Industrial seal self study guide - SKF.com

Troubleshooting (cont...)
Pressure Blow-Out
Another visible seal problem is a ruptured or inverted seal lip. Either
problem results in lip leakage (fig. 9n).
Causes
Pressures exceeding seal design limitations can cause seal rupture,
inverted lips and resultant lip leakage.
Too much pressure can
rupture the seal lip (fig. 9n).
Extreme lip wear (B) is a sign of
excess pressure. Note the lip with
pressure (A) (fig. 9o).
Corrective Actions
Check the seal cavity for excess pressure. Provide vents to reduce pressure,
or use a seal designed for high pressure applications (CRWA5).
Pressure Lip Wear
Signs of excessive pressure include extreme lip wear and lip leakage.
Causes
Excess pressure can crush the lip against the shaft. Heavy friction will
eventually force the garter spring through the lip. Excess pressure can
blow the lip completely off (Fig. 9o).
Corrective Actions
We recommend two ways to prevent seal failure caused by excessive
pressure. First, check the air vents to be sure they are clean. If not
open them to reduce pressure. Dirt or paint may block proper air flow.
Second, if the system is clean, try using a medium pressure seal such
as the CRW5 and CRWA5. Make sure the system operating parameters
are within the seal’s capability.
84
Chemical swelling
Incompatibility between the lip
material and the operating media,
including lubricants, can produce
major swelling of the seal material.
Above is a before (1) and after (2)
example of the gross damage
you may see from chemical
incompatibility.(fig. 9p).
Chemical Swelling
A swollen, distorted appearance of the seal rubber element combined
with a “soft” feel can indicate incompatibility between the lip compound
and the media being retained or excluded.
Causes
The rubber is experiencing swell, an increase in volume resulting from
the compound absorbing the attacking media. This displacement of the
rubber molecular structure reduces the physical strength of the rubber
leading to rapid wear and failure. In extreme cases, the rubber may
dissolve completely. With some compounds, heat or other agents can
also be responsible.
Corrective Actions
Consult seal catalogs and investigate to make sure that the selected
seal compound is acceptable for the media and operating conditions.
Sometimes a rubber type can be sensitive to a particular media but
still be adequate in the expected application but in other cases it can
be ruined.