A backup Ring is also called as an anti-extrusion ring that holds an elastomeric connection to its designed shape and in its correct place. As per the name, backup Ring is a protective and supporting ring made from an extrusion resistant material with the rectangular section. Under the specific condition of temperature and pressure, there is a risk of gap extrusion therefore backup Ring is used to prevent o-rings from gap extrusion in static radial sealing.
Backup rings are used in conjunction with o-rings in the high-pressure application usually above 1500 psi and also compensating loose fitting components. Backup rings are used for static application around 950 bar and for dynamic application over 100 bar. There are three types of PTFE backup rings are available which are split, solid, and spiral wound, But nowadays contoured elastomers backup rings are widely used to overcome the problems.
Some application examples of contoured backup rings are presses, excavators, machine tools, valves for the hydraulic circuit, agriculture machines, and molding machines. PTFE material backup rings are only used for low and medium loads and for higher loads filled PTFE material ( with glass fiber, carbon, bronze) is used. Injection molded backup rings (NBR, FKM, thermoplastic elastomers) are used for sealing against high pressures.
Backup rings are the perfect option to be used in extrusion failure. Advantages of backup rings are compensation of radial sealing gap, reciprocating and rotating movements possible, compensation for large temperature fluctuations, use of O-ring materials with a low hardness and in the high-pressure application. In many application two backup rings are used to provide maximum support ;one above O-ring and one below.
Concept Seal manufactures and supplies a wide range of Backup rings and materials to complement each type and to suit every application.