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Oil Sampling

Everyone knows how important oil changes are. So when is the best time to change lubes?


May 13, 2011
Kathy Smith

Everyone knows how important oil changes are. Lubricants and the additives they contain deteriorate with time due to friction heat, operating severity, evaporative hydrolysis and contamination. So when is the best time to change lubes? Too often results in wasted effort and lubricant. And too much lubrication is as harmful as too little. Overstuffed gearboxes and bearing housings cause churning, which ruins components as quickly as lube starvation.

Use sampling to get oil change frequency right. Photo: iStockphoto

An oil-sampling program will help you get the timing just right. But it’s much more than purchasing a sample bottle, filling it with oil and sending it to a laboratory for analysis. Yet many companies waste thousands of dollars doing just that, warns Darren German, the hydraulics business unit service manager for Bosch Rexroth Canada in Welland, Ont.

German, who has 20 years of hydraulic service experience, contends basing maintenance decisions on properly interpreted and understood analysis reports is one of the best return-on-investment (ROI) predictive maintenance practices available when executed in an accurate, timely and consistent manner.

He offers this customer example: the company has five plant locations with 15 machines per plant, all heavily relying on the use of hydraulics. The machines operate 24/7 and all power units are sampled once a year to satisfy quality requirements. But the customer did not understand how to read the oil analysis reports and changed the oil in all units annually, whether it needed to be changed or not.

The annual cost of oil changes is $31,500 per location, or $157,500 for all five plants. (These costs do not include labour, additional material or risk-based costs.) The annual cost for oil sampling is $3,600 per location, or $18,000 for all five plants (administration costs not included.)

That’s a $27,900 cost difference per location, or $139,000 for all five plants. Over a five-year period, this customer could save $697,500 by switching from annual oil changes to oil sampling, assuming that there will be no increases in sample package cost and that no oil changes occurred.

Start logging those savings by figuring out how much an oil sampling program will cost, the payback, what tools are needed, what training is required, and what the program is to accomplish. German notes it’s also important to understand that contaminants (dirt and water) can be built in by the manufacturer/supplier and/or introduced by the service process.

Here are some sampling tips:

• Start slowly and build the program.

• Send a sample of new oil to the lab before starting the program to establish baseline chemistry for reference.

• Use transfer carts with appropriate filtration for fill-ups.

• Eliminate tramp oil from repairs and filter carts.

• Respond promptly to clogged filter indicators.

• Change breathers as part of preventive maintenance.

• Where possible standardize on oil to avoid cross-contamination.

• Pay meticulous attention to methods and locations of oil storage.

• Always sample prior to fill-ups.

Information in this article by Steve Gahbaver is based on a presentation made by Darren German at a MainTrain maintenance conference, convened by the Plant Engineering
and Maintenance Association of Canada (PEMAC).