Careful shaft seal design can minimize the number of failures, but it is impossible to eliminate failure entirely. What follows is a look at the most common causes of shaft seal failure, along with suggestions on how these failures might be avoided. This is not a comprehensive list; rather, these are the causes you are most likely to see. Rule out all of these possibilities before assuming other causes.

BACKWARD INSTALLATION
BLISTERS
BROKEN LIP
COCKED SEAL
CORRODED SPRING
CRACKED OR HARDENED LIP
CUT LIP
DAMAGED CASE (IMPROPER BORE FINISH)
DAMAGED CASE (POOR BORE CHAMFER)
DAMAGED CASE (POOR HANDLING)
EXCESSIVE LIP WEAR
EXCESSIVE MATERIAL SWELL
EXCESSIVE STBM OR RUN-OUT
EXCESSIVE SHAFT WEAR
INVERTED LIP
MATERIAL/FLUID INCOMPATIBILITY
MISSING SPRING
OIL COKING
PAINT CONTAMINATION
SCRATCHED OR NICKED SHAFT
SEALANT CONTAMINATION
SHAFT LEAD
STICK-SLIP