Page 260 - Reciprocating Compressors Operation Maintenance

Overhaul and Repair of Reciprocating Compressors 245

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FIGURE 4-f O. Allowable piston rod runout vs. cylinder running clearance.

live point in the stroke can be selected for taking the reading. Typically,
this will be just before, or just after, bottom dead center (BDC), when
the dynamic forces on the piston and crosshead have a minimal effect on
the reading.
Third, since we know where the center of the piston is at this instant,
the monitor can correct for the geometry of the machine and display the
amount of actual rider band wear.
Bently-Nevada's Model 3300/81 Monitor provides two levels of
alarm, Alert and Danger, for each channel. This monitor eliminates the
need to periodically stop the machine and inspect for rider band wear. In
addition, the monitor provides the information to develop a wear trend as
part of a predictive maintenance program, unlike other rod drop indica-
tors that provide only an alarm on excessive rider band wear.

PRELIMINARY CHECKS IF RUNOUT EXCEEDS LIMITS

If the guidelines above have been closely followed and runout cannot
be set at the proper limits, the following checks are recommended.