REPORT OF COAL MINE GAS (FRICTIONAL) IGNITION GATEWAY COAL COMPANY CLARKSVILLE, GREENE COUNTY, PENNSYLVANIA June 9, 1969 by Henry Zavora Federal Coal Mine Inspector (Roof Control) INTRODUCTION This report is based on an investigation made in accordance with provisions of the Federal Coal Mine Safety Act (66 Stat. 692; 30 U.S.c. Secs. 451-483) as amended. Gas was ignited about 7 a.m., Monday, June 9, 1969, at the face of No. 1 entry just inby 7-1/2 room 7 butt 3 face in the Gateway mine. The incident occurred when the bits of the cutting chains of a Joy 1-CM continuous miner struck roof rock and ignited methane feeders during mining of the first sump of a reactivated place. The extent of the flame was limited to the mined sump, and the flame was extinguished immediately by the direct application of water from a hose. There were no injuries or property damage. John A. Noon, Federal Coal Mine Inspection Supervisor, Waynesburg, GENERAL INFORMATION Mine openings consist of 6 shafts and 2 slopes. Operations are in the Pittsburgh coalbed, which averages 68 inches in thickness in this area. Employment was provided for 585 persons, of whom 551 worked underground and 34 on the surface. The average daily production was 8,500 tons of coal. A block system of mining was practiced. Four entries were being developed in 7 butt 3 face toward virgin territory. Entries and crosscuts were on 85-foot centers. The No. 1 entry was about 17 feet wide and had been advanced about 105 feet from the last open crosscut at 6-1/2 room about a week prior to the occurrence. It was ventilated by means of line brattice while it was idle. The immediate roof varied from coal to rock in No. 1 entry, 7 butt 3 face and clay veins had been encountered. Roof bolting in accordance with a Bureau-approved plan was being done by means of equipment mounted on the continuous miner. Bearing plates were 6-inch by 6-inch by 1/4-inch bell-embossed steel. The last bolts installed in the place were about 16 feet and 12-1/2 feet from the face on the left and right sides, respectively. The mine is classed gassy in accordance with the laws of the State. Ventilation was induced by five fans operated exhausting and properly installed on the surface. At the time of the last Federal inspection, about 1,307,180 cubic feet of air a minute was being circulated throughout the mine and about 5,154,000 cubic feet of methane was being liberated from the mine in 24 hours. A split system of ventilation was used in the mine. Check curtains, line brattices, and permissible-type auxiliary fans were used to direct the air to face regions. At the time of the investigation about 32,470 cubic feet of air a minute was used to ventilate the 7 butt 3 face section. The air current was directed up No. 2 entry and was divided. About 11,900 cubic feet of air a minute was directed into the right split and 20,570 cubic feet was measured in the return of the left split of air. The No. 1 entry was ventilated by the left split of air. Tests made with electric methane detectors revealed methane feeders at the face of No. 1 entry. Laboratory analyses of air samples collected during this investigation are shown in table 1. The mine surfaces varied from wet to dry. Rock dust had been applied in the face area in No. 1 entry. Water was used to allay dust created during mining. The continuous miner in 7 butt was equipped with 10 water sprays. Direct-current electric power, at 250 volts, was used to operate the face equipment. Electric face equipment in use in 7 butt 3 face consisted of a Joy 1-CM continuous miner, a Joy 11BU loading machine, and two Joy 10SC shuttle cars. The equipment was permissible type and maintained in permissible condition. Trailing cables were flame resistant and provided with overload protection. The frame-ground conductor for the continuous miner was intact. Permissible electric cap lamps were used for portable illumination underground. Smoking was not permitted in the mine. Information for this report was obtained by an investigation at the scene of the occurrence and from statements made by Floyd Turcheck, Assistant Mine Foreman, and members of the crew who were present when the incident occurred: Willard Gill, continuous-miner operator; and Michael Benamatti and Charles Tedrow, roof bolters. The last Federal inspection of the mine was completed May 16, 1969. DESCRIPTION OF OCCURRENCE The crew of 7 butt 3 face section entered the mine at 12:01 a.m., When the crosscut was driven through to intersect No. 1 entry, the former last open crosscut was closed off and the air current was directed through the crosscut just completed. The production of coal was delayed while roof bolts were installed to support the roof area of the last portion mined (about 16 feet) in the crosscut. The assistant mine foreman examined the face regions of 7 butt section, including No. 1 entry, about 6:40 a.m. He detected no accumulation of methane and found no other danger. He continued his preshift examinatio for the oncoming shift by traveling the belt conveyor entry. After bolting in the crosscut was completed, fallen roof material at the intersection in No. 1 entry was loaded up. A deflector line brattice was installed from the outby rib of the crosscut and extended across part of the intersection toward the face of No. 1 entry. (See sketch.) The inby corner at the intersection was cut and loaded, and the mining machine was trammed to the face, which was about 16 feet from the crosscut just driven. The cutting head was sumped to a depth of about 2 feet at the bottom of the coalbed at the right side of the place and was raised upward to complete the shear. Hard material was encountered at the roof, and sparks were produced when the cutting bits struck it. Gas liberating freely from the sump was ignited by the sparks. The flame appeared to dance up and down in the sump. The continuous-miner operator grabbed the water hose from the miner, the bolter on the right side opened the water valve, and a stream of water was directed into the sump. The flame was extinguished immediately. The assistant mine foreman was notified of the occurrence when he returned to the face region. Further mining was not done in the place during that shift. During the investigation there were audible liberations of methane in the completed sump, and tests with electric methane detectors held against the coal indicated percentages above the lower flammable limit (off the scale). The methane was diluted at the face inasmuch as air sample bottle No. X-8940, collected at the face in the sump, contained 0.6 percent methane. The coal was 5-1/2 feet in height at the face, and the sump was 42 inches in width. At the time of the investigation at the scene of the occurrence the line brattice was along the right side of the place and had been altered between the time of the ignition and the underground investigation. Later it was established where the line brattice actually was at the time of the ignition. A spray on each cutting disk (pineapple) along the cutting chain at the front of the continuous-miner head and one spray in the hopper were not in proper operating condition at the time of the investigation. remedied promptly. This was CONCLUSION The ignition occurred when methane liberating freely at the face of the sump was ignited by sparks that resulted from cutting hard material. Contributory factors were lack of water being applied due to clogged sprays and not making the initial sump penetration on the line-brattice side of the place. RECOMMENDATIONS Compliance with the following recommendations may prevent a similar occurrence in the future: 1. Water sprays on continuous miners should be in proper operating condition when the miners are in operation. 2. Penetration at the face should begin on the ventilation (line brattice or tubing) side of the place. |