DEPARTMENT OF LABOR
MINE SAFETY AND HEALTH ADMINISTRATION
Metal and Nonmetal Mine Safety and Health
REPORT OF INVESTIGATION
Surface Metal Mine
(Taconite)
Fatal Fire Accident
October 13, 2000
Hibbing Taconite Company
Hibbing Taconite Company
Hibbing, St. Louis County, Minnesota
I.D. No. 21-01600
Accident Investigators
Donald J. Foster
Supervisory Mine Safety and Health Inspector
Arthur J. Toscano
Mine Safety and Health Inspector
William H. Pomroy
Industrial Hygienist
Michael P. Snyder
Supervisory General Engineer
Michael A. Hockenberry
Fire Protection Engineer
David T. Couillard
Mine Safety and Health Specialist
Originating Office
Mine Safety and Health Administration
North Central District
515 West First Street, Room 333
Duluth, MN 55802-1302
Felix A. Quintana, District Manager
OVERVIEW
On October 13, 2000, Clarence Brant, tractor operator, age 59, was seriously injured when flames suddenly engulfed the cab of the bulldozer he was operating. Brant sustained multiple burns in the accident and died of related complications on November 2, 2000.
The accident occurred because oil leaked onto the engine and was ignited by heat from hot engine components.
Brant had a total of 20 years of mining experience, nine at this mine. He had received training in accordance with 30 CFR, Part 48.
GENERAL INFORMATION
Hibbing Taconite Company, a surface, multi-bench, taconite operation, owned and operated by Bethlehem Steel Corporation (70.3%), Cliffs Mining Company (15%), and Stelco Inc. (14.7%), was located four miles north of Hibbing, St. Louis County, Minnesota, on the Messabi Iron Range. The principle operating officials were: Larry Dykers, general manager; John Koivisto, safety engineer; and John Correll, safety director. The mine normally operated three, 8-hour shifts per day, seven days a week. Total employment was 800 persons.
About 22 million tons of overburden and low quality ore, and 31 million tons of crude taconite ore were mined annually from several open pits using multiple bench mining methods. The overburden and ore were drilled, blasted, and loaded into 240 ton haulage trucks. The overburden was taken to the waste stockpile and the ore transported to the mill where it was crushed, ground, and passed over magnetic separators. The concentrate was then pelletized and fired in furnaces prior to rail shipment to steel mills. Yearly production totaled about eight million tons.
The last regular inspection of this operation was completed on September 28, 2000. Another inspection was completed following the investigation.
DESCRIPTION OF THE ACCIDENT
On the day of the accident, Clarence Brant (victim) reported for work at about 10:50 p.m., his normal starting time. Patrick Angelo, pit services coordinator, assigned Brant to operate the No. 321 bulldozer on the 1039 stockpile.
At 12:00 a.m., Brant was instructed to move bulldozer No. 321 from the 1039 stockpile to the surge pile. Paul Husmann, tractor operator, normally pushed material on the surge pile and took over operation of the No. 321 bulldozer once Brant arrived.
Brant was then assigned to take No. 83 front-end loader to the shop for servicing. While Brant was servicing the front-end loader, Jimmy Lahtela, mechanic, informed Angelo that he had serviced No. 319 bulldozer but he could not locate an oil leak that had been reported on the machine.
Angelo and Brant traveled to the No. 319 dozer to check it for leaks. A trail of fluid was discovered on the ramp of the stockpile but the machine would not leak while sitting still. Brant moved the machine about 200 yards, with Angelo following, before the machine began to leak. A loose fitting was discovered on the metal transmission line. Lahtela returned to the machine, repaired it, and checked the fluid levels. At about 2:20 a.m., Brant moved the machine from the 1037 stockpile to the 1039 stockpile. The move of 1.25 miles lasted about 45 minutes. Angelo checked the path of the machine for evidence of further leakage and found none. He instructed Brant to periodically check for leaks and to report any problems.
At about 3:30 a.m., Brant observed a mist surrounding the cab of the machine and then the bulldozer suddenly burst into flames. Brant tried to activate the fire suppression system and attempted to exit the cab through the right side door, the normal egress route, but the flames were too intense. He closed the door and then exited the left side of the cab. He jumped from the cab deck, through the flames, to the ground, a distance of about 9 feet. Brant rolled on the ground to extinguish his clothing and then moved away from the dozer.
John Lessar, truck driver, called the dispatcher and reported a fire on the 1039 stockpile. The guard at the main gate called 911 and notified the on-site fire fighting units. James Bradach, tractor operator, arrived at No. 319 bulldozer first and called to report that Brant was burned. Angelo arrived at the scene and transported Brant to the mine service building where emergency medical technicians and first responders administered treatment. Brant was transported to a local hospital then transferred to a burn center in Duluth, Minnesota. He was discharged on November 1, 2000 and died on November 2, 2000, as a result of pulmonary emboli directly due to burns sustained in the fire.
INVESTIGATION OF THE ACCIDENT
MSHA was notified at 8:55 a.m. on the day of the accident by a telephone call from John Koivisto, safety engineer, Hibbing Taconite Company, to Arthur Toscano, mine safety and health inspector. An investigation was started the same day.
MSHA's accident investigation team conducted a physical inspection of the accident site, interviewed a number of persons, and reviewed training records and work procedures being performed at the time of the accident. The investigation was conducted with the assistance of mine management and mine employees. The miners were represented by Local Union 2705, United Steelworkers of America.
DISCUSSION
The accident occurred at the 1039 stockpile where waste rock (low grade ore and overburden) was stored. Trucks dumped the waste rock at the stockpile and a bulldozer was used to level the material.
The equipment involved in the accident was a Caterpillar, Model D-11N, Tractor Bulldozer, Serial Number 7YG00761, entered into service on May 27, 1994. The company identification number was 319. The dozer was equipped with a Cat 3508 V-8 diesel engine, with a gross horse power rating of 817. Twin turbocharging units were located on the cab end of the engine. The external temperature of the turbochargers approached 1400 degrees Fahrenheit after 20 minutes of normal operation.
Two types of fluids manufactured by Exxon Company, U.S.A., were used in the hydraulic system of the dozer. One was Univus N 32, Petroleum lubricating oil, with a minimum flash point of 381 degrees Fahrenheit and an autoignition temperature of greater than 500 degrees Fahrenheit. The other was Torgue Fluid 30, Petroleum lubricating oil, with a minimum flash point of 320 degrees Fahrenheit and an autoignition temperature of 450 degrees Fahrenheit.
On the day shift of October 12, 2000 (two shifts prior to the shift when the accident occurred), the No. 319 bulldozer was reported to have a transmission leak. The source of the leak could not be determined at that time so the dozer was removed from service. In the early morning hours of October 13, 2000, a loose fitting was discovered on a transmission fluid line, on the front left lower side, under the radiator. A field maintenance mechanic tightened the fitting and, after checking to insure the leak had been fixed, the No. 319 dozer was returned to service.
The fire protection system installed on No. 319 bulldozer was an LT-A101 multipurpose dry chemical fire suppression system manufactured by Ansul Incorporated. The system was controlled by a Check-Fire II detection and automatic actuation system and two manual actuators. The Check-Fire II and a manual actuator were located inside the cab just to the right side of the operator's position. When the manual actuator was examined after the fire, the ring pin had not been removed from the strike button and the tamper seal on the ring pin was intact. Another manual actuator was located outside the cab on the right side of the machine directly adjacent to a 30-pound portable fire extinguisher. It had not been activated. The installed LT-A101system included two, 30-pound (nominal) dry chemical agent tanks which, when full, together contain about 50 pounds of multipurpose dry chemical agent. The system was provided with six agent discharge nozzles. This system is rated for A, B, and C class fires. The nozzles are each designed to discharge one-half pound of agent per second. Fifty pounds of agent discharged through six nozzles would thus result in a total discharge time of about 16.7 seconds.
The Check-Fire II system detected the fire automatically and actuated the system to release the entire contents of dry chemical agent in both onboard tanks, but failed to extinguish the fire. This system employed a two-stage alarm sequence before auto actuation occurred. The pre-alarm delay is the time period between the initial fire detection and latching of the alarm condition. The agent release delay is the time period between the completion of the pre-alarm time delay and the operation of the agent release circuitry. The settings for pre-alarm and agent release delays were found to be 12 and 10 seconds respectively. Therefore, the total time necessary from detection to actuation was 22 seconds, which was the default setting on the system.
The D-11 N tractor had four fire suppression discharge nozzles located in the engine compartment. One fan-discharge nozzle was centered above and forward of the turbochargers pointing down and backward. Two more were centered above and to the rear of the turbochargers on the engine firewall pointing down and forward. These included one fan discharge nozzle and one cone discharge nozzle. The other nozzle was a fan discharge in an area containing numerous hydraulic system components in the right rear portion of the engine compartment under a hinged access panel. Two additional nozzles were provided for the transmission area located under the operator's cab.
A local distributor installed the fire suppression system and Hibbing Taconite Company maintained the system.
The mine's fire brigade was activated and traveled to the fire. A 150-pound dry chemical fire extinguisher was used to initially fight the fire. This extinguisher was totally expended and reportedly knocked down the flames considerably. Fire fighting foam was then sprayed on the dozer. Approximately five gallons of foam concentrate mixed with about 250 gallons of water were used to extinguish the flames. Water was then applied to cool the hot metal surfaces and engine compartment.
The following were identified immediately after firefighting activities were conducted: The key was found in the on position, the back-up alarm was on, the transmission was in reverse, the fire suppression system control was in the alarm mode, the engine was off, and the blade was down. Based on this information, it is believed that the dozer was backing up with the blade up, when the fire began.
On November 1, 2000, representatives from Packer Engineering removed four hydraulic hoses from the machine. The hoses provided hydraulic fluid for both the right and left lift cylinders and were located in a compartment on the blade side (in front) of the radiator and radiator-cooling fan. The fitting on the transmission line that was tightened prior to the accident was examined and appeared to be intact. All of the items removed from the No. 319 dozer by the operator, Packer Engineering representatives, and the MSHA investigation team were sent to Packer Engineering, Inc. and were examined at their Naperville, Illinois laboratory on November 17, 2000, and on April 26, 2001.
The hoses that controlled the left lift cylinder had 8-10 inches of the outer jacket material burned away at the top end of the hoses, exposing the outer spiral wrapping of both hoses. The mid section of the hoses had evidence of heat (some blistering of the outer jacket) and the lower section of the hoses had some charring and blistering at the bottom end. Photographs taken on the day the dozer was towed from the accident site showed hydraulic fluid streaming from the outer left lift cylinder hose. The dirt and debris were removed to the extent possible from the spiral braiding approximately 2-6 inches from the hose connector. While moving the hose and removing the debris, seepage was identified approximately 5 inches from the hose connector. The leak in this hose was originally identified and photographed when the No. 319 dozer was moved from the accident scene to the maintenance facility and occurred while the blade was being lowered after moving the equipment. The original brown color of the hoses was readily apparent when the support brackets were removed during the examination and this is consistent with new Caterpillar-supplied hoses.
Both hoses were viewed with a Bor-a-scope. This examination revealed that the inner tube of each hose failed in a similar manner. Both hoses had been exposed to a considerable amount of heat from the outer sections of the hose, all the way into the inner tube. As each layer of spiral wire was removed, the rubber material separating each layer fell off as ash. The failures on both hoses were similar and appeared to have failed inward (from heat) and not outward (due to physical damage, puncture, or over pressure). The inner tube was brittle due to the heat. No evidence was discovered that would indicate that the hoses failed due to over pressure. The failures and condition of the hose material were consistent with failure due to fire exposure.
It could not be determined at what point the hose became damaged during the fire. It may have, however, continued to provide fuel after the fire broke out, considering the weight of the blade and the constant flow of hydraulic fluid through the leak.
Two scenarios for the start of the fire were considered. They included a leak from the left hydraulic lift cylinder hose inside the compartment to the front of the cooling fan and/or the failed O-ring at the top of the right lift cylinder. Examination and disassembly of the hoses revealed that the nature of the failure of the hoses was due to extreme heat caused by the fire.
An examination was conducted of both rubber O-rings removed from the right and left lift cylinder valves of the dozer. The O-rings were compared to two new exemplar, circular cross section, O-rings provided by the Caterpillar representative for the examination. The O-ring removed from the right lift cylinder was "lathe cut" and had a square cross-section. It was considerably larger and shaped differently than the exemplar O-ring. It had been extruded or "squeezed out" around its entire circumference. There was a failure in this O-ring consistent with "nibbling" along a one-half inch section of the O-ring. The undamaged O-ring on the left lift cylinder was molded with a circular cross-section. Caterpillar was contacted regarding the usage of a lathe cut O-ring for this application and they confirmed that the only acceptable O-ring replacement part for this application was a circular cross-section O-ring.
An air flow test was performed on another Caterpillar D-11N dozer with the engine at normal operating RPMs. The radiator fan pulled air through the radiator and out the front. The air was then forced against the blade of the dozer and pulled back toward the engine compartment. A portion of the air was forced up over the top of the engine cover toward the cab. The test revealed that the air traveled the same path as the burn path of the dozer involved in the accident.
The weather on the day of the accident was cool and clear, with very little wind.
CONCLUSION
The accident occurred because oil leaked onto the engine of the dozer, contacted hot engine components, and ignited. Due to the extensive damage from the fire, the source of the oil leak could not be determined. The hoses that controlled the left lift cylinder and the improper O-ring for the right lift cylinder were found damaged, however, it could not be determined if either caused the fire. The failure of the dozer's fire suppression system to activate quicker may have contributed to the severity of the injuries.
Related Fatal Alert Bulletin:
FAB2000M43
APPENDIX A
Persons participating in the investigation:
Hibbing Taconite Company:
Bill Williams .......... area manager - miningUnited Steel Workers of America, Local Union 2705
John Kannas .......... safety manager
Pat Angelo .......... pit services coordinator
Tim Angelo .......... mechanic supervisor
Keith Lerick .......... section manager
Allen Caligiuri .......... safety chairmanBuchanan Ingersoll
Glenn Saarinen .......... safety representative
R. Henry Moore .......... attorney at lawAndresen, Haag, Paciotti & Butterworth
James Paciotti .......... attorney at lawMine Safety and Health Administration
Donald Foster .......... supervisory mine safety and health inspector
Arthur Toscano .......... mine safety and health inspector
William Pomroy .......... industrial hygienist
Michael Snyder .......... supervisory general engineer
Michael Hockenberry .......... mechanical engineer
David Couillard .......... mine safety and health specialist
APPENDIX B
Persons interviewed during the investigation:
Hibbing Taconite Company:
Benny Caple .......... operating coordinator
Patrick Angelo .......... pit services coordinator
Jimmy Lahtela .......... auto mechanic
Richard Rojeski .......... maintenance mechanic, union president
James Bradach .......... tractor operator
Michael Modich .......... auto mechanic
Tim Angelo .......... mechanic supervisor
Steve Beliaj .......... tractor operator