Imágenes de páginas
PDF
EPUB

During the Federal inspections of September 1942 and July 1945, the analytial results of two air samples collected near the faces of active workings showed 0.38 and 0.70 percent methane respectively, but there is no record of methane ever having been detected with a flame safety lamp. During the time of the last Federal inspection, March 17-20, 1947, there were eight air samples collected and the analytical results showed methane ranging from 0.03 to 0.10 percent, s follows:

Percet Face No. 7 room off 21 north.

0.4 Full return at shaft bottom-Main return at main south overcast_ Face No. 14 room off 19 northLast crosscut between 23-24 south off 4 west-Last crosscut between 20-21 north off 4 westSecond crosscut back from face of 1 west air course entryFace No. 37 room off 22 north 4 west---

1 During the March 1947 Federal inspection, the mine was liberating methane at a calculated rate of 63,072 cubic feet in a 24-hour period.

DRAINAGE

The mine workings and haulage roads were dry, except for accumulations of water in several small sumps along the 4 west haulage road, at 3 north, which were pumped periodically into abandoned workings by a small centrifugal pump An electrically driven pump was located at the shaft bottom and was used to pump the water out of the hoisting shaft sump. Two plunger-type pumps, each of 250-gallon capacity, were located in the main pumping station at 8 north 1 west and were used to pump water from the abandoned area in the main north to the surface.

DUST

The mine was exceedingly dry and dusty and heavy deposits of coal dust were present along the roadways in working places and on the roof, ribs, and timbers in working sections. Heavy deposits of coal dust existed along the roadways in room entries and in the center of the main haulage road on 4 west. Very little effort had been made to load out excessive quantities of dust, and watering methods had not been employed to allay the dust at its source. Rock dust had been applied to the roof, ribs, and roads of active haulage entries, but such rock dusting was not maintained close enough to the working faces, and rock dust was not applied in rooms. In active entries, the rock-dusted zones at the time of the explosion terminated at the following locations : 23 and 24 south 4 west. 900 feet outby from face; 20, 21, and 22 north 4 west, 850 feet outby from face: 1 west, 1,000 feet outby from face; 18 and 19 north 1 west, 600 feet outby from face; 13 and 14 north 1 west, 500 feet outby from face; 20 and 21 north 1 west.

none.

The analytical results of dust samples collected in rock-dusted zones by : Federal coal-mine inspector during the course of a Federal inspection previous to the disaster on March 17-20, 1947, are shown in the following table:

[blocks in formation]

Roof and rib
Road
Roof and rib
Road
Roof and rib
Road
Roof and rib
Road
Roof and rib
Road
Roof and rib
Road.

14 north room entry haulage road at No. 16 room.

..do
18 north room entry haulage road at the No. 5 room.

do.
Main south haulage road in by machine shop.

do
24 south room entry haulage road off 4 west at No. 4 room

do
Main 18 south haulage road at 4 west intersection.

[ocr errors]

45. 8 49.6 22. 1 63.4 41.0 59.5 10.6 50.8 25. 6 51. 2 26.5 47.5

49

do.

Main south haulage road at 4 west

do..

73. 522

It will be observed from this table that none of the road samples contained the 65 percent incombustible matter recommended by the Bureau of Mines and that two of the roof and rib samples contained less than 65 percent incombustible matter, while four of the roof and rib samples contained more than 65 percent. It is concluded, therefore, that the haulage roads were not being redusted with sufficient frequency; however, this deficiency was not a factor in this explosion.

Additional dust samples were collected during the investigation of the explosion, the analytical results of which are shown in table 1.

TABLE 1.-Dust analyses report
(Mine: No. 5. Company: Centralia Coal Co. Collected Apr. 3-4, 1947)

[blocks in formation]

U-724. Rib and roof..
L 377. Road..
H-837... Rib and roof.
E-529. Road..
V-853. Rib and roof..
Q-378 Road
G-770. Rib and roof..
X-865... Road..
B-871.. Rib and roof..
T-258.. Road.
S-244.. Rib and roof.
C-972 Road.
X-663...

Rib
U-667. Road
H-915... Rib and roof.
L-321. Road
F-477.

and roof. P-612... Road..

At Room 15, 14 north 1 west. Yes.
..do

Yes.
At Room 15, 13 north 1 west. Yes.
.do.

Yes. On 1 west 100 feet outby 14 north. Yes. do

Yes.
On 2 west 100 feet out-by 14 north. Yes.
do.

Yes.
On 4 west 100 feet out-by 18 north.

Yes.
do

Yes.
On 3 west 100 feet out-by 18 north.

Yes.
do.

Yes.
At room 25, 21 north 4 west-

No..
do

No.
At room 25, 22 north 4 west.

No..
..do..

No.. On 2 west 150 feet out-by 18 north. No. do..

No.

[blocks in formation]

None.

Do.
Do.
Do.
Do.
Do.
Do.
Do.
Do.
Do.
Do.

Do.
Medium amount.
Small amount.
Medium amount.
Small amount. }

Do.
Very s ma il

amount.
Small amount.
Trace.
Small amount.

Do.
Do.

Do.
None.

Do.
Do.

Do.
Large amount.
Very large amount.
Large amount.
Very large amount.

43
38

30

531..
H-873..
B-340..
B-665.
X-492
Q-337..
B-166..
H-698...
G-108...
X-101...
H651...
V-595...
C-681.
C-141..

Rib and roof.. On 1 west 150 feet out-by 18 north.
Road..

do..
Rib and road. On 1 west 250 feet inby 19 north.
Road..

do
Rib and roof. On 2 west 250 feet inby 19 north.
Road.

do.
Rib and roof. At room 35, 19 north 4 west
Road..

do..
Rib and roof. At room 35, 18 north 4 west.
Road..

do.
Rib and roof.. At room 17, 18 north 1 west
Road..

do..
Rib and road. At room 17, 19 north 1 west.
Road..

..do...

Yes.
Yes.
No..
No..
No.
No..
Yes
Yes
Yes.
Yes
No..
No.
No..
No..

57 62 70 66 71 71 56 66 55 60 68 69 62 68

34 29 29 44 34 45 40

32

31
38
32

It may be observed from this table that rib and roof samples collected from rock-dusted areas in the portion of the mine affected by the explosion contained from 43 to 73 percent incombustible matter and averaged 52 percent. Road samples collected at the same locations contained from 37 to 79 percent incombustible matter and averaged 45 percent. Attention is called to the fact that some of these samples were contaminated by coal dust carried and deposited by the explosion. Rib and roof samples collected from non-rock-dusted areas in the active working sections affected by the explosion contained from 29 percent incombustible matter to 38 percent incombustible matter and averaged 33 percent. Road samples collected at the same locations contained from 31 percent to 39 percent incombustible matter and averaged 35 percent. Coked particles were present in varying amounts in all of the samples collected in non-rock-dusted areas, indicating that all of these locations were closely involved in the explosion.

Explosibility tests on the Illinois No. 6 coal bed, conducted at the Bureau of Mines experimental mine at Bruceton, Pa. (see Bulletin 167, p. 249), indicated that this coal dust required the presence of 33 percent incombustible matter to prevent ignition when no gas was present and required the presence of 59 percent incombustible matter to prevent propagation under the same conditions. It is concluded from this that much of the untreated dust in the face regions was capable of initiating and propagating an explosion, while the dust on the

92725-49

-21

rock-dusted haulage entries was on the border line insofar as propagation was concerned.

HAULAGE

Main haulage was accomplished with two 15-ton electric trolley-pole locomo tives over a single-track system from side tracks to the shaft bottom. Nineteen trolley-pole and cable-reel locomotives were used for servicing loading machines and secondary haulage. Two cable-reel shuttle cars were used to service two of the loading machines. About 300 steel end-gate-type mine cars of 3-ton capacity each were in use.

The cars of coal were hoisted on two self-dumping cages to the top of the tipple, where they were dumped. The coal hoist, which was also used for handling men and materials, was of the single-drum design, and was steam driven. One and one-fourth-inch diameter ropes were used, and the hoist was equipped with automatic overwind, overspeed, and stop controls, and a positive indicator to show the positions of the cages. Written records were kept of the daily inspections of the hoisting equipment and appurtenances.

LIGHTING

Incandescent electric lights operated from the mine circuit were installed at the shaft bottom and at irregular intervals along main and secondary haulage roads. Permissible electric cap lamps were used by the mine examiners for individual illumination underground. All other underground employees used carbide lamps for portable illumination. The mine examiners used permissible flame safety lamps which they cleaned, filled, assembled, and kept in their custody.

Smoking was permitted and practiced freely underground.

ELECTRICAL EQUIPMENT UNDERGROUND

All power was generated at the mine, except for an emergency line from an electric-power company to operate the fan. All machinery underground was operated electrically by 250 volts direct current. Two substations were located underground in well-ventilated fireproof structures.

All mining machines, loading machines, drills, shuttle cars, and cable-reel locomotives were of the nonpermissible type and received their power through trailing cables connected to power wires located in return air.

An armored 2,300-volt alternating-current cable entered the mine through the intake air shaft. With the exception of power and trolley wires on the 1 west haulage roads, all other power and trolley wires were in return air. Cut-out switches were not installed at or near the points where branch lines left the main circuit, in many instances. Cable splices were made underground by using splicing rings and friction tape. Many of the trailing cables for the portable underground electric equipment were not equipped with overload protection at the nips.

EXPLOSIVES AND BLASTING

Permissible explosives, Black Diamond No. 15 in 142 by 8 inch cartridges that weighed approximately 8 ounces a cartridge, were used for all blasting purposes in recent months. A 40-percent special dynamite in 174 8-inch cartridges had been used in brushing the 1 west haulageway about 18 months previously. No dynamite had been used in recent months. Shots were fired with No. 6 strength blasting caps and orange wax fuze ignited with the flame of carbide lamps.

Drillers worked in pairs. While one driller operated the post-mounted electric drill, the other prepared the primers and charged the shot holes. Normally, six holes were drilled in entries and crosscuts; eight holes were drilled in rooms. The holes were about 242 inches in diameter, approximately 8 feet in depth and drilled in two horizontal planes with an equal number of holes in each horizon. The bottom holes were about 3 feet from the floor and the top holes about 219 feet above the bottom holes. Primers were generally made up near the working faces and variable lengths of fuse were used to obtain the desired order of firing. The fuses were slit near the ends so that they could be ignited readily with carbide lamps. Charges of explosives varied from 1 to 2 pounds, with the larger charges being used in the top rib holes. The shot holes were charged during the working shift. Stemming of coal cuttings and surface clay was used and was made up in prepared dummies 14 inches in length. From one to three

dummies were used in each shot hole, and many charged shots were noted to be tamped with coal cuttings. Wooden tamping sticks were used. The drillers were also the shot firers, and they ignited the shots at the end of the working shift. The shot firers were given the signal to light the shots by the foreman or one of the other employees after all normal face operations bad ceased and the employees were in the man-trips or en route thereto. The center bottom holes were ignited first, the bottom rib holes next, then the top center holes, and the top rib holes were ignited last.

Cases of explosives from the surface explosives storage magazine were placed in a well-constructed explosives car, hauled by mule to the shaft, then lowed into the mine. The explosives were transported underground by electric locomotive, during the second shift, to well-constructed explosives-storage boxes located near the entrances to the working sections. The explosives were delivered to onethird of the nine working crews each night; thus a 4-day supply was delivered to each storage location at one time. Some of the storage boxes were kept locked. Blasting caps in special insulated wooden containers were hauled on a locomotive, operated by the night foreman, to the section storage locations. Cartons of fuse were delivered by the supply crew to the explosives storage boxes. The shot firers obtained a supply of explosives from the storage boxes and carried them to the working faces in small wooden boxes. Blasting caps were carried in special wooden containers and kept separated from the explosives. Unused explosives and blasting caps were returned to their respective storage locations before the end of the working shift.

MINE RESCUE

About 18 men at this mine have received mine rescue training at various times, but none have had mine rescue training in recent years.

Six gas masks were available at the mine. The nearest State-maintained mine rescue station and mine rescue team was at DuQuoin, Ill., about 40 miles from the mine. Other State-maintained and privately owned mine rescue stations and mine rescue teams were from 50 to 120 miles away. The United States Bureau of Mines rescue truck and apparatus were located at Vincennes, Ind., about 100 miles from the mine.

FIRE FIGHTING

All buildings within 100 feet of the mine openings, and vital structures were of fireproof construction. The electrical circuits were installed on insulated knobs, and enclosed switches were used. Buildings were steam heated. Twentyfour 242-gallon soda-acid, and eight 1-quart size carbon tetrachloride fire extin. guishers were placed in various buildings on the surface. Two fire hydrants and 200 feet of 142-inch fire hose were also available on the surface. The fire-fighting equipment was inspected and tested monthly and written records were kept.

The underground fire-fighting equipment consisted of 16 272-gallon soda-acid and 6 1-quart size carbon tetrachloride fire extinguishers located at the shaft bottom and other strategic locations in the mine, supplies of rock dust at the substations and pumps, and bags of rock dust placed at various locations throughout the mine. A fire-fighting organization was not maintained on the surface or underground, and an outline of the procedure to be followed in case of fire or other emergency was not provided.

PREVIOUS EXPLOSIONS IN THIS MINE

Statements of employees at the mine revealed that three minor explosions occurred in this mine prior to this disaster. They were as follows: four men were killed in 1909; one man was killed in 1915; and three men were killed in 1921. All of the explosions were reported to have resulted from blown-out shots while blasting off the solid with granular black powder,

MINE CONDITIONS IMMEDIATELY PRIOR TO DISASTER The mine was operating normally, and no unusual conditions insofar as could be ascertained had been reported prior to the time of the explosion. No interruptions bad occurred to the ventilation system. The weather was clear and fair, and no sudden changes in barometric pressure or unusual temperature changes had occurred.

A barometer kept at the mine and read by the mine examiner recorded the following pressures : March 24, 1947, 29.3 inches of mercury ; March 25, 1947, 291 inches of mercury.

Barometric pressure is believed to have had no bearing on the cause of the explosion.

The mine examiners' reports for March 24 and March 25 indicated normal miring conditions. Bad top was reported in nine of the working places, and all othe places were reported to be in a safe condition for the 2-day period.

PROPERTY DAMAGE

The explosion caused no damage on the surface. No damage was caused on the 1 west main haulage road outby the 13 and 14 north, or on the 4 west main haulage road outby the 23 and 24 south. No property damage resulted in the 13 and 14 north section off the 1 west. Three concrete-block seals erected in the mouths of the 15, 16, and 17 north off 1 west were demolished. Some doors and wooden stoppings in the 23 and 24 south off 4 west were damaged and the telephone near the mouth of the 18 south was knocked off the post to which it was fastened, but the explosion caused no other damage in this area.

Considerable property damage was caused by the explosion in the 20, 21, and 22 north off 4 west; main west entries; 20 and 21 north off 1 west; and 18 and 19 north off 1 west. The forces of the explosion demolished all the stoppings in the crosscuts between the 20 and 21 north off 4 west ; caused slight damage to locomotives in this section ; extensive damage to the cable-reel shuttle cars; damaged the drill truck; and tore down the trolley and feeder lines in the section. However, the damaged stoppings in this section will not have to be rebuilt, because the 22 north entry was cut through to the 1 west recently to provide a new air course between the 1 west and 4 west sections. The doors and stoppings on the 1 west inby the 18 and 19 north entries were demolished ; trolley and feeder lines on 1 west inby the 15 north were torn down; and the locomotives in the 1 west working section were damaged slightly. The doors and stoppings in crosscuts between the 20 and 21 north off 1 west were demolished ; timbers were blown out in the rooms 20 and 21 north permitting large roof falls, some of which fell on trips of cars; trolley and feeder lines were torn down; and slight damage was caused to the locomotives and the mining machine. The doors and stoppings in the 18 and 19 north off 1 west were demolished; some mine cars were damaged ; the mining machine and locomotives were damaged slightly; trolley and feeder lines were torn down; and trucks used by drillers and trackmen were damaged extensively. The post-mounted drills used in the sections reached by the forces of the explosion were damaged slightly. Debris, loose rock, and dust were strewn over the track and roadbed in the various sections affected by the forces of the explosion. Telephone lines were torn down in the 1 west inby the 13 and 14 north to the various working sections. Some doors and stoppings in the 18 and 19 north off 4 west were demolished or damaged and trolley and feeder lines were torn down. However, this section was abandoned some time previous to the explosion and no rehabilitation work will be required in this area.

The section of the 1 west haulage road affected by the forces of the explosion had sound roof and no falls of roof occurred. Rehabilitation work there will con. sist of removing the debris strewn along the roadway and the installation of trolley and feeder lines.

As relatively little damage was caused by the explosion in the 23 and 24 south off 4 west and the 13 and 14 north section was not affected by the forces of the explosion, coal production in these sections could be resumed at once as far as property damage is concerned. However, production in these sections should not be resumed until all excessive accumulations of coal dust are removed and the surfaces of the roof, ribs, and floor rock•dusted adequately. The damage done to gathering locomotives and face electric equipment did not appear to be extensive during the investigation. However, some of this equipment was exposed to the direct forces and flame of the explosion and thorough inspections by repairmen might reveal extensive damage. It is estimated that about 30 days will be required to repair the equipment, install trolley and feeder lines, remove debris from roadways, and other necessary work before normal coal production can be resumed. However, it will take considerable time to eliminate the factors that will prevent or minimize such disasters. This requires the removal of excessive accumulations of coal dust, full compliance with the sections of the Federal Mine Safety Code pertaining to rock dusting, and the adoption of a suitable method of allaying coal dust at the sources of dust formation.

« AnteriorContinuar »