Our 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 of 3mm or greater for machining purposes.
Our back-up rings are manufactured in either virgin PTFE, PEEKTM (from Victrex plc) or filled PTFE, depending on the application.
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 10MPa
- O-rings of low strength elastomer are used
- Adverse mechanical conditions prevail
Please consult our Technical Support Team if fluid pressure is likely to exceed 42MPa.
Available for all standard O-ring housings. Sizes to fit non-standard housings are made to order.