Weld Point of Lubricating Greases

Description

An extreme crash test of a lubricating grease, recording the maximum shock load at which the lubricating film breaks down completely and the parts weld together.

When a mining excavator bites into hard rock, the load on its joints and open gears exceeds all design norms. The weld point of lubricating greases at the RENA laboratory is the final survival test for your product. This test proves whether the thick grease is able to hold in the contact zone and prevent emergency jamming of mechanisms under colossal peak shocks. Using a grease with a high weld point is an insurance policy against catastrophic failures of the most expensive heavy machinery components. The test is conducted on a precision four-ball friction machine (FBT-3). Unlike testing fluids, preparing a thick grease requires meticulous work: the lab technician fills the cup with three steel balls in such a way as to completely exclude the entrapment of air bubbles. The fourth ball rotates at a speed of 1770 rpm. The friction node is subjected to a series of short (10-second) dynamic runs, during which the operator ruthlessly increases the axial load on the system (from 250 to 800 kgf and above). Upon reaching extreme pressures, the grease, despite its thick structure and the presence of EP additives (e.g., molybdenum disulfide), is completely squeezed out and burns off. Direct metal contact occurs, and the balls physically weld to each other into a single monolith, stopping the electric motor. This peak load is the weld point.