Seal Failure Causes

TYPE OF FAILURE

VISIBLE CONDITION

PROBABLE CAUSE

POSSIBLE CURE

Hardening

Hardening of the dynamic face has caused glazing and cracks.

Heat generated by high speed.

Slow stoke speed or use an alternative seal device.

Hardening of the whole seal. Loss of elasticity.

High fluid temperature.

Deterioration of fluid.

Compatibility of the seal to the fluid.

Lower the oil temperature.

Renew fluid.

Change to a different seal compound.

Wear

Dynamic face is worn to a glossy mirror-like finish.

Insufficient lubrication.

Check oil viscosity or use an alternative seal device.

Wear on dynamic lip of seal is egg-shaped.

Rod or piston bore is not concentric

Hone to within seal specifications or replace the worn rod or cylinder tube.

Signs of abnormal wear on one side of the dynamic lip.

Worn bearing or wear ring. Excessive lateral load.

Replace bearings. Increase bearing area.

Scarring

Cut or dent on the lip.

Storage on a nail or peg.

Improper installation tool.

Store flat in a plastic bag in a closed cardboard box.

Installation tools should not have sharp edges.

Scratched on the dynamic side.

Scars on the rod or bore or foreign material in fluid.

Hone, polish and deburr metal parts or flush the system.

Swelling

Material is soft and misshaped.

Absorption of fluid.

Fluid and seal are incompatible.

Water in the system.

Change the seal compound or system fluid.

Or flush the system.

Deterioration

Cracks and loss of elasticity.

Material easily crumbles.

High fluid temperature.

Exposure to ozone or sunlight.

Lower oil temperature.

Store seals away from sunlight and arc welding area.

Grooving

Axial cuts on the dynamic side.

Metal chips or other foreign material in system.

Imploding air bubbles.

Flush System.

Bleed air from the system.

Extrusion

Extruded material on the dynamic side of heel.

Gap between mating surfaces is too wide.

Worn bearings.

Pressure extreme.

Employ a back ring.

Replace the bearings.

Use an alternative seal.

Extruded material on the static side of the seal.

Uneven support surface.

Undersized back-up ring.

Machine surface.

Correct back up size.

Fracturing

Chunks of material torn from the dynamic side.

Excessive back pressure.

Check relief valves.

Pressure side of seal burned and broken.

Explosion of residual air at high pressure. ‘Dieseling’

Check maximum pressure

Bleed air from system.

Long cracks in the “V” portion of the seal.

Frequent high pressure shocks or spikes.

Low temperature start-up.

Use alternative style seal.

Warm system before applying pressure.

Entire dynamic side breaking off.

Deterioration of material and/or fluid.

Use alternative material or seal.

Flush system.