ROLL STABILITY OF LUBRICATING GREASES: ASTM D1831
EXPLANATION
Although this test is widely used for specification purposes, the significance of roll stability test has not been determined. The changes in worked penetration of a grease after rolling are believed to be a measure of its shear stability, under the conditions of this low shear test. The roll stability is defined as the change in consistency of a sample after a specified amount of working in a test apparatus utilizing a weighted roller inside a rotating cylinder.
TEST SUMMARY
Test Method ASTM D1403 cone penetration of an approximately 50 g aliquot of lubricating grease is determined. The grease is then subjected to low shear at 20 to 35° C for 2 h in a standard roll stability apparatus, before the cone penetration is again measured. The difference between the cone penetration before and after working is used as a measure of the effect of low shear working on grease consistency.
TEST PRECISION
Range of samples: NLGI Consistency Nos. 1 and 2
Repeatability: 11 penetration units - tenths of a mm
Reproducibility: 45 penetration units - tenths of a mm
