Back-up Rings (Anti-extrusion Rings)

Product Overview

Back-up rings are used to extend the operating pressure of an O-ring. Either one or two back-up rings are co-located within a groove of increased width, on the low-pressure side of the seal.

When pressure is applied to the sealing system the back-up ring is axially compressed, increasing its radial width to close the extrusion gap. The high shear strength of the back-up ring material is then able to contain the elevated pressures.

Unlike elastomers, which see visco-elastic extrusion, thermoplastic back-up ring materials fail if the maximum shear stress is greater than the shear strength of the material at the operating temperature.

PTFE Back-Up Rings

Back-Up Ring Part no. Format

Designator	Type
Back-up Type Designator
BUSP	Spiral Back-up
BUCU	Scarf Cut Back-up
BUEN	Solid Back-up

Material Family Designator	Description
ISO 3601 Back-up Ring Material
A1	Virgin Polytetrafluoroethylene (PTFE)
V1	Virgin PEEK

Note: Back-up rings are groove specific, the above part numbering format being only suitable for BS1806 grooves.
Hardware dimensional details are available at: http://oring-groove-wizard.eriks.co.uk/DiameterGrooves.aspx

Back-Up Ring Type	Spiral	Scarf Cut	Solid	Scarf Cut	Solid
	T1	T2	T3	T4	T5
	Spiral Turn Anti-Extrusion Ring	Scarf Cut Anti-Extrusion Ring	Solid Anti-Extrusion Ring	Scarf Cut Concaved Anti-Extrusion Ring	Solid Concaved Anti-Extrusion Ring
Single
Double
Back-Up Ring Type

ISO3601 Back-Up Rings

Back-Up Ring ISO3601 Pt No. Format