Page 305 - Reciprocating Compressors Operation Maintenance

29O Reciprocating Compressors: Operation and Maintenance

INSPECTION AND RECONDITIONING PISTON RODS

Before installing the piston/piston rod assembly in the compressor
cylinder or attempting to recondition a piston rod, inspect and measure it
thoroughly. An important part of this inspection is checking the piston
rod and the piston to be sure the assembly is able to run true to the cen™
terline of the cylinder bore.
Inspection is done by the following method:

1. Visually inspect for signs of scuffing, longitudinal scratches, dam-
aged or pulled threads.
2. Measure all diameters and lengths to determine actual sizes and
record on suitable inspection forms.
3. Non-destructively test the rod by magnaflux or magnaglow to deter-
mine if there are any signs of longitudinal scratches or signs of
cracking at threads. This is particularly important when inspecting
coated or flame-hardened piston rods.
4. Determine runout by placing the piston rod between centers or in V-
blocks and using dial indicators.
5. Determine whether the rod had been previously chrome plated or
whether the rod had been replaced by vendors other than OEM. If
so, determine the suitability of material and surface treatment.

Use the following procedures to inspect compressor piston rods:

1. Remove piston from piston rod.
2. Place piston between centers (be sure existing centers are in good
condition) or in V-blocks (see Figure 4-40).
3. With dial indicator, indicate over length of rod. Rod should not run
out more than .001".
4. Measure diameter to be sure rod is round within .001" and not
tapered more than .001" over its length, or worn undersize.
If rod is found to be worn not more than .005" undersize and still
round and not tapered, it may be used. If it is found to be more than
.005" undersized, or out-of-round or tapered more than .001", it
should be turned undersize to remove out-of-roundness and taper