Page 64 - Improving Machinery Reliability

36 Improving Machinery Reliability

tion asked for? Did you make the mistake of asking for a device that is technological-
ly outdated or redundant? Whatever the reasons, they have to be weighed and evaluat-
ed. Rarely does a vendor’s bid deserve to be discarded because of well-documented
deviations from the purchaser’s initial specifications. But extreme vigilance is still
required because few vendors comprehend the reliability improvement-driven reasons
that prompted you to specify upgraded components and configurations. Be prepared
to hear “we’ve never supplied it that way,” and “you really don’t need that.”
Deviations may deserve credits as well as debits. Procurement of the one machine
that meets all specification clauses without regard for installed cost, future operating
cost, and future maintenance cost is simply not warranted. A detailed review of user
experience has proven helpful in many cases. Such reviews may require visits to
other users’ facilities. As a minimum, telephone contact with knowledgeable mem-
bers of other users’ maintenance and technical staff seems appropriate. Such contacts
have sometimes proven quite revealing. We are reminded of the pump vendor whose
reference list showed installations that had experienced such dramatic startup diffi-
culties that the pumps were junked after a few weeks; or of the cooling-tower fan
vendor who claimed hundreds of special blades had been commissioned over a year
ago, when in fact the user had never run the fans and was disillusioned with the fan
vendor’s past performance. Again, a detailed experience check pays in most cases.
Conversely, purchasing a machine simply because it meets the basic specification
and costs less than competitive equipment may not make much economic sense. The
competing offer might be substantially more efficient or less maintenance-intensive
at only marginally higher cost, and may be a better choice.
In the case of compressors or large steam turbines, the purchaser might require
that critically important parameters, such as bearing spans, impellers, inlet Mach
numbers, etc., fall within the vendor’s proven range of experience. When deviations
from the specifications are proposed in efforts to realize efficiency gains, or in
efforts to lower the risk of compressor fouling, etc., the entire design or portions
thereof may have to be subjected to computerized analysis. We recall a case where
two competing vendors were asked to engage a world-renowned consulting company
to perform analog studies of hyper-compressor valve behavior. The losing bidder
was contractually assured payment for this work, whereas the winning bidder was to
absorb the cost as part of the quoted price.

Cost of Inspection and Expediting

A properly conditioned cost comparison should assign inspection and expediting
costs which may vary based on past vendor performance. An experienced purchaser
should have data on typical man-hours expended in resolving quality control, deliv-
ery, or performance problems with vendor A versus vendor B. If these probable
costs are known, there is no reason not to apply them to the bid sheet.

Economics of Efficiency and Extra Capacity

The values of extra efficiency and extra capacity are known and need no further
explanation. However, the pitfalls merit further consideration. Efficiency improve-