Page 297 - Reciprocating Compressors Operation Maintenance

282 Reciprocating Compressors: Operation and Maintenance

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1 Cylinder
1 Ring 1
1
\ V
' 1
Piston

FIGURE 4-33. Effect of using standard ring in oversize bore.

and replacement is less costly than having a failure and the attendant
downtime risk.
REBUILDING COMPRESSOR PISTONS

There are several types of repair and rebuilding needed with worn or
scuffed compressor pistons. These include:

1. Remachine piston ring lands to correct worn grooves, then install
wider piston rings.
2. Turn OD of piston to remove any scoring or scuffing. Build up OD
with metal spray of proper material and remachine OD to original
diameter.
3. Repair cracks in ribs or hubs in cast iron pistons by appropriate
grinding, cleaning, and welding. Piston must be remachined after
welding on OD, hub bore, and counterbores to restore welding-
induced distortion.
Note: It is not recommended to repair aluminum pistons by weld-
ing. Aluminum alloys used for compressor pistons are generally not
weldable.
4. Reapplication of babbitt sprayed rider bands. See procedure below
for proper repair.
5. Install bushing in worn hub bore and remachine to correct size to fit
piston rod.
6. Install rider bands on pistons not originally so equipped to restore
worn and scuffed diameter. Remachine for rider bands and install by
using spray bronze or aluminum material. On some piston designs,
Teflon rider bands may be installed.