Tribology of High Pressure Rotor Seals: Friction and Failure

Rotating unions for high oil pressure (30 MPa) are common in technique. For example they can be found in excavators between the turnable upper part and the stationary lower part or in the indexing tables of tool machines. These seals often cause problems. Due to the high oil pressure, their friction torque can rise up to one hundred Nm and the seals fail during operation. But with known failure pattern the user is able to judge and improve the seal and the surrounding construction. This paper summarizes the failure causes that were observed during experiments at the Institute of Machine Components over the last years.