Improperly installed seals likely will fail quickly. Symptoms of damage caused by a hammer blow during installation include visible dents on the seal back, a distorted sealing element or a garter spring that pops out. All are causes for concern and necessitate seal replacement.
Other factors ranging from possible media intrusion to undue pressure within a seal cavity can compromise seal performance. Also, it pays to review maintenance and operating practices to see if they could adversely impact sealing systems.
The central message here is to confirm the seal has been installed properly, runs within specified operating condition ranges and benefits from the proper lubricant.
What is the source of the leak? It's helpful as a reference point to determine whether the leak is in the inner or outer diameter of the seal. If you can't locate the leak, add ultraviolet dye to the sump or spray white powder on the area. After operating for 15 minutes, use ultraviolet light to show the leakage source. In addition, documenting when the leak first occurred may relate it to a change in maintenance or operating procedures.
What are the initial best practices when analyzing failures? When a seal fails, follow these five basic steps:
1. Inspect the seal before removal. Check the condition of the area, note the amount of leakage that has occurred and determine the source of the leakage.
2. Wipe the area clean and inspect for:
• nicks on the bore chamfer;
• seal cocked in the bore;
• proper seal installation;
• shaft-to-bore misalignment;
• seal looseness in the bore;
• seal case deformation; and
• paint on the seal.
3. Rotate the shaft to ascertain whether there's excessive end-play or run-out, which can indicate misalignment issues.
4. After removing the seal, check for:
• rough bore surface;
• shaft cleanliness (clean and free of carbon?);
• coked lube on the shaft;
• shaft damage;
• flaws or voids in the bore;
• shaft corrosion; and
• shaft discoloration.
5. Identify the seal style and materials and inspect for:
• primary lip wear;
• primary lip conditions;
• wear or damage to the seal's outer diameter; and
• spring damage.
Your observations will help pinpoint the failure's root cause and appropriate remedial actions to prevent repetition.
SUCCEED WITH SEALS
Optimizing a sealing system truly is a balancing act. Carefully identifying the application's requirements, evaluating all conditions and adopting a holistic approach to seal specification with a system-wide perspective will contribute significantly to how a seal performs and for how long. Partnering with an experienced manufacturer of bearings, seals and lubricants can help maximize system potential and minimize problems.
RICK D. FARRIS is director of platforms and brands for SKF USA Inc., Kulpsville, Pa. E-mail him at Rick.D.Farris@skf.com.