UNITED STATES
DEPARTMENT OF LABOR
MINE SAFETY AND HEALTH ADMINISTRATION

Southeastern District
Metal and Nonmetal Mine Safety and Health

Accident Investigation Report
Underground Metal Mine

Fatal Powered Haulage Accident

I.D. 40-00166
Coy Mine
ASARCO, Incorporated
Jefferson City, Jefferson County, Tennessee


April 3, 1996

By

J. B. Daugherty
Supervisory Mine Inspector

and

C. E. McDaniel
Mine Safety and Health Inspector


Originating Office
Mine Safety and Health Administration
135 Gemini Circle, Suite 212
Birmingham, Alabama 35209

Martin Rosta
District Manager

GENERAL INFORMATION

Thurman S. Jackson, loader operator, age 50, was fatally injured at about 5:45 a.m. on April 3, 1996, when the left front tire rolled over him after he was thrown or jumped from the loader he was operating. The victim had worked as a loader operator for the last 13 weeks. He had a total of 4 years and 20 weeks mining experience, all with this company.

The MSHA Knoxville, Tennessee field office was notified of the accident at 6:45 a.m. on April 3, 1996, by a telephone call from Daniel J. Steinhoff, safety director for ASARCO, Incorporated. An investigation was started the same day.

The Coy Mine, an underground zinc operation, owned and operated by ASARCO, Incorporated, was located adjacent to State Highway 11-E, east of Jefferson City, Jefferson County, Tennessee. The principal operating official was Robert Brown, mine superintendent. The mine was operated three shifts per day, 7 days a week. A total of 56 persons was employed.

Mining was accomplished by selective open-stope methods with random pillars left for roof support. Haulage roads and levels were interconnected and varied in width and height. Ore was mined by drilling and blasting and then transported by various types of diesel-powered haulage equipment to transfer raises. Ore was then hoisted to the surface at Coy Mine shaft by scroll dump skips.

The last regular inspection was conducted on March 22, 1996. An MSHA-approved training plan, in accordance with 30 CFR, Part 48, was in effect at the mine. The victim had received all mandatory training.

PHYSICAL FACTORS INVOLVED

The equipment involved in the accident was a rubber-tired Wagner ST-6C load-haul-dump unit, serial number DA14P0310. The loader was equipped with a Deutz, 10 cylinder air cooled, 206 h.p. diesel engine and a Clark R-32, 425 4-speed transmission. The third and fourth gears of the transmission were blocked out and only first and second gears were used. The loader weighed approximately 71,000 pounds when fully loaded.

The operator's compartment, mounted in the center of the loader, was positioned so the operator could observe the roadway from either direction traveled. Hydraulic steering was provided and controlled by a single lever-operated steering valve.

The braking system was hydraulic-operated shoe/drum, and the park brake was a hydraulic disc on the drive line. Three accumulators were provided to assure hydraulic pressure: one for the front brakes, one for the rear brakes, and one served all braking systems, including the park brake.

The park brakes were controlled from a push/pull button mounted on the dash of the loader. The service brakes were controlled by a floor-mounted foot pedal. The foot pedal mechanism consisted of anchor flanges, the pivot pin, and the brake pedal assembly. The pivot pin was secured between the anchor flanges with a 1/4 x 1 inch bolt on each side. This allowed the brake pedal to rotate on the stationary pivot pin.

Two days before the accident occurred, the left bolt holding the pivot pin to the mounting flange had backed out and the pedal became loose. The head on the bolt on the right side of the mounting flange had sheared off and appeared to look like a pin or dowel to the mechanic who replaced the left bolt and put the loader back into service.

During the accident investigation it was learned that the pivot pin had seized in the brake assembly housing. As the pivot shaft was found seized in the brake pedal assembly, repeated brake pedal usage coupled with machine vibration resulted in loosening and separation of the bolt from the pivot shaft. Because the pivot shaft had seized, reinstalling the bolt did not correct the problem. With the head of the right side pivot shaft bolt broken off, once the left bolt separated from the pivot shaft, the service brake pedal was free to come out of the proper position, resulting in loss of braking capability.

The area where the accident occurred was the 11-53 gallery drift. The drift was over 1000 feet long and 20 feet wide by 14 feet high and was inclined 22%.

Tests performed after the accident on the loader's braking system found the parking brake and service brake to be more than adequate for the area where the loader had been operating.

DESCRIPTION of ACCIDENT

Thurman S. Jackson (victim), reported for work on April 2, 1996, at 11:00 p.m., his regular starting time and was assigned the task of mucking in the 18-48 stope and hauling to the 11-53 mill hole ore pocket by his foreman Scott Blair.

Jackson obtained the loader from the shop where it had been left after being serviced and preceded to the 18-48 stope. It was normal procedure to drive into the stope then, once the loader bucket was full, to back out of the stope into the 11-53 gallery drift, then proceed forward to the mill hole ore pocket to dump the material.

During the shift, Jackson made several trips to the shop with the loader to have repairs made; however, none of the repairs involved the braking system on the loader.

At approximately 5:45 a.m. on April 3, 1996, Dean Trent, loader operator, followed by George Lowery and Donnie Longmire, truck drivers, were coming from the 10-84 stope with their vehicles to go to the mill hole ore pocket. As Trent approached the entrance to 11-53 gallery drift he heard a loud noise. He stopped his loader and moments later saw the loader the victim had been operating going down the drift at a high rate of speed. He did not see Jackson in the operator's cab.

The three men left their vehicles and went down the stope 71 feet to where the loader had stopped against the rib. When they approached Jackson's loader they looked in and around it but could not locate Jackson. Trent went to get help and Lowery and Longmire, went up the drift about 220 feet and found Jackson. They checked for a pulse and could get no response from Jackson who was laying face down in the drift.

Lowery and Longmire then went to the foreman's office and met with Trent and Scott Blair, shift foreman, who were getting the stretcher. They returned to the accident site and transported the victim to the shaft and then to the surface where the rescue squad was waiting. Jackson was taken to Jefferson Memorial Hospital where he was pronounced dead on arrival. He died as a result of crushing injuries sustained when the loader he had been operating ran over him.

Apparently, when Jackson backed the loader from the 18-48 stope into the 11-53 gallery to change direction of travel, he was unable to stop the loader since the brake pedal had separated from its proper mounting position. As the loader continued backward down the slope it gained momentum and Jackson was unable to stop or control the loader. Damage to the loader and scrape marks in the gallery drift indicated that the loader struck both ribs while descending approximately 600 feet before stopping. Lack of control or impact with the rib either caused Jackson to jump or be thrown from the loader. When the loader stopped it was found that the transmission was in neutral and the park brake set. The brake pedal was found in the gallery drift 11 feet from the victim and 213 feet from the loader.

CONCLUSION

The cause of the accident was the improper maintenance and repair on the loader's brake pedal assembly which caused the pedal to become separated from the mounting flanges.

VIOLATION

Citation No. 3052054

Issued on May 3, 1996, under the provisions of 104(a) for a violation of Standard 57.14100(b):

A miner was fatally injured when he jumped, fell, or was pulled out, and ran over by a Wagner model ST-6 scoop tram loader he had been operating in the 1153 Gallery. An examination of the loader's service brake pedal actuator cam assembly revealed a seized pivot shaft on the service brake pedal. The continuous use of the service brake assembly with a seized pivot shaft contributed to the service brake pedal separating from its proper pivoting point position and subsequently compromised the service brake capability.

This citation was terminated on May 3, 1996. A new pedal actuator cam assembly was installed on the loader.

[FAB96M10]