What is the Dropping Point in Lubricating Grease?

One of the most important components in any plant is the lubrication. Lubricating greases are a semi-solid structure that consists of three main components - oil, additives, and the thickener, and it is used primarily to reduce friction in a number of critical components and applications. This includes gearboxes, bearings, bushings, and other contact points. By reducing friction, you effectively extend the life of your machinery by avoiding costly repairs and replacements.

What is Dropping Point?
In order to properly lubricate your equipment, you need a quality lubricating grease. When reviewing a lubricating grease, an important indicator of quality is its dropping point. The dropping point is the temperature at which the grease passes from a semisolid state to a liquid under defined test conditions. A grease should have a dropping point that is safely above the highest operating temperature so the grease will not run out of the application. The way to properly test for the dropping point is by heating up the lubricating grease under defined test conditions until the first drop falls from a standard test cup apparatus.

Dropping Point Results
It's important to differentiate between the maximum temperature that the grease is usable and the maximum temperature that it holds its form. Dropping point tests are checking for its form stability and are not the only factor to consider when determining the upper operating temperature of a grease. The dropping point can range up to 300°C, or 572°F, but there are other factors that could lower the recommended upper operating temperature such as the flash point of the base oils, decomposition temperatures of the additives, and the oxidation of the grease at elevated temperatures. The thickener type and quantity of thickener can also impact the grease dropping point.

Remaining Useful Life (RUL)
Although the dropping point test can give you insight into the remaining useful life of a grease, it is important to note that the dropping point only measures one trait of a grease, and the RUL estimation should be based on a combination of tests measuring a variety of traits.

Dropping point tests are a useful tool in determining the temperature at which grease begins to become fluid. By conducting this test, you can gain knowledge to apply when selecting the best grease for an application.