Back up ring installation

They are also called Anti Extrusion Rings and are typically used with O Rings to eliminate extrusion at high pressures. For single acting applications — 1 Back-up Ring is sufficient, however for double acting applications — 2 Back-up Rings are necessary in order to prevent extrusion on both sides.

Single Turn and Spiral Cut Back-up Rings overpass this issue as they can both be opened a little in process of installation without deforming them. PTFE rings in a spiral cut are very popular as it simplifies proper fitting and relatively rejects the extrusion gap in the ring.

Furthermore, all split rings are liable to damage during the installation process. The use of Back-up Ring may be a practical solution to block the diametrical clearance gap and provide support for the O ring when the stress on it is increased to the point when it can no longer withstand being extruded into the diametrical gap.

A Back-up ring is created from a firmer and more rigid material than the O Ring. If the pressure is one-sided, it is sufficient to install the seal on the side opposite the pressure. With pressurization on alternate sides, two back-up rings should be used, one back-up ring on each side of the O-ring. The risk of gap extrusion is typical under high pressures or with small ring cross sections in static but also dynamic applications.

A back-up ring must always be used together with an O-ring. The back-up ring itself provides no sealing. To help you quickly and easily find the best solution for your products, please send us your product inquiry via the form below.

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