an Engineering & Service Bulletin

Technical Topics

J.H. WRIGHT & ASSOCIATES

IMPROVING BEARING LIFE BY WATER REMOVAL

The saying "Oil and Water Don't Mix" is unfortunately not very accurate. In fact, most lubricating oils will hold up to 1000 PPM water (0.10%) in a dissolved form. Even worse, the oil at this point will probably not have a cloudy appearance.

The above information, while of some minor interest in passing would not cause one to take any action unless you happen to be using this oil to lubricate bearings; anti-friction in particular.

Since ball and roller bearings have a very small area of actual contact, the condition of the lubricant at this interface is extremely critical. If the film for any reason is ruptured or breaks down - bearing life goes down the tubes.

Consider these test results of The Timken Bearing Company. Assuming 100% bearing life is achieved at 100 PPM water (0.01%) the life at 500 PPM (0.05%) is reduced by 65%! At 500 PPM, the oil is probably going to appear perfectly serviceable.

Most plant engineers and maintenance personnel are by now familiar with the several labyrinth-type lip seals on the market. Inpro® is probably the most advertised. These seals have shown phenomenal bearing life improvements in the plants that have installed them. Primarily they protect the bearings from contamination, both solid and liquid. Even so, they can do nothing about water that enters the lubricant as a result of the 95% relative humidity we have on the Gulf Coast.

There is really only one way to effectively remove this dissolved water from oil - boil it out. Unfortunately, if you heat lube oils up to 212°F; you damage the oil unnecessarily. For that reason, it is better to heat the oil under vacuum, so heating to 150°R will release the moisture.

Shown below is a schematic of how this water removal is accomplished. We have a small unit at our shop for demonstration purposes - punch the attached "Bingo Card" if you're interested.

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