Page 111 - Improving Machinery Reliability

Muchinery Reliability Audits and Reviews 83

plants in this size range experience emergency shutdowns of a few hours’ duration,
flare losses alone can amount to $400,000 or more. Evidently, the incentives to build
reliability into the machinery installation are very high. This is generally recognized
by contractors and plant owners who allocate funds and personnel to conduct relia-
bility reviews before taking delivery of the machinery, during its installation, or even
after the plant goes on stream.
Of course, reliability assurance efforts made before delivery of the machinery are
more cost effective than post-delivery or post-startup endeavors aimed toward the
same goals. However, the questions remain how to optimally conduct these efforts,
how to man them, and which components or systems to subject to close scrutiny.
This is where an analysis of available failure statistics will prove helpful. A review
of the failure statistics of rotating machinery used in modern process plants will help
determine where the company’s money should be spent for highest probable returns.
Moreover, failure statistics can often be used to determine the value of and justifica-
tion for these efforts.
Experience shows that a petrochemical project in the $800,000,000 range would
optimally staff machinery reliability audits with four engineers for a four-month
period, and machinery reliability reviews with two engineers for a period of 2-3
years. The total cost of these efforts would be in the league of $800,000-$950,000. If
this sounds like a lot of money, the reader may wish to contrast it with the value of a
single startup delay day, say $550,000, or the cost of two unforeseen days of down-
time-perhaps accompanied by the thunder of two tall flare stacks for the better por-
tion of two days.
Machinery reliability audits and reviews can be a tremendously worthwhile
investment as long as they are performed by experienced engineers. Of course, this
presupposes that a perceptive project manager will see to it that the resulting recom-
mendations are, in fact, implemented.

Rotordynamic Design Audits*
By far the most prevalent and also most important design audit effort is focused
on turbomachinery rotordynamics. It is in this area that design weaknesses can often
be spotted and appropriate changes implemented before the equipment leaves the
manufacturer’s shop. Large multinational petrochemical companies are sometimes
staffed to handle these audits. However, in most instances this audit task is entrusted
to independent consulting companies with the experience and technical resources to
perform this critically important task soon after a purchase order has been issued.

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“Source: J. C. Wachel, Engineering Dynamics Inc., San Antonio, Texas, USA. Originally presented
at the 15th Turbomachinery Symposium, Texas A&M University, Corpus Christi, Texas, 1986.
Reprinted by permission.