Page 271 - Reciprocating Compressors Operation Maintenance

256 Reciprocating Compressors: Operation and Maintenance

* Is the repair made with sound engineering judgment?
* Is the repair done with care and proper manufacturing techniques,
such as, squareness, parallelism, and finishes?
* Are the materials used in making the repair equal or better to the
ones available from the manufacturer?

CYLINDER REPAIR AND MAINTENANCE

A regular schedule for inspection of cylinder bore and piston should be
determined as soon as the projected usage and service conditions can be
established. At the outset, make frequent inspections and keep a detailed
record of observations. Tabulate the information, and once a pattern is rec-
ognized, adjust the time span between inspections and service accordingly.
Thoroughly inspect all components for wear and damage. Inside and
outside micrometers should be used when checking cylinder bores, pis-
ton diameters, and rod diameters. Cylinder bores should be measured at
6-12 and 3-9 o'clock, at both ends and the middle. Visually inspect the
bore, counterbore, and valve ports for cracks. Use dye penetrant, if
cracks are suspected.
Problems generally found with compressor cylinders include:

1. Cylinder bores worn out of round, especially on horizontal
machines. (Wear is usually in an hourglass shape from front head to
back head.)
2. Cylinders worn to an excessive (oversize) bore dimension.
3. Water passages fouled with deposits or water treatment chemicals.
4. Air passages fouled with dirt and carbon deposits.
5. Lubricating oil passages clogged.
6. Valve seat and cover gasket surface pitted or eroded.
7. Head-to-cylinder water ports eroded.
8. Cracks in cylinder bore.

INSPECTION OF CYLINDERS

Cylinders are inspected either visually or, with greater precision, by
measuring bore size.
Visual inspection should be done at every shutdown, for example on
the occasion of a valve change-out. This can be accomplished by looking
through the valve ports and inspecting the bore for any sign of scuffing