Theoretical study of solid back-up rings for elastomeric seals in hydraulic actuators

The use of back-up rings to support elastomeric seals in high-pressure hydraulic systems is well established in the industry. However, little is known about the operation of such devices and how they affect or interfere in the sealing mechanism of the seals they accompany. This study is an attempt to model solid, soft back-up rings in terms of elastohydrodynamic lubrication and establish their exact role in a sealing system in terms of sealing performance (leakage). The model is applied on a typical case of a linear hydraulic actuator for a wide range of sealed pressures (1–35 MPa) and operating temperatures (−55 to +135 °C), and with one ring installed on the low-pressure side of the actuator. A system of a rubber seal and a properly selected and installed back-up ring is shown to be often significantly more efficient in terms of fluid leakage than the seal without the back-up ring. A study reveals the effect of various parameters of the ring (e.g. the elastic modulus and the surface roughness) on the sealing mechanism and shows the optimum selection to minimize leakage.