Compression Set
- Flat-sided cross-section (one or both sides)
- O-ring takes on the shape of the groove
- Loss of seal resilience / springback
Guidance
O-Ring Failure Diagnosis
Match the symptoms you can see on a failed seal to the most likely failure modes. Select your observations and we rank the 12 common O-ring failure modes by fit, with the causes and the fixes for each.
Select the symptoms you can see
Tick every observation that matches your failed seal. We rank the likely failure modes by how many of your symptoms they explain.
Reference: 12 common O-ring failure modes
Extrusion & Nibbling
- Ragged or chipped edges on the low-pressure side
- Nibbled / bitten appearance
- Material forced into the clearance gap
Spiral Failure
- Cuts at 45° angles around the circumference
- Corkscrew / spiral tear pattern
- Twisted appearance
Thermal Degradation
- Radial cracks on the hottest surfaces
- Surface hardening / embrittlement or softening
- Discoloration
Chemical Degradation
- Blisters, cracks or discoloration
- Swelling, softening or shrinkage
- Loss of measurable hardness
Installation Damage
- Cuts, nicks, scrapes or notches
- Small skinned or peripheral cuts
- Localized failure not following a pattern
Explosive (Rapid Gas) Decompression
- Blisters, pits or splits on the surface
- Internal fractures / ruptured appearance
- Random surface ruptures after pressure cycling
Abrasion Wear
- Flattened / worn surface on one side
- Loss of material on the dynamic contact face
- Scored or polished wear band
Over-Compression
- Parallel flat surfaces with possible cracking
- Compound forced into available space
- Severe deformation
Weather / Ozone Cracking
- Fine surface cracks perpendicular to stress
- Cracking on exposed (stretched) surfaces
- Surface crazing over time
Outgassing / Extraction (Vacuum)
- Shrinkage and hardening
- Weight loss
- Loss of sealing force under vacuum
Improper Sizing / Gland Design
- Leakage with no obvious material damage
- Loose fit or excessive stretch
- Inconsistent sealing
Not sure which mode applies?
Failure diagnosis often hinges on details a photo or sample reveals. Send your observed symptoms and likely mode to Harkesh engineers — we will review the application and recommend a compound and gland design that prevents a repeat failure.
Guideline only. Values and ratings are representative at ambient conditions and are not a warranty of performance. Actual results vary with temperature, pressure, concentration and exposure time. Validate for your specific application — our engineers can help.
The most common O-ring failure modes
Most sealing failures fall into a handful of recognisable patterns, and the visible damage on the ring usually points straight to the root cause. Compression set is the most frequent: the O-ring flattens to the shape of its groove and loses the elastic springback that maintains contact stress. It is driven by excessive temperature, over-squeeze, an under-cured compound or chemical swell, and is best prevented with a low-set elastomer such as FKM, FFKM or HNBR held within a 15–30% static squeeze.
Extrusion and nibbling leave ragged, bitten edges on the low-pressure side, where the elastomer is forced into the clearance gap under high pressure — the fix is anti-extrusion backup rings, a tighter gap or a harder 90 Shore A compound. Spiral failure shows 45° cuts and a twisted, corkscrew tear when a ring slides and rolls at once in reciprocating service, pointing to surface finish, lubrication or modulus problems.
Chemical degradation appears as blisters, swelling, softening or shrinkage and signals an incompatible elastomer for the media — reselect with our compatibility data and move to FKM or FFKM for aggressive chemicals. Thermal degradation shows radial cracks, hardening or discoloration on the hottest surfaces when the temperature exceeds the compound limit, calling for a higher-temperature material such as FKM, FFKM or VMQ. Correctly naming the mode is the difference between fixing the seal once and replacing it repeatedly — when the diagnosis is unclear, our engineers can review a sample or photo and recommend a compound and gland design.