Page 110 - Improving Machinery Reliability

Chapter 3

Machinery Reliability

Audits and Reviews

Audits Versus Reviews

For the purpose of this textbook, machinery reliability audit is defined as any rig-
orous analysis of a vendor’s overall design after issuance of the purchase order and
before commencement of equipment fabrication. Reliability review is defined as a
less formal, on-going assessment of component or subsystem selection, design, exe-
cution, or testing.
Reliability audits tend to use outside resources for brief, concentrated efforts dur-
ing the first two months after issuance of the purchase order.
Reliability reviews are assigned to one or more experienced machinery engineers
who would be involved in a project from the time specifications are written until the
machinery leaves the vendor’s shop for shipment to the plant site.
The primary purpose of the audit is to flush out deep-seated or fundamental design
problems on major compressors and drivers. A secondary purpose is to determine
which design parameters should be subjected to non-routine computer analysis, and
whether follow-up reviews should employ other than routine approaches.
Machinery reliability reviews are aimed at ensuring compliance with all applica-
ble specifications. These reviews also judge the acceptability of certain deviations
from applicable specifications. Moreover, an experienced reliability review engineer
will provide guidance on a host of items which either could not, or simply had not,
been specified in writing.

Where to Concentrate Audit and Review Efforts
Reliable and efficient machinery is probably the most important factor ensuring
profitable operation of process plants. This contention becomes law in the petro-
chemical industry where economic considerations often mandate the use of single,
unspared machinery trains to support the entire operation of steam crackers produc-
ing as much as 800,000 metric tons (-1.76 billion lbs) of ethylene per year. When

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