Page 274 - Reciprocating Compressors Operation Maintenance

Overhaul and Repair of Reciprocating Compressors 259

Cylinder bore finish should be a minimum of 16 RMS for lubricated
compressors and a minimum of 8 RMS for non-lubricated cylinders or
lubricated cylinders used at operating pressures above 2500 psi,
Note: A compressor cylinder bore that is "out of round" or tapered
cannot be corrected by honing. It must be rebored. Honing will only
result in a smooth "out of round" or "tapered" bore,

Cylinder Reboring

Correcting an out-of-round, tapered, or barrel-shaped bore is done by
reboring. After the cylinder has been corrected by boring, all tool marks
must be removed by honing as previously described.

• Rebore cylinders when the maximum measured bore diameter is
.00075" times the nominal bore diameter. This difference applies to
measurements within any circumference, plane, or to any difference
in measurements along the bore axis.
Example: Nominal bore—10,000" diameter
Maximum allowable bore difference =10 (.00075)
= .0075"
Therefore, if the minimum bore diameter is 10.0025", the maxi-
mum measured at any point should not exceed 10.010".
Note: When compressing a gas with a molecular weight less than
17 or over 700 psi differential across the piston rings, reduce the
multiplier to .0005" times nominal bore diameter.
• Maximum out-of-round diameter
1. Metallic rings—.001 "/inch of bore diameter up to maximum of
.015" regardless of bore diameter.

2. Teflon rings—.002"/inch of bore diameter up to a maximum of
.018" regardless of bore diameter.
• Taper
Maximum taper for length of bore is .0005" per inch of stroke.
• Ridges
Rebore all sizes that have a ridge of .007" to .010" at the end of
piston ring travel.