty and I noticed it was smoking
and very hot and, I believe, I saw small sparks, as I was
in a hurry to get back up stairs. We had another ex-
perience at same elevator. The men were cleaning out
the pit and were using a portable light without protector,
and at noon time the men went to dinner and didn't put
the light out, and when we got back from lunch we noticed
a lot of smoke corning from the pit and we got a hose and
put water on it. I believe it was only smoldering at the
time as I didn't see a flame, but think there would have
been a flame if it would have had a draught."

SThere were three distinct cases reported from Minneapolis.
S Case No. 5. "The superintendent of a large Northwestern ele-
S vator relates that during the period that he has been engaged as
S superintendent of an elevator he can recall from twenty-five to
S thirty fires which originated from carbon lights. The dust coating
S on the globes became aflame and dropped to the floor, a small
fire resulting."
We wanted to get the name of the elevator and the superin-
tendent so that the information for the lamp companies could
be accurate and complete. This case was reported by Mr. Lind
of Minneapolis and was taken up with him with this result:
"During your recent visit here attending conference
held in this office you will perhaps recall a discussion we
had regarding experiences Mr. D. K. Whalen has had with
carbon lights. Mr. D. K. Whalen is manager of the Ex-
change Elevator, St. Louis Park, a surburb of Minneapolis.
It will be remembered that at a previous visit I had with
Mr. Whalen the question of various electric lighting equip-
ment was discussed with him, and at that time he related
some experiences he has had with carbon lights. After
relating these experiences, you advised that I again get in
touch with Mr. Whalen, and particularly some of the men
who have had like experiences, for the purpose of verifying
or substantiating through these men the facts of the case.
Mr. Whalen advised that during his connection with
the Exchange Elevator no less than twenty-five or thirty
smoldering carbon globes have been observed in this plant.
By this is meant that the dust would gather on the globe
in layers, and because of the intense heat coming from
a carbon light, said dust would begin to smolder, and very
often this smoldering dust was seen to drop to the floor
where it came in contact with dust there, but nothing of
any serious nature happened to develop.
At a recent conference with Mr. Whalen and some of
the help, it was brought out very clearly by these men
that they had the same experiences in the past. This is
merely to advise you, as you requested, of the correctness
of Mr. Whalen's experiences."
I understand that Mr. Brady saw this supelrintendent further
and that he also has information, if I am correct, that the work-
men made the statement that the\ actually shoveled the fire out,
so that the fire actually took place when this smoldering dust

reached the dust on the floor. Mr. Brady after talking with Mr.
\Whalen stated:
"Case No. 5 was witnessed by Mr. D. K. Whalen of
the Exchange Elevator, Minneapolis. In a talk with Mr.
Whalen on the telephone to confirm his experience will
say that he claims to have actually seen the dust ignited
and glowing. The dust coating on the globes became
aflame, dropped to the floor and ignited dust down there.
He claims there is no question about this, and that actual
flame was seen."
When I was in Minneapolis we got in touch with Mr. Whalen
and cleared up to my satisfaction that the dust was actually seen
glowing by the superintendent and workmen.
The two other cases reported were witnessed by Mr. 0. E.
Lee, superintendent of the Interstate Elevator and Mr. R. W.
Cote of the Cargill Elevator Company, where these fires were
thought to have occurred, but as I remember they were not sure
that they) saw the flame.
Since we had our conference at Cleveland, Mr. Rice, who was
to handle this matter, had an experience in St. Louis, in which
hlie stated to mie hlie understood that the dust was seen to be
glowing-had reached the point of incandescence. The statement
"glowing very brightly" was taken up by Mr. Rice directly with
this company in St. Louis. That was a recent case in St. Louis,
and there were a number of others, some on the Pacific Coast re-
ported1 by Mr. Botlnar and some others in different parts of the
country. I have referred to only a few eases in the 17 or 18
cases reported. In a number of them it seems almost certain that
the dust was actually seen to glow or reach the incandescent
point, while other cases were reported where the dust was only
smoking or snloldering.
If the reports had been all alike, the work at Cleveland might
seem to indicate difficulty in producing an explosion or fire from-,
this cause. In the tests we have not been using light fluffy
elevator dust, but mostly starch d(lust. Whether it was not the
right kind of dust or conditions were not similar to operating
coiiditimons will have to be determined later by further experiment.
It is a question that seems to be an important phase of the
electrical work, because we have felt that possibly if the fire would
drop through the proper proportion of dust and air an explosion
would occur, but we have no information to indicate that such is
the case. Fire probably would occur when that dust on fire
reaches the floor. You will be interested, probably, in knowing

that in connection with the program sent to the lamp companies
at their request sometime ago we outlined lines to be followed
in experimental work. Twenty-four distinct lines were sug-
gested by the men on the work. At the conference with the
engineers of the lamp companies in New York recently it was
decided that these lines of work should be divided, some to be
taken up at Cleveland, 0., sgme at Harrison, N. J., some at
Bloomfield, N. J., and some in the electrical laboratories at
Pennsylvania State College. On some of the lines that have been
suggested, of course, the lamp companies have the information
available, but there is still quite a little work to be done ex-
perimentally on the problem and we are hoping that even in view
of the uncertainty as to what we can do after July 1, we can
take care of this phase of the work. The lamp companies have
been co-operating with us so splendidly that we hope to be able
to make some provision for a continuation of the work.
When I was in Denver some time ago the manager of one of
the large grain interests in the Northwest (I think hlie tuld me
he had 175 plants) took up this question with me. He tuld mec
that they had ordered one Marine type fixture for every plant
so that the superintendent could try it mout and see bow lie liked
it. I thought that was a very marked achievement, because the
company took it up with us at W\Vashington and mnierely on our
suggestion immediately got in touch with electrical companies
and secured this equipment. The trade is demanding and re-
questing information on this line. As we discussed at Cleveland.
we say we cannot use lanterns, we cannot use open lights. we
condemn gas jets, we are findings fault within electronic light,. and
we are unable to recommend a light that i; ,;ife. I amn \ery
happy to state that thle enlgineecrs of thlc l:Lmnip c,11Ipatlie, feel lnow\
that it will be possible to overc'Ime this (i Iicultv. It nmav
require a vapor-proof globe in all cases. In lack of further
information we are recommending that yTapr-pr,,f i.4loi'. should
be used in all cases to g t u11 a;wa frm th l.,w (dLn.gtrr; that
present themselves.
I have cnifined nimvself cnlirtwl\ t,, toibs wiirk witlt tlit clct'lric
lamp companies becatlus Mr. lox fr''om tlhc lilis,,n l.;tip] \\'ork-
is here with us. Soni m n mi. ay have ntii'tlilg ainl lili,,'n1.l tI
offer regarding case's which \h ve .\1c\ e ihVn ,lier'c! 1,\ \onu i 1,r 1mi i4,tl
to your attentlioIn wl re cl1uit Iitt, r';aciLud thet' i tc h f t,'.ctit state
and fire resulted.

Dr. DUVEL-W-e have this very interesting paper before
us and as Mr. Price has said, in this work we have enjoyed the
,assistance and co-operation of the three big electric companies, the
Edison, Westinghouse, and National lamp companies, and I want
to say in this connection that I think that has been very helpful
co-operation in every way. We have the pleasure of having
with us this morning Mr. Fox of the Edison Company and I
would like to have him open this discussion and present some
of his own results and reports, in fact, I might suggest that he
present these results, first, and the discussion can follow.

By E. B. Fox, Commercial Engineer, Edison Lamp Co.
Mr. FOX-(First makes sketch on blackboard, Fig. 1.) We
have had several letters requesting information about a mill


1..Steel Wire
Shock Absorber

FIG. 1.
Mill type l;amp.

type lamp and tlcre seems to be possibly a little misunderstand-
ing as to just Vllwhat that lamp is. The mill type lamp some people
think burns at a low temperature, but there is really very little
difference in temperature between the mill type and the regular
vacuum lamp). This mill type lamp was invented for places
wvlwre you have a great deal of vibration. In an ordinary lamp
when the filamenits are burning they get soft and are apt to come

together, stick and lock, which cuts out part of the filament and
the rest of it is burned at a much higher temperature, which cuts
down the life. In the mill type, part of the filament is held by
short anchors (Fig. 1-A) and that brings this part of the filament
(indicating) out of the plane of the adjoining part and makes it
impossible for the two to lock together, no matter how much vibra-
tion there may be. There is also a little steel connection in the
form of a spring (Fig. 1-B), so that the stem is able to vibrate.
This last simply makes the lamp stronger. The difference in
temperature between the two lamps is not over five or ten de-
grees Centigrade.
The thing that got the lamp companies started on this dust
explosion work was that the Millers' Mutual made a ruling that
gas-filled lamps could not be used in flour mills. We found
they had no particular information as to what the risk was sup-
posed to be. They knew that the gas-filled lamps were hotter
and for that reason considered it safer not to use them. So we
started investigations. Our first experiments showed that we
could get explosions by breaking any of the three kinds of lamps,
gas filled, vacuum, or carbon-the only exceptions were in the
case of the small sizes of carbon and vacuum lamps (below 30
watts)-no explosion occurred. So it doesn't look as if there
is any question of ruling against any particular type of lamp.
Now, in our present experiments we are using a hot plate. You
have probably.seen the ordinary hot plate that is used under
chafing dishes, etc. This is connected up with a thermo-couple.
We had trouble making the connections, which has held up the
work somewhat. With this plate we found that we could not
get incandescence below 500 degrees Centigrade. We have no
lamps that show over 356 degrees Centigrade. So we have been
trying to get all the information we could as to fires started by
lamps and up to the present time haven't been able to get any in
our experimental work, though because of the large number of
instances reported it seems probable that we may succeed if the
bulb is raised to a high temperature by some unusual condition.
Though not directly in line with this question, it might be a
good thing to realize that mill owners are spending a great deal
of money for very poor lighting. Take an ordinary vacuum
lamp-your light goes out in this way (indicating Fig. 2 broken
line curve).
Practically all horizontal at the sides. That is tile way
they are burning them, directing no light d',iwn here ( indicat-
ing below the bulb). If they put on a shade of some kind, the

light is re-directed and you get it where you want it. (Fig. 2.
Solid line curve. The dot-and-dash line shows bowl frosted
lamp with shade.) It seems to me that this point should be
taken up with them. They might be able to use smaller lamps
and there would be less danger from broken bulbs. Vapor
proof fixtures are made with a shade, so they are at no dis-
advantage from that standpoint. I noticed one particularly
bad case in Weehawken, N. J. A man had hung a 100 watt
light in front of the scale beam so that the light was between
the scale and his eyes. If he was unable to see the scale I
suppose hlie would hang a larger light in the same place. Mr.
Reed spoke in his paper about having surfaces which would

FiG. 2.
Sh.iwini, (listrilh ti-itl frum hare liamp and with shade.

not collect the dust. That was one point I wanted to ask
him about. We all know you cannot get any particular angle
which wnuii't collect some dust. Is there any particular angle
to which you referred, Mr. Reed?
Mr. REE)D-Of course the angle of repose of dust will
depend on the nature of the dust accumulated. I made that
statement more or less as a means of preventing large dust
accumulations from forming. For instance, in some points
(if an elevator as much as six inches of dust can accumulate,
for example, on window ledges. If they were built up this
way (indlicating a sljopingi surface) instead of straight out,
less dlut coul(l acc iumulate.

Mr. FOX-I supposed that was what you meant. Now
only one other thing-I think probably most of you have seen
the questions made up at the last meeting. I think we have
asked an awful lot of questions. However, we hope we shall
be able to get some of them answered.
Dr. BAILEY-Did I understand you to say that the hottest
temperature, even at the surface of these globes, is 356 degrees
Centigrade? Of course the temperature on the inside would be
considerably higher?
Mr. FOX-The actual temperature of the glowing filament
of the Mazda "B" lamp is about 2200 degrees, the Mazda "C"
lamp about 2800 degrees and melting point of tungsten about
3400 degrees Centigrade.
Dr. BAILEY-I don't understand just what is meant by
"B" type and "C" type.

Mr. FOX-The "B" lamp is our vacuum lamp. The "C"
lamp is filled with nitrogen or argon.
Mr. PRICE-We understand. Mr. Fox, that in the hot
plate tests the minimum temperature was 540 degrees?
Mr. FOX-Between 500 and 550.
Mr. PRICE-So we have a difference of 200 degrees.
Mr. BOI)NAR-About what was the color of the glowing
Mr. FOX-I haven't seen the plate. Haven't been able to
get out to Cleveland since they), had it connected up. I am
going out in about two weeks.
Mr. BODNAR-Did your firm also make temperature
observations on the surface of the ordinary Mazda lamp bulb?
Mr. FOX-Thev made some tests with nitrogen filled
Mr. DEDRICK-Would there be any objection to making
the globe cylindrical in form and having on the top a non-
conducting material, as asbestos, between the sockets, so
that the dust falling on the top of the bulb) would not be
heated? That wiuld do( away with the angle of the globe.
Mr. F()X-I think possibly I can explain that. Thlle
Mazda "'C" lan1) is. of course, thle hottest. '[lie bull) is
filled withli an inert gas and in the neck of the bulb we have a

mica disk (A), which keeps the stem (B), as shown in figure
3, quite cool. The hottest point of your bulb is at C, figure 3.
Our reason for putting in that disk is to keep the base and
also the stem cool. We have to have a special glass for this
stem, because we find that other glasses above certain
temperatures become conductors and the glass is broken
down around the leads and gradually you get a leak. If
the bulb were cylindrical, the disc would not be as effective
in keeping the hot gas away from the stem seal.
We make tubular lamps for moving picture machines. The
blackening takes place in this lamp up above the filament as the
lamps are burned tip up. Practically all the regular lamps
are burned tip down and there would be no way of protecting
the stem.
Mr. DEDRICK-I had reference to the settling of the dust
on the top of the lamp.


Fic. 3.
Mazda "C" type lamp.

Mr. FOX-You see all of these bulbs will be blown by
machinery and I don't know whether we would be able to
increase the angle.
Mr. BATES-I understand from the drawing (Fig. 2) that
the radiant energy is given out in about that shape. Natur-
ally heat would be given out in about the same way. Have
you considered the idea of an inverted pear shaped globe
where the chance for dust collection would be on the taper,
and above that some formn of energy disbursement so that
tl'e part where it went through the globe, instead of being an
;i1igle like this would be an angle like this and no chance for
the lust to settle? It appears the dust would collect up here

and you could guard against that, possibly, by having an air
space in there.
Mr. FOX-Well, that particular lamp is a vacuum lamp.
Is that what you are referring to, or are your referring to a
gas filled lamp? I am afraid that this bulb shaped like a
strawberry, with the filament at the small end, would not be
practical for manufacturing reasons.

Mr. BATES-Another thing occurred to me-that the in-
creased temperature of the gas filled lamp is probably due to
the fact that you get both the heat of radiation and conduction.
Mr. FOX-Yes.
Dr. BAILEY-356 degrees was measured an the surface
of the bare bulb. Wouldn't that amount to more if the bulb
were coated with dust? W\Vouldn't that dust coating hold in
the heat?
Mr. FOX-Of course with a heavy coating the temperature
Mr. REED-Can you tell me in general figures just what
per cent of the present bulb would be covered with dust? I
judge about 60 to 70 per cent.
Mr. FOX-Probably. Not much less.
Mr. REED-In other words the light will be decreased at
the same time.
Mr. FOX-Yes, cut down 40 to 50 per cent in two or three
weeks simply by dust collection. If we put a vapor proof
fixture around the bulb there you have your straight walls and
less chance for the dust to collect.
Dr. DUVEL-That would also protect thle bulb from dust a
great deal.
Mr. FOX-Yes.
Dr. DUVI\TI.-Thle accumulation there w,,uld he slight and
they would clean it off from time tu timC.
Mr. MicCOL.l.AM--.-Ahout what percutnltage decrease in
illumination is caused by a vapor proof globe?
Mr. FOX-Ihlardly appreciable as the globes are of clear

Mr. BODNAR-Do you think it would be necessary to have
a vapor proof globe if you have a shade? I believe there is
a natural rise of air through the top opening of the shade, so
that no dust would settle when using a shade. Is that the case?
Mr. FOX-From a question of protecting the lamp from
breakage you want all the protection you can get.
Mr. HELMKAMP-Don't you think it would be possible
to equip this globe with some sort of shade and have the whole
thing together?
Mr. FOX-They do make such a shade and globe. The only
thing we want to be sure of is that all these precautions are
Mr. BRADY-Just why did the insurance companies rule
against the nitrogen lamp?
Mr. FOX-They knew it was hotter and desired to be on
the safe side. They had run no tests, but told us they would be
glad to have us do so.
Mr. BROWVN-How long was that dust accumulation allowed
to remain on the bulb in making the tests?
Mr. FOX-Only one hour on the one I saw, as the test was
made just before I was leaving and I didn't have time to wait
Sany longer. In some cases it was allowed to remain on four
and five hours.
Mr. BROWN-I was wondering what difference that would
make. Of course in some of the plants it is allowed to
accumulate for months and becomes baked on.
Mr. BODNAR-In one of the elevators that' I visited I found
a 75 watt Peerless Mazda in the dust on the floor. A little
dust had collected on it and I added a little more. In less
than two minutes it started to smoke and I don't think I had
over 1/32 of an inch c f dust on it. It doesn't take very long.
Mr. FOX-We have no difficulty doing that at all, but we
can't get the dust to burn. Another possibility in some of these
cases where they think they), have seen fire is that, when you
get dust charred on the bulb you see the filament through it
and it appears as if the d(lust were glowing.
Mr. PRICE-I wanted to ask Mr. Fox if there have been
ainy) further developments since our conference in New York
;about a month ago?

"..ii,:ii ... .
^ Mr. FOX-Mr. Dows, I believe, has gotten the machine run-
Sning in which he is going to have the lamps surrounded by a
dust cloud for a long time.
Mr. PRICE-For the information of our men I was wonder-
ing if you could tell us what plans the lamp companies have
regarding future work.

Mr. FOX-Our present plans are to keep on experimenting
until we can make definite suggestions to the fire underwriters.
Mr. DEDRICK-I will make a statement in regard to a
lamp being lowered into a bin and lying for a while covered up.
That happened in Chicago at one of the plants. It just hap-
pened at the time of my visit and while I was talking to the
men. I had made a point in regard to the possibility of having
fires and explosions from electric lamps. A man came toward
us with a shovel which was a mass of coals with an electric lamp
which was broken. (This was ground feed, oats, I believe.)
It was on the point of flaming, that is, it wvas all live coal. It was
found that one of the fellows had lowered a lamp into a bin
to see how much was in the bin, then left the lamp there in
about two feet of dust or material. Someone smelled smoke and
found the lamp burning, pulled it up, and went down into the bin
and discovered the mass of coals, which were shoveled out to
remove all the fire. The superintendent was there and it empha-
sized the dangers of being negligent in using lights, putting them
down into bins and leaving them. I don't think that lamp was
down there more than half an hour or possibly three-quarters of
an hour.
Mr. FOX-I don't think there is any doubt about that occur-
ring. We have even had a case of a man who took a lamp
and put it in the bed to keepl) his feet \w;arm (it was a cold night
in winter), and it burned up the bIed. (L.aughter.)
Mr. BATES-A circumstances just caine to my mind. though
not actually along the lighting uLest ionu, of an incident that
occurred in an elevator not a luindrlrd miles from here, of the
overloading of an electric circuit by connecting an electric miois-
ture machine onto ai or(linary lighting circuit. This was a four-
compartment machine, each comp)artmlnint requiring about 4.6
amperes of elect riCitv at 100 volts. That would be equivalent
to something like 75. 25-watt lamps, which, of course is greatly
overloading the circuit and endangering the elevator from fire
due to the heat gcincrated in the circuit. That is juit oIe case

that we have seen, but as electrically heated moisture machines
come into use more generally, it is something that we should
look into very fully. The machines should be properly connected
by wires of sufficient size to satisfy the underwriters' code for
electric circuits.
Mr. HIBBARD-Don't you think a fuse plug there would
take care of that, a fuse to melt at about 8 or 10 amperes?
Mr. BATES-A 10-ampere fuse would be of no use on a cir-
cuit where 20 amperes were required. Then some one would
probably substitute a tenpenny wire nail for the fuse.
Dr. DUVEL-That's the difficulty. In those cases, heavy
wire is often used. As there are more of these machines coming
into use this is an interesting question. Is there further discus-
sion of this matter? This question of electric lighting in eleva-
tors is undoubtedly a very important one. There have been
some interesting developments in the last six months and we
feel that in another six months' time something will come out of
this. If there is no further discussion on this we will pass to
the next paper.
Mr. Riley will give us some of his experiences in the presenta-
tion of dust explosion work before high school students.

Mr. Chairman: In February, while in Springfield, Ohio,
I visited the two high schools there and presented our work,
and seeing how well it was received by both faculty and students,
I decided to visit the high schools, wherever it was possible to
do so, providing, of course, that it did not interfere with my
other work in any way. In presenting this work I give a short
talk on conditions necessary to produce a dust explosion and
then go on to tell what the United States Grain Corporation, co-
operating with the U. S. Department of Agriculture, is doing to
eliminate these dangerous conditions in the mills and elevators
of this country. After this brief talk I give the demonstrations,
using various dusts, such as elevator dust, flour, corn starch,
wood dust, spice dust (from spice mills) and pulverized sugar,
and after giving the demonstrations I try to answer any ques-
tions that may be asked. In one school I visited I discovered
an instructor who evidently had never had an opportunity to

read any of our literature pertaining to grain dust explosions and
was still instructing his classes according to the old form of
text books that teach dust explosions in mills and elevators are
caused by spontaneous combustion. This instructor informed
me that explosions in mills and elevators had been discussed in
the class-room the week previous to my visit to the school and
he had informed the students that they were due to spontaneous
combustion. He advised me that he would be glad to use any
literature that the Department had in his work in the school and
he hoped to be able, on receiving this literature, to go more
deeply into the subject of dust explosions. It may be well to
mention here the fact that every principal and instructor I have
met, while visiting the schools on this work, hlias stated his in-
tention of following up this work and has asked for bulletins
and publications on the subject, in order to prepare himself to
give the information to his students. I have experienced no
difficulty in arranging for the presentation of the work at the
various schools visited, but always found the faculty only too
glad to allow me the time I needed to give the talk and demon-
strations. In some schools visited I have been ushered into one
of the class-rooms by the principal, introduced to the instructor
in charge and have then introduced myself and my work to the
students, but in a few of the schools I have been received on a
more elaborate scale, one school in Buffalo going so far as to
have the school orchestra of eighteen or twenty pieces take their
places on the stage with me and render a few selections, both
before and after the talk and demonstration. I am sorry to
say that I have not had that experience very often. The attend-
ance at this one meeting numbered 1,500 students and my au-
dience never ran under 80 students at any time. At another
Buffalo school I visited, the students endeavored to show their
appreciation of the work and my efforts in their behalf by having
the cheer leader step onto the stag:- where he lk-d the students in
the school yell, ending with "Yea. Riley." As the attendance
numbered from 800 to 1.000, it was sni)ce "Yca." Many ques-
tions were asked by the faculty and stll(iUnts inII regard to dust
explosions and their .prevention, an(l I ellieve from the interest
taken in this work. that the time given to it was not wasted, for a
in my opinion the best way ti; prcatd this w(irk of du.t explosion,
prevention is to bring it 1befire, the factultv :andl ,.tlud'nts in high
schools, and if. for lack of funds men are 1x1't :v:tilable to pre-
sent it, films that we nxow have' could bw turned over to thle State
educational authorities and through then could lie sent to the

various high schools in that State, giving special attention to
schools in sections where the grain or milling interests are largely
interested. I believe that by doing this the work will have a
far-reaching effect, and before many years have passed we will
have mills and elevators that will be explosion proof, or, in other
words, free from dust.
Dr. DUVEL-This has brought out some very interesting ex-
periences on our educational campaign that has been carried on.
You will probably wonder why the Grain Corporation got off
into this phase of dust explosion work. Of course, when we
first started it wvas primarily to protect our own interests, but
we felt that as we were co-operating with the Department of
Agriculture we could not be severely criticised, and as Mr. Riley
has stated some good will come out of it, even though the De-
partment of Agriculture is not going to be in position to follow
this work up.
Mr. PRICE-Special motion picture films of a popular nature
are nowv in preparation by the Department. They will be avail-
able for general use and can be circulated among the schools
and colleges. They have been prepared with a view to meeting
the need suggested by Mr. Riley.
Dr. DUVEL-Is there any further discussion?
Dr. BROWN-It seems to me that the question of presenta-
tion work in High Schools better be carried just a little bit fur-
ther and take it in the colleges. 1 might state that I recently had
the privilege of addressing a college audience. The president
introduced me and we put on our performance and I feel that
it was worth while; it was well received. I feel that agricultural
colleges at least would be very much interested in the discussion
of this question and particularly as related to the field work and
threshing end of it, and that the milling colleges, where they
give milling courses, would be interested. It might also be
taken up in other branches of college activity and be extended
by tlhe films which we are having prepared at the present time.
Dr. l)UV\II,-I agree fully with Dr. Brown. By getting this
into agricultural colleges, you get in direct contact with those
who intend following this line of work. I believe it would be
;L tilie tlllg if tilhe I)epalrtment could pIrepare something very
definite for a series of lectures for the agricultural colleges to
go right into or to be male a part of their courses, and arrange
to furnish them films or loan them films or slides, or something
to demonstrate.

SDr. BAILEY-I think they should also go to a number of
engineering departments. We are training a number of men in
engineering aspects of cereal work and those men do not get
much chemistry. Sometimes they go away-leave college with a
bad misconception. Then we are increasing our technical de-
partment. They are sending men where these films would be
very useful. They are keen for that sort of thing and we are
looking for them all the time.
Dr. BROWN-I think that Dr. Bailey's idea might be ex-
tended not only to include those men who are getting into cereal
work, but to all types of industrial work.
Dr. BAILEY-There are many men who will go into the
cereal industry, and I think they should certainly be provided
with this material. I think the men who are in college now
should get this training.
Mr. RILEY-I think the engineering courses should give
consideration to this work.
Dr. DUVEL-Is there any further discussion?
Mr. REED-I think the colleges should be visited before
high schools. Mr. Riley says that by reaching the high schools
you reach them all, but you reach them before it would be neces-
sary. I doubt very much if they would hold a meeting at tlhe
high school I attended; such a man would be at a disadvantage.
Mr. RILEY-One of the meetings I held happened to be in
his state and they were very glad to have me there. The super-
intendent of education informed me that if I could nut get
there, to send a request to \Vashingtoii that such a deinonstra-
tion be given and to use his name in this request.
Dr. DUVEL-There is 110 (10111 oult t tll;hat 'e'.1le are gettinlg"
more interested in his subject. We\ have about c,,vered the dis-
cussion on this subject; it is now after twelve anl. I beliCeve, we
had better adjourn until this afternoon. I am1 gladi to annouTnce
that Mr. Barnes will attend our meeCCtinlg tills afternoi)31 and give
us his views of the imlortaInce (If this work.
Adjourned until 1 :30 p1). 1m.


April 23, 1920.
DR. H. H. BROWN, Presiding.
Dr. BROWN-The meeting will please come to order. This
afternoon we expect to have a discussion of some of the results
of our actual work in the field during the past year, and more
particularly the results of our inspection work. As you know,
the work of the Department, in co-operation with the Food
Administration last year, was divided into five districts. On ac-
count of curtailing some of the activities and having cut down the
force, in the present campaign the country was divided into three
districts. We will now hear reports of the results of work in
these different districts, first in the East, then in the Central North-
west and then the Pacific Coast. We will have all these reports
and then follow with the discussion covering the entire country,
rather thlian taking the various districts. I take this opportunity
to call upon Mr. H. R. Brown, who has charge of the Eastern

Mr. BROWN-Mr. Chairman: I had prepared a regular paper
on this subject showing statistics by grade and number, but as
one man who came into the office said, there are. "white lies,
black lies, and statistics", I therefore tore that paper up and you
will have to take my word. The plants visited in the east were
mostly those carrying Grain Corporation stocks. I think our
best results have been obtained by the use of our miniature ele-
vator and the cheese-cloth demonstration. We hope to be able
to give you a demonstration later in the afternoon. I think we
have this elevator demonstration down pretty fine now and quite
an improvement on our former demonstrations. I might also call
your attention to the method of giving the cheese cloth demon-
stration,-another improvement which I discovered about two
weeks ago. In large halls where we have held meetings with an
attendance of about 1000 people, I noticed that they had some
trouble in seeing just howv the fire is started. I found that by
putting a larger atLount in the cheese cloth and tying it on the
end of a pole and then shaking the pole over the flame, that this
makes the demonstration much more effective. There are two
a 78

other points I want to bring out in taking up the results of this
work, and that is, demonstrations given before fire departments
and the high schools. Mr. Riley told you about the high school
demonstrations, and I think that matter was thoroughly discussed.
It is agreed that it would be a fine thing to bring this matter
to the high school students and also to the engineering societies
in the colleges or technical schools of the country. I think our
men made special efforts in different cities to take up this matter
with the various fire departments. In this way we have ob-
tained the co-operation of these men in reporting fires in mills
or elevators. On certain occasions we have been able to get to
the scene of the fire right with the company, the Chief taking
the men to the fire in his car and they were there to see what
was going on. This happened to Mr. Riley and Mr. Helmkamp.
They happened to be at the fire house when the alarm came in.
In one case the Chief called up the man at the hotel and picked
him up on the way. They have been taught that it is especially
dangerous to turn a stream of water into a cloud of dust. They
have also been taught that it is to their advantage to visit the
plants frequently and endeavor to impress upon the employees
the necessity of keeping the place clean, not only for their own
protection but also in the case of the firemen who would be
called upon to fight the fire. There is one special feature I want
to call to your attention. Mr. Witmer is the hero in this case.
One elevator down in Philadelphia we have been after them for
three years to put in an improved lighting system. They have
been using open gas jets in this plant, so the foreman said, for
forty years at least. We have called this to the attention of the
manager, the foreman, the superintendent, and even taken the
matter to the railroad company and the owners of the elevator,
and they said their plant had been operating for forty years and
nothing ever happened We had just about given up this case,
when Mr. Witmer seemed to get on the right side of the manage-
ment. I am now pleased to say that an improved lighting system
has been installed in this plant, which is one of the results for im-
proving plants in the eastern district. A small number of ex-
plosions have occurred in the east. Later on we are going to
take up several minor explosions.-two plants in Buffalo, and the
Cincinnati explosion. Mr. Riley will tell you of the explosion at
the Spice Works in Cincinnati and at the H. 0. plant in Buffalo.
Mr. Helmkamp will give you a short account of the explosion in
the Curtiss plant in Buffalo. Mr. Price. in his summary of the
work for the entire country, will give you some figures and

statistics, I believe, on the results of inspection work, showing
improvement in the condition.
Dr. BROWN-I am sure this is an interesting report. Before
we go on with a discussion of it, I take pleasure in calling upon
Mr. Brady to give us the result of his inspections of the central
and northwestern district.

Mr. BRADY-Mr. Chairman: Our work has been confined
mostly to the Grain Corporation plants. We have a large area
to cover and it was our object to visit these plants at least once a
month and make inspections of them. In doing that we found
we could devote but little time to outside work. However, we
used to get ten days out of every month whereby we could go
to the various outlying plants, and we invariably tried to put
on a show for the benefit of the larger mills. We always carried
our pictures with us and invariably found a place around the
mill where we could give a demonstration and put on the pictures.
We found that the millers were very grateful for this work, and
believe that we did considerable good in educating the men along
the dust explosion hazards. We recieved very good co-operation
from the fire departments through that portion of the country
also, and in Minneapolis the Chief now has the men make a
regular inspection of the elevators in that city, due primarily to
the work that we have started there. We had occasion to in-
vestigate two explosions in that territory,-one was the Kansas
City explosion in the Murray Elevator, the other an aluminum
goods manufacturing company plant at Manitowoc, Wisconsin.
In connection with the small meetings which we have had at the
various small outlying plants, there has also been put on in that
district probably 15 or 20 large meetings in the larger cities, such
as Chicago, Milwaukee and Minneapolis, where Dr. Brown or
Mr. Price have made addresses. No doubt Mr. Price has the
figures and knows the number of meetings held in that territory,
and as for making the summary. Mr. Price can fix up the figures
on that I believe. We have made around 855 inspections in that
territory altogether since the Grain Corporation took over this
work. That completes the report for the northwestern district.
l)r. BRO\\WN-Iefore we go uin to the next report. I believe
it would be interesting, Mr. llrady, if you could tell us some

specific instances of improvement that has been brought about
S in your district as a result of the inspection work.
Mr. BRADY-Well, I will take Chicago, for instance. I just
had a letter from Mr. Farrell, in charge of the inspection work
there for the Grain Corporation, and in that letter he said that
he was very pleased to note that of late the reports which have
been coming in from us had been showing a marked improvement
in that a good many houses that were formerly in the "B"
class had been raised to "A." I might say that in general that
covers the entire northwestern and central district. There is no
question but that the houses in Minneapolis have been improved,
and one of the insurance men was remarking to me along those
lines, just the other day, that since we started the work up there
the elevators had been gradually improved, and hlie felt that it was
in a large measure due to the educational work that had been
done in the district.
Dr. BROWN-Of course, we realize that the greatest amount
of grain in this country is handled through the Middle West
and works east, and some of us who are in the East sometimes
forget that they have grain on the Pacific Coast, and that they
have problems out there, so that it has been necessary to extend
our work to that section as well as to others. Mr. MIcCollam,
who has had charge of the work in that section, will now tell us
something of the results obtained there.

Mr. Chairman: In making this report. I ju-,t want to speak
very briefly about four things: First, the inspection work; sec-
ond, the very beneficial educational tour on which I)r. Brown
was associated with us in our district; third, the co-operation
which we have had throughout our whole district with the State
Industrial Accident C(,mmission; fourth, the interest which other
manufacturers and industries have taken in our work. In re-
gard to the inspection work. Mlr. Bodner and myself (lid all of
that, and I am sure that I can report an ipnijrovement in all of
the plants on the Pacific o'ast that needed improvement. Be-
sides giving attention to the ;rain Corporat in stocks in storage,
which, of course, alwa'as came first, we concentrated mour atten-
tion on the mills and trlcv'atcr!% which particularly needed clean-
ing and which needed imnprovmenlt. I might cite two instances

particularly in which mills were improved. One of these in-
stances was a mill in San Francisco which was improved from
a "CC" mill to a "BB." The other was a mill in Seattle which
was improved from a "CC" mill to a "BA," and I do not think,
in this latter instance, there can be very much more desired in
the way of improvement. I have no explosion to report-no
disasters or explosions in the Pacific District. The only in-
teresting experiences along those lines I covered in my talk this
In regard to Dr. Brown's meetings in the Pacific District, I
might say that the meetings were held at Spokane, Tacoma, Port-
land, Seattle, San Francisco, Los Angeles, Stockton and Salt
Lake City. The one at Stockton was held at the Sperry Flour
Company. A very large number of employees were present,
and I think it did a lot of good. All of the meetings were very
well attended with the exception of the one in Spokane, although
that had a very representative audience present. The co-opera-
tion of the State Industrial Accident Commission has been very
complete. Every State in my district has an Industrial Accident
Commission or a Safety Department. In the State of California
one of their engineers has been assigned to accompany me on
inspections that I made throughout the State and this has been
accomplished in a good many instances. He has an automobile
which makes it very pleasant for me, and we often tour around
and visit plants together. He confines himself mostly to plants
that I want to visit. In Oregon the co-operation with the State
Industrial Accident Commission there was started by a confer-
ence which we had in Portland with the State Labor Commis-
sioner and the Chairman of the Safety Board. Mr. Bodnar and
myself put on a demonstration for them and told them all we
knew about dust explosions. They were very much interested
and promised co-operation. Since then that has been carried out,
and on numerous inspection visits made by Mr. Bodnar he has
been accompanied by a Safety Inspector. In Washington that
has been carried out also-Mr. Bodnar having been accompanied
by the Safety Inspector. In Utah and Idaho, the Safety Depart-
ments there are in their infancy, but I was promised in Idaho
that as soon as they got their Safety Department working they
would be delighted to arrange a tour through the whole State,
at their expense, visiting any of the plants that I designated
which I think should receive attention, which I think was a very
generous offer. In regard to the interest in our work in Cali-
fornia, I might say that the industries there are very much in-

terested. Just before making this trip, I had an interview with
Mr. McBride, of the California-Hawaiian Sugar Refineries, at
Crockett, California, turning out 1,700 tons of refined sugar a
day and 40 tons of powdered sugar. Mr. McBride said that he
wished it might be possible to have a man stationed at the re-
finery for some months to study the dust collection problems
that they have there, and also that it might be possible for the
plant to stand some of the expense, if such was necessary. Just
to give you an idea of the interest which has been taken in our
work, the other day we had a request from the Seattle Manu-
facturers Association for a demonstration and lecture before that
body. The request came in from the Secretary.
Dr. BROWN-I certainly think that good work has been done
on the Pacific Coast. WVe are a long ways from it but even
though our work now has to be discontinued I can readily see
where somebody could tour all of Idaho at the expense of the
State, and possibly spend a few pleasant months on the Pacific
Coast in the sugar industry.
These three subjects are now before you gentlemen for dis-
cussion. You have all worked in one or more of the various
districts, and while we are later to have a general discussion
of your personal experiences in making inspections, in which
I hope each one of you will take a hearty part, we would like
to have some discussion regarding the results of the work in these
particular districts.
Mr. PRICE-I want to ask the men in the different districts
what, in their estimation or feeling, has been the effect upon
the trade or industry? Have you been well received, or have
you met with any opposition, and what has been the general feel-
ing in the respective districts?
Mr. BROWN-I do not believe there is a single plant in
the East where we have had any trouble in making the regular
inspections once a month or every six weeks. Now and then
we would get into a discussion with the 'mnien as to how clean
a plant should be kept, but as far as there being any real opposi-
tion or objection to our work, there is absolutely none at all in
the district. In fact, we are commended for the work and the
management is willing to carry out every suggestion we make.
If we call their attention to dust accumulations, they are generally
removed even before we leave the house.
Dr. BROWN-I think Mr. Price had in mind not the ques-

tion of objection, but of the receptivity of the industry to the
SMr. PRICE-Yes. Do we get what we want done, or gen-
erally speaking, do you feel we have gotten anywhere?

Mr. BROWN-Yes, I think the management of the different
plants has taken up this question a little more seriously possibly
during the last six months or year than they did at first. I do
not know that we are any more welcome now than we have
always been. They always treat us very courteously-the ele-
vator superintendent usually arranging to take us to the plants
in cars. I might call your attention to the case in Baltimore,
where the elevators carried Grain Corporation stocks, and on
our visits there the superintendents asked for our advice on a
number of questions and have carried out our suggestions.

Dr. BROWN-I think it might be interesting if we would
know the condition of the worst elevator in this district and its
present condition.

Mr. BROWN-The worst case was an elevator where they
were using open gas flames in a dusty room. They now have
installed the latest improvements. In another elevator on a
number of visits we found lanterns being used in the plant.
They have electric lights, but when they start unloading or load-
ing cars, the first floor gets so dusty that they can't see the electric
lights, and the man carries the lantern around to find his way.
We have taken that question up and I do not believe there is a
lantern used in that plant. So practically all our suggestions have
been carried out to the letter.
Mr. BRADY-As a whole we hav6 had very good co-operation
from the men. In Minneapolis, the Chamber of Commerce men
have their association there and meet once a month, that is, the
managers of these large terminal elevators meet there once every
month. At the start we sent out the reports to the Zone Agent,
and then it appears that these managers got ratings of the various
elevators which were posted up on the floor of the Exchange.
They at once started to compare their ratings at this meeting
and some of then were go(ul and some were bad. That had
a tendency to stimulate their interest in trying to have one ele-
vator compare favorably with the other as far as good rating
was concerned. WeC did IAnt continue that practice, but there is
no question but that it had its effect. Once they got that rating,

the manager made it a point to impress upon his superintendent
to keep that plant in good shape. As far as keeping the plants
clean and carrying out the suggestions we made along those lines,
we have had very good co-operation. We have also had to
contend with the lantern in Minneapolis to some extent, as you
have had in the Eastern district. As a' whole, most of the
superintendents understand the hazard of using a lantern, and
we have only two or three in that city who continue along this
line. The milling journals aud trade journals have given us
good co-operation, by giving notices, whenever we desired them,
relative to meetings, and they have written up the results of some
of these larger meetings, such as Dr. Brown and Mr. Price
have conducted.

Dr. BROWN-How about the receptions you have received,
Mr. McCollam?

Mr. McCOLLAM-The receptions that I have received have
been all that could be desired On the Pacific Coast there are
three large milling companies, and every one of them is progres-
sive, and they all seemed determined to co-operate with me as
much as possible, and I believe in the case of one of the com-
panies especially, they carried out nearly every suggestion that I
made, and I believe that is the right attitude; that is, it reflected
on the other two companies as well. I might say that I made
a good many personal friends in the milling and grain trade.
That may be desirable in one way and it may be undesirable in
another way. It made it rather hard to make rigid inspections.
On the other hand, they always seemed glad to get my suggestions
and really mean to carry them out. I might say with respect to
one large mill whieh is thirty miles from San Francisco, and
it takes a day to make the inspection, that is, making the trip
and making the inspection, and getting back, I was always re-
ceived warmly and treated to lunch every time I visited there.

Dr. BAILEY-I wish to note briefly my opinion on the situa-
tion in the Northwest. I think it is very difficult for the men
who actually are in the work to size up the situation as well
as some of those outside. My feeling has been, especially in
the last few months, that this work is leaving a profound impres-
sion on the industry in the Northwest. A great deal has been
accomplished in setting those people to thinking, and giving them
definite, concrete suggestions to carry out in the future in either
remodeling or rebuilding plants in that district.

Dr. BROWN-I am sure this statement is very gratifying,
especially from one who was at one time associated with us,
and since that time and before has been associated with the trade.
He has been able to obtain a perspective that we probably could
not get. I would like to ask the men in charge of the district
to say in just one or two words whether they feel that the work
has been better received in the past year than it was last year,
or in the past few months; or what has been the receptivity of
the trade; has it been increasing or decreasing?
Mr. BROWN-In our work, I will say "yes," it has been
improving during the last year. I think the fact that the work
was taken up in co-operation with the Grain Corporation has
to a certain extent given us a better introduction at the plants.
Perhaps the management has a very healthy respect for the
Grain Corporation, or perhaps the work has been brought to
their attention more forcibly through articles in magazines, and
they seem to be more familiar with the work now and are
more anxious to obtain our opinion on the subject.

Mr. BRADY-I feel about the same as Mr. Brown along
those lines. There is no question but what they are paying more
attention to the dust hazard than they have before. That is
simply due to the educational work that has been done along this
line. As far as being received any better now than we have
been in the past, we are getting about the same reception.
Mr. McCOLLAM-I think Mr. Brown has struck the key-
note of the matter when he said the work was becoming very
well known among the milling trade. It is really a necessity,
and I think they have realized that now, and that is why we
have been received in such a hearty manner by the trade.
Dr. BROWN-Is there any further discussion upon this side
of our inspection work? If not, I think we will proceed to the
general discussion of experiences.

D)r. BRC)XVN-I am sure that all of us who have been in
llic field, who have been in contact with the trade, and pIr-
ticularlv you men who have had an actual contact with the
men who are working in the plants, must have some very
interesting things to tell us of your experiences, of the results

of your particular work. I am sure we would be very glad
to have a general discussion of this question from each and
every one. Don't hesitate and wait one upon the other, but
somebody start. If you don't I will call upon someone.

Mr. HELMKAMP-I might say that at the start of the
work in Buffalo, N. Y., we started putting on demonstrations
and visiting each elevator and in all my visits there we had
very good meetings. However, when I got to the Central
District this work had been very well covered by Professor
Fitz and Professor Swanson in the states of Kansas and
Oklahoma and even though most of these plants had had a
demonstration put on, I found no trouble, except in possibly
a half dozen instances where they did not desire any demon-
stration. So I think that alone shows that the work could
be continued along these lines.

Mr. BODNAR-In connection with the small blower that
we have been using for giving dust explosion demonstrations
is an experience that occurred to me for the first time. I was
giving a demonstration with corn starch. The glass tube had
something like two inches of dust in it and the resulting ex-
plosion from this amount of dust was sufficient to make the
windows and doors of the office in which the demonstration
was being given rattle quite audibly. As nothing like this had
ever occurred during a demonstration in my experience, to
prove that no wind from the outside had caused the windows
and doors to rattle, I immediately recharged the blower with
a trifle more dust than on the previous occasion. This time
there was no doubt about it. Even the small amount of dust
I was using was sufficient to develop a pressure which had its
effect on the windows and doors. The manager and the men
around showed quite a bit of interest in the demonstration.
The manager of the elevator declared that if I ever revisited
their, plant I would certainly find it cleaned up properly.

Mr. WITMER-I feel that the "baby" elevator and the
cheese cloth demonstrations were a great assistance in our
work. I find that after giving demonstrations to the men at
the different plants they were more careful and took a greater
interest in keeping their plants clean. In several instances
which I recall, the workmen when not busy with their regular
work would be found removing dust accumulations from
within the building, although having no instructions to do so.

c", "

Mr. PRICE-I had hoped Mr. Witmer would tell us about
the demonstration in which he assisted here in New York,
using the "baby elevator."
Mr. WVITMER-That demonstration was in a church,
possibly the accoustics may have had something to do with
it. The report was very loud. The top went off very suc-
cessfully and I believe everybody was surprised and dumb-
founded when they beheld the flame shoot out of the elevator.
We had quite a gathering-one hundred, possibly-and every-
one seemed to be greatly interested.
Mr. ROETHE-Mv contact with the officials and em-
ployees of different mills and elevators has been limited to
visits in connection with tests made along static studies and
for that reason I have not had the chance to get around as
much as most of the men, but I was particularly impressed
during my two weeks of investigational work last summer by
the attitude shown by the different managers and foremen,
particularly at Seattle and Minneapolis. When we stated
the nature of our visit the managers were very anxious to
help us in every way possible. They were interested even to
the extent of accompanying us from floor to floor to see what
developed and were very anxious to receive any information
which would enable them to eliminate static charges, and I
would very much like to see a further study made over a suc-
cession of days during the winter, perhaps, in order that con-
clusive results could be obtained and this information be
compiled and published in an approved form.

Mr. LIND-I can cite possibly two instances. I will refer
now to a new terminal in Minneapolis, a three million bushel
plant of recent construction. I happened to be there possibly
two nimonths ago, and I was furnished with a guard who showed
me throughout the entire plant and who also called particular
attention to the various improvements that they have, in-
stalled with reference to handling the dust hazard. Prior to
this last visit I had also had a talk with the superintendent at
a meeting that took place in one of the large elevators, an-
other plant close by, in which he said they were experiencing
considerable difficulty in their tunnels with reference to dust
;iccuInulation. This 'tunnel was two blocks long and while
they used a pick-up system on the return end, they were not
able to eliminate the accumulation entirely and for that reason
would like to have me accompany him through an inspection

tour of the tunnel, which I did. At this time the tunnel was
in a very dusty condition and I suggested then a collecting
system, hooded over the entire length of the conveyor belt
at intervals of possibly 40 feet, and he then suggested that it
may not meet with the approval of the various state weigh
masters and the State Grain WVeighers Commission, but they
were willing to experiment further and they did so. After
the installation had been completed I again went over the
plant with this superintendent and they had these suction
hoods installed about every 40 feet. The belt conveyor is 36
inches wide. It is a direct suction in a sense but indirect in
another sense, as the hoods are possibly 6 inches or more
away from the surface of the belt. Since thile installation
they now have no trouble whatever with dust accumulations
and you can see the entire length of the tunnel from the ele-
vator end to the mill end. There were several other rcom-
mendations that I advised, which have been made, among
them the installation of vapor proof globes throughout the
entire tunnel.

Dr. BROWVN-I am sure that we greatly appreciate this re-
port and I might state in that connection that we have always
had excellent co-operation with the large companies in Minne-
apolis. To give you a little idea of their interest in the (lust
question I might relate an incident which occurrc(l in Minl.-
apolis in the Fall-when we had our meeting there in Nove.mber.
Mr. Fitzimnons and I dropped around to the office of the largest
flour company and we found there one of the officials of another
large flour company. Among other things, we were discussing with
him the dust question. I e told me that they were considering
an installation whereby they would precipitate the dust and
keep it from coming out of their collectors 1Iy use of a spray,
in other words, by means of washing the air. I raised the ob-
jection that they would waste that product. I le said: "It is not
a question of the loss and value of the dust. It is a question
of preventing dangeroutis conditions."

Mr. REE.I)D-I think most of you men have had suomne inter-
esting experiences, but I consider that I've hadI the most inter-
esting experience of any of you. I don't think ainy of you have
ever had two policemen knock on 'outr ,door at 6 o'clock i1
the morning and hand you a subpcenia. I din't think atn\ (if %-'[I
have had the experience of reading what \you ulid nol say in the
morning newspaper. I wish to relate secral other very inter-

testing experiences that I have had. In one case down in West
Virginia I interviewed the general manager of the largest mill
in that section of the country. In my efforts to explain the work
to him I received a cool reception. He told me that he knew
all about dust explosions and that I had better go upstairs and
talk to the miller. He objected to the men seeing a demonstra-
tion. In the interview with the miller I was given every and
all consideration that could be gives to me. After I had seen
the miller I walked down stairs to get my elevator in shape and
in walking through the mill floor I noticed this same general
manager, with a cigarette in one hand, strolling through the
building. In talking to me, with a cigarette in one hand, he
said: "I read all your literature and I know everything about
dust explosions." He knew all about dust explosions and yet
there he was strolling through the mill with a lighted cigarette.
There were two explosions in that plant and in one case the
plant was destroyed by a fire from a dust explosion. The miller
related two instances where explosions had originated in the
Another instance down in Virginia, I interviewed the head
Miller of a very large mill in that section. I told him I wanted
some dust to blow up the small elevator. He said, "I don't know
of any place unless we go down in the basement." We went
down into the basement. The electric light bulb had burned out.
"Would it be safe to strike a match?" he asked me, even after
I had told him about the dangers of open flames in mills and
Mr. McCOLLAM-I am very much interested in that spray
method of collecting dust. That is a method used in chicle re-
fineries. They take that into solution and crystallize it out
again. I had hoped you would say something about electro-
magnetic or electrostatic collection of dust.
Dr. BROWN-Well, I don't believe we want to discuss that
particular question right now. I might bring that out possibly
in the paper I may give in the morning. I will keep that in mind.
Mr. REED-You just minade a statement that one concern
considered the necessity of removing the dust more essential than
the necessity of keeping the dust and selling it. In other words
you laid more stress on the removal of the dust than on its value.
I was inspecting a feed grinding plant in Pittsburgh last year, in
which the manager staled hlie wanted all the dust he could get,
for feed, as he paid good money for it.

Dr. BROWN-Another pleasant experience. We will pass
this up at the present time and unless someone else has some-
thing to say on this subject will pass on to the next paper.
Mr. DEDRICK-I would like to relate a little experience
on the effect that the big explosion at Cedar Rapids had in
Chicago. Shortly after our work ended with the Government
I received a telephone call from a large elevator concern asking
me to come over. They wanted to have an interview in regard
to making some suggestions. They were very much alarmed
over the possibility of having a dust explosion at their new
plant-feed plant-concrete-supposed to be one of the latest
improved plants. So I went over and we had a little talk and
they requested me to go over both elevator and feed plants and
make certain suggestions to the superintendent and make a
written report, with drawings, suggesting the different points
where they might make improvements. Mr. Hibbard and I spent
half a day or more going over the plant. Wherever there was
dust made, as at the elevator heads, bottom of the boots, in
basement, along the belt conveyors, certain rolls and feeders,
faulty dust collector connections, etc., we made a drawing. They
were having one difficulty with their bins which were made of
steel and rather narrow. The material packed in the hopper
outlet so that when they came to draw it out it would bank up
in the hopper. They had to make holes at the junction of the
spouts and hopper so that they could use a pole to poke and
start the stuff. I suggested the plan of putting an agitator in
the bins with arms extending out so that they could work it
from below, so that this would start the stuff without having it
come down with a rush and causing a great litter and clouds of
dust. There were, I think, altogether, about 15 different points
where they could make improvements, and I made drawings
showing how these could be accomplished. When I submitted
the report they assured me they were going to follow these out.
I don't know whether they did or not, as I was never there again.
I left the work shortly after that. Perhaps Mlr. Ilibbard would
Mr. HI-IBBARD-t was at the lplanlt about three months ago
and they were still "going to follow out those recommendations."

Dr. BROWN-WVe have next on the program a review of the
various explosions which have occurred during the past year.

As there are several of these and our afternoon is somewhat
crowded and we are planning to have a little talk from Mr.
Barnes, from Dr. Alsberg and possibly from some other men re-
garding some other phases of the work, I feel that we should
limit the papers and discussion on these subjects to not over ten
minutes each and consequently I am going to call you at the end
of five minutes. This will give you one minute to sum up and 4
minutes for discussion. The first paper will be by Mr. Reed on
the Kansas City explosion. Before we have the discussion I
will then call upon Mr. Helmkamp and we will have the general
discussion of the two.

By MR. J. 0. REED.
The Murray elevator at Kansas City, Mo., was destroyed by
a dust explosion on September 13, 1919. Fourteen men were
killed, ten injured, and the property loss was estimated at
$650,000. The plant was constructed entirely of concrete, tile,
and steel, and the most modern type of machinery obtainable
was used. The Murray elevator was a plant of one and one half
million bushels capacity, and consisted of three units, the working
house and the two units of storage tanks. The explosion, accord-
ing to the result of the investigations that were conducted after
the explosion occurred, originated in the basement. Now this
basement was perfectly tight. The walls in the working floor
were tight and for that reason the working floor walls and the
floor of the working floor were blown out. The explosion propa-
gated up through the manlift tower on the side of the elevator into
the "Texas" and blew out the tile walls of the "Texas". I don't
think there is an explosion which has ever occurred in a grain
elevator in this country in which there was more force displayed.
I doubt if tie Cedar Rapids explosion displayed any more force.
The story of the explosion will probably be of interest to some
of you. The men in the plant were cleaning up and during the
course of the cleaning-up process the explosion occurred. Of
course the newspaper reports came out later on and made the
statement that there was so much dust stirred up in the sweeping
process of the plant that a spontaneous combustion of dust took
place and an explosion naturally would result. I would like to
give you just a few points in the recommendations that we made.
The first inspection was made on the 5th of September, 1919. In
this inspection the following notations were made regarding the

-condition of the plant, for instance, the equipment was said to be
good and the maintenance very poor. These are the direct state-
ments which were made in the report: "Clean up this house and
keep it clean. Employ sweepers. Install vapor proof globes and
remove all carbon filaments." At the end of the report the state-
ment was made: "This plant is dangerous and even though fire-
proof, will explode if its present condition is permitted to exist."
That statement was made on the fifth day of September. On the
12th of September another inspection was made and the state-
ment was made in the report that the maintenance of the plant
was still poor and that the first recommendations should be carried
out. Now I would like to give you, or just state to you the con-
dition of that plant the day before the explosion occurred-but
I haven't time. The Coroner's record contains all the evidence if
you are interested.
Dr. BROWN-Mr. Helmkamp will give us a little of the effect
of the explosion on the inspection work in the vicinity of Kansas

It was not until one month after the explosion at the MIurray
elevator in Kansas City that I took up the inspection work in that
vicinity. One of my first visits was to the officers and the man-
agement of the Murray Grain Elevator. My reception there was
all that could be expected. All the recommendations which were
offered by our force were gladly received and I am pleased to
say that a great number of them are being carried out in re-
constructing their plant.
During my inspections of plants in the Southwcst for the first
few months the subject of the Murray CxlIIIsioll was brought up
a great many times. Of course when there was any misunder-
standing at any time as to the cause I corrected them and ex-
plained the cause of the disaster to tlhe best of inv ability.
The terminal elevators in (O)maha and Kansas Cityv, with tlhe
possible exception of one or two, I found to b e tlhe cleanest that
I have ever found in any one locality' alnd I think that this is the
one big improvement which can be said to result from the Kansas
City explosion. In nearly all cLses recommendations were very
gladly received and in many cases I was asked to pay particular
attention to certain parts of the plant or to certain equipment in

the plant in order to determine the dust explosion hazard. At all
times every possible courtesy was shown to the men engaged in
this work.
Another improvement resulting directly from the Murray
explosion was hiring of regular sweepers by all the plants that had
heretofore had none, while those having sweepers put on addi-
tional men in order to keep the plant in as good a condition as
The explosion brought forth renewed activity on the part of
the fire underwriters and insurance men. These men, who in the
past had regarded a fire-proof plant as an extremely safe hazard,
now began to hustle about and reinspect the plant with the dust
explosion hazard in view. Several times during my inspections I
encountered these men and together we inspected the plant and
discussed the various hazards, So as another result, I might say
that the Kansas City explosion brought home forcibly to the
insurance and fire underwriters the dangers of dust explosions,
and the fact that a fire-proof plant was not explosion-proof.
In summary I will say that the effect of the explosion on in-
spection work in the Southwest was not only to make the in-
spection work easier because of the fact that the superintendent
made it a point not to hide any of the dangerous places, but
would point them out and inquire for the remedy; but also the
fact that recommendations were gladly received, although in some
instances they were not followed out as promptly as you would
judge. However, in many cases the plants which had been rated
as in C condition by Mr. Reed were found to be in A condition
upon my next inspection.

Dr. BROWN-Mr. Helmkamp has not used all of his time.
Mr. Reed may utilize the one and one-half minutes remaining
to tell us about the condition of that plant.

Mr. REED-The elevator was found to be in a bad condi-
tion. Only the floors had been swept up, where there was an
indication of sweeping. Everywhere there were dust accumula-
tions overhead and no effort had been made to remove these
accumulations. At places there was so much dust oh the flange
of the "I" beams that no more dust could accumulate there, be-
cause the angle of repose had been reached. Every here and
there were piles of dust. In the basement there was.very much
dust, especially overhead and on the trunking of the dust collect-
ing system used for collecting the sweepings. This dust on the
trunking of the dust collecting system was very black, old, fine

-and dry. I gathered this dust, with the help of one of the Grain
Corporation men, in a portion of a burlap sack and secured all
I desired within about one lineal foot on the pipe. There was an
excessive amount of dust in the shaft containing the stairways,
elevator lift, and main rope drive. There were piles of dust and
growing grain in the tunnels leading underneath the storage
tanks. The dust was several inches thick on and underneath
two grain cleaning machines located in the northern end of the
working floor. The switch and fuse boxes were still very dusty.
There was an excessive amount of dust and oil on the journals.
There was a hot bearing on the countershaft driving the fan on
the top floor with a great amount of oil on the journal. Oil, it
appeared, had run through the top floor from the blower fan,
and a large pan had been placed underneath this floor to catch
the oil. On the top floor I found a very poor extension cord
worn at the socket. There were many carbon filaments used for
lighting everywhere in the plant. There was no protection on
electric light bulbs and almost all thee bulbs were very, very
dusty. No vapor proof bulbs were used in the plant. I tried
to inspect several elevator boots, but was unable to pull the slide
out from underneath the revolving buckets, so I do not know
whether these boots were clean or not. The trunkings of the
dust collecting system were in a very bad condition and needed
repair. On the top floor there was a partially filled fire ex-
tinguisher. Replacements, such as belting, elevator buckets,
ropes, sacking, etc., were piled everywhere on the working floor
and were covered with dust. The superintendent stated that the
fan on the dust collecting system had broken down before my
first visit and that it was for this reason that the plant was dirty,
but I observed on both my visits that the fan was in operation.
There was a great accumulation of d(lust under a large machine
in the basement. Workmen had swept around but not undlerneath
this machine. The general condition of the elevator, as comn-
pared with other modern elevators of the same type that operate
at full capacity daily, was dirty and dusty. \Vithout doubt the
Murray Elevator was the poorest kept anti dirtiest elevator in
Kansas City.

Dr. BROWN-Now y',u have the repoLrt of this explosion
and its effects on the plants in that vicinity before you.

Dr. BAIL.EY-I note from the photographs that apparently
the grain drier was completely demolished. Was that especially
dirty ?

Mr. REED-That was demolished, I think, due to the fact
that the walls in the working house were blown out.
Dr. BAILEY-Well, you don't think then, that it was the
result of an explosion within the drier?
Mr. REED-No sir.
Dr. BAILEY-Grain driers usually are especially hazardous
since the dust there is thick and dry.
Mr. RILEY-If the explosion had taken place, in the drier
the elevator wall would have been blown in, would it not?
Dr. BAILEY-I was not assuming that the explosion origi-
nated in the drier, but that it might have propagated through the
Mr. PRICE-The tremendous force exerted by the explosion
is indicated by the fact that parts of the 16-inch concrete wall
were found a considerable distance from the elevator, so any
equipment or mechanical devices were subject to a great deal of
force by something falling as the explosion occurred.
Mr. REED-The entire working shed of the plant was blown
away. There was nothing left of it. I wish I had better photo-
graphs here. I would like to show you just how the drier house
was blown out. There is no indication that the explosion oc-
curred in it, as part of the drier house would then probably have
been on the working floor.
Dr. BROWN-You mean that the indication would be that
it propagated from the working house through the drier?
Mr. PRICE-I would like to suggest, in connection with this
explosion at Kansas City, that the superintendent was in charge
15 years as I recall it, and never had any previous experiences
of this nature and was recognized as being very competent. I
have had the question asked a number of times: "What reason
can you give why this explosion did not occur before?" Now I
know how we feel about that, but that to me is one of the peculiar
things about these dust explosions, and why it would occur in
the Murray Elevator in Kansas City and not in any others.
Dr. BROWN-I might state that here is a copy of Mr.'Reed's
inspection report. The first inspection was on the fifth of
September. It states: "This plant is dangerous and even though
fireproof will explode if the present condition is permitted to