Page 397 - Improving Machinery Reliability

Chapter 9

Spare Parts and Their Effect

Spare Parts Philosophies
This many-faceted topic is sometimes neglected because it seems to defy solution.
After all, the determination of required spare parts seems to be an educated guess at
best. Yet unless a policy is established and spare parts procured, a startup can be in
serious trouble before it even gets off the ground.
A solid review of failure statistics can provide help with and justification for spare
parts recommendations. Historically, problems with major unspared machinery have
caused commissioning or startup delays in one out of two train installations without
reliability reviews, and in one out of six or seven train installations employing pre-
installation reliability reviews. In either case, centrifugal compressors and steam tur-
bines have experienced the bulk of the difficulties, followed by large gear-speed
increaser units, electric motors in size categories above 1000 HP, reciprocating com-
pressors, gas turbines, and gas expanders. Principal parts affected are tabulated in
Table 9-1. Also, Table 9-1 makes an attempt to list spare parts recommended to be
stored for initial startup operations and spare parts to be kept on hand for routine,
post-startup operation. The relative frequency of replacement or repair is indicated
by numbers ranging from 5 (high frequency) to 1 (low frequency).

Spare Parts Storage and Retrieval

The best source for information and sound recommendations on spare parts stor-
age and retrieval is not necessarily an existing petrochemical plant. A reputable con-
sulting company specializing in warehousing and inventory control is often better
qualified to set up hardware and software systems to serve this function adequately
and efficiently.
Inefficient storage and retrieval will result when major turbomachinery rotors are
not hung vertically or when they have to be shipped to storage facilities away from
the plant location. Inefficient storage and retrieval will also result when spare parts
for one compressor are stored at one end of the building and parts for another com-
pressor are stored near the opposite end, and when parts are not properly cross refer-

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