Back-up rings

O-rings are often used as static sealing elements in hydraulic systems. However, they tend to extrude into the clearance already at low pressures and are thereby destroyed. A common solution is to use O-rings of a material with increased hardness, e.g. 90° IRH.

This provides a certain improvement, but the sealing ability decreases in cold since rubber materials with a hardness of 90° IRH lose too much of the elasticity in temperatures below -15 to -20 °C. Additionally, such material ages much faster already in moderate heat and turns brittle.