Reliability Centered Maintenance (RCM)
RCM is a strategy for examining manufacturing assets (machinery and process) in a systematic manner to establish expectations, limitations, and priorities with the final objective of identifying for each piece of equipment the cost effective measures necessary to maintain reliable performance. The process tends to be matrix based and starts with the creation of an equipment list if one does not already exist. The following seven questions are then applied to each selected asset:

• What are the functions and associated performance standards of the asset in its present operating context?
• In what ways does the asset fail to fulfill its functions?
• What causes each functional failure?
• What happens when each failure occurs?
• In what way does each failure matter?
• What can be done to prevent each failure?
• What should be done if a suitable preventive task cannot be found?

In short, RCM takes an overall view of the entire scenario (machinery and process) and through a series of deliberate questions, obtains answers down to a detailed level. Once it is determined exactly what must be monitored, why, and how frequently, a decision is made as to the most appropriate monitoring technique. This monitoring technique may well fall into the realm of Predictive Maintenance (PdM). It can be simple (listen, smell, etc.) or more complex (vibration, oil analysis, infrared thermography, etc.). Although RCM references PdM techniques, it does not address detail in this field. Instead, RCM is a method to govern the application of Predictive Maintenance. In other words, PdM is where “the rubber meets the road."

The precise moment that the concept of RCM started may not be entirely clear. However, the roots trace to frustrations encountered with aircraft failures. Specifically, some failures could simply not be controlled through Preventive Maintenance (PM) techniques, fostering the development of alternative approaches. By the late 1950’s, the size and complexity of the commercial airline fleet had grown significantly, further compounding the task. By 1960, the U.S. Government had become rather serious about the issue and promoted the formation of a task force consisting of representatives from both the Federal Aviation Administration and the airlines to investigate the capabilities and limitations of PM. The result of this effort was the establishment of the FAA/Industry Reliability Program. The task force developed a propulsion system reliability program and each airline, in turn, developed reliability programs in specific areas of maintenance. According to John Moubray in his book entitled Reliability Centered Maintenance, the outcome of the study revealed the following:

Scheduled overhaul has little effect on the overall reliability of a complex item unless the item has a dominant failure mode. The study clearly showed that Preventive Maintenance alone would not always guarantee reliability. There are many items for which there is no effective form of scheduled maintenance. In the early 1970’s, the U.S. Government requested United Airlines to issue a report on the methods employed by civil aviation to prepare maintenance programs for aircraft. The title of this report was Reliability Centered Maintenance. Hence, at this point, the expression seemed to be fully recognized and accepted.

Reliability Based Maintenance (RBM):
RBM is a maintenance strategy based on integrating the benefits of Preventive Maintenance (PM), Predictive Maintenance (PdM), and Proactive Maintenance in a manner that eliminates machinery failures, thereby assuring that the maintenance effort produces capacity rather than being a burden. The intent is to redirect maintenance from being considered a “necessary evil” to being productive and a positive asset to the operation. RBM is a trademarked expression attributable to Forrest Pardue at Computational Systems, Inc (CSI). As with RCM, the initial use of the RBM expression seems to be a bit nebulous. However, the overall objective is similar to RCM, but with a definite focus on the manufacturing sector.

The expressions RCM and RBM tend to be used loosely and are frequently interchanged. It is the author’s opinion that RCM favors a broader perspective by addressing a specific questioning process that sets the stage for further action. Both approaches lead to condition monitoring as the end result. Without PdM neither approach would be successful. Hence, PdM is the common denominator.

RCM versus RBM:
As a rule, with large complex operations, the initial application of RCM provides superb guidance as to where to place the effort and funding. With simpler operations, RCM may not be required and the direct application of Reliability Based Maintenance (RBM) and PdM is sufficient. Namely, a quicker and better return on investment can be achieved by eliminating the RCM step. For example, a very large oil refinery with thousands of employees would clearly benefit from RCM to bring the proper focus to the project. The additional cost of RCM for a small plant of a hundred employees or so would probably not be justified. The reason is that, with just a few personnel, the necessary information to make the right decisions is more easily available and RCM would tend to complicate the issue. Certainly, it makes good business sense to keep the use of Consultants to a minimum. Either way, a disciplined approach to surveying the situation is prudent.