Shape: KAV concave
The max. Permissible operating pressure depends on the gap dimensions.
The operational application limits use are dictated by the O-ring selected. It is only the resistance of the sealing system to pressure which can be increased by the back-up ring.
The back-up ring is a closed ring concave in cross-section. It is produced entirely as a closed ring with no seams. The back-up ring’s concave cross-section provides the O-ring with a larger contact surface, having the effect of allowing the O-ring almost fully to retain its circular shape under high pressures and to be less liable to deformation. This means that the shape of the O-ring is supported better and it can therefore withstand higher pressure loads. This produces a better sealing effect and increases the seal’s service life. The back-up ring is of symmetrical profile. This allows it to be used in both internal and external sealing systems.
Back-up rings are installed behind the O-ring at the side not subject to pressure where the pressure load is applied at one side only. The concave side faces the O-ring and the flat side the gap. Where the pressure direction varies or in order to avoid an installation error from the outset, use should be made of two back-up rings, i.e. one at each side of the O-ring. When use is made of back-up rings, the installation housing must be created in accordance with the manufacturer’s specifications. It is often the case that installation housings are wider than simple O-ring installation housings.
Back-up rings are often used in hydraulic systems, especially in hydraulic valves and hydraulic pumps, and also for sealing cylinder bottoms and heads (in conjunction with O-rings). However, back-up rings are also used in many other fields of industry as a whole, e.g. for sealing ball valves.