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DISCUSSION OF DUST SAMPLES
A study of the analyses of the 10 dust samples collected, as shown in table 3 on the preceding page, indicates that nine of the samples are sufficiently high in combustible material to propagate a mine explosion.
Sizing tests of the dust samples show that 77.0 percent of the roof and rib dust and 77.0 percent of the road dust is less than 20 mesh size.
Experiments have shown that any coal dust (with the exception of anthracite dust) that will pass through a 20-mesh screen may enter into an explosion, and that the finer the dust, the greater the ease with which it is able to propagate the explosion. By taking the average combustible content of the dust samples for rib, roof, and roadway combined it will be observed that at all sample locations the dust was sufficiently high in combustible material, and of sufficient fineness, to propagate a mine explosion.
Parts of the mine have been rock-dusted in the past few years, but no rock-dust has been applied for approximately 1 year. Calcium chloride is applied to the floors in the shuttle car runs, and V-trough rock-dust barriers are erected in some air courses.
Ten samples of dust were collected at five points in the mine. Three locations were chosen along rock-dusted entries in various sections of the mine to represent average rock-dusted conditions, and two other representative locations were chosen in parts of the mine which had not been rock-dusted. A study of the analyses, from table 3, of the six dust samples containing rock dust shows that five of the six samples collected are sufficiently high in combustible material to propagate a mine explosion.
In the interest of safety, the rock-dusting program should be resumed.
Rock-dusting, to be effective, must be done thoroughly and must be continued. Before rock dusting is done, all combustible material, so far as possible, should be removed from all underground openings. The rock dusting should be done first from the active faces outby, and advanced as the faces advance. In addition, rock-dust should be distributed upon top, bottom, and sides of all underground openings of every description to within at least 40 feet of all working faces, and areas not rock-dusted should be kept wet. Although the volatile combustible ratio varies to some extent with the composition of the coal, the Bureau of Mines recommends that at least 65 percent of incombustible matter be present to prevent propagation of a coal-dust explosion.
All underground haulage at the No. 5 mine is accomplished by trolley and cable-reel locomotives supplemented by shuttle cars.
Tracks are well alined and ballasted with coal and rock, and in many places are dry and dirty along the sides of the roadbed. Main entries are laid with 60-pound rails. Side entries and rooms are laid with 25-pound rails to a 42-inch gage on sawed ties 24 inches apart. All rails are connected with suitable splice bars and are properly fastened down. Main-line switches only are provided with switch throws, and these are of the vertical type. Guardrails and lights are provided, but guardrails and frogs are not blocked. All switches should be complete with parallel throws and bridle bars, and all frogs, and guard and lead rails should be blocked.
Electric derails, with red and blue lights, are placed at strategic points along the main haulageways for protection against run-away trips.
CLEARANCE AND SHELTER HOLES
It was observed that ample clearance was not provided on the wide side, along some of the main haulageways. There should be a continuous clearance on the side opposite the power lines of at least 30 inches from the nearest obstruction to the farthest projection of any moving equipment.
Room necks and crosscuts are used as shelter holes along the haulageways, and they were observed to be obstructed by road cleanings and other debris. Clean shelter holes should be provided along the haulageways and at main-line switches. They should be suitably marked, not over 60 feet apart, and should be located on the opposite side of the track from the power wires.
Two 15-ton trolley locomotives and 19 6-ton combination trolley and cable-ree! locomotives, operated on 250 volts, direct current, are used. They appeared to be maintained in good operating condition. Braided trailing cables are used as a rule, and they are equipped with hook nips, which are not fused. All trailing cables—whether on locomotives, drills, mining machines, or loading machinesshould be equipped with properly fused nips, for the protection of the machines and to reduce the fire hazard. The locomotives were not equipped with gongs or other audible signaling devices. They were not generally protected by means of fuses, circuit breakers, or switches. In the interest of safety and good operating practice, locomotives should be provided with an efficient audible warning device, and should be protected by fuses or circuit breakers.
There are 314 endgate type, steel mine cars of 3-ton capacity in use. They are fairly tight, are equipped with link and clevis couplings, and are maintained in a good state of repair. The cars are not provided with brakes, but sprags are used when necessary.
Illumination along the haulageways is accomplished by the spacing of 100-watt or 50-watt lamps at irregular intervals. The haulage roads are adequately lighted.
Trip lights are not used on the ends of pulled trips, nor on the front end of pushed trips. An efficient trip light should be placed on the rear of all pulled trips and on the front of cars being pushed. Main-line haulage is controlled by trappers using telephones and by a block signal system.
Man trips are operated between the shaft bottom and the working sections. They are in charge of the entry foreman. However, it was observed that men were riding in the man trip on the trolley wire side, and were unloading from the man trip at the shaft bottom before the trip came to a complete stop. This is a dangerous practice and should be prohibited; also, enough cars should be provided for man trips to permit all men to ride on the side opposite the trolley wire.
The shaft bottom is provided with a run-around, whereby the bottom crew can go from one side of the shaft to the other without passing under the cages.
Trip-riders were observed riding on the front bumper of pushed trips, and jumping off arkit running ahead of the moving trip to open doors. This is a dangerous practice and should be prohibited, as many men have lost their lives riding on the front end of pushed trips, and jumping off and on moving trips, in coal mines. Passing tracks should be maintained near the working sections, to eliminate the necessity of pushing trips. Trips should not be pushed on main haulageways, except at partings or under some emergency. Ties or short pieces of rails are used to rerail cars or locomotives. Locomotives should be equipped with suitable rerailers, jacks, and other tools for rerailing cars or locomotives.
ELECTRICITY UNDERGROUND All underground electrical equipment is operated on 250 volts direct current from five generators on the surface and one generator located underground. The direct current is conducted from the surface down the hoisting shaft by means of armored cables.
The underground motor-generator set of 300-kilowatt capacity, located 134 miles south of the shaft, receives power from the surface at 2,300 volts alternating current by means of armored cable through a bore hole located near the motor-generator set. This power is then converted to 250 volts direct current for mine use, and is distributed throughout the mine by insulated cables properly installed on insulated hangers.
These cables are installed on the trolley wire side as a rule, and are provided with sectional cut-out switches of proper design,
Trolley wires are properly installed on insulators, and are provided with sectional cut-out switches, which are equipped with insulated handles. The ends of the wires are turned back and supported by turnbuckles.
However, it was observed that the trolley wires were not guarded at man-trip stations and at other places where men are required to pass under them. Trolley and bare power wires should be adequately guarded where the wire is less than 642 feet above the top of the rail at places where men are required to pass under them. It should be adequately guarded and sectionalized at man-trip stations, in order to afford full protection to the workmen.
The rails are well bonded, and cross bonds are used at switches and at regular intervals along the haulage.
Seven telephones are located at key points about the mine and on the surface. It was observed that they were not properly grounded nor fused, and at some points the telephone lines were in contact with the 250-volt feeder cables. It is believed that to afford full protection to the telephones and to the men using them, the telephones should be grounded and fused, and that the telephone wires should be installed on the opposite side of the track from the power wires.
UNDERGROUND MOTOR-GENERATOR SET
The underground motor-generator set is housed in an incombustible building, which is not provided with fire doors. All underground electric stations should be equipped with fireproof doors, arranged to close automatically in case of fire.
The set is properly grounded, and a dry wooden platform is provided in front of the switchboard. The switchboard is provided with automatic circuit breakers, low-voltage controls, overload relays, and fuses. Ample space is provided around the back of the switchboard to permit workmen to make repairs in sa fety.
Fire protection consists of one barrel of sand, and two 1-quart capacity Pyrene extinguishers,
COAL-CUTTING EQUIPMENT The coal-cutting equipment consists of six nonpermissible short-wall mining machines equipped with 9-foot cutter bars. Cutter chain locks are not provided for the cutter chain while the machine is being moved. All of the machines appear to be maintained in good operating condition. Machines are not fused, nor are the machine cables provided with fused nips. Both rubber-covered, parallel, duplex cables and braided cables are used. Temporary cable splices are made with ringed cable splices, insulated with friction tape. The temporary cable splices are used during the life of the cable. Extreme care should be exercised to make these splices mechanically and electrically suong, since they are in reality permanent splices. The cables and the machines should be protected by proper fuses. The machines are inspected daily by repairmen, but no record is kept of these inspections. Records of these inspections should be kept and checked.
Three plunger-type pumps, equipped with open-type motors, switches, and controls, are used to handle the water in this mine. Fireproof houses are not provided, and it was observed that the wiring was in poor condition, and in some places presented a contact hazard. T'he belts and gears were unguarded, and the motors were not grounded nor fused. One pump in the first west, south was observed to be connected up and in running condition with the resistance, starting box, and switch lying on the gob. This condition should be rectified immediately.
All permanent pump installations should be completely enclosed, and constructed of incombustible material to prevent mine fires. The pump frame should be properly grounded, the motor should be fused, and the belts and gears should be properly guarded.
MECHANICAL LOADERS All coal is loaded mechanically by seven mobile loading machines of the nonpermissible type. The machines are not fused or provided with circuit breakers, nor are the trailing cables provided with fused nips. Water is not used on the loading head, and, as a consequence, the places are extremely dusty during loading operations. The amount of dry dust in suspension in conjunction with carbide lights not only offers an explosion hazard, but reduces visibility to the
danger points. Water should be used in this mine in all cutting and loading operations. Fire extinguishers or rock-dust were not observed in the vicinity of these machines, and should be supplied.
DRILLS Seven post-mounted, open-type, electric drilling machines are used for drilling. They are equipped with rubber-covered duplex cables, and are not grounded, fused at the nips, nor provided with thread-bar guards. All electric drills should be equipped with permissible motors, with guards over the thread bars, and should be properly grounded.
FIRE PROTECTION UNDERGROUND
Fire protection underground consists of soda-acid and Pyrene fire extinguishers, sand barrels located at the underground substation, and a short water line at the shaft bottom. To afford adequate fire protection, additional equipment such as tank cars and extinguishers should be located near the shaft bottom. These should be available at all times for transportation to the various parts of the mine. In addition, fire extinguishers should be provided at each section.
UNDERGROUND OIL STORAGE Oil is transported into the mine in the original containers, and stored in open crosscuts or along the sides of the haulage roads. This storage constitutes a fire hazard. To reduce the fire hazard resulting from the present oil storage system, not more than a 2 days' supply of each kind of lubricating oil and grea se should be stored at any one location in the mine at any one time. In addition, underground storage places for lubricating oil and grease should be of fireproof construction.
Lubricating oil and grease in face regions or in other working locations should be in tightly closed metal containers.
Approximately 95 percent of the underground employees wear safety hats, and about 50 percent wear safety-toed shoes. Very few employees wear respirators. Shop men are provided with safety goggles, and are required to wear them while engaged in any type of work in which the possibility of an eye injury is present. All men working in and around the mine should wear safety clothing.
All tools are furnished by the company, and are maintained in good working condition. The tools are hauled into and out of the mine in a special car, and this is a commendable practice.
The No. 5 mine is connected on the north to two worked-out and abandoned mines, viz, the Centralia No. 1 and No. 2. In the area of the three mines approximately 350 oil wells have been drilled.
Some of these wells have not been plugged; some were improperly plugged; in some the casings have collapsed in the mine; and some are pumping oil and salt water at the present time.
The locations of some are known, but in other cases the locations are faulty or unknown.
At the present time many of the operating wells are pumping a mixture of oil and salt water, in which the salt water predominates in a ratio of 8 to 1 or more. The mixture is pumped into tanks at the surface and allowed to separate by gravity. The disposal of the salt water is the major problem, and some of the operators have solved it by pumping the salt water into dry or abandoned holes, known locally as “disposal wells."
Recently the Illinois Department of Mines and Minerals issued an order prohibiting the disposal of salt water by means of "disposal wells," and has succeeded in locating and plugging a number of them. However, as this practice is more or less furtive, it is necessary for the State inspectors to locate possible "disposal wells" by search. At the present time, a number of State inspectors are in Centralia engaged in this work.
Salt water is now entering the No. 5 mine from the abandoned No. 2 mine. It is undoubtedly originating from oil wells, as it has the characteristic taste of a solution of mixed chlorides with a possible saturation of from 8 percent to 12 percent. The quantity is not excessive at the present time, but due to the fact that the No. 5 mine has always been dry, and is equipped to pump only small amounts of comparatively pure mine water, the present pumping facilities are inadequate. Both the ferrous and nonferrous parts of the pumps are being consumed by the acid water about as fast as replacements can be made.
Accurate information was impossible to get due to the fact that the No. 1 and No. 2 mine workings could not be traveled. However, the following is presumed to be true: An anticline runs through the territory between the No. 5 and the No. 2 mines, and at the present time water is standing in the No. 2 shaft at approximately the level of the top of the anticline. Based on this information, the presumption is that all underground workings lying below this level are filled with water, and that the water entering the No, 5 mine is the overflow at the apex of the anticline. There is also the possibility that areas above this level may be filled with explosive gas, as methane in large quantities is known to be coming out of some of the abandoned wells.
In any case, the potential hazard exists of unknown amounts of water, or water and gas, which may be released into a working open-light mine. Another possible hazard exists in the fact that one of the working entries of the No. 5.. mine is approaching a section of the abandoned No. 2 mine. As the faces of these working entries approach the abandoned area, bore holes should be kept at least 20 feet in advance of the face, and similar 45° angle holes, 25 feet deep, should be made on each side.
In view of the foregoing, it is thought that substantial seals shjuld be constructed in all openings or connections between the No. 5 mine and the abandoned area. At least one of these seals should be fitted with a pipe and valve to permit sampling of air behind the seals, and the ones in the low spots should have valveless drainage pipes so that the water may be released and pumped from behind the reals as it acumulates. To eliminate t'e hazard at its source, the No. 1 and No. 2 mines should be pumped out, and all “disposal wells' should be eliminated.
There are approximately 25 oil wells penetrating the coal bed within the No. 5 mine. Some of these wells went through the coal bed in pillars, and some of them are in open rooms, entries, or crosscuts. Among these are producing wells, dry wells, and disposal wells.
In the interest of safety and the protection of property, the Bureau of Mines recommends that: Oil and gas wells penetrating strata below beds of coal should be protected by a pillar of coal extending at least 50 feet on every side of the well bore.
If oil or gas wells penetrate open workings:
(a) A surrounding wall or pier of cement, masonry, or concrete of a diameter exceeding the height of the excavation, or at least 48 inches, should be constructed.
(b) The casing should be surrounded by an outer steel casing extending from 20 to 30 feet below the coal bed, and open to the outside atmosphere for relief of any gas liberated.
Every oil or gas well penetrating a coal bed should be properly plugged with concrete for at least 10 feet above and below the coal bed when abandoned, and the record filed with the State department of mines and minerals.
Accumulations of inflammable litter in the form of explosive boxes, boards, and waxed paper were observed in the vicinity of explosives-storage boxes. Piles of paper sacks that had contained rock dust were observed near rock-dust barriers. All accumulations of this kind should be immediately removed from the mine because in conjunction with carbide lights they present a serious fire hazard.
Coal and coal dust cleaned from between the entry tracks were thrown to the side, in such a way as to obstruct shelter holes and clearance.
('arbon dioxide leaking from seals in the first west, south, is entering the intake air current before it reaches the first working section. The months of all entries and all seals in the first west, south, should be examined by the day examiner before the men go to work. This area should also be patrolled con