DEPARTMENT OF LABOR
MINE SAFETY AND HEALTH ADMINISTRATION
North Central District
Metal and Nonmetal Mine Safety and Health
Accident Investigation Report
Surface Nonmetal Mine
Fatal Powered Haulage Accident
Sora Limestone, Inc. (quarry)
Sora Limestone, Inc.
Rockwood, Wayne County, Michigan
I.D. No. 20-02241
December 2, 1996
Donald J. Foster, Jr.
Jack L. Webb
Mine Safety and Health Inspectors
Federal Building, U.S. Courthouse
515 West First Street, #228
Duluth, Minnesota 55802-1302
James M. Salois
Dale W. Scott, mechanic, age 38, was fatally injured about 4:50 p.m. on December 2, 1996, when he was pinned between the boom arm and the cab frame of a skid steer loader. Scott had a total of two years and three months mining experience, all as a mechanic at this operation. He had received training in accordance with 30 CFR Part 48 and annual refresher training had been conducted on January 29, 1996.
Craig S. Chall, safety director, notified MSHA by leaving a message about the accident on the Lansing, MI field office answering machine at 9:30 p.m., the day of the accident. An investigation was started the following day.
The multiple bench Sora Limestone, Inc. quarry, owned and operated by Sora Limestone Inc., was located at 20837 North Huron River Road, Rockwood, Wayne County, Michigan. The principle operating officials were Angelo E. Iafrate Jr., president; Robert Adcock, superintendent; and Craig S. Chall, safety director. The mine was normally operated one, 10-hour shift per day, six days a week and a total of 10 persons was employed. The mine was operated under a lease agreement on property owned by U.S. Silica Company. Limestone mining started at the quarry in the early 1970's and the quarry had been operated by Sora Limestone Inc. since June 21, 1993.
Limestone was drilled and blasted from multiple benches with heights that varied from 20 to 45 feet. It was then loaded by front-end loader into haul trucks and transported to the crushing plant where it was crushed, screened, and conveyed to stockpiles. The finished products were used in the road building and general construction industry. The last regular inspection was completed on November 22, 1995, and another regular inspection was conducted after the fatal accident investigation. The mine was not represented by a union.
PHYSICAL FACTORS INVOLVED
The skid steer loader involved in the accident was a 1992 Thomas, Model 9201T173HL, serial number LK000145H. It was purchased used in May, 1995, and an owner/operator's manual was not available at the mine site. The maximum speed was 7.3 miles per hour (mph) and the operating weight was 6,650 pounds. The rated operating capacity was 1,700 pounds and the loader was powered by a Kubota, 52 horsepower (HP), 4 cylinder diesel engine, model V2203. The hydraulic system relief pressure was 2150 pounds per square inch (PSI).
The loader was 11 feet 7 inches long and 5 feet 9 inches wide, wheel to wheel. The cab frame was 7 feet 6 inches in length, 3 feet 4 inches wide, and the canopy height was 6 feet 10 inches from the floor. The wheel base was 3 feet 3 inches and the ground clearance was 8 inches. A wooden block, 2 feet long, 9 inches high, and 11 inches wide, had been placed under the center of the undercarriage and the left front and rear tires had been removed.
The loader was operated by two hand control levers, one on each side of the operator's seat. The right lever controlled the forward and reverse travel for the drive system on that side of the loader when moved to the front or rear. It also moved left or right, controlling the bucket cylinders for filling or dumping the bucket. The left lever controlled the forward and reverse travel for the drive system on the left side. It also moved left or right and controlled the hydraulic boom cylinders, which raised or lowered the loader's boom arms. Moving the lever to the extreme right would place the boom in float position. Slight movement of the control levers in any direction would activate the intended function.
The loader was provided with a roll-over protective structure (ROPS) and a seat belt. The ROPS was enclosed on the sides with expanded metal and had a plexiglass window across the rear. The only access into the operator's cab was from the front of the loader.
A manually operated safety seat bar had been installed on the loader at the factory for operator protection. In the raised position the seat bar was designed to automatically center and lock out the control levers, preventing any movement of the machine when persons would enter or exit the operator cab. The forward and reverse control levers were connected to the safety seat bar by a linkage system located under the seat. The system had been altered by removing the right control lever bushing and bolt and cutting off the end of the left control lever arm lock. The alterations allowed the control levers to be operated from outside the cab with the safety seat bar in the raised position. This could be accomplished by reaching over the boom arms when in the down position or, more readily, under the boom arms when elevated.
The side-to-side motion of the control levers was connected to the safety seat bar by a system that activated two steel cables extending from under the seat to the hydraulic valve bank controls in the rear engine compartment. This system was also intended to lock out when the seat bar was up. Both of the original steel cables had been replaced and were out of adjustment, resulting in misalignment of the side-to-side lock outs.
A post accident test of the side-to-side lock out system with the seat bar raised indicated the right control lever would not lock at all and the left control lever locked only after it was manually moved one inch to the right. The lever then locked the boom into the down position with continuous pressure against the cab frame.
The estimated time for the boom to close against the frame was three to four seconds with the loader elevated on the center block and the bucket tipped down. Once the motion began, the only way to stop it was to lower the safety seat bar, releasing the lock and manually reversing the boom with the control lever. The seat bar could not be reached from outside the cab when it was in the raised position.
The loader was used for cleanup and was last operated on Friday, November 29, 1996, when it was parked at the shop around 3:00 p.m. because the left bucket tilt cylinder was leaking oil. There were no other defects reported. No maintenance work was conducted on the machine prior to the day of the accident.
Scott was the only mechanic at this mine and primarily worked alone in the shop, located about 200 feet from the mine office and scale house.
DESCRIPTION OF ACCIDENT
Dale Scott, mechanic (victim), reported for work at 9:30 a.m. on December 2, 1996, after stopping at a distributor to order and pick up parts for the Thomas skid steer loader. At the mine office he met with James Iafrate, foreman, and Charles Wright, foreman of the company's Sylvania mine. Scott told Iafrate that he was going to repair the oil leak on the loader tilt cylinder, tighten the tram chains, and the loader should be ready for operation at about 12:30 p.m.
After the meeting, Iafrate and Wright left the mine property and Scott traveled to the shop and drove the loader inside. At about 12:00 p.m., Iafrate returned to the mine and instructed Miguel Esquivel to see if the loader was ready. Esquivel went to the shop at about 12:30 p.m. and discussed the loader status with Scott, who told him that it would be a while before it was ready. At 3:45 p.m., Esquivel returned to the shop to check on the loader and Scott told him it probably wouldn't be ready that day. There was no other contact with Scott until he was found after the accident.
About 4:50 p.m., Russell Insco, front-end loader operator, parked his loader for the day and walked into the shop to talk to Scott. He saw Scott between the loader cab and bucket boom cross arm but did not realize any thing was wrong until he was a few feet away. He could not feel a pulse and yelled to Carl Witforth, truck driver, to call 911. James Turner, front-end loader operator, was at the mine office and heard the call for help. He ran to the shop to assist Insco.
The Rockwood Fire Rescue units arrived at 5:05 p.m. The firemen shut the loader engine off and installed additional blocking under it, then Turner moved the loader boom to free Scott. The Wayne County Medical Examiner arrived and pronounced Scott dead due to multiple injuries to the chest and abdomen.
There were no witnesses to the accident but the loader that pinned Scott was found with the engine running and the seat bar in the raised position. A wooden block had been placed under the center of the undercarriage and the left rear tire was leaning up against the hub as if it was about to be put back on. The left fender was resting on top of the tire.
The rear end of the loader was touching the floor and the bucket tilt cylinder on the right side was fully extended with the lip of the bucket contacting the concrete floor. The left tilt cylinder had been bypassed and marks on the floor indicated the bucket lip had moved 4 inches toward the cab frame and the right front tire was elevated 12 inches above the floor. The bucket boom arms had a cross member located above the top of the bucket.
Scott had worked on the left bucket tilt cylinder, subsequently bypassing it. He had also removed the hoses from the auxiliary hydraulic circuit and tightened the left tram chain. There was oil and used parts located on the floor behind the loader, indicating that after the hydraulics had been worked on the machine was moved forward and raised. Apparently, the wooden block was placed under the cab frame and was used as a fulcrum when the bucket tilt or boom cylinders were used to raise or lower the loader. With just one block under the loader, slight movement of the bucket created an unstable condition.
It is believed Scott attempted to place the rear left tire back on the hub and the rear of the machine was too low. Rather than jacking the loader up to elevate the hub, he attempted to release pressure on the bucket, which was holding the rear of the loader down, while the loader was positioned on the wooden block. Instead of getting into the loader operator's compartment, he positioned himself between the boom cross member and the cab frame. He apparently started the loader and moved the left control lever.
At that point, with the engine running and the safety seat bar up, the left control lever locked in, causing the boom cylinders to retract and remain under pressure, pinning Scott between the cross arm and loader cab.
The direct cause of the accident was the failure to block the Thomas skid steer loader against hazardous motion while performing maintenance on it. The mechanic was not effectively protected from the hazardous motion of the loader when he engaged the controls to move it. The safety seat bar linkage defects permitted control lever operation from any reachable location and contributed to the accident.
Order No. 4546999
Issued 12/3/96 under provisions of Section 103k of the Mine Act:
Citation No. 4547000
Issued 12/4/96 under provisions of Section 103j of the Mine Act for violation of 30 CFR 50.10:
Citation No. 4547105
Issued 12/23/96 under provisions of Section 104a of the Mine Act for violation of 56.14105:
Citation No. 4547106
Issued 12/23/96 under provisions of Section 104a of the Mine Act for violation of 56.14100b:
Before operating or performing maintenance on powered haulage equipment, the owner/operator's manual should be provided and reviewed by the operator or maintenance personnel for safety precautions. The manual for the Thomas skid steer loader was obtained from the manufacturer after the accident and a copy has been provided to the company. The safety precautions contained in the manual address the hazards involved with this accident. /s/ Donald J. Foster, Jr.
Mine Safety and Health Inspector
/s/ Jack L. Webb
Mine Safety and Health Inspector
Approved by: James M. Salois, District Manager
Related Fatal Alert Bulletin: