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FIRE SAFETY described the case of an hydraulic excavator working on overburden at a surface mine; a haul truck driver passing by noticed flames in the excavator engine bay and alerted the excavator operator by radio. The fire erupted from the engine bay, momentarily engulfing the excavator cabin before subsiding to the engine bay where it continued to blaze. The operator escaped by jumping 3.5 m to the ground, but was not injured. Attempts to control the fire with handheld extinguishers were unsuccessful and the excavator was destroyed. The machine, according to the report, was fairly new and appeared to be wellmaintained, but was not fitted with an automatic fire suppression system. It was equipped with two 9-kg fire extinguishers, one located on the side of the engine bay and one located at the front of the excavator on the opposite side of the cabin. Neither extinguisher could be accessed to fight the fire. Subsequent investigation by a consulting forensic fire investigator concluded that the fire originated from a cracked hydraulic oil filter housing that allowed oil to escape and ignite on contact with hot engine components. The aluminum housing was designed to be installed with a socket or box-end wrench, applied to a cast nut at the bottom of the housing. However, sharp-tool marks on the oil filter housing indicated that it was installed with a pipe wrench or similar tool and most likely had been over-tightened. The housing cracked at the location of the sharp-tool marks. TycoÕs Ansul LVS fire suppression system protects a Caterpillar 777D haul truck. The report—in addition to offering a list of measures that can prevent or minimize hydraulic-system fires (see sidebar)—concluded that an automatic fire suppression system would probably have contained the fire at an early stage, and strongly suggested that such systems should be installed on all heavy mobile equipment operating at mines. Advocating Automation That recommendation would get vigorous endorsement from the leading suppliers of automatic fire-suppression systems to the mining industry, such as AFEX Failure to use the correct tool for the job resulted in a hydraulic-system oil leak and fire that destroyed this excavator. www.e-mj.com Systems, United Technologies' Kidde Fire Systems subsidiary and Tyco Fire Protection Products (TFPP), for example. They stress the importance of automatic systems in preventing or minimizing asset damage, improving worker safety and avoiding calamitous economic losses from mine fires, whether in mobile equipment or fixed plant facilities—and each offers system options that can be configured for a wide range of environmental conditions and specific fire-suppression requirements. Mike Stromberg, global product manager–vehicle systems for TFPP, told E&MJ; that hydraulic system-related fires—in which fluid leaking or spraying from breaches in high pressure lines comes in contact with hot metal surfaces—are quite likely the most common type of fire encountered on mobile mining equipment. As far as frequency of occurrence per type of vehicle, he noted that, "Just because there are so many haul trucks used throughout the industry, we see more truck-related fires than anything else, but fires involving large hydraulic excavators tend to be more catastrophic." Somewhat surprisingly, there doesn't seem to be a significant difference in the number of fires reported in older equipment as opposed to newer models, according to Stromberg. This can be attributed, at least partly, to new engine technology that involves higher fluid line pressures and increased operating temperatures. FEBRUARY 2013 • E&MJ; 45