Why Seals Fail in High-Stress Applications

Why it happens:

• Sustained temperature accelerates polymer relaxation
• The elastomer's crosslink network breaks down over time
• The seal loses the spring-back that keeps it energized against the gland

How engineers prevent it:

• Specify a material with higher temperature capability for the application. FKM and HNBR retain resilience in demanding conditions where standard nitrile would relax.
• Confirm compound performance at the actual service temperature, not a laboratory ambient.
• Design the gland to the compound's manufacturer specifications.
• Request compound performance testing and traceability documentation before production release.

Where it shows up: 

• Aerospace engine and brake systems, industrial hydraulics, oil and gas surface equipment.

Abrasion failure occurs when repeated contact between a seal and a moving surface removes material from the seal face. Over time, the sealing edge thins until leakage begins. Abrasion is a common cause of dynamic seal failure in agricultural, construction, and mining equipment.

Contributing factors:

• Rough or corroded shaft surfaces
• Abrasive particulate in the sealed media
• Continuous rotation or long-stroke reciprocation
• Inadequate lubrication at the seal interface

Prevention strategies:

• Match seal material to the abrasive load. Polyurethane holds up in high-load, high-abrasion service common on construction equipment. PTFE-based materials handle high-particulate rotary applications.
• Add wiper or excluder seals ahead of the primary seal to keep contaminants out of the gland.
• Use rotary lip seals designed for the specific shaft speed and media.
• Specify a shaft surface finish appropriate for the seal type.

Symptoms:

• Visible swelling or shrinkage
• Hardening, softening, or surface tackiness
• Blistering, cracking, or checking on the seal surface
• Loss of tensile strength or elongation

Prevention:

• Verify compatibility against manufacturer resistance charts before specification.
• For aggressive chemistries, move up the material ladder. FKM handles fuels and many aggressive chemicals. FFKM handles the most extreme temperature and chemical environments, including semiconductor and chemical processing service.
• For sour gas (H₂S), specify a sour-gas-resistant compound engineered for the service.
• Retest compatibility when a customer changes fluid formulations. FTIR analysis can confirm a compound matches an approved reference sample.

Signs of thermal failure:

• Cracking, checking, or hardening of the seal surface
• Chalky residue on the seal or mating surface
• Loss of elasticity at ambient temperature after service
• Discoloration, often darker or chalky

Prevention:

• Match the compound's continuous-use rating to the maximum sustained service temperature, not the average.
• Account for pressure-induced heat rise in dynamic applications.
• For extreme heat, move to FFKM, PEEK, or PTFE-based constructions. PEEK maintains high mechanical strength at elevated temperatures.
• Add thermal barriers or insulate the seal area where feasible.

Extrusion happens when pressure forces a seal into the clearance gap between mating parts. Repeated pressure cycles nibble away at the extruded material until the seal loses cross-section and leaks. It is a common failure mode in high-pressure hydraulic systems and downhole tools.

Prevention:

• Minimize the clearance gap through tighter tolerances and gland design.
• Add anti-extrusion backup rings in PTFE, PEEK, or fabric-reinforced material.
• Specify a harder compound for high-pressure service.
• Design glands to the compound manufacturer's pressure class recommendations.
• Where it shows up: hydraulic cylinders, downhole tools, high-pressure valves.

Explosive decompression, sometimes called rapid gas decompression (RGD), happens when a seal absorbs gas under pressure and the pressure drops faster than the gas can safely escape. The trapped gas expands inside the seal, causing internal ruptures and surface blistering. It is a common cause of seal failure in oil and gas service.

How engineers prevent it:

• Specify compounds engineered for rapid gas decompression service.
• Use composite blends and hardness levels validated for the pressure drop rate expected in the application.
• Confirm material selection with performance testing and traceability documentation before deploying in critical service.
• Where it shows up: high-pressure gas systems, downhole equipment, control valves, and reactors in the energy sector.