On June 14, 2003, a maintenance repair foreman, age 25, was fatally injured while changing liner plates in a jaw crusher. Salyards was inside the crusher positioning a wedge bar to secure the upper liner plate when the liner dislodged, striking him.
“A policy should be implemented requiring risk assessments to be conducted prior to performing maintenance or repair tasks.”
Incident Investigators
The relining jaw crusher accident occurred because the procedure used to remove and install the crusher liner plates was inadequate. A section of angle iron was wedged against the metal crusher wall to secure the liner plate. The foreman entered the crusher and stood on a narrow ledge while attempting to install the wedge bar to fasten the liner plate. The angle iron dislodged and the 3,100 pound liner toppled over.
The foreman had a total of 5 years, 12 weeks of mining experience all at this mine.
BACKGROUND
San Emidio Plant, a sand and gravel operation, owned and operated by Calmat Co., was located at 16101 Hwy 166, Mettler, Kern County, California. The principal operating officials were Gary Goellner, regional operations manager, and Frank Parra, plant manager. The mine normally operated three 8 hour shifts a day, two production and one maintenance, six days a week. Total employment was 36 persons.
Sand and gravel was mined from a single bench pit. Mined material was transported by trucks to the primary jaw crusher. The material was crushed and conveyed to the main plant where it was sized, washed, stockpiled, and sold for construction aggregate.
The last regular inspection of this operation was completed on June 10, 2003.
DESCRIPTION OF THE ACCIDENT
On the day of the relining jaw crusher accident, the foreman reported to work at 12pm, his normal starting time. The foreman directed Frank Buffuna, repairman/ welder, and Jason Morris, plant repairman, to work on the screens. The foreman went to the pit where he operated a dozer to build a road. At about 2pm, Morris and Buffuna finished working on the screens, gathered tools, and got the crane ready to change out the stationary liners in the primary jaw crusher. Morris and Buffuna washed down the crusher and the new liners in preparation to install them. About 4pm, they drove to the pit area to pick up the foreman and ate lunch. After lunch, they went to the primary jaw crusher to remove the stationary liner plates and install the new liners.
Morris and Buffuna loosened the bolts on the retaining wedge. The foreman climbed over a 46 inch railing and descended into the jaw crusher to weld on an eye to lift out the old liner. He then climbed out and directed Buffuna, who was operating the crane, to lift the liner out. The same procedure was used for the removal of the second liner. The foreman then told Buffuna to wash out the crusher and grind area and prepare to reinstall the new liners. During this time the foreman and Morris went to get the dozer from the pit and fuel it up for the next shift, before returning to the primary crusher.
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The first liner was lowered into the crusher with the crane. The foreman entered the crusher to install a 1½ inch by ½ inch angle iron bar by wedging it against the liner and the opposite side of the crusher wall. The angle iron bar was used to hold the 3,100 pound liner in place. It also provided a place to stand while the wedge bar was bolted to hold the liner in place. The second liner was lowered into the crusher using the same procedure. At about 8:00 p.m., the foreman was having difficulty positioning the wedge bar to secure the liner and presumably stepped onto the angle iron support. The foreman fell into the crusher and the liner toppled over pinning him in the crusher.
Morris yelled to the foreman to see if he was okay but didn’t get a response. He then shouted to Buffuna that the liner had pinned the foreman. Morris went to the conveyor belt to check on the foreman. Buffuna called on the radio for help and went to help Morris. The 3rd shift employees started to arrive and heard the call. Jerry Declippel, loader operator, Lenord Aleman, Jr., loader operator, and Gary Crowell, dump truck operator, went to the primary crusher and helped hook up the crane to the liner plate to lift it and free the foreman. Crowell and Buffuna started CPR and first aid until the EMT arrived. The foreman was taken by life flight to the hospital where he was pronounced dead. Death was attributed to crushing trauma.
INVESTIGATION OF THE ACCIDENT – RELINING JAW CRUSHER
MSHA was notified at 8:30 p.m., the same day, by a telephone call, from Stephen Hopkins, safety and health specialist, to Ron Goldade, assistant district manager. An investigation was started the next day. An order was issued pursuant to Section 103(k) of the Mine Act to ensure the safety of miners. MSHA’s accident investigation team traveled to the mine, conducted a physical inspection of the accident site, interviewed a number of persons, and reviewed training records and information relating to the job being performed by the victim. MSHA conducted the investigation with the assistance of mine management, miners, the California Division of Occupational Safety and Health, and Local 12, International Union of Operating Engineers.
LOCATION OF THE ACCIDENT
The relining jaw crusher accident occurred at the primary crusher located in the plant area.
THE NORDBERG JAW CRUSHER
The crusher was a Nordberg Model C140 jaw crusher. The feed opening of the crusher was approximately 55 inches wide and 42 inches deep. The minimum discharge setting was 5 inches and the maximum was 12 inches. The jaw crusher was being used for primary crushing. It was purchased new in September, 2000, and installed at its present location. The jaws were set in an open-bottom V. One jaw was fixed to the frame, while the movable jaw was pivoted to swing from its top edge. The powered movable jaw was driven toward the fixed jaw to impose a crushing force on the material between them. The movable jaw then moved back to allow the material to drop further into or through the gap. The size of the material was progressively reduced during the successive crushing strokes of the movable jaw. The crushed material dropped onto a conveyor belt and was transported to the plant for further milling.
LINER PLATES AND BRACES
The fixed and moveable jaws consisted of two liner plates made of manganese steel. These plates were about 53½ inches wide, 41 inches high and weighed 3,100 pounds each. The liner plates were interchangeable and reversible and were considered replaceable wear parts. According to interviews, the plates were rotated approximately every three months and replaced about every six months.
The lower liner plate was held in place by a tightening wedge and three T-head bolts. The upper plate was held in place by an upper wedge, a tightening wedge, and three T-head bolts. The victim had replaced the lower plate on the fixed jaw and was attempting to install the wedges and T-head bolts to secure the upper plate.
A brace was placed between the liner plates during the replacement procedure. A 16 inch long piece of 1½ inch by ½ inch angle iron had been placed between the lower jaw plates to hold the new plate in position until the wedge was bolted to fasten it. A 36 inch long piece of the same angle iron was used to temporarily support the upper liner at the time of the accident. The ends of the angle iron braces were not tapered to match the angle between the liner plates, resulting in a minimal metal to metal contact between the surfaces.
ACCESS ISSUES
Access into the crusher was made by climbing over a 46 inch hand rail and then descending into the crusher that was about six feet deep. The crusher had slick metal sides and there was no adequate place for employees to stand while performing the task of replacing the liner plates. Upon entering the crusher employees stood on a narrow steel ledge located along the crusher wall.
TRAINING
The foreman had a total of 5 years, 12 weeks mining experience all at this mine. The foreman received all of his training in accordance with CFR 30, Part 46. He had changed the liner plates in the jaw crusher several times prior to the accident.
ROOT CAUSE ANALYSIS – RELINING JAW CRUSHER
A root cause analysis was conducted and the following causal factors were identified:
Causal Factor: A risk assessment to identify possible hazards and establish safe procedures was not conducted prior to performing the task of replacing the liner plates in the jaw crusher.
Corrective Action: A policy should be implemented requiring risk assessments to be conducted prior to performing maintenance or repair tasks. Potential hazards should be identified and procedures to safely complete the task should be established and followed.
Causal Factor: The liner plate was not properly blocked against motion to prevent it from moving. A piece of 1½ x ½ inch angle iron was wedged between the installed liner and the new liner that had been positioned in the jaw. This created a small area of metal to metal contact resulting in an unsafe blocking method.
Corrective Action: The operator should develop and implement procedures that ensure machinery components are blocked securely in place before any work is done in or around them. Personnel assigned to perform maintenance or repair tasks should be knowledgeable in the safe work procedures.
Casual Factor: A safe method was not provided for miners to enter the crusher and install the liner plates. The victim had to stand on a narrow steel ledge inside the jaw crusher in order to install the wedge that fastened the liner plate.
Corrective Action: The operator should develop and implement work procedures that ensures a safe means of access is provided for persons assigned to enter the jaw crusher.
CONCLUSION
The relining jaw crusher accident occurred because the foreman was not provided a safe access to install the liner plates in the jaw crusher. The angle iron bar that secured the liner plate in place dislodged and the liner plate fell into the crusher, striking him.
ACKNOWLEDGEMENTS
UNITED STATES DEPARTMENT OF LABOR MINE SAFETY AND HEALTH ADMINISTRATION Metal and Nonmetal Mine Safety and Health
INVESTIGATORS
STEVE PILLING, Supervisory Mine Safety and Health Inspector
PAUL WILDRICK, Mine Safety and Health Inspector
ISA BEL WILLIAMS, Mine Safety and Health Specialist
RICHARD SKRABAK, Mechanical Engineer
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