REPORT RELATING TO KOEHLER PERMISSIBLE

FLAME SAFETY LAMP FROM

THE HELEN MINING COMPANY, HOMER CITY MINE
HOMER CITY, PENNSYLVANIA

Introduction

The subject flame safety lamp was received from the District Manager, Coal Mine Safety District A, on April 10, 1970 along with a request for testing and inspection of the unit.

Internal and External Examination of Assembled Lamp as Received

The

The lamp had a round brass tag stamped with the number 1 attached to the lamp hook. The name P LAZERATION was on a plastic-type plate glued to the outside of the magnetic lock ring in the area of the magnetic lock. lamp was covered with a layer of rock dust. The top of the lamp wick was about 1/16 inch below the top of the wick tube. The lamp was properly assembled and the magnetic lock functioned. There was no evidence of damage to the burner glass, inner air admission ring, gauzes, bonnet, lamp rods, magnetic lock ring, igniter assembly, wick adjusting assembly, or dome top. There was a dent in the bottom edge of the fount indicating the lamp had struck or was struck by an object.

Safety Tests

The lamp as received was positioned in the test gallery so that the igniter was externally operated. Explosive mixtures of natural gas and air ranging from 7.5 percent to 9.5 percent natural gas were used in the gallery. Six hundred operations of the igniter, in both still and moving mixtures, produced bursting explosions within the lamp in the upper gauzes, on the fount top, and around the inner air admission ring. The lamp was jarred and shaken during the tests. There were no gallery ignitions.

In the next series of tests, the warm lamp with a 3/4-inch-high flame, was raised up into still and moving explosive natural gas and air mixtures ranging from 7.3 percent to 9.5 percent natural gas. The flame rose up into the gauzes, there was a bursting internal explosion within the lamp after which the flame extinguished. There were no gallery ignitions.

Disassembly and Inspection After Testing

The lamp disassembled readily. There was a thin layer of coal dust on the fount top and on the inside of the burner glass. The burner glass was the unlined type and marked MONAX. The gauzes were steel, had tight seams, showed no evidence of overheating, and had no broken strands. The fount surface was smooth and the fount threads were not damaged. The aluminum air admission ring bottom surface had no dents and its gauzes were clean. The ring seated firmly and fully on the fount surface. Both asbestos washers were in position. The magnetic lock was operative as was the wick adjusting assembly. The igniter functioned during all the tests and produced a 3/4-inch walking flame when first operated. The bonnet and magnetic lock ring assembly were in good condition.

Conclusion

The lamp met the permissibility requirements of Schedule 7C.

APPENDIX B

Memorandum

To

:: Mr. John Nagy, Bureau of Mines, Bruceton, Pa. From : B. C. Parks, Pittsburgh Mining Research Center

Subject:

Mineralogical examination of rock specimen from Homer City
Mine, Helen Mining Co., Homer City, Indiana County, Pa.

I have made a microscopical examination of the rock specimen you sent to this laboratory Friday, April 17, and report the following information:

The specimen in question was revealed to be a fragment of a nodular or concretionery rock mass, commonly referred to in mining terminology as a coal ball, nigger head, or sulfur ball. These rock bodies most usually are found at the top of a coal bed, or perhaps more frequently in the roof rock immediately above the coal fragments. Fragments of coal attached to your specimen clearly indicate to me that it was embedded in roof rock immediately overlying the coal.

The composition of the rock specimen as revealed by the microscope consisted of over 30 percent pyrite (iron sulfide FeS2) and silica (quartz Si02), the remaining dominant mineral. The hardness of pyrite is 6 to 6-1/2 and that of quartz is 7. The hardness of your rock specimen is attested by the fact that in cutting thin slices out of the rock for microscopic preparation, our rock saw (diamond blade) produced a continuous stream of sparks extending for at least a good inch below the saw blade that continued during the entire cutting action. It is easy to visualize that in the case of a gassy mine, if a cutting machine or drill encountered one of these rocks, the flow of sparks generated by this action might in all probability ignite the methane gas and float dust.

There is enclosed a thin slice from the Homer Mine fragment cut with our diamond saw. By examining the slightly polished surface of this slice, the extent of pyritic mineral matter in the rock can readily be detected.

Memorandum

То

From :

: W. Dan Walker, Jr., District Manager, District A

John Nagy

Subject: Rock specimen from Homer City Mine

As requested, the rock specimen from Homer City Mine was examined. Mr. Forrest Walker's analysis showed it contained 62.0 percent total silica. Mr. Bryan Parks made a microscopic examination. His report (attached) states most clearly that incendive sparks would be produced by machine bits striking this rock. I concur with his statements. Substantiation of these opinions is given in Inf. Circ. 7727 by the following paragraphs on page 13:

Of the rocks encountered in coal mines, siliceous or quartz-
bearing sandstones present the greatest frictional ignition
hazard; they are closely followed by iron pyrites. Some micaceous
sandstones also have been found to constitute a hazard. Shales
are considered less dangerous than sandstone, but some bituminous
sandstones, which look like shales, can produce incendive sparks.
It has been found that rocks with less than 35 percent quartz can
give dangerous sparks. There is some indication that the moisture
content of rocks may affect their incendivity.

In contact between rocks and metals the nature of the rock is
far more important than that of the metal. Although little if
any difference was observed between various steels in contact
with rocks, in high-speed machine operations the surface hardness
of the metal might have an effect. Sharp glancing blows proved
most effective in producing ignitions by friction between steel
and sandstone. In contact between steel and pyrite, the most
hazardous conditions occurred during rubbing or sliding friction,
which produces fine dust. In tests with cutters, the sharpness
of the bits was found to be an important factor. Blunt bits are
more hazardous than sharp bits because they produce more fine
coal dust and upon encountering pyrite may produce and ignite
pyrite dust. Another important factor in cutting or drilling is
overloading machines; this can produce much heat and bring about
conditions that lead to ignition.

/s/ John Nagy

John Nagy

APPENDIX C