These are numerical values that provide a rough guide to anti-seizure properties of lubricants. In either case, the higher the value, the greater the anti-seizure property.The two tests are essentially based on the same principle. The bottom three balls are stationary balls held in a cup filled with the test lubricant, while the top ball is a rotating ball attached to a spindle. First, test hydraulic pressure is applied without rotating the spindle. Then, the spindle is rotated at a specified speed as applicable to the test being conducted, with the occurrence of seizure checked at the end of specified time period.
Weld load by Shell four-ball test (N):
Tested at 1768 rpm × 10 seconds. Shows the load at which steel balls become welded together.
Load carrying capacity by Soda four-ball test (MPa):
Tested at 768 rpm x 1 minute. The load recorded immediately before the occurrence of seizure (seizure threshold load) is defined as load carrying capacity.