Page 306 - Reciprocating Compressors Operation Maintenance

Overhaul and Repair of Reciprocating Compressors 291

.oor MIX.
7 -.001* Max.

.005
.001* MM. out of round
.001* Max. t«jwr«d
Typical
C«nt*ra

FIGURE 4-4O. Verifying trueness of piston rod.

and built up to size. Material and method must be compatible with
the rod base material, pressure, and gas being compressed.
5. Indicate rod in the area of piston fit. This area must be concentric
with diameter of rod within .001".
6. Measure the diameter of this fit area. If more than .002" undersize,
it must be built up and reground to size (normally no wear occurs in
this area).
7. Indicate thread diameter at both the crosshead end and piston end.
These must be concentric with rod diameter within .001".
8. Indicate shoulder or collar where piston fits to rod; this must be per-
pendicular to diameter of rod within .001". If indicator shows more
than .001" runout on the shoulder or collar, it must be machined so
runout does to exceed .001".
9. With the crosshead nut and piston nut screwed on rod (be sure nuts
are facing in proper direction), indicate seating faces. These should
not run out more than .001". If runout is greater than .001", the faces
must be machined.
If the surface of the rod in the packing area is scuffed, scored, or
scratched in any manner, the rod must be turned undersize to
remove all damage and then built up to size. Both material and
method must be compatible with rod material, pressure, and gas
being compressed. If indicating rod shows a bend at piston fit area
or at either of the thread ends, the rod should be scrapped. Do not
attempt to straighten.