Page 404 - Improving Machinery Reliability

368 Improving Machinery Reliability

Product Defects

1. Poor quality output
2. Decreased yield
3. Excessive scrap
4. Returns, rework, recycle, refeed

What Exactly is RCM?

RCM, or reliability-centered maintenance, is an outgrowth of the recognition that
conventional, time-based maintenance may not be cost-effective. As the term sug-
gests, it is an approach to the attainment of optimum equipment reliability by per-
forming only known-to-be necessary maintenance. In an operations context, RCM
encompasses the review of equipment functions, functional failures, and the conse-
quences thereof. No predetermined maintenance actions are taken. Instead, each fail-
ure mode is subjected to a decision logic exercise to determine if a maintenance
action is indeed required and what that action should specifically consist of. General-
ly speaking, these determinations would initially point to one of several categories of
maintenance actions that fit under the collective term reliability-centered mainte-
nance. These categories would include:

1. Scheduled discardhestoration maintenance
2. Fixed interval overhauls
3. Condition-based, or predictive maintenance
4. Servicing on an as-needed basis
As can be seen, this is a significant departure from the traditional approach of peri-
odic overhaul maintenance. Failure modes, a detailed understanding of how equip-
ment fails, and a thorough understanding of failure consequences become important
in maintenance planning. Only those assets that show a clear age-related pattern are
subjected to periodic, time-based maintenance. Equipment exhibiting evidence of ran-
dom failure or likely to undergo progressive deterioration is subjected to predictive
monitoring and allowed to stay in a service as long as it continues to meet the intend-
ed function and performance in a safe and economically viable fashion. These are
important qualifiers to keep in mind, and we will have to come back to them later.

RCM: The Rest of the Story
An astute observer once commented that RCM is about making the right choices.
This would include the right choice between replacing failed parts versus upgrading
to improved parts, deciding whether these parts should come from OEM or non-
OEM suppliers, making the right decision whether to engage in an often expensive
failure mode and effect analysis (FMEA), picking the right hazard management tech-
nique, repair technique, installation method, oil replacement frequency, root-cause
failure analysis technique, grout formulation, bearing-internal clearance-and literal-
ly hundreds of other issues that will affect equipment reliability and failure frequen-