RCM

Reliability-Centered Maintenance (RCM) is an on-going process used to determine the most effective strategy for maintaining equipment. It is based on understanding how equipment degrades, and understanding the risks and consequences associated with a failure. It identifies the optimum mix of applicable and effective maintenance actions that will mitigate the risk at the lowest cost.

RCM uses a systematic, logic-based approach that bases the decisions on sound technical rationale and economic justification. It considers operational experience and failure history to validate and support those decisions. The RCM process provides an excellent means for capturing and documenting the knowledge of the most experienced operators and technicians.

The early development of RCM concepts are attributed to maintenance policy events in the airline industry in the late 1960s and early 1970s. In an attempt to maximize the safety of airplane passengers and maximize the reliability of airplane equipment, a task group was formed to investigate maintenance practices and to challenge the traditional concepts of successive overhauls. The traditional concept promoted the belief that all equipment degrades over time, and that a specified age can be defined where overhauling that equipment will ensure safety and operating reliability.

The resultant work of this task group demonstrated that the correlation between age and failure rate was not as expected and that the basic premise of time-based maintenance was false for the majority of equipment. The results of this task group can be summarized in the following three significant discoveries:

• Scheduled overhaul had little effect on the overall reliability of equipment unless the item has a dominant failure mode and the maintenance action directly addresses that dominant failure mode.
• There were many items for which there is no effective form of scheduled maintenance.
• Cost reductions in maintenance could be achieved with no decrease in reliability. A better understanding of the failure process in complex equipment has actually improved reliability when some maintenance actions were eliminated.

RCM subsequently evolved as a process that recognized that there are three primary types of maintenance actions: reactive, preventive, and predictive. Monitoring and failure detection are a subset of predictive actions. A thorough understanding of an equipment’s failure process and the consequences of failure enabled a proactive approach
defining which actions would best reduce the risks associated with failure.

The principles and applications of RCM as they evolved in these early developments are documented in Nowlan and Heap’s publication, Reliability-Centered Maintenance.* Nowlan, F. Stanley and Heap, Howard F., Reliability Centered Maintenance, Dolby Access Press, 1978.