united states mine rescue association Mine Disasters in the United States
The Helen Mining Company
Homer City Mine Explosion
Homer City, Indiana County, Pennsylvania July 3, 1983 No. Killed - 1
The Homer City mine was opened in May 1969, and is located about 4 miles Southwest of Homer City, Indiana County, Pennsylvania, off Legislative Route 32022. The Helen Mining Company is a wholly owned subsidiary company of The North American Coal Corporation, Cleveland, Ohio.
The mine is opened by a double-compartment slope 2,200 feet in length and five concrete-lined shafts, two of which are double compartment, into the Upper Freeport coalbed which ranges from 37 to 80 inches in thickness. The shafts range from 614 to 682 feet in depth.
A total of 370 persons, 340 working underground, produce a daily average of 4,400 tons of coal on three coal producing shifts, 5 days a week.
The last safety and health inspection of the entire mine was completed on June 22, 1983. The Homer City mine, because of high methane liberation, is also on a 103(i), 5-day spot inspection schedule. Numerous wells extract natural gas from below the coalbed in this area. One of these active wells penetrates the coalbed in E-Butt section.
Conditions Immediately Prior to the Explosion
On July 3, 1983, the weather was mild and clear most of the day. Thundershowers arrived in the area of the Horner City mine about 5:00 p.m. Temperatures ranged from 77 degrees Fahrenheit at 8:00 a.m., and reached a high of 92 degrees Fahrenheit at 4:00 p.m.
The explosion occurred when the mine was idle for a vacation period scheduled from June 25 to July 10, 1983. Production ended with the afternoon shift on June 24, 1983, and the only work performed in the mine during the vacation period was some limited maintenance work and patrolling of power lines, haulageways and pumps every shift.
Finding of Fact
The volatile ratio of the channel sample collected in E-Butt section was calculated to be 0.29 indicating that the coal dust is explosive.
During the last Safety and Health inspection, the three fans exhausted a total of 954,098 cubic feet per minute of air from the mine, and the mine liberated 2,701,000 cubic feet of methane in 24 hours.
During the last Safety and Health inspection, 0.3 percent methane was found to be in the immediate return off the working faces of E-Butt and 0.6 percent methane was detected at the regulator near the mouth of the section.
The mine was idle because of vacation at the time of the explosion. The last production was on the afternoon shift of June 24, 1983. Patrolling and some scheduled maintenance were the only work performed at the mine during this period.
Swanhart arrived at the power center in the E-Butt section at approximately 11:00 a.m. in the course of his normal patrolling duties.
At approximately 4:05 p.m., Dwyer and Mitsko entered the mine. Mitsko's initials in D-Butt at the power center indicated that he was in the section prior to the explosion.
At approximately 5:40 p.m., an explosion occurred in the E-Butt section. On the surface, all the lights in the hoisthouse went out and the fan signal, located in the hoisthouse, sounded.
Syster arrived at the No.3 fan at approximately 6:30 p.m. He discovered that the fan was down and according to the fan recording chart, had not been operating since approximately 8:15 that morning.
Shortly after 6:00 p.m., Vresilovic contacted Dwyer and informed him that possibly a fan was not operating. About the same time, the automatic belt warning signal for E-Butt was transmitting over the mine phone. When Dwyer learned that Mitsko had not been contacted, he informed Vresilovic that he was going to E-Butt.
Upon entering the E-Butt section, Dwyer observed that the air was hazy and the entry blackened. He had proceeded inby the E-Butt switch approximately 800 feet when his jitney derailed. He then continued on foot for an undetermined distance, until he had to retreat because of a burning sensation in his eyes.
After being notified, Hancher, McElhoes, and Dwyer entered the mine about 8:05 p.m. and traveled to E-Butt. They quickly concluded that an explosion had occurred and returned to the surface to arrange for assistance.
The Florence Mining Company Nos. 1 and 2 mine rescue teams started to arrive at the mine approximately 10:30 p.m., and about an hour and a half later had enough members to make up two teams.
At approximately 5:20 a.m., the first fresh-air base was established on the No.2 track entry inby 13R crosscut in E-Butt section.
The victim was removed from the mine at 12:50 a.m., July 6, 1983. At approximately 7:00 p.m., the same day, the E-Butt section was explored and ventilated.
During the exploration and recovery of E-Butt section, extreme caution had to be used throughout when exploring inby fresh air bases. Mine rescue teams frequently encountered high concentrations of methane, carbon monoxide, and low oxygen. Air samples analyzed showed concentrations as high as 26 percent
methane, 4.73 percent carbon monoxide, and oxygen as low as 4.10 percent.
The E-Butt (001) section had been developed approximately 4,000 feet by three entries. The No.1 entry, which contained the belt conveyor was an intake aircourse used to ventilate active working places. The No.2 entry was an intake aircourse containing the track, and the No. 3 entry was the return aircourse.
The daily mine methane liberation from the coal seam as determined by analysis of vacuum bottle and air measurements taken in the main return aircourses immediately inby the main fans during an inspection of the entire mine between April 6 and June 22, 1983, was 2,701,000 cubic feet.
On May 18, 1983, the daily methane liberation rate from the E-Butt section as calculated by air and methane readings was 272,000 cubic feet.
The last mine foreman's weekly examination for methane and hazardous conditions prior to the explosion was conducted on June 30, 1983. The recorded results indicated that 285,120 cubic feet of methane was being liberated in E-Butt section every 24 hours.
The No.3 fan, which ventilated the E-Butt section, exhausted 444,750 cfm of air from the mine at a recorded pressure of 6 inches of water.
During the investigation, simultaneous air measurements were taken at specific locations ventilated by the No.3 fan, to determine affected air flow before and after No.3 fan was stopped. Air measurements were taken and recorded at the locations with all the fans running at normal water gauge. With the No.3 fan shut down, the second set of air readings showed that air quantities were greatly reduced or, in many cases, air direction was reversed. Air movement in E-Butt virtually stopped when No. 3 fan was shut down.
Each of the three mine fan installations is equipped with a single switch to activate the fan signal alarm system. In the No.3 fan, the switch was mounted on a wall of the fanhouse and a 2-inch diameter pipe extended from the switch into the fan duct to sense the mine ventilating pressure. The device is designed so that when the ventilating pressure decreases to less than negative 0.12 inches of water, the switch will open the electrical contacts activating the alarm system at the mine portal and the hoisthouse.
From an examination of the fan charts following the explosion, it was revealed that at approximately 8:15 a.m., on July 3, 1983, the No.3 fan stopped. The switch on this fan did not activate the alarm system because the Nos. 1 and 2 fans were
still in operation and were maintaining a negative pressure of approximately 1.0 inch of water in the No.3 fan duct.
At approximately 5:40 p.m., when the explosion occurred, the pressure in this fan duct changed enough to activate the switch and thus the alarm system alerting mine personnel that the fan was not operating.
During the investigation, a mine dust survey was conducted in the affected area of the mine. Coke was found in all samples collected inby crosscut 10L in the belt entry, 8L in the track entry, and 12R in the return entry.
The investigation team concluded that the explosion originated in the No.2 entry inby crosscut 36L where the victim and a track-mounted battery-operated personnel carrier were found. Coke deposits confirmed that methane and coal dust entered into the explosion.
Flame and major forces of the explosion propagated from the origin, traveled inby to the faces and then outby to the mouth of E-Butt. The explosion developed pressure to destroy, damage, or otherwise disrupt ventilation in E-Butt from the
faces to a distance 4,000 feet outby to an overcast located at the mouth of E.
Dispersed inert material (rock dust) is considered by the investigation team as the major mechanism that limited the flame propagation in E-Butt following the explosion.
Based upon observations made during the investigation, coal dust was a factor in propagation of the explosion in E-Butt. The duration of the No.3 fan stoppage and also on the rate of methane liberation in E-Butt, however, led the investigators
to conclude that the explosion was predominantly a violent methane explosion.
Melted wire insulation, charred paper, melted brattice material, melted plastic, soot deposits and coke on roof, posts, mining equipment and in other places was visibly evident in the E-Butt section from the faces as far outby as 13 crosscut in No.1 (belt) entry.
There was evidence of flame found in the faces of E-Butt. Flame of an explosion will propagate into a dead-end area of an entry (faces) only if the atmosphere therein contains an explosive gas/air mixture.
Major forces of the explosion propagated from the origin and traveled inby in Nos. 1 and 2 entries to the faces of E-Butt and outby in all three entries toward the mouth of the section.
All permanent stoppings inby 17 crosscut were completely destroyed. Steel roof mats were ripped away from roof bolts and bent in all directions. Posts were dislodged and scattered through the entries. Power conductors were torn apart. Cover plates were torn off of equipment and miscellaneous material was thrown around the section. The belt feeder was moved several feet and the belt and belt wires were severed and strewn throughout the No. 1 entry. Damage to ventilating devices was observed as far outby as the mouth of the section.
The victim suffered extensive flash burns with evidence of smoke inhalation and carbon monoxide poisoning. There were no significant contusions, abrasions or lacerations and no fractures were found.
The direction of the explosion forces and testimony to the effect that there was no occurrence which would have caused the electrical relay contacts to be broken under load, indicates that the explosion could not have initiated at the section
Based upon location of positions of operating controls on the personnel carrier, flame, direction of the forces of the explosion, and physiological condition of the body of the victim, the investigators conclude that the ignition of methane originated at the track-mounted, battery-operated personnel carrier located in No.2 entry just inby No. 36L crosscut.
It is the consensus of the investigators that the ignition source was the arcing created in an open compartment by the resistance contactors opening and closing as Mitsko trammed the personnel carrier toward the faces.
Four of the conditions and practices in the Findings of Fact contributed to the explosion and constituted violations of the Federal Mine Safety and Health Act of 1977 and the mandatory standards contained in 30 CFR. These are listed below:
The volume and velocity of air ventilating E-Butt (001) working section off of Muddy Run Submains on July 3, 1983, was not sufficient to dilute, render harmless, and to
carry away flammable, explosive and harmful gases which permitted methane, an explosive gas, to accumulate in this area.
On July 3, 1983, on the 4:00 p.m. to 12 midnight shift, evidence revealed the person who was required to enter the idle Muddy Run. Submains areas in the performance of his duties was not properly equipped with means approved by the Secretary for detecting methane.
On July 3, 1983, at approximately 8:05 a.m., the No.3 mine ventilation fan stopped. The automatic signal device placed at the No.2 shaft portal to be seen or heard by a responsible person did not give an alarm when the No.3 mine ventilation fan stopped.
On July 3, 1983 on the 8:00 a.m. to 4:00 p.m. shift, the two certified persons were performing their duties including making a fire examination (checking high-voltage cables) along the track haulage in the idle Burrell Mains, 1st South, 4th South, C, D, and E Butts of Muddy Run Submains and Muddy Run Hains.
At approximately 8:05 a.m., the No.3 mine ventilation fan stopped, which was the ventilating system for the above areas. With the No.3 fan down, a dangerous condition existed, which was not observed by the two certified persons entering these areas.
The investigators concluded that at 8:15 a.m., on July 3, 1983, the No. 3 fan ceased operation. This disruption in ventilation virtually stopped the flow of air in E-Butt and allowed methane to accumulate to an explosive range in the E-Butt section.
Atapproximately 5:40 p.m., Sylvester Lee Mitsko (victim) entered the unventilated area on a track-mounted, battery-operated personnel carrier. The electric components of the personnel carrier were housed in an open-type electrical compartment which allowed the methane to easily migrate inside.
The victim's operation of the carrier tram control, opened and closed contactors within the compartment, creating arcing, which ignited the explosive methane-air mixture. The open compartment also easily permitted flame to escape once the methane was ignited.
The escaping flame propagated further into the explosive methane-air mixture in the No.2 entry and surrounding areas. The following conditions and/or practices contributed to the cause of the accident:
The automatic signal device which was installed in the No. 3 fan ducting did not glve an alarm at the manned No. 2 shaft portal when the No.3 mine ventilation fan shut down.
The day shift assistant foremen who traveled and worked in the Muddy Run area of the mine between 8:00 a.m. and 4:00 p.m., failed to recognize that the ventilation had been drastically reduced.
The person (Mitsko) who was required to make examinations in E-Butt did not have in his possession a means approved by the Secretary for detecting methane.