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haul trucks continued through the system could cause a catas- trophic failure of the entire engine," he said. At Highvale, preventative care follows a strict timetable. Key items on the engine maintenance schedule include oil changes every 500 hours, engine valve inspections every 3,000 hours, fuel injec- tor change-outs every 6,000 hours and full service performed at the midpoint of an engine's life. The Secrets of Long Life In addition to following a routine main- tenance schedule, owners of Series 4000 engines should pay attention to fuel quality, according to Ran Archer, sales manager for MTU mining engines at Tognum America. Fuel contamination must be minimized and the fuel must comply with lubricity requirements to facilitate the motion of injectors and other components. In addition, Highvale tries to improve fuel cleanli- ness by using systems that filter fuel as it's transferred from delivery trucks into fuel tanks. A standout in MTU's diverse lineup of mining engines is the Series 4000 engine family from 1,000 to 3,000 kW (1,350-4,020 hp). It delivers reliable, fuel-efficient performance down to -50°C and up to 5,000 m. Future gen- erations of EPA Tier 4 final MTU mining engines will meet EPA Tier 4 emissions standards without requiring exhaust aftertreatment — an industry exclusive. They will feature cooled EGR, a two-stage turbocharging sys- tem, an improved common rail fuel injection with increased injection pressure, and a new combustion process with modified valve timing (Miller process). will be overhauled for reuse. Meanwhile at Highvale, the haul truck that housed the engine is back on the job, powered by a spare engine kept by the mine opera- tor, Prairie Mines & Royalty Ltd. (PMRL) to minimize downtime caused by engine replacements. The engine now being overhauled will serve as the spare when the work is completed. At Highvale, long engine life is crucial because an engine overhaul is an added business expense. Equally important, engine reliability reduces vehicle down- time, which can cost the mine tens of thou- sands of dollars a day in lost revenue. "Minimizing downtime is more important than anything," said Jim Richter, PMRL's truck maintenance planner at Highvale. "We have a fairly small fleet, so truck avail- ability needs to be very high." Maintaining High Standards Why did the engine exceed expectations by 3,000 service hours? This impressive November 2012 feat was due to MTU's high engineering standards and disciplined adherence to the manufacturer's maintenance and fuel quality recommendations. PMRL personnel try to make sure that mainte- nance is performed within 50 hours of MTU guidelines. MTU adheres to a proactive mainte- nance philosophy. "We're a little more aggressive in our practices," said Matlock. "We don't believe in running components until they break. Our phi- losophy is to proactively replace compo- nents before they reach the end of their life expectancy." Matlock says preventative measures pay off in the long run. It results in scheduled downtime, boosting mine production. In addition, replacing com- ponents before they break eliminates the possibility that broken components will do further damage to the engine or other components. "If a turbocharger breaks, for example, metal debris traveling Highvale's haul truck fleet operates on high-quality fuel, said Richter, who believes this helped prolong the life of his 23,000-hour engine. The results are well worth the extra effort. "We don't have any fuel issues with any of the equipment we have here," Richter said, adding that he's heard reports of injec- tor-failure problems at other mines. When injectors fail, he explains, the result is uneven fuel distribution in the cylinder, which causes hot spots that can burn out pistons and dry out cylin- der walls—and ultimately cause engine failure. The longevity of haul truck engines at Highvale is linked to preventative mea- sures such as using clean fuel and per- forming recommended maintenance on schedule. "If you're careful about things like that," said Archer, "MTU engines will run a long time and help drive down operating costs." At Canada's largest surface coal mine, Highvale haul trucks are expected to keep working well into the future, because there's always more coal to haul and profits to be made. This article originally appeared in MTU's customer magazine, MTU Report. www.coalage.com 23