Introduction
Reliability centered maintenance is the process of finding the best possible maintenance strategy for every asset in your organization.
RCM analysis provides a structured framework for analyzing the functions and potential failures for a physical asset (such as an airplane, a manufacturing production line, etc.) with a focus on preserving system functions, rather than preserving equipment.
The guiding principle is that different assets require different styles of maintenance management. Some demand continuous high-tech monitoring, while others are best left to the run-to-failure model.
RCM is used to develop scheduled maintenance plans that will provide an acceptable level of operability, with an acceptable level of risk, in an efficient and cost-effective manner.
Objective
The objective of RCM is to answer the following questions:
- What are the functions and associated desired standards of performance of the asset in its present operating context (functions)?
- In what ways can it fail to fulfill its functions (functional failures)?
- What causes each functional failure (failure modes)?
- What happens when each failure occurs (failure effects)?
- In what way does each failure matter (failure consequences)?
- What should be done to predict or prevent each failure (proactive tasks and task intervals)?
- What should be done if a suitable proactive task cannot be found (default actions)?
Methodology
- Prepare for the Analysis
As with almost any project, some preliminary work will be required to prepare for the RCM analysis. Some important up-front activities include assembling an appropriate cross-functional team, making sure that all members of the analysis team understand and accept the ground rules and conditions of the analysis (e.g., scope of the analysis, definition of “failure,” etc.), gathering and reviewing relevant documentation, etc.
- Select the Equipment to Be Analyzed
RCM analysis requires an investment of time and resources, an organization may wish to focus analysis resources on selected pieces of equipment, based on safety, legal, economic, and other considerations. Selection Questions and Criticality Factors are two methods of equipment selection that are commonly employed.
- Identify Functions and Potential Functional Failures
One of the primary tenets of the Reliability Centered Maintenance approach is that maintenance activities should be focused toward preserving equipment functionality. Therefore, it follows that the first step in analyzing a particular piece of equipment is to identify the function(s) it is intended to perform. Many RCM references recommend including specific performance requirements in function descriptions, which will help to specifically identify functional failures.
Functional failures describe ways that the equipment may fail to perform its intended functions. This may include failure to perform a function, poor performance of a function, over-performance of a function, performing an unintended function, etc.
- Identify and Evaluate the Effects of Failure
This helps the team to prioritize and choose the appropriate maintenance strategy to address a potential failure. Many RCM references contain logic diagrams that can be used to evaluate and categorize the effects of failure. These logic structures often differentiate evident vs. hidden effects and whether the issue has safety, environmental, operational and/or economic consequences.
- Identify Causes of Failure
The cause of failure (sometimes also called failure mode) represents the specific cause of the functional failure at the actionable level (i.e., the level at which it will be possible to apply a maintenance strategy to address the potential failure). This determination is based on engineering judgment and relies on the team’s experience and skill with the RCM analysis process.
- Select Maintenance Tasks and Packaging
The RCM analysis team’s decision of which strategy (or strategies) to employ for each potential failure may be based on judgment/experience, a pre-defined logic diagram (connected to the failure effect categorization), cost comparisons or some combination of factors. Many RCM guidelines include task selection logic diagrams based on the Failure Effect Categorization. When safety is not an issue, another is to compare normalized cost values for the available maintenance strategies and select the maintenance task that provides the desired level of availability for the minimum cost.
Once the appropriate schedule maintenance tasks have been identified, the final step is to package them into a workable maintenance plan. This may involve choosing time intervals at which groups of tasks can be carried out most effectively and efficiently.
