A Study on Leakage Due to Deterioration of the Sealing Surface on Grease Seals

This paper describes one of fundamental remarks for perfect sealing, regarding the compatibility between a rubber compound and a lubricant. In the field, leakage occurred on rotary lip seals for grease-lubricated machinery. In most cases, the sealing lip had been hardened and deposition was found on the surface. In order to investigate the causes of the leakage, bench tests, pin-on-ring tests and observation tests were performed focusing on rubber and grease compounds. As a result, deposition similar to that occurred in the field was reproduced in specific cases. The results obtained suggested that a sort of solid MoDTC in grease would react with the fillers in rubber, causing surface deposition and leakage.