Page 106 - Improving Machinery Reliability

78 Iniproving Machinery Reliability

lation is far more than a mere comparison: it is a master checklist of relevant items,
some of which can have a profound influence on equipment safety, reliability, main-
tainability, and availability. Bid tabulations highlight the strengths and weaknesses
of certain proposals. They indicate which items are acceptable or unacceptable,
which items require follow-up, or which items require that the vendor be challenged
outright to explain inconsistencies, design extrapolations, or oversights.
Bid conditioning refers to the assignment of dollar credits and debits for strengths
and weaknesses, pluses and minuses, in a vendor’s offer. Credits and debits may be
assigned to reflect differences in contractually defined operating efficiencies, com-
ponent strength differences, uprate capability, tolerance for occasional overloading,
better or inferior maintainability, likelihood of delivery delays, extra expediting and
inspection efforts, field service capabilities, spare parts requirements, etc.
Bid-conditioning efforts for large unspared turboniachinery can be extensive and
time consuming. Inevitably, though, the exercise will be worth the effort. Figure 2-
16 shows a fictitious bid tabulation sheet for centrifugal compressors. Figure 2- 17
explains some of the many entries for which credits and debits must be assigned, or
which must at least be considered before a final “conditioned” value can be calculat-
ed for each of the three offers.
We have alluded to cost considerations other than pure bids prices. With progres-
sively higher energy costs, pump efficiency becomes a major factor. In some loca-
tions, the yearly cost (in 1998) of one horsepower now often exceeds $500, and one
might have justifiable concern that quoted efficiencies could be falsely inflated.
Mere consideration of quoted efficiencies should be replaced by certified test-stand
efficiencies, field feedback, and perhaps contractual penalty clauses. Credits and
debits for efficiency deviations must compare the future value of money and the
anticipated operating life of pumps. Depending on the rate of return acceptable for
energy conservation on the project, the value of one horsepower saved may justify
an incremental investment of several times $500-perhaps $4,000 in 1998 dollars.
Credits can be assigned also to recognize lower maintenance costs. If it is possible
to make such an assessment based on comparisons of repair costs, the credit or debit
number can be used outright. If only repair frequencies are available for comparison,
it should be remembered that average pump repairs often cost in excess of $7,000
per event (including shop labor, materials, field labor, and burden) in 1998.
There is value also in demonstrably better, heavier, more easily groutable base-
plates for large horizontal centrifugal pumps. Again, a rule of thumb: $1,200.
Unlike a bid tabulation sheet listing only API data and cost, bid conditioning
serves to bring all offers on the same common denominator by assessing all relevant
parameters. The bid tabulation, shown in Figure 2- 15, illustrates this supplementary
input. It can be seen that more often than not, the best centrifugal pump is neither the
most expensive nor the least expensive one on the bid slate. The best pump manufac-
turer is one who realizes that addressing a user’s concern allows him to outflank the
competition. And the most capable reliability engineer is one who heeds the advice
given by John Ruskin: “There is hardly anything in the world that some man cannot
make a little worse and sell a little cheaper, and the man who buys on price alone is
this man’s lawful prey.”