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Lubricating Greases

出版	ASTM International, 2010
ISBN	08031842209780803184220
URL	http://books.google.com.hk/books?id=V4_SvQEACAAJ&hl=&source=gbs_api

註釋THE ESSENTIAL FUNCTION OF ANY LUBRICANT IS to prolong the life and increase the efficiency of mechanical devices by reducing friction and wear. Secondary functions include the dissipation of heat, protection from corrosion, power transmission, and removal of contaminants. Generally, fluid lubricants are difficult to retain at the point of application and must be replenished frequently. If, however, a fluid lubricant is thickened, its retention is improved and the lubrication intervals can be extended. A lubricating grease is simply a lubricating fluid that has been gelled with a thickening agent so that the lubricant can be retained more readily in the required area. Lubricating greases have a number of advantages over lubricating fluids. Some of these are: Dripping and spattering are significantly reduced Less frequent applications may be required Greases can be easier to handle Less expensive seals can be used Greases can form a seal in many cases and keep out contaminants They can adhere better to surfaces Some greases may reduce noise and vibration Some grease remains even when relubrication is neglected Greases are cost-effective Grease was previously defined as a gelled lubricating fluid. Although this simplistic definition conveys the general concept of a grease, a more extensive discussion is required to provide a fuller understanding of just what constitutes a lubricating grease. A lubricating grease is a semifluid to solid product of a dispersion of a thickener in a liquid lubricant. Wherever the term grease without the qualifier, lubricating, is used in this publication, it shall mean lubricating grease and exclude commercial grease. Tallow, lard, and other animal fats are items of commerce called grease. Even if a commercial grease is used to lubricate, it does not always satisfy the requirements for a lubricating grease, because it is not a liquid lubricant thickened with a dispersed solid. Additives, either liquid or solid, are usually included to improve grease properties or performance.