Page 409 - Improving Machinery Reliability

Maintenance for Continued Reliability 373

Also in Appendix A, consider the maintenance cost breakdown by work order.
Best-of-class companies use predictive maintenance in their efforts to determine
when it’s time to perform preventive maintenance. Remember that the system fur
causing quality is prevention, not appraisal. Where does your plant fit in on the cost
breakdown table? Note, especially, how an increase in preventive maintenance effort
will drive down costly emergency work and repairs.

Choosing Wisely in a Stressful Environment
Recall that by all accounts RCM does not respond to random failures. Aerospace
and process industries represent two different worlds. Let us, nevertheless, suppose
that we, just as Boeing, McDonnell-Douglas and the European Airbus Conglomer-
ate, have installed equipment, subsystems, and components that are life cycle cost
optimized. Assume further that, just as is the case in the aerospace field, voluminous
statistical and experimental data attested to the fact that our assets will virtually
always fail in one of the predictable wear-out modes, which is ideal for the applica-
tion of RCM. Are we now able and willing to invest in the people and resources
whose diligent efforts are expensive initially, but will pay out in the long run? Do we
have the patience to defer seeing returns on this investment for some time, and
meanwhile let the competitor brag about higher profits? How do we explain the
whole thing to our shareholders? Are we committed to provide continuity to the
RCM effort? Do we have an understanding of the limitations of contractor person-
nel, and can we separate fact from fiction when we hear marketing-driven, exuberant
representations made by the technology consultant selling RCM training?
We have sometimes seen how, in their efforts to sell RCM technology to an ever
wider spectrum of potential users, its marketers have plotted density functions, cumu-
lative distributions and hazard functions that may apply to aircraft components for
which pertinent statistics exist. One of our earlier books (Reference 6) describes the
“monorail mistake,” which involves going from one idea to another in an inevitable
manner, ignoring all qualifying factors. Yet, there are many qualifying factors that
have to be considered or overcome before valid parallels between the aerospace busi-
ness and the process industries may be drawn. Indeed, two different worlds!
Specifically, for instance, there is often no valid failure cause or failure origin
linkage between the aircraft fuel pump and the refinery’s ethylene reflux pump.
Where the former operates under highly consistent and predictable conditions, the
latter may be subjected to operator error, excessive pipe strain, coupling friction,
shaft misalignment, baseplate weakness, soft-foot conditions, lubricant contamina-
tion, low-flow recirculation due to over-sizing, and at least 40 additional factors that
can be shown to influence life expectancy, reliability, and optimum service intervals
of pumps in a typical process plant environment. The list could go on to steam tur-
bines, mixers, extruders, compressors, and other equipment requiring some form of
maintenance. Our premise is simply that, in spite of these influencing factors being
discussed in the literature, not enough companies are engaged in remedying these
known impediments to achievement of best-of-class maintenance performance. As
this text shows, many of these impediments are relatively easy and inexpensive to
rectify. It would thus be far more productive for process plants to start by systemati-