Tribological investigation of friction coefficient in pneumatic seals with a special pin-on-disc setup

This article presents an experimental method for measuring friction in seals for pneumatic actuators using a pin-on-disk tribometer in a linear reciprocating sliding motion. A special device was designed to test a segment of seal cut out of a seal ring to replicate the working conditions of the piston seals. Friction tests were carried out with spring-energised seals made of graphite-filled PTFE. The counterpart for the friction test was a portion of an actual cylinder barrel of a pneumatic actuator. The coefficient of friction was measured under different loads to replicate several mounting preloads. Moreover, the experimental results were compared to the friction coefficient measured with a flat pin of the same seal material against a flat counterpart. The comparison between the two test setups allowed the authors to study the effect of the contact geometry and the applied load on the tribological performance of the seal. These preliminary measurements of stiffness and coefficient of friction are the basis for further investigations and measurements of elastic, viscoelastic and friction properties at the lip-barrel contact to develop a wear-damage model of lip seals.