Machinery Lubrication magazine published by Noria Corporation
Issue link: http://www.e-digitaleditions.com/i/258778
GreAses By dr. Anoop KumAr, royAl mAnuFACturing I It's hard to imagine a machine operating without grease in it, as the majority of dynamic machine operations run on bearings, which need grease for lubrication. Historically, the utilization of grease to lubricate a wheel and axle occurred just after the discovery of the wheel. The first universal greases were crude forms of lime mixed with vegetable oils. These classes of grease continued to be used for almost all kinds of applications requiring lubrication until the industrial revolution. However, in the last few decades, remarkable progress has been made in terms of machine design. This has affected oper- ating parameters and thus the requirements for lubricating greases. As operating parameters like speed, load, temperature, etc., vary significantly based upon the equipment, it is practically impossible for a single grease to handle all the diversified appli- cations. Consequently, a large number of lubricating greases have been developed, resulting in thousands of greases on the market. The concept of one universal lubricating grease covering all types of applications no longer holds true. Also, from a selec- tion and suitability standpoint, the vast array of available greases can be confusing to consumers. Grease Composition Lubricating greases basically are composed of a thickener (10 to 15 percent), base oil (80 to 90 percent) and performance Choosing a multi-Purpose Grease: lithium Complex or Calcium sulfonate? PrOPErTY DESCrIPTION LITHIUM MULTI-PUrPOSE GrEASE LITHIUM COMPLEX GrEASE CALCIUM SULFONATE GrEASE COMMENTS Stability Mechanical Stability +30 +30 <20 A lower number is better Roll Stability 8-10% 8-10% <5% A lower number is better High Temperature Drop Point ~350° F ~500° F +550° F Higher drop point, better high-temperature properties High-Temperature Life ~80-90 hours ~80-100 hours >120 hours A higher number is better Water resistance Water Washout (175° F, 1 hour, % weight loss) 5-10 5-10 <5% A lower number is better Water Spray Off (% grease washed off ) >50% 20-60% <30% A lower number is better Roll Stability in Presence of Water (2 hours, 10% water) >10% >10% <10% A lower number is better Extreme Pressure Weld Load (kgs.) 250-400 250-500 >500 A higher number is better Timken (lbs.) 40-45 40-80 >60 A higher number is better Wear Scar Diameter (mm) 0.5-0.6 0.5-0.6 <0.5 A lower number is better Compatibility with Lithium Greases Very Good Good Easy for changeover Table 1. Comparison of fully formulated greases 34 January - February 2014 | www.machinerylubrication.com