September/October 2004

Operations Maintenance

Controlling Contamination
Keeping fluids clean produces superior performance in loaders and other vital equipment.

by Jim Redpath

Contaminants are always present in the fluid systems of mining equipment, and wheel loaders are no exception. Without a thorough contamination control approach, wheel-loader hydraulic systems and fuel-injection systems are susceptible to rapid wear that erodes productivity and increases maintenance costs.

But where do these contaminants come from? Sometimes contamination is introduced during assembly. Other times, it enters while the machine is working or being serviced. Regardless of the source, when contaminants invade a system, they impair machine performance and reduce component life.

Equipment manufacturers have always recognized the need to minimize contamination. But in recent years, contamination control has become an even higher priority. To meet customer needs for increased performance, improved efficiency, and longer life from wheel loaders and other mining equipment, manufacturers have designed products with advanced electro-hydraulic components and high-pressure fluid systems. Today’s hydraulic systems operate at pressures of 6,000 psi and higher. Fuel system pressures can reach nearly 40,000 psi. To achieve these pressure levels, machine designs must incorporate extremely tight tolerances. That makes them especially vulnerable to contamination that cannot be detected by the human eye.

Too small to see

Contaminants are measured in units known as microns. One micron is equivalent to one-millionth of a meter. A grain of salt is about 100 microns in diameter; a human hair is about 80. The human eye cannot see particles smaller than 40 microns, yet a 5-micron particle can still damage mining equipment systems.

Most manufacturers assess the cleanliness of their fluid systems by counting and measuring the particles present in the oil and comparing those results to an International Standards Organization code. An ISO contaminant code contains two numbers. The first refers to the number of 5-micron and larger particles in a one-millimeter oil sample. The second indicates the quantity of 15-micron and larger particles in that same sample. A 21/17 rating, for example, means that one millimeter of oil contains up to 221 (about 2 million) particles 5 microns and larger, as well as 217 (130,000) particles 15 microns and larger. A one-millimeter oil sample that earns a 21/17 rating is equivalent to a 55-gallon drum of oil contaminated with a half teaspoon of very fine dust. Although that’s considered clean by ISO standards, it’s not acceptable for new mining machines.

In fact, if a machine meets the 21/17 standard — and the hydraulic pumps operate at 32 gallons per minute, eight hours a day, 200 days per year — more than 625 pounds of dirt is being run through the hydraulic system annually. By improving cleanliness to ISO 18/15, the amount of dirt in the system can be reduced to about 80 pounds per year. Achieve a 16/13 rating, and the number drops to 20 pounds.

Doing the dirty work

No matter how much grime is circulating through a hydraulic system, the effects of contamination are serious. Some of these effects include the following:

Productivity declines, often without your knowledge. As particulates build up on metal surfaces and impede hydraulic flow, system efficiency erodes. But even a skilled loader operator may not notice a drop in responsiveness until the system has lost nearly 20% of its power. With a reduction of that magnitude, only four days worth of production for every five days on the job are being achieved.

Component life suffers. Contaminants accelerate wear and shorten component life. A three-year independent study of hydraulic systems found that some hydraulics components lasted up to 10 times longer with proper contamination control.

The odds of a catastrophic failure increase. Contaminants pave the way for other problems throughout the drive train. Left unchecked, severe contamination leads to unplanned failures, unscheduled downtime, and higher repair costs.

It’s never too late

No matter how old mining equipment is — or how effectively a maintenance operation is currently being managed — it’s never too late to launch an attack on contamination. Research shows that even high-hour machines achieve longer component life when strict contamination control procedures are applied. In a sense, an aggressive contamination control initiative is like a stop-smoking program. Even if years have been spent perpetuating bad habits, they can be stopped now and have the equipment’s life extended significantly.

Here are three ways to get fight back against contamination:

Clean house internally. Make sure that everything to minimize contamination during operation and maintenance is being done. And don’t forget to ask for help from your product support provider.

Find out what the area dealer is doing to reduce the risk of contamination during service work. Observe your field technician. Visit the shop. Inquire about the tools and processes that are used. Ask about technician training. And take advantage of the dealer’s oil analysis services.

Learn more about the manufacturer’s commitment. Take a plant tour, ask the dealer, or check out the Web site. Look for information that indicates a true commitment to contamination control. A world-class company will not only operate clean facilities and ship clean products, it will work in partnership with its dealers and customers to minimize contamination over the life cycle, teaming up to improve performance, increase productivity, extend component life and reduce operating cost.

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Jim Redpath is Corporate Contamination Control Manager for Peoria, Illinois based Caterpillar Inc.  He has 38 years of experience working in the heavy equipment product support field.

Reprinted from Aggregates Manager Magazine
September/October 2004