Page 164 - Reciprocating Compressors Operation Maintenance

f SO Reciprocating Compressors: Operation and Maintenance

Lift limitation is obtained in different ways in different designs and,
therefore, cannot be readily specified. Manufacturer's instruction books
are usually quite detailed in this regard and should be carefully followed.
Above all, do not alter the original lift without consulting the manu-
facturer,

VALVE FAILURE ANALYSIS

When valve failure analysis is undertaken, component appearance
must first be investigated to determine causes of failure.
Valve failures can be classified as resulting from three general causes:

1. Wear and fatigue
2. Foreign materials
3. Abnormal mechanical action

Wear and Fatigue

Wear, as such, cannot be completely eliminated. It can be minimized
by proper lubrication, design, and selection of materials.
Most valves require some means of guiding. Wear at the guides, if
severe, can result in sloppy action, cocking, poor seating, and failure.
Wear must never be permitted to develop to this degree.
Fatigue is the result of repeated cyclic stress. The stress level, as well
as the stress range, must be considered in any design. However, barring
abnormal action, well-designed valves have a good record of withstand-
ing fatigue.
Both wear and fatigue are adversely affected by abnormal mechanical
action.

Foreign Materials

Foreign materials may be listed in the following categories:

1. Liquid carryover
2. Dirty gas
3. Carbon formation
4. Corrosive elements