Backup Ring Extrusion Gap Calculator

Check the extrusion gap against the elastomer limit and size the backup ring groove width.

Backup Ring Extrusion Gap Calculator overview

Backup Ring Extrusion Gap Calculator overview is computed deterministically from the parameters encoded in this page's address, so the same inputs always produce the same result and the same OAS-XXXX verification hash.

Governing gland dimensions

Governing gland dimensions is computed deterministically from the parameters encoded in this page's address, so the same inputs always produce the same result and the same OAS-XXXX verification hash.

Squeeze, fill and extrusion checks

Squeeze, fill and extrusion checks is computed deterministically from the parameters encoded in this page's address, so the same inputs always produce the same result and the same OAS-XXXX verification hash.

Engineering summary

Governing parameters and computed results for Backup Ring Extrusion Gap Calculator.

Governing parameters and computed results for this calculation
Parameter Value
Mode static

Frequently asked questions

What squeeze percentage should a static AS568 gland use?
Static face and radial seals target 15% to 25% squeeze. Below 15% the seal may not seat against surface finish and pressure; above 25% compression set accelerates and the elastomer takes a permanent set.
How is the AS568 dash number related to cross-section?
The dash series fixes the cross-section: 0xx is 0.070 in, 1xx is 0.093 to 0.103 in, 2xx is 0.139 in, 3xx is 0.210 in and 4xx is 0.275 in. The 9xx series are SAE Boss ORB sizes at 0.087 in.
When does an O-ring gland need a backup ring?
Add a backup ring when the extrusion gap exceeds the elastomer's allowable gap at the operating pressure and temperature. The backup ring groove width grows with each ring: the 0-ring, 1-ring and 2-ring widths are tabulated per dash size.