Features - Autumn 2009 Features

In previous Lube Notes we looked at the role lubricants play in overcoming the effects of friction. In this installment, I want to examine one specialized type of lubricant: grease lube. Looking at previous civilizations, we can see that man has tried several methods to provide basic lubrication to load-bearing surfaces; axles have presented one of the most challenging applications. As far back as 1400 BC, mutton fat and beef tallow were used on chariot axles to reduce friction in order to allow for more speed and to slow down wear. One can only imagine the pressure on the maintenance men to make the chariot go faster and to avoid axles catching on fire from the continuous friction. While there is evidence of lime being added to these fats in order to make their lubricating properties last longer, few other improvements to the composition of grease are known to have been used until we reach the magic year of 1859.

What happened in 1859? Colonel Drake drilled the first ever oil well in Pennsylvania; since then, the world has not been the same. In petroleum oil, man found a lubricant that could be manipulated in a variety of ways to produce greases much superior to the lubricants that preceded them. In turn, more advanced and effective greases have been produced in recent decades with the advent of synthetic greases.

The word grease is derived from the Latin word crassus meaning fat. We can see where the name came from (mutton fat, beef tallow); however, grease lube, for modern purposes, is not to be construed as fat. The American Society for Testing Materials (ASTM) defined grease in 1916 as: A solid to semi-fluid product of dispersion of a thickening agent in a liquid lubricant. In plain English, this means A lubricant composed of lubricating fluids (oils), thickened by mixing chemicals to produce a semi-fluid to semi-solid consistency.

Now that we know a little of the history of grease and how grease is defined in modern lubrication; when, where and why is grease lube used? While lubricating oils are able to lubricate any friction-causing situation, greases offer unique characteristics that are well suited for:

• Situations requiring less dripping or spattering of lubricant
• Hard to lubricate bearings or joints where reducing frequency of lubrication is needed
• In dirty, dusty or hazardous environments where additional sealing is needed to prevent lubricant contamination.
• For intermittent operation. Oil drains away from critical bearings when the equipment is stopped but grease stays in place.