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Reliability Centered Maintenance (RCM)

ALCL 130


A logical, structured process used to determine the optimal failure management strategies for any system based upon system reliability characteristics and the intended operating context. RCM defines what must be done for a system to achieve the desired levels of safety, operational readiness, and environmental soundness at best cost. RCM is a continuous process that requires sustainment throughout the life cycle of a system, utilizes data from the results achieved, and feeds this data back to improve design and future maintenance.

General Information

RCM is based upon some important Principles:

  • Function-oriented concept - The analysis attempts to preserve all functionality of a system, not just its operational capability
  • System focused - It is more concerned with maintaining the overall function of an entire system, not just the individual components that make up a system
  • Reliability centered - It takes into account the relationship between operating age and experienced failures. In short, RCM is not overly concerned with simple failure rate, but rather with the probability that a failure can occur at specific ages
  • Recognizes design limitations - Its objective is to maintain the inherent reliability of equipment as it is designed, thereby acknowledging that any change in inherent reliability is the result of design rather than effective maintenance. Maintenance can, at best, only achieve and maintain the level of reliability provided by the design. However, inherent to an effective RCM analysis is the idea that maintenance feedback can actually improve the original design.
  • Driven by both safety and economics - safety is the primary criteria
  • Defines failure as any unsatisfactory condition - this holds true whether it be a loss of function or a loss of quality. In the case of the former condition, operational capability is lost; in the case of the latter, operational capability continues but at an unacceptable, and even degraded quality.
  • RCM tasks must be effective - That is, they must reduce the probability of a defined failure, but at the same time be cost effective.
  • Acknowledges that "run-to-failure" is an acceptable decision - this is acceptable for some equipment, so not all failure modes require a maintenance intervention task.
  • RCM is a living system -  It gathers historical data and uses it to improve future design and maintenance tasks. This feedback is an important part of the proactive maintenance element of the RCM program.

RCM Analysis (RCMA)

One of the key objectives of the RCM analysis is to develop a maintenance schedule that would ensure that reliability of a system is enhanced. In essence a maintenance task would be implemented prior to the failure occurring.

Using the decision tree process of RCM analysis, a complete analysis of each functional significant item and their assigned failure modes can be conducted. DoD Manual (DoDM) 4151.22M, Reliability Centered Maintenance Manual as well as MIL-STD-3034A, Reliability-Centered Maintenance (RCM) Process, give detailed instructions and provide a guide for RCM analysis. The results of the analysis provide a clear decision as to which preventive maintenance tasks should be developed to support the system.

As electronics failure patterns (rates) generally exhibit a constant failure rate, the RCM analysis will have its most impact on electromechanical and mechanical based maintenance activities. The RCM analysis when used in conjunction with the Failure Modes Effects and Criticality Analysis (FMECA) can be used to identify potential hidden safety related failures for electronic systems. When the RCM analysis is used with the FMECA early in the design process, safety related failure modes can be removed from the system during the design phase. As the maturity of the design progresses this option becomes increasingly more difficult and expensive to address.