Selection of correct lubricant type, grade and quantity is very important for the bearing lubrication. Incorrect lubricant type, wrong grade or incorrect quantity of the lubricant are detrimental to the bearing life. Frequent failure of bearings causes more downtime and loss of production. Bearings that are properly lubricated with minimal contamination will operate at lower temperatures and run for longer periods of time. Anti friction bearings in process pumps can either be grease, mineral oil, or synthetic oil lubricated. The primary purpose of oil, or the oil constituent of grease, is to separate the roller elements and raceway contact surfaces, lubricate the sliding surfaces within the bearings, and provide corrosion protection and cooling.
Viscosity is the single most important property of a lubricant. Use of the correct viscosity lubricant for the speed and loads ensures the development of a full oil film between rotating parts. When the incorrect viscosity is used, the load carrying ability of the lubricant is negatively affected. The oil degrades to a point where it is too thick to penetrate between the surfaces and the oil supply may not be adequate to prevent sacrificial contact. Viscosity is influenced by load, temperature, water, contaminants, and chemical changes. The OEM operation manual should be consulted for recommendations on viscosity but it is also important to measure the oil sump operating temperature since viscosity decreases as temperature increases
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