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shot firer, after igniting the shots in room 38, proceeded to room 39 through one
First A. C. room 1 west: Face shot down.
1 west entry: Face and crosscut to left shot down. (See Probable Point of Origin.)
2 west entry : Face shot down.
First A. C. room 2 west : Face undercut and machine loaded on truck and moved back from face.
Second A. C. room 2 west : Face shot down. Loading machine at face, nips off.
The preceding data together with the fact that the bodies of the two shot firers were found at or near the man-trip on 1 west approximately 250 feet from the face indicated that the blasting operation was completed in this section, insofar as the ignition of the fuzes was concerned, when the explosion occurred. Five places were blasted in this section on the afternoon of the explosion. Assuming that at least 6 minutes had elapsed from the time the first shot was ignited to the time the first shot was detonated, it is believed that the shot firers had sufficient time to ignite all of the shots and travel to the man-trip loading station where their bodies were found, before the first shot exploded.
All of the coal falls in the 1 west section, except the one at the face of 1 west, appeared to be normal and there was no evidence of blown-out shots.
PROBABLE POINT OF ORIGIN
The 1 west entry had been driven approximately 85 feet beyond the last open crosscuts to the right and left, and a crosscut had been turned to the left about 20 feet back from the face. (See sketch, appendix C.) A switch was in the process of being installed at this crosscut when the shift ended on the day of the explosion. A wooden spike box was upset and the spikes spilled on the floor, in. dicating forces outby. About 10 feet outby the spike box was a track wrench which had evidently been moved outby from the place where the trackman had been working. About 15 feet outby the track wrench, a tie had been lifted up and one end moved outby. A trackman's hammer was found near the last open crosscut to the left. It is believed that this hammer was moved outby from the point where the switch was being laid. Heavy deposits of plastic coke were present on the corner of the outby rib of the last open crosscut to the left. A bit box was upset at the bit station (see sketch, appendix C), with forces indicated outby. An oil barrel that was located at the bit station was blown outby for a distance of about 20 feet. Partially burned paper dummy bags, which were located at the bit station before the explosion, were found in the last open crosscuts to the right and left, indicating that when the forces from 1 west reached the junction of these crosscuts with 1 west, the explosion spread through openings in all directions from this point.
There was no evidence of a blown-out shot at the face of 1 west. There was, however, some indication that would lead to the belief that the top rib shot was underburdened. The fact that the shot did not pull all of the coal at the right rib in a normal fashion suggests that an underburdened shot may have occurred.
In any event, a blown-out shot of explosives that was stemmed with coal dust, or an underburdened shot of explosives could have ignited the coal dust. The dust cloud could have been raised by the shot which ignited the dust, or it could have been raised by preceding shots in the same working place or the adjacent crosscut.
Permissible explosives will not produce dust explosions often, even if fired in the hazardous manner and under the hazardous dust conditions described in this
report. But, when such hazardous practices and conditions are continued over a long period of time, the right combination of circumstances, such as a blownout or open shot and an ignitable dust cloud in the presence of such shot, will likely precipitate an explosion sooner or later.
SUMMARY OF EVIDENCE Conditions observed in the mine following the explosion, together with information available from previous Federal coal-mine-inspection reports, provided ample evidence as to the point of origin and cause of the explosion. Facts based on this evidence are summarized as follows:
1. The mine was dry and dusty, and heavy deposits of fine coal dust were present on the roof, ribs, floor, and timbers of all active working sections in the mine.
2. Rock dust had not been applied in rooms, nor in entries for a considerable distance back from the working faces.
3. Methane in an appreciable amount was not found during recovery operations, and only a very small quantity of methane was found in air samples collected in poorly ventilated working faces during the investigation. No evidence was found to indicate that methane was involved in this explosion.
4. The explosion occurred at the end of the shift after all face operations had ceased, except for the blasting operations. Blasting was the only operation in progress capable of raising an ignitable dust cloud into the air at the time the explosion occurred.
5. Permissible explosives were being fired in a nonpermissible manner with caps and fuse, and coal dust was being used for stemming.
6. Major forces of the explosion radiated from the face workings of the 1 west entry in all directions toward open workings.
7. Flame from the explosion died away rapidly upon reaching rock-dusted zones in entries and upon reaching old abandoned workings in which falls covered up much of the coal dust which was left by the mining operations.
8. The only working place in which there was definite evidence of forces traveling outby in the area between the face and the last open crosscut was the face of 1 west entry.
9. There was definite evidence of radiation of forces to the north, south, and east at the junction of 1 west and the last open crosscuts to the right and left.
CAUSE OF THE EXPLOSION
Representatives of the United States Bureau of Mines who investigated the disaster are of the opinion that the explosion originated at the face of 1 west entry, that it was strictly a coal-dust explosion which was propagated by coal dust throughout four working sections of the mine, and that the coal dust was raised into the air and ignited by explosives fired in a dangerous and nonpermissible manner. LESSONS TO BE LEARNED FROM THE CONDITIONS AS THEY RELATE TO THE EXPLOSION
1. The outstanding lesson to be learned from this disaster is that mines which liberate little or no methane are not immune from widespread and tragic explosions if dry and dusty conditions exist therein and adequate measures are not taken to control the dust hazard.
2. This explosion has forcefully demonstrated the need to reevaluate the dustexplosion hazard. Up to the present time, it has not been customary for the coalmining industry, the Bureau of Mines, State Departments of Mines, or any other group dealing with mine safety matters to regard dry and dusty conditions in mines as constituting an imminent danger of such magnitude as to warrant the withdrawal of men, particularly if the mine does not liberate methane. If explosions of this type are to be prevented, it will be necessary to regard dry and dusty conditions in mines as being imminently dangerous in the future and to withdraw the men from the mine or portion thereof where such dangerous conditions exist, until appropriate measures have been taken to remedy such conditions.
3. The partial rock dusting of mines as a remedy for the coal-dust explosion hazard leads to a false sense of security. In this instance, the application of rock dust on haulage entries did not prevent the explosion from propagating from room to room through crosscuts. A study of the conditions revealed that this explosion propagated throughout four sections of the mine by traveling mainly through rooms and dying out as it reached the rock-dusted haulage roads
and old abandoned areas. The spread of dust explosions from one working place to another will be prevented by means of rock dusting only when rock dust is applied in all working places up to and including the last open crosscuts. The application of rock dust along the haulage entries in this mine appears to have prevented the propagation of flame to the shaft bottom and probably saved the lives of 31 men.
4. Permissible explosives, charged and fired in a permissible manner, are safe explosives. Permissible explosives. stemmed with coal dust and fired with fuse in a dependent sequence are dangerous. The maximum safety will be obtained, however, when all shots are fired in a permissible manner while all mpen except the shot firers are out of the mine.
5. Evidence obtained during the recovery operations indicated that 44 mei working in two sections of the mine, not affected by the flame or violence of the explosion, could have saved themselves if they would have had a knowledge of the principles of erecting barricades after explosions.
RECOMMENDATIONS Recommendations concerning the safe operation of this mine were made in reports of previous Federal inspections, the last inspection having been made March 17–20, 1947. Recommendations in this report, therefore, are limited to conditions as they related to explosion hazards. RECOMMENDATIONS BASED ON THE FEDERAL MINE SAFETY CODE FOR BITUMINOUS
COAL AND LIGNITE MINES OF THE UNITED STATES
ARTICLE IV. EXPLOSIVES AND BLASTING
Sections 5a1 and 5a2.- Permissible explosives should be fired only with electric detonators of proper strength by means of permissible shot-iring units.
Section 5a5.-Unless all shots are fired in series or in group series, an examination should be made of each shot, before it is fired, to see that it has a burden in all directions of at least 18 inches. If groups of shots are fired in series, an examination should be made of each series, before it is fired, to see that all holes in the series have a burden of at least 18 inches.
Section 5a6.-Boreholes should be stemmed with at least 24 inches of incombustible material or at least one-half of the length of the hole should be stemmed if the hole is less than 4 feet in depth.
Section 5a7.-Examinations for gas should be made immediately before and after each shot, if shots are fired while men other than the shot firers are in the mine,
Section 5d.-All shots or series of shots should be fired immediately after charging, where shooting is done while men other than the shot firers are in the mine.
ARTICLE V. VENTILATION AND MINE GASES Sections 3a and 38.—The main intake air current should be divided into splits utilizing air crossings where needed, so as to ventilate all parts of the mine effectively. The number of men working on one split of air should not be more than 100 in order to conform to the requirements of the Illinois State Mining Law.
Section 3c.—The quantity of air reaching the last open crosscut in any pair or set of entries should not be less than 6,000 cubic feet a minute.
Section 6.-Stoppings in crosscuts, between intake and return air courses, in entries other than room entries, should be built of solid, substantial incombustible material, such as concrete, concrete blocks, brick or tile.
Section 10d.-Mine examiners should begin their examination in the first working place in their assigned territory not more than 4 hours before the shift for which they are examining enters the mine.
Section 107.At least once during each working shift while the men are in the mine, the face bosses or other designated officials should examine all working places with a permissible flam safety lamp for methane noxious gases, and oxygen deficiency.
ARTICLE VI. COAL AND ROCK DUST Section 10.-Coal dust should not be permitted to accumulate on haulage roads or on the roadways of the working places.