Issue link: http://read.dmtmag.com/i/859318
1 800 255 4417 www.castrol.com/GPS Greases Background & Properties July 2017 Industry Specifications There is little standardization for grease testing in the industry, but there are several industry tests that rate a grease's performance characteristics. To determine whether a grease can offer extreme pressure (EP) protection, pumpability, mobility and stay-in-place performance, review the results of these critical industry tests: Grease Tests Penetration The test for penetration is one of the primary quality control tests for the grease industry. Many grease suppliers quote penetration test results as a performance indicator for their product. Unfortunately, penetration alone simply measures the consistency of a grease and does not indicate how a grease will perform in a component. The penetration test involves a one pound cup of grease, held at a controlled temperature, with the air bubbles removed from it. A weighted cone is dropped into the grease. The depth of the cone immersed in the grease is measured in millimeters. A range of penetration in millimeters determines the NLGI grade of the grease. The farther the cone penetrates the grease, the lower the NLGI grade. A grease's pumpability or mobility characteristics cannot be predicted from penetration test results. Timken OK Load The Timken test measures a grease's ability to withstand extremes of load and pressure. It is performed under line-to-line contact with a specific amount of pressure applied to a greased block. The test is run for ten minutes, and at the end of the test, the block is rated in terms of how much it is scored. A little scoring is considered a pass; a significant amount of scoring is a fail. The Timken test is performed with different weighted loads, usually between 10 and 70 pounds. A typical value for the Timken test is a 40-pound pass. An excellent value for the Timken test is a 70-pound pass. The latter grease exhibits outstanding extreme pressure protection over standard greases. Greases able to pass the Timken OK Load test have balanced additive packages containing extreme pressure agents. Maintenance managers using a grease in high load applications should research Timken test results. 4-Ball Weld Another test designed to measure extreme pressure properties, the 4-Ball Weld, evaluates point-to-point contact using ball bearings for better reproducibility and more consistent data. Three greased, rotating balls are placed in a cup and one stationary ball is on top. A load of up to 800 kilograms is added to the ball bearings. The test runs for one minute (under load for 10 seconds) and if the balls keep rotating for the full minute, the grease has passed. If the balls weld together before one minute has passed, the test shuts down and the grease fails. A typical EP grease will usually weld around 250 kilograms. Grease with excellent extreme pressure properties can handle a load of 800 kilograms—the highest test load. F 5