Anti-Extrusion Ring Selection Guide for Oilfield Seals

An anti-extrusion ring, often called a backup ring, supports an elastomer seal where pressure can force the material into the clearance gap. It cannot correct an incorrect groove, excessive wear, damaged hardware or a seal compound that is unsuitable for the medium.

When a backup ring may be needed

Risk increases with pressure, temperature, softer elastomers, larger extrusion clearance, worn mating parts and repeated pressure cycling. Dynamic motion can add friction and wear. The decision must consider the whole gland rather than a pressure number alone.

Pressure direction

For one-direction pressure, the backup ring is normally positioned on the low-pressure side of the elastomer so it supports the seal against extrusion. Reversing pressure can require support on both sides. Verify the equipment drawing because groove style and assembly direction can change the arrangement.

Material and geometry

Backup rings may use engineered polymers or other materials selected for temperature, chemical exposure, strength, friction and installation method. Common forms include solid, split, scarf-cut and spiral designs. A split design can simplify installation in a closed groove but the gap geometry must not create a leakage or extrusion path.

Information required for selection

• Groove and mating diameters, including tolerances.
• Maximum radial or diametral clearance under pressure.
• Pressure magnitude, direction and cycling.
• Temperature range and all contacted fluids.
• Static, reciprocating or rotary movement.
• Seal size, cross-section, material and hardness.
• Available space and installation access.

Inspection before reuse

Check for flattening, cutting, spiral failure, heat damage, chemical attack and permanent deformation. Also measure metal wear. Replacing the ring without correcting excessive clearance may only postpone another failure.

For a Royal Way review, submit a dimensioned groove drawing or clear measurements, the seal specification, pressure direction, medium, temperature and quantity through Request Quote. We will not assign a pressure or sour-service capability without sufficient evidence.

Related Products

For flowline repair applications, review Hammer Union Seals. For standard sealing sizes, see AS568 O-Rings & Sealing Rings.

Reference sources

The Parker O-Ring Handbook provides general gland, clearance and backup-ring guidance. Equipment drawings and the selected material data remain controlling.