Page 301 - Improving Machinery Reliability

272 Improving Machinety Reliability

out” pumps were originally furnished with conventional stuffing boxes that could
accommodate only relatively small diameter mechanical seals. Whenever one of the
plant’s 417 pumps undergoes a shop repair, new covers with considerably more
favorable seal housing dimensions are fitted to the casing. The bottom line results
show that after two years of routinely upgrading in this manner, the value of avoided
repairs ($362,152) exceeds the additional maintenance cost outlay ($344,960) for
installing the pump enhancements.

Many Different Cost Justification Methods are Available to the Reliability
Professional
We have attempted to show how a number of straightforward calculation
approaches can be, and are being applied, to determine life cycle costs, cost-benefit
ratios, or payback periods for reliability improvements in process plants. A resource-
ful reliability professional will, of course, diligently collect and compile failure sta-
tistics for equipment and components at his or her plant site. However, this diligent
professional would continue to reach out for other data sources to augment and vali-
date in-house data. It should be obvious that much of these “other” data could be
used for the purpose of setting goals and would allow comparisons among plants or
industry segments.
Finally, the occasional lack of data need not be a deterrent to making judicious
assumptions and well-explained “educated guesses.” While our estimates may some-
times be a bit off the mark, pursuing the various cost justification options will
always be better than the status quo, or a complacent “business-as-usual” approach
to equipment reliability improvement.

Life Cycle Cost Assessment: The Rigorous Method*

Life cycle costs (LCC) are summations of cost estimates from inception to dispos-
al for both equipment and projects as determined by an analytical study and estimate
of total costs experienced during the lifetime of the equipment. The objective of
LCC analysis is to choose the most cost-effective approach from a series of alterna-
tives so the least long-term cost of ownership is achieved.
LCC analysis helps engineers justify equipment and process selection based on
total costs rather than the initial purchase price. Usually the cost of operation, main-
tenance, and disposal costs exceed all other costs many times over. Life cycle costs
are the total costs estimated to be incurred in the design, development, production,
operation, maintenance, support, and final disposition of a major system over its
anticipated useful life span. The best balance among cost elements is achieved when
the total LCC is minimized. As with most engineering tools, LCC provides best
results when both art and science are merged with good judgment.

*Contributed by H. Paul Barringer, P. E., Barringer & Associates, Inc., Humble, TX and David P.
Weber, D. Weber Systems, Inc., Maineville OH.