Nuraseal - Seal Failures and Possible Causes

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Nuraseal Sealing Products | Filton® Rotary Union Products

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Seal Failures and Possible Causes

Nuraseal makes every effort to ensure that all seals shipped meet or exceed the requirements as indicated by your purchase order. Our high quality manufacturing processes and inspection procedures are designed to provide you with the level of performance you demand from your seals in all of your applications.

It is important to recognize that seals wear over time and weaken. Eventually, they will need to be replaced and, in extreme cases, they may fail for any number of reasons including improper maintenance, incorrect installation procedures or a variety of other reasons. In many cases, it is possible that a seal failure points to another part of the system that has failed or been compromised.

Visually inspecting worn seals will often reveal possible causes (and therefore possible cures) for conditions encountered in sealing applications. The following checklist suggests some of the more common causes of sealing failure.

FAILURE CONDITION	VISIBLE EVIDENCE	POSSIBLE CAUSE	POSSIBLE SOLUTION
WEAR	• Glossy mirror-like finish evident on dynamic face	• Lubrication is insufficient	• Check the viscosity of the oil and ensure adequate lubrication • Consider an alternate sealing device
	• Dynamic lip shows egg-shaped wear pattern	• Rod or piston bore is not concentric	• Check seal specs and hone as required • Replace worn rod or piston cylinder
	• One side of the dynamic lip shows abnormal wear	• Worn bearing or wear ring • Possible excessive lateral load	• Replace bearing • Increase the bearing area
HARDENING	• Glazing and cracking evident on the dynamic sealing face	• Excessive heat generated by high speed	• Decrease the stroke speed. • Consider alternate sealing devices
HARDENING	• Loss of elasticity and hardening of the seal	• Excessive fluid temperatures • Deterioration of the fluid • Possible seal and fluid compatibility problems	• Decrease fluid temperature • Replace the fluid • Change to a different sealing compound
SCARRING	• Cut or dent evident on lip	• Incorrect installation, possibly from a tool • Improper storage prior to installation (nail, peg, etc.)	• Review proper installation procedures and avoid the use of any tool with sharp edges • Store flat in a sealed container such as a box of sealed plastic bag
SCARRING	• Scratches evident on dynamic side	• Scars (or burrs) on rod or piston bore • Contamination or foreign material in the fluid	• Clean, hone, polish and be-burr metal parts in contact with seal • Flush the system and replace the fluid
MATERIAL DETERIORATION	• Loss of elasticity • Material cracks and easily crumbles	• Excessive fluid temperatures • Exposure to ozone or sun	• Decrease fluid temperatures • Store out of sunlight and away from arc welding areas
SWELLING	• Material is soft and has lost its shape	• Absorption of fluid by material • Incompatible material and fluid • Water in system	• Change to a different sealing compound • Flush the system and replace the fluid
GROOVING	• Axial cuts evident on the dynamic side	• Metal or other foreign particles in the system • Air bubbles in the fluid	• Flush the system and replace the fluid • Bleed air from the system
FRACTURING	• Torn and missing pieces of material evident on the dynamic side	• Excessive back pressure	• Inspect relief valves
	• Burnt and broken material evident on pressure side of seal	• Residual air explosion at high pressure (dieseling)	• Investigate maximum pressure • Bleed air from the system
	• Long cracks evident in the "V" portion of the seal	• Frequent high pressure spikes or shocks • Start-up temperatures low	• Consider an alternate sealing device • Allow for adequate warm-up prior to applying pressure to the system
	• Material broken off from entire dynamic side	• Material and/or fluid deterioration	• Consider an alternate sealing device or material compound • Flush the system and replace the fluid
EXTRUSION	• Extruded material evident on heel of the dynamic side	• Gap between mating surfaces is too wide • Bearings are worn • Excessive pressure	• Consider using a back-up ring or alternate sealing devices • Replace bearings • Investigate causes of the excessive pressure
EXTRUSION	• Extruded material evident on static side of seal	• Support surface is uneven • Back-up ring may be undersize	• Have the support surfaces machined • Install the correct size back-up ring