PHYSICAL FACTORS INVOLVED

The accident occurred at the five corners area of the plant where an excavation approximately 32 feet wide, 60 feet long, and 12 feet deep had been dug to access a 30-inch diameter steel waterline. The excavated area was about 150 yards from the agglomerator building. The waterline was a return line from the agglomerator to the concentrator building and the flow had become obstructed. Three other excavated areas, all about 50 yards apart, had also been dug in order to locate the source of the problem. A rectangular opening had been flame cut into the pipe at each location. The opening in the pipe, where the accident occurred, was approximately 25-1/2 by 48 inches and was cut in order to examine the insides of the waterline.

The plug installed in the opening was a Model #262-560, large multi-size Muni-ball pneumatic plug, manufactured by Cherne Industries, Inc. The deflated plug was approximately 22 inches in diameter and 58 inches in length and could be used in pipes from 24 to 42 inches in diameter. The rubber sides of the plug were tapered, leaving an opening over which inner and outer cast iron plates were bolted together to seal the ends. The cap on the front end plate had been modified with two short extensions. One extension served as a water and air relief outlet and the other was used to introduce compressed air into the plug. Both extensions were equipped with quarter-turn ball valves and the air inlet extension was equipped with a pressure gauge. Both outer plates were stamped with a notice "MUST INFLATE TO MAXIMUM OF 25 P.S.I.G. (1.7 BAR)". A 3/4-inch air hose connector had been attached to the air inlet extension on the front cap with a quick-coupler fitting. The plug showed signs of deterioration as characterized by cracks in the elastomers throughout its outer surface. Cracks had split into the polyester cords in the middle ply of the three-ply wall of the plug.

Air was supplied from a 3/4-inch hose attached to an Ingersoll Rand, Model P125 WJDU compressor, which was mounted on a truck. This compressor had a starting pressure of 45 p.s.i. and was equipped with a load button which, when activated, allowed the discharge pressure to reach 109 p.s.i. The pressure could not be regulated down to 25 p.s.i., as required by the plug manufacturer.

The manufacturer's safety instruction manual for the plug stated in part: Prior to inflation, the front of the plug must be positioned into the pipeline a minimum distance of one pipeline diameter; always inflate plugs to recommended pressure; pressure sources used must be equipped with pressure regulated output; pneumatic plugs must be removed from service and tested or destroyed when evidence of deterioration or wear is observed. Always stay out of the danger zone during pneumatic plug inflation. The danger zone exists in front of the plugged pipe opening, expanding outwardly in a cone shape.

DESCRIPTION OF ACCIDENT

On the day of the accident, David Pulis (victim) reported for work at 3:00 a.m. His normal work shift started at 7:00 a.m., but the night shift team leader was absent and Pulis and another shift manager split the night shift, each working an additional four hours.

A short time after Pulis arrived, he and David Santelli, shift manager, went to the excavation nearest the agglomerator building where they found that the plug, which had been installed two days prior by Phillips, Getschow Company, had deflated and was floating in approximately 3 feet of water. David Puttonen, equipment tender, and Jeffery Wallner and Todd Meier, attendants, were assigned to help the shift managers reinstall the plug.

At about 4:50 a.m., after the water in the excavation had gone down, the plug was reinstalled in the pipe, however, it was not inserted at least 30 inches into the pipe in accordance with the manufacturer's installation instructions. Pulis operated the compressor and Santelli attached the air hose and inflated the plug. The pressure gauge on the plug was under water and could not be seen. After the plug was inflated, Pulis shut off the compressor and checked for leaks. He and Santelli saw air bubbles indicating a leak and water was seeping around the plug. Santelli opened the relief valve and bled some air out of the plug. Pulis restarted the compressor, then returned to the pipe and knelt down over the opening with a flashlight to check for seepage. He then turned the air hose on to further inflate the plug.

About 30 seconds after Pulis opened the air valve, the plug ruptured violently. He was thrown several feet away by the force of the blast. Pulis was unconscious and first-aid treatment was administered immediately by co-workers. The local 911 emergency assistance number was called and an ambulance arrived a short time later. Pulis was transported to a local hospital where he was pronounced dead. The four other employees were not seriously injured.

CONCLUSION

The accident was caused by failure to follow the manufacturer's recommendations. The plug was not positioned to the prescribed depth in the pipe and the maximum inflation pressure was exceeded. The deteriorated condition of the plug was a possible contributing factor. The lack of task training was also a contributing factor.

VIOLATIONS

Minnesota Ore Operations, USX Corporation

Order No. 4558083 was issued on August 23, 1998, under the provisions of Section 103(k) of the Mine Act:

A fatal accident occurred between the step one and two concentrator and the agglomerator (pellet) plant when a bladder being used to plug a 30-inch waterline failed. This order is issued to assure the safety of persons in the affected area until it can be returned to normal mining operations as determined by an authorized representative of the Secretary. The operator shall obtain approval from an authorized representative for all actions to recover equipment and/or restore operations in the affected area.

This order was terminated on August 26, 1998. Conditions that contributed to the accident have been corrected and it was determined that normal mining operations could safely resume.

Citation No. 7805750 was issued on September 21, 1998, under the provisions of Section 104(d)(1) of the Mine Act for violation of 30 CFR 56.14205:

A shift manager was fatally injured at this mine on August 23, 1998, when a pneumatic pipe plug that he was installing ruptured. The plug was used beyond its designed capacity in that the maximum air pressure of 25 p.s.i. was significantly exceeded during inflation. The plug was clearly labeled. The shift managers who overinflated the plug displayed a serious lack of reasonable care, constituting more than ordinary negligence and an unwarrantable failure to comply with a mandatory safety standard.

Order No. 7805751 was issued on September 21, 1998, under the provisions of Section 104(d)(1) of the Mine Act for violation of 30 CFR 56.14100(b):

A shift manager was fatally injured at this mine on August 23, 1998, when a pneumatic pipe plug that he was installing ruptured. The plug was defective in that the rubber was cracked, cords were exposed and damaged and, overall, the plug showed excessive wear and deterioration. By attempting to use the defective plug, the shift managers who installed it displayed a serious lack of reasonable care, constituting more than ordinary negligence and an unwarrantable failure to comply with a mandatory safety standard.

Order No. 7805752 was issued on September 21, 1998, under the provisions of Section 104(g)(1) of the Mine Act for violation of 30 CFR 48.27(c):

A shift manager was fatally injured at this mine on August 23, 1998, when a pneumatic pipe plug that he was installing ruptured. The two shift managers and three workers assigned to install the plug did not have previous experience in this task and had not been instructed in the safety and health aspects and safe work procedures of the task. The mine operator was aware of the training requirements.

Phillips, Getschow Company

Citation No. 7805755 was issued on September 21, 1998, under the provisions of Section 104(d)(1) of the Mine Act for violation of 30 CFR 56.14205:

A shift manager employed by the mining company was fatally injured at this operation on August 23, 1998, when a pneumatic pipe plug that he was installing ruptured. Precautions contained in the plug manufacturer's instructions were not followed. The plug was being used beyond its designed capacity in that it was not properly installed, inflated, and monitored. The contractor foreman who initially installed this plug displayed a serious lack of reasonable care, constituting more than ordinary negligence and an unwarrantable failure to comply with a mandatory safety standard.

This citation was terminated on October 5, 1998. The contractor has instructed employees to follow manufacturer's recommendations regarding installation, use, and maintenance of pipe plugs.

Order No. 7805756 was issued on September 21, 1998, under the provisions of Section 104(d)(1) of the Mine Act for violation of 30 CFR 56.14100(b):

A shift manager employed by the mining company was fatally injured at this operation on August 23, 1998, when a pneumatic pipe plug ruptured. The plug was defective in that the rubber was cracked, cords were exposed and damaged and, overall, the plug showed excessive wear and deterioration. The contractor foreman who initially installed this plug displayed a serious lack of reasonable care, constituting more than ordinary negligence. This is an unwarrantable failure to comply with a mandatory safety standard.

This order was terminated on October 5, 1998. The contractor has instructed employees to follow the manufacturer's recommendations regarding installation, use, and maintenance of pipe plugs.

Related Fatal Alert Bulletin:
FAB98M36