Page 258 - Reciprocating Compressors Operation Maintenance

Overhaul and Repair of Reciprocating Compressors 243

must be made by companies that have experienced personnel and who
can determine whether a compressor foundation is bad and whether it is
out of alignment.
Operating a compressor with bad foundation/grout and misalignment
is extremely risky. Failure, damage, and degradation typically involve:

* Main bearings
* Crankshaft breakage
* Piston scoring
* Packing failures
* Piston rod scoring
* Crosshead shoe wear

PISTON ROD RUNOUT

Piston rod runout is a measure of how well the cylinder is lined up
with the frame and, also, how well the internals of the compressor (pis-
ton, rod, crosshead) are lined up with each other and the frame and cylin-
der combination. This runout is checked and adjusted with all parts
"cold"; the ambient temperature should be in the 60°-68°F range.
Prior to performing runout measurements, cylinder and support, cylin-
der frame head, and doghouse nuts should be properly set or torqued. Oil
scraper and packing should be loosened to prevent binding. Runout
should be set during erection; followup measurements are needed when-
ever regrouting, major parts replacement, overhaul, etc., are performed.
The following procedure is a guide for obtaining and interpreting
runout readings using dial indicators.

* Initial setup. Use a dial indicator with facilities to be securely fas-
tened to a non-moving surface in or on the housing. The compressor
piston is to be set at its maximum outboard stroke by barring the unit.
The dial indicator traveling pin is to be positioned anywhere along
the rod where it is convenient.
To measure horizontal runout, set the pin on the horizontal center-
line of the piston rod. For vertical runout, the vertical centerline is
used. Both vertical and horizontal runout are extremely important
and both are to be measured.