Back to Lube-Tips™ Back Issues.

Machinery Lubrication Magazine Reliable Plant Magazine Motor Oil Selection Guide Synthetic Oil Resources

Book Bits

For those studying for lubrication-related certification, read this section from "Mechanical Wear Prediction and Prevention" carefully:

The primary way by which a lubricant influences friction and wear is by reducing adhesion and there are three general mechanisms for this. One is by absorbtion on the contact surfaces. The second is by chemically modifying the surface. The third is by physical separation of the surfaces. The first two mechanisms tend to reduce the strength of the bonds at the junctions, while the third tends to reduce the number of junctions. Secondary effects of lubrication are: cooling of the interface, modification of the stresses associated with the contact, and flushing of wear debris or contamination from the contact region. Because lubricants tend to lower friction, the heat and shear action developed at the contact interface is reduced. For fluid lubricants, additional cooling occurs as a result of the lubricant transporting heat out of the contact area. The lubricant can also influence the distribution of load within the contact by supporting some of the load.

Click here for more information about The Mechanical Wear Prediction and Prevention.

Today's Tip

• When I change oil in a gearbox I put an air wand (from shop air or portable air source) down into the vent plug. This blows oil residue and deposits off the surface of the gear teeth and casing. It also pushes sediment off the case bottom. I usually hold up a shield to keep the splatter down. Afterward, I like to flush the box with a lower viscosity oil of the same type for a few minutes and then drain again using the air wand. In the past, I used to just drain and fill, but now with this method the oil in the sight glass looks like a new gearbox, with very little residue. The procedure is faster as well. (Tip submitted by: Stan W. Strickland, Georgia Pacific Thanks, Stan!)

Each tip published will earn the sender $10. Click here to submit your tip.

Q & A

"What is meant by the oil viscosity of a grease?"

We can think of greases as thickened lubricating oils. The part of the lubricating grease that actually performs the work in the loaded bearing is the oil in the grease, not the thickener in the grease. The truth is that they work hand in hand, but the determining factor in a grease's ability to support a load is the oil viscosity. In the supplier Product Data Sheet, the oil viscosity is listed just below the grease NLGI rating. For highly loaded equipment, it is generally wise to use grease with heavy base oils. In high-speed equipment it is generally wise to use greases with moderate viscosity oils.

Copyright © 2001, Noria Corporation. All rights reserved. Please do not reprint or host on your website without explicit permission. However, if you found this newsletter helpful, we grant you permission, and strongly encourage you, to e-mail it to a business associate or a friend. Thank you. The presence of advertising in Lube-Tips does not constitute an endorsement of the products or services in such ads. Further, because results will vary widely based on a number of factors, Noria Corporation cannot warrant the results, the accuracy or the completeness of any material published herein.

Lube-Tips is published by Noria Corporation. Oil Analysis and Lubrication Experts