Haul Trucks

Never Say Die

Posted on 17 March 2014 by Nicole Burdiss, Images by John Sibold

An engine in service in an American coal mine has already doubled its anticipated runtime.

In a coal mine in the Appalachian mountains, the engine used to shift overburden provides a prime example of how important the partnership is between the mine operator and MTU engineers and distributors. The target runtime of the engine was 20,000 hours up to the first engine overhaul, but it has now clocked up double that figure. What is the secret? The answer is a robust engine design as well as precise tuning of the engine to its application and perfect maintenance.

Tough ambient conditions also challenge the engines, which require regular maintenance.

There are cities in the world that never sleep. New York, for example, is a bustling metropolis where the lights never seem to go out. The same would hardly be expected of Logan, a little US town in the state of West Virginia. But here is the coal mine of Apogee Coal, a subsidiary of Patriot Coal Mine, the American mine operator. That makes Logan very much a 24/7 place. The surface coal mine relies on 17 of the world’s largest haul trucks to remove layers of dense overburden to reach the mineral seam. Once the haul trucks have cleared the way, excavators then move in and begin mining the mineral from the hillside, yielding on average three million tons of steam coal annually that is then sold to fuel the thermal market, largely used to generate steam-electric power.

Benny Dixon (left) is responsible for maintaining the haul trucks in service in the mine. His local partner is Curtis Bartlett from Western Branch Diesel, the MTU distributor.

Long service life under tough conditions

With temperatures fluctuating from zero to 105 degrees Fahrenheit, the typical life expectancy of an engine operating within one of the groundshaking haul trucks at Logan is approximately 20,000 hours. The Series 4000 Tier 2 engine from MTU, however, is something else. Installed in a Komatsu 830 haul truck, it has been running 50,000 hours – equivalent to 20 hours per day and 6,000 hours per year – carrying loads weighing up to 240 tons and twice-enduring “conditions that are extreme,” as Benny Dixon, responsible for haul truck maintenance at the Patriot Coal Mine, reports.

Engine perfectly tuned to application

How did this remarkable engine last so long after the truck was repowered with the MTU engine? According to Dixon, the root of this success lies in MTU’s expert engineering and the tailored service plans and expert repower recommended by its distributor and maintenance partner, Western Branch Diesel. Traditionally, a 16-cylinder engine powers the Komatsu 830. However, because a large part of this particular haul truck’s role at Apogee is downhill hauling – often without a load – it was greatly overpowered, according to Curtis Bartlett, Off-Highway Sales Engineer at Western Branch Diesel.

To maximize efficiency, Bartlett and the team at Western Branch Diesel recommended reducing the existing 16-cylinder engine to a 12-cylinder MTU Series 4000 engine to decrease horsepower from 2,200 to 1,875. Ultimately, this strategic move reduced fuel burn by five to seven percent and helped double the life span of the engine. “The name of the game is to customize as much as possible,” said Bartlett. “That’s how we’ve been able to extend life cycle intervals on thesecomponents.” Repowering Komatsu 830s with MTU engines is not a rare occurrence. It’s a task that could take approximately four days, and at a mine site where there is no workshop or electricity, the process is both an art and a science. More than 750 of all Komatsu haul trucks in use today have been repowered with MTU engines, according Randy Murphy, Senior Sales Manager, Global Mining Sales at MTU. For Patriot Coal, these calculated repowers have been instrumental in maximizing fuel efficiency and exceeding life expectancies, demonstrated by the four other MTU powered Komatsu haul trucks in operation at Patriot Coal sites with more than 40,000 hours each before any engine overhaul

“One thing I’ve noticed through the years is that if the distributor and mine maintenance team work closely together and stick close to schedule, then they exceed what we publish as a recommended time to overhaul,” said Randy Murphy, Senior Sales Manager, Global Mining Sales at MTU.

The engine has clocked up over 50,000 hours without any engine overhaul – thanks to a robust engine design, a tailor-made maintenance schedule and fine-tuning of the engine to its application.

Fuel system a crucial factor

One critical goal of any engine’s maintenance schedule is to protect its precious fuel system. While the drop in engine size was vital in reducing the life span-dictating fuel burn, custom maintenance also played a significant role in doubling the lives of these MTU engines. To avoid catastrophic failure, special precautions are taken to maintain fuel quality and protect the system’s fuel injectors. Mapping out service schedules 12 to 18 months in advance, Bartlett and Dixon worked closely to determine ideal oil change, fuel injector and turbo change out intervals for each individual engine. Once those maintenance schedules are in place, the mine site does not deviate from them.

”Support team second to none“

“The Western Branch Diesel product support team is second to none. Without its outstanding service, we would not have gotten two – almost three – lives from these engines,” said Dixon. “It’s not just an oil change, they take care of whatever problems we have.” The oil change interval for a Series 4000 is traditionally 500 hours. However, based on the engine’s custom application, Western Branch Diesel extended engine oil change intervals to 750 hours, with filter changes every 250 and injector changeouts at 10,000 hours. Why such emphasis on the fuel system? Fuel component failures, given their severity, translate into unplanned downtime and massive revenue loss.

The haul trucks in the Apogee coal mine mostly carry full loads downhill and return uphill empty. Hence they are powered by 12-cylinder MTU Series 4000 engines instead of more powerful 16-cylinder engines.

Using the custom maintenance schedule designed together with Western Branch Diesel, the Patriot Coal haul truck fleet averages a near 92% uptime. “When it comes to maintenance, it’s OK to schedule downtime. What really hurts is when you have unscheduled downtime, leaving you with a haul truck that is not operational,” said Bartlett. Western Branch Diesel also takes extra steps to reduce downtime. In anticipation of an engine replacement, Bartlett and team prepare a full engine module to ensure that the switch is as efficient as possible to minimize downtime.

“We’ve had a module waiting to replace this engine for two years. We’re going to have to put it in long-term storage,”Curtis Bartlett

Coal production for over a century

Info
Coal production for over a century West Virginia is the largest coal-producing state in the Appalachian region, and second largest coalproducing state in the nation. (Only Wyoming yields more.) The state’s coal mining history dates back to the late 1800s, when extraction was inarguably primitive compared to today’s standards. Wielding simple pickaxes, shovels and carts, miners would unearth and haul coal from hillsides and underground tunnels. Today, modern coal miners are highly skilled at operating complex, computerized heavy equipment in unforgiving environments, and they rely on powerful, rugged engines to power a wide range of mining vehicles and equipment from excavators to drills to large haul trucks.

The content of the stories reflects the status as of the respective date of publication. They are not updated. Further developments are therefore not taken into account.

Point of Contact

Randy Murphy
Tel.:
+1 248 560 8092
E-mail:

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