Issue link: http://read.dmtmag.com/i/859318
Greases Background & Properties castrol.com/GPS 800 255 4417 May 2025 GPS Industry Specifications Water Washout Water Washout, like Penetration, is another widely quoted industry test. But the results are not always valid. In the Water Washout test, an open-faced bearing is doused with a steady stream of water. However, test results can be difficult to replicate from different grease suppliers. Water Washout results are quoted in terms of percentage of grease washout. Water Spray Off A much better test for stayability in wet environments is the Water Spray Off test. During this test, a 2- by 4-inch metal panel is sprayed with a light coating of grease and weighed. Water at 100°F is then sprayed onto the panel at 40 psi. Once the test is complete, the grease that remains on the panel is weighed and results are quoted in terms of percentage of grease sprayed off. is is a much more realistic test for heavy-duty grease users for two reasons. First, there is less chance to manipulate data; therefore, it is a much more reproducible and repeatable test. And second, the test conditions—water being sprayed at 40 psi— is what many maintenance managers actually face on the job. US Steel Mobility Mobility is another test that, in and of itself, does not give grease users a lot of usable information. Its purpose is to predict pumping ease or difficulty at various temperatures. e US Steel Mobility test uses a packed grease cylinder with a small capillary at the bottom of the cylinder. Grease is packed into the cylinder and allowed to flow through the capillary with gravity behind it. Mobility is generally tested at 60°F and measured in grams per minute. It is safe to assume that grease with good mobility will also have acceptable pumpability, since pressure, not gravity, will be forcing the grease from the drum to final application. But for a grease to be effective, mobility/ pumpability must be balanced with stay-in-place capabilities. Most greases sacrifice tack and adhesion to have good mobility and pumpability. Mobility and pumpability information alone will not relay how well the grease will stay in place once in use or in the presence of water. Mobility numbers should always be quoted alongside water spray off results. As a norm, mobility of 200 grams/minute at 60°F and water spray off of less than 20 percent is considered very good for grease. e ultimate grease is one that offers the pumpability of an NLGI 1 grease with the tack and adhesion of an NLGI 3 grease. To take the mobility information one step further, it is helpful to have mobility numbers for a full range of ambient temperatures. For example, a grease can flow at 1,000 grams/minute at 60°F and 0 grams/minute at 20°F. Look for mobility information on temperatures of 0, 20, 40, 60 and 77°F to get a complete understanding of how a grease will flow and pump during all temperatures and seasons. Dropping Point A grease's dropping point is the temperature at which the grease changes from a semi-solid to a liquid state. e dropping point is not the grease's operating temperature. As a rule of thumb, a grease's operating temperature is approximately 100°F to 150°F lower than the published dropping point. Dropping point is noted when a grease becomes so hot that the oil separates from the soap and runs out of the cup. F6