Back up rings are designed to prevent the extrusion of O-rings in high pressure working enviroment, which can lead to seal failure and leakage. By providing additional support to the O-ring, back up rings ensure reliable sealing performance under extreme conditions.

Back Up Ring Designs

Back up rings are typically designed to complement the O-ring’s shape and size. Common designs include:

Materials for Backup Rings

Back up rings are made from materials that offer high strength, low friction, and resistance to wear and deformation. Common materials include NBR,FKM,PTFE,PEEK. Here is the table showing the properties of different material:

Material	Hardness (Shore A)	Working Temperature Range	Max Working Pressure	Working Environment
NBR	90 Shore A	-40°C to +120°C	Up to 20 MPa	Oil, water, gases, hydraulic systems
FKM	90 Shore A	-20°C to +250°C	Up to 30 MPa	High-temperature and hemical environments where exposure to oils, fuels, acids,solvents.
PTFE,PEEK		-50°C to +260°C	Up to 80 MPa	Ideal for harsh chemicals, high-temperature environments, and where low friction is needed (such as in food, pharmaceuticals, and chemical processing).

Applications of Back up rings

Industry	Common Applications	Typical Materials Used	Key Benefits
Hydraulic Systems	Cylinders, pumps, valves in heavy machinery	NBR,PU, FKM	Ensures high-pressure sealing in hydraulic circuits
Oil and Gas	Drilling equipment, pipelines, subsea systems, wellhead equipment	PTFE, FKM, HNBR	Withstands extreme temperature and pressure variations Resistant to aggressive chemicals and oil exposure
Industrial Machinery	Presses, compressors, hydraulic presses, molding machines	NBR, FKM, PTFE	Improves sealing performance and operational efficiency

Assembly Illustration

The back up rings are often installed on the low-pressure side of the O-rings to counteract the direction of extrusion forces.

Thanks to contact with OBT for O-rings and back up rings solution in high-pressure sealing systems.