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From "The Practical Handbook of Machinery Lubrication":

Influence of Contaminants on Bearing Life

When bearings operate in a clean environment, the primary cause of damage is the eventual fatigue of the surfaces where rolling contact occurs. However, when particulate contamination enters the bearing system, it is likely to cause damage such as bruising which can shorten bearing life dramatically.

Furthermore, when dirt from the environment or metallic wear debris from some component in the application is allowed to contaminate the lubricant, wear can become the predominant cause of bearing damage. If, due to particulate contamination of the lubricant, bearing wear becomes significant, changes will occur to critical bearing dimensions which could adversely affect machine operation.

In general, the important parameters influencing bearing wear are contaminant particle size, concentration, hardness and lubricant film thickness. Increases in all of these parameters except film thickness, will increase bearing wear.

Increasing lubricant viscosity will reduce bearing wear for a given contamination level.

Bearings operating in a contaminated lubricant exhibit a higher initial rate of wear than those not running in a contaminated lubricant. But, with no further contaminant ingress, this wear rate quickly diminishes as the contamination particles are reduced in size as they pass through the bearing contact area during normal operation.

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Today's Tip

• Here is an idea for storing drums outdoors for extended periods with drum covers: Prior to placing the drum cover on the drum, mark where the bung is on the side of drum. 90 degrees to the bung lay a wicking device (i.e. strand from an industrial mop) over the chime so that half is on top edge of drum and half is hanging outside of the drum. Install drum cover as normal. If possible a 1x2 board or equivalent should be used to set the back edge of the drum edge on to create a slope so that any condensation forming inside of drum cover can be directed downward toward the wick and wicked out to the ground. Note: Wick, if placed 90 degrees to the bung will be 180 degrees from board or on down side of slope. (Tip submitted by Randy Wilson, Eastman Chemical. Thanks Randy!)

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Q & A

"Regarding bypass filters that heat the oil to 200°F. Do they remove water and or glycol from the oil? Wouldn't this prevent your oil analysis from being able to detect water or glycol?"

Because the heater is designed to vaporize low boiling point volatiles such as water and fuel these contaminants would not show up in the oil analysis in their original concentration. While this could make it difficult to detect or assess the severity of leaks and abnormal ingress of fuel and water it is still probably much better to vaporize them from the oil as soon as possible. The same is true for soot and dirt. High soot levels can be an indication of many problems such as air cleaner restriction, high blow by, and general combustion efficiency problems. Removing the soot to achieve contamination control is better than leaving it in the crankcase so that oil analysis can detect it in an unaltered state.

Regarding glycol, 200°F is not hot enough to vaporize ethylene glycol. However, such temperatures can contribute to glycol being converted to glycolic acid, formic acid, sludge and varnish. Normal engine operating temperature will usually do the same thing. Therefore you typically don't test for glycol in the lab but rather the elemental additive residuals that ingress with glycol into the crankcase oil (Na, K, Si, B, etc).

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