| 1.1 Lip Wear |
| Primary Causes | Failure Mode | Causes | Suggestion |
| Rough shaft surface |
Excessive lip wear and traces on the lip circumferential direction.
|
Shaft surface roughness exceeds Ra = 0.2-0.8μm and leads to excessive wear. |
Finish the shaft to surface roughness to Ra = 0.2-0.8μm. |
| Change the shaft to which the surface roughness is compatible. | |||
| Insufficient lubrication | Excessive lip wear. | Improper lubrication can cause accelerated shaft wear. | Change lubricant compatibility with lip and quantity of lubricant reaching seal. |
| High internal pressure |
Excessive lip wear.
|
The internal pressure exceeds the seal limit. | Use pressure type seal. |
| Design a vent in the application to release the pressure. | |||
| Contaminants |
Excessive lip wear. Nicks, scratches, or cuts at lip contact area.
|
Dust and mud adhere between the shaft and lip causing lip wear, nicks, scratches or cuts and the lip contact area. | Shaft and seal (word) contaminated by dust or mud during installation. |
| Add a dust lip design in the application. |
| 1.2 Eccentric Wear |
| Primary Causes | Failure Mode | Causes | Suggestion |
| Seal cocking |
Asymmetric contact between lip and shaft.
|
Seal installation. | Use proper installation tool. Check installation force to insure complete installation. |
| Insufficient or improper bore chamfer. | Provide proper amount of lead in angle for chamfer. | ||
| Excessive seal interference with rubber O.D. seal. | Check bore I.D. and seal O.D. for proper dimensions. | ||
| Poor alignment |
Asymmetric contact between lip and shaft.
|
Poor initial alignment. | Review design and assembly operations and provide accurate alignment. |
| 1.3 Lip Damage |
| Primary Causes | Failure Mode | Causes | Suggestion |
| Improper shaft chamfer | Lip damage visually. | Incorrect chamfer size and angle. | Adjust the chamfer size and angle, and smear lubricant on chamfer when installing. |
| Improper installation | The chamfer has burrs causing lip damage when installing. | Cut the burrs. | |
| Improper lip contact | Lip contacts sharp bodies when assembling or transporting. | Prevent contacting seal lip during assembling and transporting. | |
| Contaminants |
Contaminants packed in seal area.
|
Failure of auxiliary lip. | Look for cut or damaged auxiliary. |
| Look for auxiliary lip worn excessively. |
| 1.4 Lip Harden |
| Primary Causes | Failure Mode | Causes | Suggestion |
| Insufficient lubrication |
Lip harden and has crack.
|
Lubrication is not enough that cause dry running. | Supply lubrication oil exceeding the seal level. |
| High temperature | Lip harden and has crack. | The temperature exceeds the rubber heat-resistance limit. | Change the rubber to good heat-resistance material. |
| High internal pressure | Contact width is large and lip is hardened and has cracks. | The internal pressure exceed the seal limit. | Use pressure type seal. |
| Design a vent in the application to release the pressure. |
| 1.5 Softening or Swelling |
| Primary Causes | Failure Mode | Causes | Suggestion |
| Improper lip material |
Lip softens or swells.
|
Volume change of material very high. |
Refer to elastomer physical data and check fluid. |
|
Reversion. |
Check elastomer/fluid compatibility specifications. | ||
|
Exposure to solvent used during teardown. |
Review teardown procedure and elastomer compatibility specifications. | ||
| Operational contamination of fluid being sealed. | Check for possible exposure to unspecified media coming in contact with seal. |
| 1.6 Inverted Lip |
| Primary Causes | Failure Mode | Causes | Suggestion |
| Improper shaft chamfer |
Whole or part of lip inverted.
|
Incorrect chamfer size and angle. | Adjust the chamfer size and angle, and smear lubricant on chamfer when installing. |
| Improper installation | Lack of proper concentricity assembly. | Adjust the concentricity and smear lubricant on chamfer when installing. | |
| High internal pressure | Circumferential tear behind lip. | Look behind lip at base for circumferential tear caused by pressure or fatigue. |
| 1.7 Spring Fall Off |
| Primary Causes | Failure mode | Causes | Suggestion |
|
Improper shaft chamfer |
Whole or part of spring falls off.
|
Incorrect chamfer size and angle. | Adjust the chamfer size and angle, and smear lubricant on chamfer when installation. |
| Improper installation | Lack of proper concentricity assembly. |
| 1.8 Tears in Lip Area |
| Primary Causes | Failure Mode | Causes | Suggestion |
| Improper removal | Tears in lip area | Caused during disassembly or removal. | Review teardown and seal removal methods and check tools used. |
| High internal pressure |
|
Circumferential tear behind lip. | Look behind lip at base for circumferential tear caused by pressure or fatigue. |
| 1.9 Seal Distort |
| Primary Causes | Failure Mode | Causes | Suggestion |
|
Improper installation |
Seal distorts that change the contact width.
|
The improper installation tool that cause seal distorts. | Improve the installation tool. |
| 1.10 No Wear on Seal Lip |
| Primary Causes | Failure Mode | Cause | Suggestion |
| Shaft defect | Shaft surface has defect visually. | Change contact position between shaft and lip. | |
| Rotating direction |
Processed shaft in a lathe had directional when rotating the shaft (x40).
|
Use plunge grinding to change property of direction. |
|
| Offset |
Poor alignment of shaft.
|
Change to the seal that can bear poor alignment. | |
| Make sure the shaft and bore is concentric. | |||
| Wrong installation |
Wrong installation direction.
|
Turn seal oil side toward to oil. | |
| Shaft wear |
Contaminants attached on the seal or shaft when assembling the seal. | Prevent mud and dust contaminate shaft and seal when assembling the seal. | |
| Lubrication went bad and mixed contaminants. | Avoid overusing the lubricant. | ||
| Contaminants entering the lip that caused wear. | Have a dust lip design. |
| Primary Causes | Failure Mode | Causes | Suggestion |
| 2.1 Seal Distort | Seal distort | Improper installation tool causing the seal distort. | Use the proper installation tool. |
| When the seal distorts on a certain location. | Prevent the seal from dropping or impacting. |
| 2.2 Cocked Seal |
Before removing the seal, the seal cock can be seen by eyes.
After removing the seal, there is eccentric wear |
Bore dimension is too small to install the seal that causes seal cock. | Use the suitable bore size |
| No bore chamfer that causes seal damage during installing. | Chamfer the bore. | ||
| Use the improper installation tool. | Use the proper installation tool. |
| 2.3 Seal is tightly wedged |
Bore damaged, seal O.D. rubber extruded
|
Bore I.D. is too small to install the seal that causes seal damaged. | Use the suitable bore size |
| No bore chamfer that causes seal damage during installing. | Chamfer the bore. | ||
Installation tool is not parallel with the bore that causes the seal extruded. |
Require the installation tool is parallel with the bore. |
| 2.4 No wear on seal lip | Contaminants attach the bore and seal OD. and damaged the bore surface during installing. | Avoid contaminant attaching on the bore and seal during installing. | |
| Assembly bore surface has pits or is too rough. | Pay attention to surface roughness. | ||
| Bore chamfer has burrs that cause bore surface damage. | Trimming the burrs of the bore chamfer. |
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