Machinery Lubrication

Machinery Lubrication March April 2018

Machinery Lubrication magazine published by Noria Corporation

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www . | March - April 2018 | 23 introduction to the machine. While in the machine, you must use effective seals to keep out contaminants or utilize a strategy of grease purging to keep the contaminants at bay. Of course, this only works if the grease you use to purge is confirmed to be clean. In addition to particles and the damage they can do, you must consider moisture in greases as well. When high moisture is present in oils, phase separation or cloudiness allows you to see these very high levels. However, the same clarity seen in dry oils is not present in greases. As moisture levels increase in greases, these high levels are not always visually obvious. As Jim Fitch pointed out in a recent Machinery Lubrication article, "… it takes only a small amount of water (less than 500 parts per million) to substan- tially shorten the service life of rolling-element bearings." Using this as a guide, we find that out of 22 greases tested in this same cleanliness study, only one met this criteria for dryness. Most greases showed moisture levels higher than 1,000 parts per million (ppm), with the wettest greases in the study having more than 10,000 ppm. Not all greases are equally affected by moisture, and the grease types that showed the highest level in this study have been cited to be less sensitive to the effects of higher moisture levels. However, it is interesting to note that one grease saw its moisture concentration cut in half (from nearly 15,000 ppm to almost 9,000 ppm) after being placed in service within the machine. Even so, it may not be a good strategy to use your machines to dry out greases. Perhaps the first steps would be understanding the moisture levels your new and stored greases are starting with, then working with your suppliers and improving your storage methods to reduce the initial moisture levels as low as possible. By doing so, you stand to gain substantial increases in bearing life and grease performance. Perhaps it's time to take the focus on lubricant cleanliness, which has been applied so effectively to oil, and expand it to include grease. Many of the tools that work for oil, such as filtration and mois- ture removal technologies, aren't readily applicable to grease. However, there are several things you can do to improve grease cleanliness, starting with taking the required measurements to determine just how clean (or dirty) your current grease supply is. While a continued focus on oil cleanliness remains important, the next logical step in making substantial gains in equipment reliability and life extension may be achieved by taking a closer look at the contaminants hiding in your greases. ML © 2017 Beckman Coulter, Inc. Beckman Coulter, the stylized logo, and the Beckman Coulter product and service names used herein are trademarks or registered trademarks of Beckman Coulter, Inc. in the United States and other countries. Anzeige Pods 2017_RZ.indd 1 29.06.17 13:29 Visit us at Booth #317

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