TRICO’s Kristopher Some has written about the oft-overlooked issue of grease selection in plant lubrication programs.
Many plants have a coupling grease, a motor grease and one general purpose grease for everything else.  The general purpose grease may be the proper grease for some applications but not all.  Selecting greases should have the same priority given to oil selection.
Grease is used when oil is either not convenient or not practical.  It can lubricate accessibility-challenged equipment for extended lengths of time, and forms a thicker film than oil in high temperature and shock loading conditions. Grease can also create a seal to prevent contamination ingression.
Viscosity is an important physical property of lubricants, and care should be taken in selecting the viscosity of grease. Grease being thickened oil, reverts back to the base oil viscosity when subject to shear force.
Using incorrect grades of great can cause churning and overheating, reducing bearing life. By using the correct viscosity of grease on the appropriate equipment, it is possible to extend up-time.
Grease contains thickeners which are grouped into three types. Thickeners are a chemical matrix which holds the oil until pressure draws the lubricant out.
Soap thickeners are created by chemically reacting a fatty acid and a metal. Complex soap thickeners are made up of a fatty acid, a metal and another acid. Non-soap thickeners replace the fatty acid with synthetic chemicals.
Grease of different thickeners should never be mixed. The mixed grease could have undesirable properties due to chemical interactions.
Base oils are combined with a thickener to form synthetic and mineral greases. Additives found in oil can also be found in grease, with the most common being EP additives, which can damage motor windings. When changing over from one grease to another, it is important that the additives and base oil are compatible between the two.
Like oils, grease does not have an unlimited shelf life because the base oil will oxidise. Grease should be stored in a clean and dry environment, with stock rotated. Each grease being used should have their own grease guns to avoid cross contamination.

Key contact:
Trico
www.tricocorp.com

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