According to Caterpillar, catching a problem before failure results in repair costs of 5 - 25 percent of the engine value. Catching after failure causes repairs of more than 65 percent of the engine value.

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Book Bits: A Case for Regular Oil Drains

From the book "The Practical Handbook of Machinery Lubrication"

This book identifies five reasons for regular oil drain intervals. Here's number one:

Self Generation of Contamination in the Oil. Every engine, hydraulic pump, gear set or other component very slowly wears as it operates, and these tiny, sub-micronic particles of such elements as iron and copper, become catalysts which slowly attack the oil, causing acids to form.

These tiny metal contaminants, combined with carbon soot particles resulting from the combustion process in engines, also circulate in the system and through their abrasive action, create more wear. These solid particles become just like a fine grinding compound and will slowly scratch and score bearing surfaces, turbocharger bearings, crankshaft journals, cylinder liners, and hydraulic pump and valve surfaces.

Normal full-flow filters are generally rated at about 10 micrometers and 40 micrometers in hydraulic systems and engines respectively, and will not remove these sub-micronic particles.

Furthermore, if these filters become plugged, or if the by-pass valves within them remain open for long periods of time, such as at cold start up, contaminated oil will be pumped throughout the system.

It is important to remember that if the levels of self-generated contamination are allowed to increase until some damage by abrasion is caused, it will be too late to prevent more on-going damage, even if the dirty oil is drained.

More information about the book "The Practical Handbook of Machinery Lubrication"

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QUESTION: Does storage temperature influence oil separation or bleeding in grease?

Get the answer.

"How hot is too hot for a grease-lubricated bearing?"

In the final analysis, if the bearing is hot enough to evaporate the oil off of the grease between relubrication cycles, then it is too hot for grease lubrication.

The answer to this question, though, depends on several factors. Let's address a few of them.

When dealing with elevated temperatures we should first ask "What is the source of the heat?". Is it ambient? Is it from the process (transmitted down the shaft)? Is it wear related? Is it lubrication related?. These questions have a lot of impact on our selection of the grease type and in determining the appropriate answer to the question.

If the temperature is from the process or atmosphere, and we know that we have to deal with that condition perpetually, then we should adjust the grease composition to meet the requirements. Perhaps we should select a synthetic oil with a non-soap thickening system that gives us a low evaporation rate. If the temperature is not process or atmosphere related, then we should make sure that we are not over-filling the bearing with grease. Too much grease in a cavity causes churning and excessive temperatures. Too little grease, or too infrequent relubrication, may cause friction-generated heat.

If we are using precisely the right volume and we are sure that the heat is internally generated rather than atmospheric or process related, then perhaps we should examine whether the grease has sufficient strength to support the dynamic load. In this case we might look at selecting a grease with a heavier viscosity base oil.

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