Description James Walker's back-up rings are normally supplied as a spiral of two turns. This enables the back-up ring to be opened with ease for fitting over a shaft, and ensures the 'O' ring is supported around its entire diameter.
Single turn back-up rings can also be supplied, and these are usually endless to ensure good support. However, they can be scarf split if required, although we do not recommend this because extrusion can occur at the split.
Smaller sizes of back-up rings are available only as a single turn. This is because spiral back-up rings need an inside diameter greater than 3mm for machining purposes.
Materials Our back-up rings are manufactured in either virgin PTFE, PEEK® (from Victrex plc) or filled PTFE, depending on the application.
Why use back-up rings? Back-up rings are installed to prevent extrusion of the 'O' ring. Two back-up rings - one either side of the 'O' ring in its housing - are needed when the application is double acting.
They are normally recommended for applications where:
Pressure of the fluid medium exceeds 100bar, or
'O' rings of low strength elastomer are used, or
Adverse mechanical conditions prevail.
Please consult our Technical Services Team if fluid pressure is likely to exceed 420bar.
How supplied Available for all standard 'O' ring housings. Non-standard sizes made to order.
Description
