Industrial seal self study guide - SKF.com

Lip Wear
Look for clues in the sealing member of the seal. A small cut, nick
or abrasives continually laying at lip/shaft interface could be the source
of the leak. But if everything looks intact, it’s time to look at the wear
pattern of the lip (fig. 9g).
Causes
A new seal which has never been installed has a sharp edge at
the contact point. Following a period of normal operation, the lip’s
sharp edge will be flattened some by normal wear. If the lip has
been substantially worn away, the seal may not be getting enough
lubrication, the shaft may be corroded, the vent in the lube system
may be blocked, or the finish too rough. Extreme wear could also be
caused by shaft-whip (DRO). It could also be caused by excess
pressure or by misalignment (STBM).
A
B
Corrective Actions
Check the shaft-to-bore alignment. Correct the alignment. Provide
proper lube for the seal if there isn’t enough. Repair the shaft if the
shaft is not properly finished. Use a seal designed to exclude abrasive
contaminants if there is an abrasive build-up. Clean and open vents
that are blocked to reduce pressure. If conditions warrant, consider
using a seal designed for high pressure.
Outer Case Damage
A “curled” or rolled edge of the seal metal case indicates damage.
The damaged zone may feel rough.
Causes
The housing bore may have a square corner or not have had a proper
lead-in chamfer. Without it, the seal may bind on insertion. This can
cause cocking or create a beveled or rolled end for part of its circumference.
It’s also possible that the bore diameter and tolerance are
incorrect.
Corrective Actions
Insure that the bore does not start with a square corner. Per industry
standard, it should have a 15˚-30˚ angle and the corners should be
smooth and free of burrs. Confirm that the bore size is correct for the
seal.
C
The illustration above compares
the lip on a new seal (A) to one
with normal wear (B) and one with
excessive wear (C) (fig. 9g).
Examining the Outer Shell
No Chamfer
The beveled edge (chamfer) on the
leading edge of the bore provides a ramp
for starting the seal straight. Without it,
it is virtually impossible to get the seal
installed correctly. A 15˚-30˚ angle, clean
and burr free, is recommended. (fig. 9h).
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