Analytical study of the extrusion of rectangular elastomeric seals for linear hydraulic actuators

Abstract

Rectangular elastomeric seals used on reciprocating piston rods in high-pressure hydraulic actuators often suffer from extrusion damage at the low-pressure side of the actuators. The extrusion takes place at the narrow clearance between the rod and the actuator, where the seal develops a ‘nip’ under conditions of high sealed pressure and/or high friction with the rod, which is amplified in the absence of a back-up ring. This form of strain can lead to permanent damage of the seal and impair the sealing performance of the system. This paper deals with the modelling of this kind of seal extrusion. Algebraic equations were developed to describe the shape and contact pressure of the extruded part of the seal with the rod. A study is presented about the effects of various operating parameters on the extent of seal extrusion in order to minimize the risks of damage. It was found that only the use of a back-up ring can adequately cancel the seal extrusion mechanism.