How to spot lubrication warning signs

Phil Grellier
Tags: maintenance and reliability, condition monitoring

Knowing the condition of your lubricants is essential to keeping manufacturing plants running smoothly. This can be accomplished through a thorough oil analysis program that tracks multiple critical wear-related characteristics of oil in service by comparing the results with previous reports, and noting the trends. Such a program helps identify contamination, lubricant degradation, abnormal machine wear, and problems with sampling. It also can transform a lubrication program from time-based to condition-based, eliminating unnecessary changes.

 

Total acid numberThis measures the amount of oxidation that the fluid has undergone since startup. It is a useful measure of the performance of a lubricant, and a good predictor for when it should be replaced. As lubricant fluid is used and exposed to the air its oxidation level increases, decreasing the effectiveness of the lubricant. A total acid number that is significantly higher than its initial value is a key warning sign of lubrication problems. Equally important is a system’s particle count. This provides information about the cleanliness of the system and performance of the filtration system. Dirt and other impurities accumulate in the lubricant, decreasing its effectiveness. A properly functioning filtration system can extend the life of this measure, but if the particle count increases significantly from its initial values this is an indication that the lubricant should be replaced.

 

WaterWater is a major enemy of lubricants. Especially in moist environments, where the lubricant is exposed to open water or steam, the water content of a lubricant can significantly impact performance. Different lubricants have varying tolerances for water content. For example, a polyalkylene glycol has higher water limits than a polyalphaolefin product. Each lubricant has its own guidelines on acceptable parts-per-million (ppm) water levels. These can be obtained from your lubricant supplier. Regardless of the lubricant you use, water content that exceeds acceptable levels is a serious warning sign of impending lubricant failure.

 

MetalsMetals analysis can reveal information about the wear in your system and the performance of certain additives. Metals are found in lubricants both as a result of additives in the fluid and as a result of wear, depending on the type of lubricant and the configuration of your system. The typical oil sample test targets common engine metals such as copper, aluminum, and iron in order to provide a measure of the amount of metal “ingested” by the lubricant. As with water content, different lubricants have varying tolerances for metal content. Again, plant managers should consult with their lubricant supplier to best predict when metal analysis results indicate the need for lubricant change.

 

Particle AnalysisParticle analysis can help detect metal contamination and ensures that the lubricant system has correct filtration, specifications which can significantly increase the amount of time required between lubricant changes.

 

Viscosity Perhaps the most simple and common-sense test of lubricant wear is a lubricant’s kinematic viscosity, or thickness. By tracking a fixed amount of oil as it travels through a lubrication system, increases in viscosity can easily be measured. An increase in viscosity is directly related to lubricant wear. As a rule of thumb, lubricants should be changed before their viscosity changes more than 10 percent.

 

Many of the best lubricant suppliers offer oil analysis programs that track many of the conditions of lubricants, predicting when the ideal time to change lubricants. Check with your lubricant supplier to see if such a program is available to you.

 

About the author:

Phil Grellier is the global solutions development manager for Dow Corning Molykote. For more information, e-mail phil.grellier@dowcorning.com or visit www.dowcorning.com.


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