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What You Should Know About The Viscosity And Purity Of Bearing Lubricants In Pumps

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Properly-lubricated bearings are essential to the long-lasting, reliable operation of pumps. Without lubrication, bearings quickly break down and fail, leading to pump down time and potentially expensive repairs or replacement. If you are responsible for the maintenance or operation of a pump, then it is essential for you to understand what factors can lead to inadequate lubrication. Below are two important characteristics of pump bearing lubrication and how you can properly apply what you have learned when working with lubricants:


Lubricants are manufactured from a variety of source materials, including mineral and synthetic resources. Additives are commonly incorporated into lubricants to yield additional benefits. However, it is important to understand that viscosity is the top "personality trait" of bearing lubricants. Viscosity, the thickness of the lubricant, must be correctly chosen or the bearings will fail at some point.

If the viscosity of the lubricant selected is too low, the protective lubricating film will not adhere to the surfaces of the bearings. Both the balls and the bearing raceways will heat up under the increasing friction and ultimately fail.

However, an excessively-high viscosity can also cause significant problems. Thick lubricants may not properly circulate inside the pump, and some bearings may not receive lubricant coverage as a result. In addition, bearings moving within an overly-thick lubricant creates drag resistance. This may lead to premature wear on related moving parts.

Here are a few practical ways to ensure your lubricant viscosity is correct:

  • Always choose the proper lubricant viscosity for the particular pump being used by consulting manufacturer specifications.

  • Beware of any modifications made to pumps and how those might affect the lubricant viscosity, particularly if those changes involved bearing replacement.

  • Whenever you are in doubt, consult with your facility's mechanical engineering staff for assistance in choosing an appropriate lubricant viscosity.


Another important characteristic of bearing lubricants is purity. An impure lubricant can be devastating to the bearings of a pump; here are a few ways that lubricant purity can be compromised:

  • Internal contamination – this results when the internal processes of an operating pump results in lubricant contamination. For example, normal wear of moving components results in fine metallic shavings that can accumulate. These tiny bits of metal can work their way into bearings and create an accelerated wear process by grinding down the balls and raceways.

  • External contamination – external contamination occurs whenever the lubricant is introduced in an impure form or whenever careless maintenance procedures are utilized. As an example, if an equipment mechanic adds lubricant stored in an open container to the pump, then they are likely introducing a variety of contaminants: water, sand, soil, combustion byproducts, and other foreign matter.

  • Operational contamination – this happens due to the ordinary operation of the pump and the ability of contaminants to "invade" the pump and its bearings. Operational contamination of lubricants can occur whenever seals permit the transfer of atmospheric gases, including water vapor. In addition, other substances, such as dust, can work their way into the pump and lubricant reserve, if the pump isn't adequately protected at its vulnerable spots.

As a result, it is important for you to maintain the purity of lubricants used within your pumps. There are several steps you can take to keep lubricants free of contamination:

  • Regularly clean or replace lubricant filters.

  • Keep lubricant containers sealed tightly when not in use.

  • Replace lubricants in clean environment where conditions can be controlled. Be sure that any equipment used during the lubricant change process, such as a funnel, is also kept clean.

  • Use drying agents or moisture-removal equipment to reduce ambient moisture levels in the vicinity of the pump.

For more information on specific types of pumps, check out companies like PFC Equipment, Inc.