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Hardening of the dynamic face causing glazing and cracks.
Heat generated by high speed
Slow stroke speed or use alternative seal device.
Hardening of the whole seal. Loss of elasticity.
High fluid temperature. Deterioration of fluid. Compatibility of seal to fluid
Lower oil temperature. Renew Fluid. Change to different seal compound.
Hardening
Dynamic face is worn to glossy mirror-like finish.
Check oil viscosity. Use alternative seal device.
Example of Seal failures and their causes

Type of Failure

Visible Condition

Probable Cause

Possible Cure
Wear
Insufficient lubrication
Wear on dynamic lip is egg-shaped.
Rod or piston bore not concentric
Hone to within seal specs. Replace worn rod or cylinder tube.
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
Scratches on the dynamic side
Scars on the rod or bore. Foreign material in fluid.
Hone, polish, and de-burr metal parts. Flush system.
Swelling
Material soft and misshaped
Absorption of fluid. Fluid and seal are incompatible. Water in system.
Change seal compound or system fluid. Flush system.
Deterioration
Grooving
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.
Axial cuts on the dynamic side
Metal chips or other foreign material in system. Imploding air bubbles.
Flush system. Bleed air from system.
Extrusion
Extruded material on dynamic side of heel.
Gap between mating surfaces too wide. Worn bearings. Pressure extreme.
Employ back-up ring. Replace bearings. Use alternative seal.
Extruded material on static side of seal.
Uneven support surface. Undersize back-up ring.
Machine surface. Correct back-up size.
Fracturing
Chunks of material torn from 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.
Breaking off of entire dynamic side
Deterioration of material and/or fluid
Use alternative material or seal. Flush system.
SEAL FAILURES

Rod Seals

Before installing seals the following should be observed:

    * Make sure the rod has a lead in chamfer, if not, use an installation tool.
    * Chamfer or round sharp edges.
    * Cover screw threads.
    * Carefully clean all parts making sure any machining debris are removed.
    * Grease or oil housings for seals and rods to aid installation.
    * Do not use sharp tools to fit seals.

Installation into a split housing.

Installation into a split housing is relatively simple. The shape of the seal corresponds to the housing it is to be fitted in. The seal should not be allowed to twist when fitted.

When fitting the rod into the housing, the seal will need to be sized. If the rod has a long enough chamfer it will probably be suitable for this. If not, a sizing sleeve should be used.
Installation into a closed housing

For seals manufactured from polyurethane, nitrile or similar elastomer a fitting tool is recommended.

Where a fitting tool is not available or suitable the seal should formed into a kidney shape. The seal should have no sharp bends.
FITTING TIPS
Insert the seal into the groove, then apply pressure to the kidney as indicated by the arrow in Figure 2.
When the seal is in the housing, reshape by hand. Finally, resize the seal using either the rod itself, provided it has a sufficiently long chamfer, or a mandrel manufactured from a polymer material with good sliding properties. It should have a chamfer of 10-15° over 30mm.
Piston Seals

Before installing seals the following should be observed:

    * Make sure the cylinder has a lead in chamfer, if not, use an installation sleeve.
    * Chamfer or round sharp edges.
    * Cover screw threads.
    * Carefully clean all parts making sure any machining debris are removed.
    * Grease or oil housings for seals and rods to aid installation.
    * Do not use sharp tools to fit seals.

Installation into a split housing.

Installation into a split housing is relatively simple. The shape of the seal corresponds to the housing it is to be fitted in. The seal should not be allowed to twist when fitted.

When fitting the rod into the housing, the seal will need to be sized. If the cylinder has a long enough chamfer it will probably be suitable for this. If not, a sizing sleeve should be used.
Installation into a closed housing.

Installation of polyurethane and nitrile rubber seals are relatively straight forward. These will generally stretch over the piston and slot into the groove with no further adjustment required.

The installation of PTFE seals though will require the use of installation aids.

PTFE seals can be installed easier if the are heated up in oil or water to between 80
C to 100C

Do not use tools with sharp edges to stretch the seals.
For the series production installation of PTFE piston seals, the use of installation tools are recommended. These parts should be manufactured from a polymer material with good sliding properties.