ASTM D2596 Measurement of Extreme Pressure Properties of Lubricating Grease
The extreme pressure properties, Load Carrying Capacity, of greases uses the Shell 4-Ball Extreme Pressure Test Machine. A rotating upper ball is loaded against three stationary lower balls. The initial loads are low and exhibit elastohydrodynamic properties. As loads increase beyond E.H.P., the lubricant passes through the high pressure boundary film region. At the highest load the lubricant can stand the boundary film is lost and welding occurs.
This test is very good at comparing the extreme pressure and boundary lubrication properties of comparative samples or competitive types of formulations. The Load Wear Index Value, Last Non Seizure, Last Seizure and Weld Load are reported.