Firemen and Prevention of Grain Dust Explosions
One of the Worst of Fire Hazards—Educational Campaign by Government to Teach Cause and Prevention—Recent Disastrous Explosions—The Creation of the Dust Hazard—How Firemen Can Assist
THE importance and necessity of prevention of grain dust explosions and fires was recognized in the early stages of the world war. When the matter of food conservation was being given every consideration it was apparent that every effort should be made to prevent the loss and destruction of our stores of foodstuffs in the mills and elevators throughout the country. The necessity of this conservation was brought home in a very definite manner in October, 1917, by a very disastrous grain dust explosion and fire in one of the largest elevators in the East. In this one case alone, as told in a paper read before the annual convention of the Illinois State Firemen’s Association, the grain loss was equivalent to bread rations for an army of 200,000 soldiers for an entire year. It developed in the investigation of this explosion that the workmen and operators of grain plants throughout the country were not familiar with, or fully acquainted with, the dangers of dust explosions and fires.
Campaign to Prevent Dust Explosions
This led to the inauguration of a special campaign of dust explosion and fire prevention by the U. S. Department of Agriculture with which you are no doubt familiar, and in which many of you have cooperated in a very effective manner. A number of significant facts stand out prominently during the period in which this campaign was conducted. It is interesting to note that for a period of 220 months prior to October, 1917, the time at which the campaign started, four very disastrous dust explosions resulting in large loss in life and damage to property occurred. From October, 1917, to May, 1919, a period of 19 months, there were no disastrous dust explosions and fires in any of the plants in which the dangers were brought to the attention of the workmen. On the other hand, your attention is directed to the fact that from May, 1919, to September, 1919, a period of about four months, live disastrous dust explosions occurred in the United States and Canada, resulting in the loss of 70 lives and damage to foodstuffs and property in excess of $6,000,000.00.
The urgent need for a continuation of the educational campaign was recognized by Mr. Julius H. Barnes, President of the U. S. Grain Corporation. During the war period when the Grain Corporation was handling large stocks of Government grain they were not called upon to pay one dollar for explosion or fire loss. In order to provide similar protection against grain dust explosions and fires, Mr. Barnes arranged for the extension work to be continued during the present year. A special series of meetings were arranged throughout various parts of the country in which the recent findings regarding causes and methods of prevention of dust explosions and fires were presented. The meetings, which some of you, no doubt, have attended, are still being held in the Pacific Coast section and in the far West and are giving very valuable results. Much of the success of this work, as has been stated, has been due to the assistance of and cooperation with interested agencies throughout the country. This cooperation is still being continued and in the present campaign and meetings that are being held reports received indicate that these meetings are proving of very great value to the milling and grain trade in the various sections of the United States. We desire to express our appreciation at this time of the assistance rendered by the various agencies and commissions with whom the Government has been cooperating, all of which indicate what can be accomplished when interested parties support a project of this kind.
Lack of Knowledge Blamed
From the early stages of the work it has been very evident that the workmen and the owners of the industrial plants as well have not understood or been familiar with the conditions under which dust explosions and fires might occur. In many cases where industrial plants have been destroyed by explosion or fire “spontaneous combustion” has been assigned as the cause. In many cases it developed that the assigning of this particular cause meant that the investigators could not arrive at a definite conclusion as to what was the immediate cause of the explosion, and in cases where it was surrounded by any mystery of any kind spontaneous combustion was a good cause to give. It develops now that dust explosions have been occurring for several years in industrial plants throughout the country and that they were not given any special technical or scientific consideration until quite recently.
Early Grain Dust Explosions
The explosion in the flour mills of the Washburn-Crosby Company, at Minneapolis in May, 1878, appears to be the first record of disastrous dust explosions in the United States. Following this a number of other explosions occurred, and many of you are no doubt familiar with the flour explosion in 1893, at Litchfield, Illinois. This particular explosion is of special interest to this association because the records indicate that the explosion followed a fire which had been burning for a period of at least 30 minutes. It is one of the cases where explosions have been caused by fires which have been burning for some time before proper conditions present themselves for dust explosion.
Although a number of dust explosions occurred after the one in 1878, the matter was not given special attention until 1913, following a very disastrous dust explosion in a feed grinding plant at Buffalo, N. Y., in which a large number of workmen were killed and considerable property damage was done.
Early Coal Dust Explosions
The possibility of disastrous losses from dust explosions has been fully indicated by occurrences of this nature in coal mines throughout the country. In 1917, 1,147 miners lost their lives due to explosions of this nature, over 600 having been killed during the month of December alone during that year. This led to the creation of the Federal Bureau of Mines, which has been devoting special attention to the establishing of causes and the development of methods of prevention of these explosions and fires. Up until a few years ago it was felt that it was necessary to have gas present in the coal mines before an explosion could occur. Investigations by the Federal Government have indicated that the danger is not due alone to the presence of gas, but a far greater danger is due to the presence of inflammable coal dust.
How Illinois Suffered
The records show that a number of dust explosions have occurred from time to time in the state of Illinois. In addition to the explosion already referred to at Litchfield during the progress of fire, explosions have occurred at other plants where grain products were being handled.
In one instance, an explosion occurred in the elevator building of a glucose factory as a result of which two men were killed and seven injured. The material that caused the explosion was a light powder known as “gluten feed,” which is manufactured from corn by the removal of starch, oil, etc., and sold on the market as cattle feed. The evidence at hand after the explosion led to the belief that the cause of the explosion was due to a stream of sparks starting from the plates of an attrition mill. The mill was operating at a very high speed. The gluten feed was taken from the attrition mill to a separate building known as the feed elevator by means of an air draft operating through a 16-inch galvanized iron pipe about 375 feet long and carrying the gluten 140 feet in elevation. When the fire reached the elevator building enough dust was jarred into the air to produce favorable conditions for the explosion which followed. This explosion clearly shows that the greatest violence was at a point some distance away from the point of the fire.
A later explosion occurred in a starch factory and was accompanied by a large loss of life and property. Reports indicate that 14 men were killed and 19 injured as a result of this explosion. The explosion is described as being terrific in nature and the effect was felt at some distance from the plant.
Another disastrous dust explosion occurred in a grain elevator in this state in the early part of 1916. Considerable grain was damaged as a result of this explosion which was assigned to the clogging of one of the elevator legs. This particular cause has been assigned to a number of very disastrous dust explosions in grain elevators throughout the country. Other cases on the records indicate that dust explosions have occurred in fertilizer plants, wood working establishments and similar industries where fine and inflammable dust appears during the operating processes.
Recent Grain Dust Explosions
Considerable attention has been directed to the dust explosion and fire problem in recent months throughout the United States, due to the large number of disastrous occurrences of this nature. In May, 1919, a violent dust explosion occurred in a grain elevator in Wisconsin in which three lives were lost and several others injured. During the same month a very disastrous dust explosion occurred in a starch factory in Iowa, in which 43 lives were lost and over $3,000,000 property damage done. This appears to be the most disastrous dust explosion on the records and caused considerable damage to private property throughout the entire city.
In August, 1919, a grain elevator operated by the Canadian Government was destroyed by dust explosion and fire in which ten lives were lost. In September. 1919, the most disastrous grain elevator explosion on record occurred in an elevator in the Middle West, resulting in the loss of 14 lives and great property destruction. These recent cases have emphasized the urgent necessity for the adoption of precautionary measures and for close attention to be given to the prevention of these disastrous explosions and fires.
Developments in Recent Investigations
The investigations of the more recent explosions and fires have developed two prominent points: (1) A socalled modern “fire-proof plant,” is not by any means explosion proof. Provision must be made for effective dust removal. (2) In the construction of modern plants consideration must be given to dust explosion and fire prevention. It is not possible for a dust explosion to spread or propagate without a sufficient quantity of dust being present. It means, therefore, that the engineers in the construction of the mills and elevators must give consideration to this particular feature and not provide methods of construction whereby dust will be allowed to accumulate throughout various parts of the plant.
How Dust Hazard is Created
In an effort to explain how dust explosions and fires occur, several theories have been advanced. It can be safely said, however, that it is necessary for the dust and air to be mixed in proper proportions and an externa! source of heat or flame applied. It is not possible to have a “spontaneous” dust explosion. Investigations and experiments have shown that it must be ignited by a source of heat or flame equal to the ignition temperature of the dust.
In this respect it has been found that a dust explosion is very similar to a gas explosion. The ignition temperatures of the dust vary just as the ignition temperaures of the gases, and, no doubt, have lower and higher explosive limits. These are now being determined by special experiments.
Fire Fighting Hazards
In addition to the simple causes such as matches, open flames, lanterns, etc., a number of mechanical causes have been developed in the progress of investigation. The electrical equipment is now demanding considerable attention and experiments are being conducted to determine the possibility of igniting dust by electric arcs. It is safe to say, however, that at this time it is possible to produce dust explosions by electric sparks and that definite cases are on record where electric lamp globes have been broken in dusty atmospheres, resulting in explosion and fire. Special attention is now being given this phase of the project and an effort is being made to determine the safe methods and practices to be engaged in.
The attention of the Department, however, has been directed to the possibility of explosions occurring during the process of fire fighting, in plants where inflammable dusts are produced. This is the phase of the project in which this association would, no doubt, be directly inter ested. In a recent case in the East, the firemen were injured by an explosion that occurred during the progress of the fire. At the time it was thought to be due to the presence of inflammable material such as gasolene, oil, etc., in the plant. It developed during the investigation that a stream from the hose struck a pile of finely powdered cork used in the manufacturing process and that the flames from the fire ignited this dust which was forced into suspension when the water stream struck the pile of cork. This, together with other cases, emphasizes the importance of bearing this matter in mind during the fighting of fire in industrial plants where these inflammable dusts are produced. The danger might be decreased by the use of a spray instead of a heavy water stream.
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It has been found that in addition to the removal of both the causes of explosions and the dangers of dust conditions that the propagation of flame can also be prevented. At the present time consideration is being given to the application of inert gases as a method of prevention of flame propagation. Laboratory and small scale experiments have indicated that carbon dioxide can he obtained by washing flue gases and the propagation of flame prevented by the introduction of these inert gases into the milling and conveying systems. If this method proves successful it is hoped that it may have a practical application in connection with the grinding of inflammable materials.
It has been found that the propagation of coal dust explosions can he prevented by the use of inert dusts, such as shale, limestone or ash. Consideration is also being given to the practical application of this inert dust in industrial plants.
Assistance by Firemen
It is felt that this association as well as other firemen’s associations in the various states can render valuable assistance and help in the prevention of grain dust explosions and fires. The following lines of cooperation are suggested :
- Acquaintance with industrial plant conditions in the various fire districts. The inspection and removal of dust explosion and fire hazards.
- Continuation of educational work in local section along plan carried out by the Federal Government of the United States
- Reporting cases of dust explosion and fire promptly to the Federal Government for further investigation. It has been found that investigation of minor cases, where damage is small, has sometimes thrown more light on the question than the large disastrous explosions where the evidence is entirely destroyed.
- By endeavoring to have consideration given to dust explosion and fire prevention in the construction of industrial plants.
- Recognition of the dust explosion hazard during the progress of fire fighting.
Due to the conduct of the educational campaign, both during the period of the war and at the present time, it lias not been possible to devote the necessary time to research investigations. The necessity for the continuation of the research investigations for the purpose of developing effective methods of prevention has been fully emphasized by the large number of recent explosions and fires in this country. Provision should be made for a thorough study of the problem in order that all possible causes can be considered and the necessary experimental work can be carried on to test out the methods of prevention which the engineers develop. The large scale of operations and the size of our modern plants with their large volume and capacity increases the amount of dust and thereby the explosion and fire hazard. Although much attention has been given the problem in recent years, there still remains considerable further research work to lie conducted before the problem can be advanced to a point where successful preventive measures can be applied.