Page 268 - Root Cause Failure Analysis

256 Root Cause Failure Analysis

Table 22-2 Common Failure Modes of Rotary, Positive-Displacement Compressors
1

Sliding Vane
Sliding-vane compressors have the same failure modes as vane-type pumps. The
dominant components in their vibration profile are running speed, vane-pass fre-
quency, and bearing-rotation frequency. In normal operation, the dominant energy is
at the shaft’s running speed. The other frequency components are at much lower
energy levels. Common failures of this type of compressor occur with shaft seals,
vanes, and bearings.

Shaft Seals
Leakage through the shaft’s seals should be checked visually once a week or as part of
every data-acquisition route. Leakage may not be apparent from the outside of the
gland. If the fluid is removed through a vent, the discharge should be configured for
easy inspection. Generally, more leakage than normal is the signal to replace a seal.
Under good conditions, the seals have a normal life of 10,000 to 15,000 hours and
should be replaced routinely when this service life has been reached.