Compression set
The ring stays flattened after removal instead of springing back round. Usually caused by excessive heat exposure, wrong hardness for the application, or a compound with poor elastic memory — check operating temperature against the compound's rated range first.
Extrusion / nibbling
Small bites or a ragged edge on the low-pressure side of the seal, caused by the O-ring squeezing into the gland clearance gap under pressure. Points to excessive clearance, worn hardware, or a hardness too low for the working pressure — a harder compound or back-up ring usually resolves it.
Chemical attack (swelling or shrinkage)
Swelling, softening or blistering signals the compound is absorbing the process fluid — a compatibility mismatch, not a manufacturing defect. Shrinkage and hardening instead point to a fluid extracting plasticizer from the compound.
Spiral failure
A helical twist pattern around the ring's circumference, almost exclusive to dynamic (reciprocating) seals with excessive stroke length or insufficient lubrication. Often resolved with a lower-friction compound or surface treatment rather than a material family change.
Send us the failed part
For any recurring failure, FITCO's technical support reviews the failed ring alongside your operating parameters — fluid, pressure, temperature, stroke, gland dimensions — to isolate whether the fix is material, tolerance or groove design.