DEPARTMENT OF LABOR
MINE SAFETY AND HEALTH ADMINISTRATION
Metal and Nonmetal Mine Safety and Health
REPORT OF INVESTIGATION
Surface Nonmetal Mine
Fatal Machinery Accident
December 9, 2002
Ottawa Lake Quarry
Ottawa Lake, Monroe County, Michigan
I.D. No. 20-00041
Stephen W. Field
Mine Safety and Health Inspector
Fred H. Tisdale
Mine Safety and Health Inspector
Terence M. Taylor
Senior Civil Engineer
Steven J. Vamossy
Cindy S. Shumiloff
Mine Safety and Health Specialist
Mine Safety and Health Administration
North Central District
515 West First Street, Room 333
Duluth, MN 55802-1302
Felix A. Quintana, District Manager
On December 9, 2002, Raymond J. Bermejo, Sr., truck driver, age 47, was fatally injured when a section of a conveyor belt walkway he had been removing fell on him.
The accident occurred when a section of walkway, attached to Conveyor Belt No. 3, fell on the victim while he was removing support bolts with a cutting torch. The section of walkway was covered with limestone build-up and was not blocked to prevent movement prior to removing the support bolts.
Bermejo had a total of 1 year, 40 weeks and 3 days of mining experience.
Ottawa Lake Quarry, a surface limestone operation, owned and operated by Stoneco, Inc., was located at Ottawa Lake, Monroe County, Michigan. The principal operating official was Larry Hertzfeld, superintendent. The mine was normally operated three, 8-hour shifts, five days per week. Total employment was 22 persons.
Limestone was drilled, blasted, and loaded into haulage trucks by a rubber-tired front-end loader. The material was crushed, screened to size, and conveyed to stockpiles. The finished products were used in the construction industry.
The last regular inspection of this operation was completed on December 16, 2001. Another inspection was conducted following this investigation.
On the day of the accident, Raymond J. Bermejo, Sr. (victim) reported for work at 6:00 a.m., his normal starting time. A safety meeting was held at the clock house. Mark C. Draper, working foreman, discussed the quarry maintenance tasks for the day with Bermejo and four other employees. Bermejo was assigned to assist others to remove the two lower sections of the walkway near the tail pulley of Conveyor Belt No. 3. Draper told the workers to remove the spilled limestone material from the walkway sections prior to removing them.
A short time later, Randy E. Mapes, primary crusher operator/lead man, gave Bermejo instructions regarding which handrailings to remove and which bolts to cut off to remove the walkway. Mapes then left to work near the pony conveyor. After removing the handrailings with a hand grinder equipped with a cutting wheel, Bermejo walked to the pony conveyor and told Mapes that he had run out of acetylene for the torch set. Mapes obtained a full acetylene tank, brought it to Bermejo, and returned to the pony conveyor.
Fifteen to 20 minutes later, Mapes returned to help Bermejo and found him pinned under the lower section of the walkway with his clothing on fire. Mapes yelled to Dennis J. Duncan, loader operator, to get help and medical assistance. Mapes then shut off the torch set that was pointed away from the victim and used snow to put out the fire. Mapes, with the help of Duncan, tried unsuccessfully to lift the walkway off Bermejo. Matthew W. Corbine, truck driver, and Cory Lee Coutchure, crusher operator, arrived. A nylon strap attached to a bobcat skid-steer loader was then used to lift the walkway off Bermejo.
CPR was performed until emergency personnel arrived and transported Bermejo to a local hospital where he was pronounced dead. Death was attributed to asphyxia due to the weight of the walkway.
MSHA was notified of the accident at 11:15 a.m. on December 9, 2002, by a telephone call from Dave L. Furiate, corporate safety director, to Donald Stefaniak, mine safety and health inspector. An investigation began on the same 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 conducted a physical inspection of the accident site, interviewed employees, and reviewed conditions and work procedures relevant to the accident. MSHA conducted the investigation with the assistance of mine management and employees.
Crushed limestone of minus 6-inch size was conveyed from the primary crusher in the quarry to the plant area by a series of conveyor belts. Conveyor Belt No. 1 transported the material from the crusher onto Conveyor Belt No. 2. This second belt transported the crushed limestone upgrade within the quarry to a transfer point where it dropped into a box/chute and then onto inclined Conveyor Belt No. 3. This 710-foot long belt conveyed material out of the pit and across the road to the plant side for processing. The accident occurred near the tail pulley of Conveyor Belt No. 3 in the area beneath the transfer chute.
Conveyor Belt No. 3 was 36 inches wide and was first installed in 1996, but was later moved in 1998 to its present location in the pit. The belt was supported by a steel truss structure that was 24 inches deep and 47 inches wide. It consisted of angle-shaped members that made up the bottom chords, top chords, and diagonals. The top and bottom chord angles measured 2-1/2 inches x 2-1/2 inches x 5/16 inch. The diagonal angles measured 1-1/2 inches x 1-1/2 inches x 3/16 inch.
A walkway ran along the west side of the belt. It consisted of 24-inch wide pan grating that was constructed in 12-foot long sections. The pan grating was one piece of sheet metal in a U-shape. The flat bottom was 24 inches wide and the side plate toe guards were 4-1/2 inches high. At the top of each side, the toe guards were flanged outward approximately 1 inch. To join adjacent sections of walkway together, a 7-inch wide x 4-inch high x 1/8-inch thick splice plate was used on the outer face of each side of the toe plates. Each splice plate had holes drilled for the eight, 3/8-inch diameter bolts used to make the connection.
The walkway was supported by a series of 2-1/2 inch x 3-7/16 inch x 1/4-inch lateral angles that cantilevered from the two bottom chords of the truss structure. The lateral angles were on approximately 6-foot center-to-center spacings. At each of the two lateral angle connection points, there were two bolts. One bolt was 1/2 inch in diameter and 2 inches long, and connected the lateral walkway support angle to the horizontally oriented leg of the bottom chord angle. The second bolt was 1/2 inch in diameter and 4-1/4 inches long, and connected the lateral walkway angle to the vertically oriented leg of the bottom chord angle by a "J-clip" adapter.
The lower section of pan grating was supported at the tail by a lateral angle, at midspan by a lateral angle, and at its upper end by the two splice plates. To remove the pan grating, the victim had begun burning off the bolts with a cutting torch. Limestone spillage had accumulated to a depth of approximately 12 inches on the lower section of pan grating that was to be removed first. The accumulated spillage material was not removed prior to the dismantling process.
At the transfer point from Conveyor Belt No. 2, spillage accumulated on the walkway of Conveyor Belt No. 3. Reportedly, this spillage had to be cleaned off once a week. To prevent build-up on the walkway, the operator was planning to remove the lower 24 feet of the walkway. Two sections of 12-foot long pan grating were to be removed. A stairway was then going to be fabricated and installed to provide access to the remainder of the walkway.
No specific, step by step demolition procedures were discussed or implemented and there were no witnesses to the bolt removal sequence. Several employees reported that at the morning pre-shift meeting, the foreman stated that the spillage should be removed before dismantling the lower walkway section. There had been no discussion involving blocking the walkway before removal.
The victim was found beneath the fallen section of pan grating, somewhere between the mid-span walkway support and the upper end splice plate. The lower pan grating section had not been cleaned off and was still heaped with accumulated limestone. The 12-foot long section of pan grating alone was estimated to weigh 180 pounds. The accumulated material had an estimated density of 100 pounds per cubic foot and an estimated volume of 14.5 cubic feet. This resulted in an additional limestone material weight of 1450 pounds.
At the tail end of the pan grating, both of the east-side bolts for the walkway support angle were still present, although the longer bolt with the J-clip was slightly loose. On the west side, that is the side closest to the pan grating, the longer bolt had been burned through. Most of the shank of the longer bolt was still hanging from the J-clip attached to the bottom chord angle. In contrast, although the shorter bolt had also been burned, it appeared that there may have been a pre-existing fatigue crack. The failure surface on the short bolt shank was relatively flat. Neither of the two bolt heads was found, but there were some molten fragments found on the ground beneath the connection.
At the midspan lateral angle support of the pan grating, the two east-side bolts had been burned off and both shanks were hanging from the bottom chord. On the west side, the inner short bolt had been burned off and the shank was still protruding from the west side bottom chord. The longer bolt on the west side was not found, but there was considerable burn evidence on the upward leg of the bottom chord angle indicating the bolt was probably torch cut.
At the upper end of the lower pan section, the support was provided by the splice plate on each side of the pan grating. Both splice plates were still attached to the adjacent pan grating section with four bolts each. The other four bolts on the east side that connected the lower pan section to the splice plate were burned off. The splice plate also had considerable burn damage. Three of the four bolt holes in the splice plate were oversized and elongated by the burning process. All three of the bolt heads were found protruding from the fallen pan grating. On the west side of the pan grating, the four bolts that connected the pan grating to the splice plate also appeared to be burned. There were burn markings on the splice plate at all four hole locations. Only one of the four bolt heads was found protruding from the fallen pan grating. In addition, on the west side, the splice plate was bent outward and the flange/lip above the toe plate on the fallen section was deformed upward as it fell away from the splice plate connection.
The clearance between the elevation of the walkway when it was still in place and the existing ground surface was 26 inches at the north (tail) end and 44 inches at the south end splice plate. The general slope of the inclined section of the truss was 11.5 degrees.
A Victor ST900C cutting torch, an oxygen tank, and an acetylene tank were found near the conveyor. The torch was still burning when the victim was discovered beneath the fallen pan grating and the flame was pointed away from the victim.
There were no witnesses to the bolt removal sequence. Based on the position of the victim, the burn evidence on the bolts and the connection locations, the victim had probably burned through all the bolts at the south end splice and both bolts holding up the walkway support angle at the north (tail) end. With the splice plate bolts burned off, the material load on the walkway at the south end of the pan grating would have been carried by the two flanges above the toe guards resting on the top edge of the splice plates. At the time of the failure, it is believed the victim had just burned through the two west-side bolts that provided support to the middle of the walkway. Once those bolts were burned through, the north end of the walkway would have dropped and the load would have immediately transferred to the flanges resting on the splice plates at the south end. At that instance, both the south end pan grating flanges and the burn-damaged splice plates became overloaded. They both deformed, allowing the pan grating and material to fall on the victim.
Metallurgical tests were conducted by Modern Industries, Incorporated on the short bolt shank, nut, and washers taken from the north support angle connection. The testing confirmed that it was an A325 high strength bolt. Micro-cracks were found on the bolt threads and the flat washer, indicating the presence of cyclic loading fatigue. Fatigue could have been the result of drive motor vibrations transmitted through the transfer chute of Conveyor Belt No. 2 to the tail span of Conveyor Belt No. 3. The separation surface was relatively flat with black burn oxidation deposited over most of it. The flatness of the burn surface may have been the result of a pre-existing fatigue crack and/or the horizontal inclination of the torch flame. One portion of the surface appeared shiny; however, according to the metallurgical tests, it is believed that the oxidized scale had flaked off at that location. A cross section of the bolt shank indicated heat damage to a depth of 1/4 inch below the separation surface of the shank. The overall burn damage destroyed any evidence of fatigue on the actual separation surface.
Training and Experience
The victim's normal job was truck driver and he had received training in accordance with 30 CFR, Part 46. Although the victim had performed general plant service duties in the past, he had no prior experience removing walkways from conveyors.
The weather conditions at the time of the accident were clear and cold; the ground was covered with snow.
Causal Factor - The walkway was not blocked prior to removing support bolts.
Corrective Action - Establish safe procedures prior to performing any maintenance work. Analyze all maintenance tasks to identify possible hazards. Thoroughly train employees in safe job procedures and hazard recognition before any work begins. Include a requirement in the established safe job procedures that no work be performed until machinery or equipment is blocked.
Causal Factor - The victim removed the support bolts while positioned under the walkway.
Corrective Action - Include a requirement in the established safe job procedures that no work be performed under machinery or equipment being dismantled until the machinery or equipment is blocked.
Causal Factor - The limestone build-up was not removed from the walkway prior to removing the support bolts.
Corrective Action - Include a requirement in the established safe job procedures that the build-up material is to be removed before any work begins.
Causal Factor - Management did not provide any direct supervision.
Corrective Action - Include a requirement in the established safe job procedures that direct supervision be provided when non-routine maintenance work is being performed.
The accident occurred when a section of walkway, attached to Conveyor Belt No. 3, fell on the victim while he was removing support bolts with a cutting torch. The section of walkway was covered with limestone build-up and was not blocked to prevent movement prior to removing the support bolts. A task analysis had not been conducted to identify possible hazards and establish safe procedures to follow when performing the required work. Management had directed those assigned to the task to clean the spillage from the walkway prior to removal, but did not follow-up on those instructions to ensure that they were followed. No direction was given to require blocking the walkway from motion during the removal process. Specific demolition procedures were not discussed or implemented.
Order No. 6150030 was issued on December 9, 2002, under Section 103(k) of the Mine Act:
A fatal accident occurred at this operation on December 9, 2002, when a catwalk fell on a miner as the miner was cutting away the catwalk from the No. 3 over-the-road conveyor. This order is issued to assure the safety of all persons at this operation. It prohibits all activity in the area of the No. 3 over-the-road conveyor until MSHA determines that it is safe to resume normal mining operations in this area. The mine operator shall obtain prior approval from an authorized representative for all actions to recover and/or restore operations to the affected area.This order was terminated on December 12, 2002, after the conditions that contributed to the accident no longer existed.
Citation No. 6138705 was issued on December 23, 2002, under Section 104(a) of the Mine Act for violation of 30 CFR 56.14105:
A fatal accident occurred at this operation on December 9, 2002, when an employee was removing the lower section of walkway attached to No. 3 over-the-road inclined conveyor belt. The section of walkway, measuring 12 feet in length by 2 feet in width and covered with material build-up, fell on him while he was cutting the walkway support bolts with a torch. The section of walkway was not blocked to prevent movement prior to removal of the bolts.This citation was terminated December 27, 2002. The mine operator established and discussed procedures with all employees involved to dismantle the remaining section of the over-the-road conveyor walkway in a safe manner.
Related Fatal Alert Bulletin:
Persons Participating in the Investigation
Dave L. Furiate ............. corporate safety directorMine Safety and Health Administration
John V. Portala ............. loader operator/union steward
James W. Carmichael ............. environmental health and safety specialist
Stephen W. Field ............. mine safety and health inspector
Fred H. Tisdale ............. mine safety and health inspector
Terence M. Taylor ............. senior civil engineer
Steven J. Vamossy ............. civil engineer
Cindy S. Shumiloff ............. mine safety and health specialist
Randy E. Mapes ............. primary crusher operator/lead man
Dennis J. Duncan ............. rubber-tired front-end loader operator
Matthew W. Corbine ............. production truck operator
Christopher J. Hassen ............. drill operator
Cory Lee Coutchure ............. primary crusher operator
Mark E. Draper ............. working foreman