PTFE back-up ring

Back-up rings are manufactured from extrusion resistant material as protection and support elements, normally with a rectangular cross-section. For static applications they are used together with an elastomer seal – usually an O-ring – placed in the groove. Because there is a tight fit between back-up ring and bore hole or rod it prevents the O-ring from extruding into the sealing gap under pressure. Back-up rings can be used in static applications as well as in translational movements or slow rotations. 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.