Page 313 - Reciprocating Compressors Operation Maintenance

298 Reciprocating Compressors: Operation and Maintenance

• Rebore and bush to crosshead pin bores in crosshead. Use the same
material as the crosshead for bushings or use a bronze bushing with a
flange on the inside of the crosshead.
• Repair damaged crossheads by welding and remachining. This is not
always possible. It is feasible only if material is steel,

CROSSHEAD PINS

Generally crosshead pins do not wear but may become galled or
scored. Reconditioning may be done in a variety of ways:

• Turn old pin down and make new pin bushing to suit.
• Grind pin true and build up by chroming back to standard size.
CROSSHEAD GUIDE REPAIR

Crosshead guides are either built integral with the compressor frame or
are separate and bolted to the frame. The guides form slides for the
crossheads; they must have a good surface finish and must be in line with
the centerline of the cylinder.

• Crosshead guides can be rebored in place or in the service center.
This is usually a field job because it is much cheaper to machine a
guide in place than it is to remove the guide from the foundation.
• Removable guides, such as tail rod crosshead guides, can be plated
back to standard size.
• If a guide was overheated due to lack of lubrication, the guide will
have to be checked for cracks. Try to determine if the guide is
cracked before boring is started.
• Cracks or bad sections of the guide can sometimes be repaired by
metal stitching. This is similar to inserting a piece of cast iron in the
damaged area and remachining (see earlier discussion in this chapter).

CRANKSHAFT REPAIRS

Repairs to forged crankshafts can be done in many instances, depend-
ing on type of damage, material of shaft, and size of shaft. Most crank-
shafts used in compressors are carbon steel forgings; however, some are
cast nodular (ductile) iron.