ASTM D1404 Estimation of Deleterious Particles in Lubricating Grease
Some particles in grease, such as graphite and molybdenum disulfide are intentionally added to assist in the lubrication process. Other particles, called deleterious particles, may also be present in new or used greases. Deleterious particles may arise from contaminated raw materials, poor storage leading to dimerization and agglomeration of additives, and processing errors in filtration, mixing, milling and temperature control. Deleterious particles in used greases typically come from the environment or arise from wear debris. These particles may be classified as "abrasive" or "non-abrasive". Abrasive particles may damage system components and cause premature bearing failure. This test determines the amount of abrasive deleterious particles in lubricating greases. It may be used as a quality control tool for new greases, to determine particle levels in service greases and to determine the level of abrasive particles in molybdenum disulfide and graphite raw materials.
The grease is placed between two specially prepared plastic sheets. A standard load is applied and the sheets are rotated against one another in a prescribed arc. The apparatus is disassembled, and the sheets are examined for the arc-shaped scratches resulting from deleterious particles. The total number of scratches on both sheets of plastic is reported.