Page 196 - Reciprocating Compressors Operation Maintenance

182 Reciprocating Compressors: Operation and Maintenance

FIGURE 3-44. Unfavorable increase in coefficient of thermal expansion of
PTFE with temperature (Source: Burgmann Seals America, Houston, Texas),

Causes of Abnormal Wear

Causes of abnormal wear include the following:

* Temperature. Changes in temperature can put packing back to the
high wear rate of the initial wear out/wear in cycle. Radical changes
in cylinder or packing temperature can be caused by failure of the
cooling system, excessive cylinder temperature, and sticking of the
rings, that is, excessive friction.
• Lubrication. If lubrication is thinned beyond the point of effective-
ness by the gas or by excessive temperatures, metal contact can
occur, resulting in high friction temperatures and excessive wear.
Buildup of gummy or sticky carbon deposits due to poor lubrication
or reaction with the gas can cause restriction of free movement of the
rings, further contributing to excessive wear.
• Blow-by. Caused by improper break-in or erosion due to leakage past
the bore of the rings after a sudden temperature change, blow-by can
lead to excessive wear.
* Moisture. Causing pitting, erosion, or corrosion to take place on the
rubbing surfaces during shutdown, moisture can lead to unusual
abrasive conditions.