Machinery Lubrication magazine published by Noria Corporation
Issue link: http://www.e-digitaleditions.com/i/601893
ML Many machines run at speeds and loads far below the maximum rated by the manufac- turer. Other machines are just the opposite, operating in excess of catalog speeds and loads. All of this has a sharp effect on the machine's viscosity needs. One way to stay alert to inadequate viscosity (or excessive viscosity) is to "listen" to the machine. This can be done using the following techniques: Oil Analysis — Test for viscosity/viscosity index, contamination (fuel, water, dirt, etc.), oxidation stability, thermal stability, wear metals, etc. Look for both root causes (of thin oil) and the effects of viscosi- tystarved machines. Sound — Bearings, pumps and gears emit sharply different sounds when they are starved of lubricant or viscosity. Heat Monitoring — Use infrared heat guns and cameras to detect hot spots and unusually high oil and component tempera - tures. Machines with resistance temperature detectors (RTDs) and temperature gauges can report important temperature excur- sions on the oil, coolant and bearing metal (thrust, journal, etc.). Oil Level Change — Contaminants such as fuel, process chemicals and even water can sharply change oil viscosity when they enter the oil. This can often be viewed as a sudden rise in the oil level at gauges and sight glasses. Stressed Frictional Surfaces — Cylinder walls, journal bearings, gear teeth and cams are examples of machine surfaces that can frequently be inspected periodically for abnormal wear from oil or viscosity starvation. Out-leakage — A sudden lowering of oil viscosity can sometimes increase leakage across multiple points. LUBRICANT STARVATION VS. VISCOSITY STARVATION The dangers of lubricant starvation have been discussed extensively in Machinery Lubri- cation. This condition describes machines and critical surfaces that receive an inade- quate supply of oil or grease. Viscosity starvation is different. The amount of lubri- cant may be adequate, but the load-bearing ability of the lubricant is impaired by thin oil. Keep both forms of starvation in focus with your condition monitoring program. About the Author Jim Fitch has a wealth of "in the trenches" experience in lubrication, oil analysis, tribology and machinery failure investigations. Over the past two decades, he has presented hundreds of courses on these subjects. Jim has published more than 200 technical articles, papers and publications. He serves as a U.S. delegate to the ISO tribology and oil analysis working group. Since 2002, he has been director and board member of the International Council for Machinery Lubrication. He is the CEO and a co-founder of Noria Corporation. Contact Jim at jfitch@noria.com.