WHY WOULD I USE A BACK-UP RING?
Back-up rings are thin rings designed to prevent O-ring extrusion under pressure. They fit in the gland between the seal and the clearance gaps to provide zero clearance
Back-up are not designed to have any sealing function in their own right. They are simply there to support the actual sealing elements by stopping them from extruding under higher pressures, or where metalwork clearance is larger than ideal.
Back-up rings for O-rings can be contoured or flat. They come in the form of a solid ring, a split ring or even a spiral ring, depending on the environment that the back-up ring is expected to operate in, and for ease of fitting.
Back-up rings are placed behind the seal if it is a single acting system, or on both sides for double acting. They are made of a harder material than the seal itself. You must always consider the environment expected for any particular seal and its back-up rings. It is also important to consider the degree of acceptable friction losses, in order to provide the most suitable solution, as a back-up ring may increase the friction present in a system.
Rocket Seals carries Buna, PTFE Single Turn (split) and PTFE Spiral Back-up rings in most standard sizes.