Page 367 - Reciprocating Compressors Operation Maintenance

352 Reciprocating Compressors: Operation and Maintenance

CORRECT COMPRESSOR PARTS

The importance of obtaining and using correct compressor parts can-
not be overemphasized. Compressor users traditionally buy materials
from the lowest-price vendor. But this approach fails to consider true life
cycle costs. Purchasing shoddy items only adds to total costs, causes
more rejected parts, unscheduled shutdowns, and increases employee dis-
satisfaction because workers are forced to work with inferior parts.
Because of the compressor manufacturer's inability to supply parts on
a timely basis and at reasonable cost, users try to find alternative sources
of supply for critical parts. Unfortunately, there are many aftermarket
suppliers of compressor parts whose products do not meet the safety and
reliability requirements of modern process plants. Their parts are often
not made with proper materials, properly engineered to perform the func-
tion required, or manufactured to proper standards (tolerances, square-
ness, parallelism, surface finish, etc.).
Many shops have basic machine tools but lack technical knowledge of
compressors. Although they are often able to sell at a low price, their
parts are actually higher priced when failure takes place. Usually a shop
of this sort will take an old worn part and make a drawing by "reverse
engineering" that part. This reverse engineering has two major draw-
backs that a machine shop cannot overcome. It does not provide any
information on optimum tolerances, and it does not tell whoever copies
the part exactly how it was produced in the first place. This discrepancy
can spell the difference between success and failure,

INSPECTION OF COMPRESSOR PARTS

Regardless of the source, all compressor spare or replacement parts
should be inspected carefully. It has been found that 8% to 10% of all
parts, including those from qualified suppliers, do not meet material or
dimensional requirements or have defects such as cracks in coatings.
This figure can be as high as 85% to 90% on least-cost or unqualified
suppliers.
Therefore, an inspection program is mandatory for incoming com-
pressor parts and materials. This inspection should be performed imme-
diately upon receipt, and no material should be put into stores without
inspection.