Definition - What does Back-Up Rings mean?
Back-Up Rings are supporting rings which are used along with O-rings, quad rings or any other type of sealing rings so as to prevent extrusion or leakage of fluids. The fluid leakage which is prevented by these types of rings usually happens through the seal material when the equipment works under excessive differential pressure or when there is a high chance of wear and tear in dynamic sealing conditions.
Petropedia explains Back-Up Rings
Back-up rings are very rigid hence they are responsible for holding plastic seals such as Polyethylene and elastomeric seals at the correct place. These types of sealing rings are commonly used with O-rings, lip seals, and as reciprocating shaft seals. They are also used for piping connections joining two different materials - typically one flexible and one rigid. They are available in spiral, cut or uncut designs in filled or unfilled PTFE, Turcon, elastomers and thermoplastics based on ISO 3601, AS 568.