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Reliability Centred Maintenance (RCM) is generally used to achieve improvements in fields such as the establishment of safe minimum levels of maintenance, changes to operating procedures and strategies and the establishment of capital maintenance regimes and plans. Successful implementation of RCM will lead to an increase in cost effectiveness, improved asset availability and reliability (machine uptime), and will help provide a greater insight to the level of risk that the organisation is managing.
It is defined by the Standard SAE JA1011, Evaluation Criteria for RCM Processes, which sets out the minimum criteria that any process should meet before it can be called RCM. This starts with the 7 questions below, worked through in the order that they are listed:
1. What is the item supposed to do and it’s associated performance standards?
2. In what ways can it fail to provide the required functions?
3. What are the events that cause each failure?
4. What happens when each failure occurs?
5. In what way does each failure matter?
6. What systematic task can be performed proactively to prevent, or to diminish to a satisfactory degree, the consequences of the failure?
7. What must be done if a suitable preventive task cannot be found?
RCM is an engineering framework which defines a complete maintenance regime. It regards maintenance as the means to maintain the functions stakeholders may require of their assets in a defined operating context. As a discipline it enables stakeholders to monitor, assess, predict and generally understand the working of their physical assets.
The initial part of the RCM process which is to identify the operating context of the machinery, and write a Failure Mode and Effects Analysis (FMEA) of the machinery based on its operating context.
The second part of the analysis is to apply the “RCM logic”, which helps determine the appropriate maintenance tasks for the identified failure modes in the FMEA. Once the logic is complete for all elements in the FMEA, the resulting list of maintenance is “packaged”, so that the periodicities of the maintenance tasks are rationalised. It is important not to dismiss the applicability of maintenance in this phase.
The RCM process is kept live throughout the “in-service” life of the asset, where the effectiveness of the maintenance is kept under constant review and adjusted in light of the experience gained.
RCM can be used to create a cost-effective maintenance strategy to address dominant causes of equipment failure. It is a systematic approach to defining a routine maintenance program composed of cost-effective tasks that preserve important functions.
The important functions (of a piece of equipment) to preserve with routine maintenance can be identified; their dominant failure modes and causes determined; and the consequences of failure can be ascertained. Levels of criticality are assigned to the consequences of failure. Some functions are not critical and are left to “run to failure” while other functions must be preserved at all cost. Maintenance tasks are selected that address the dominant failure causes. This process directly addresses maintenance preventable failures. Failures caused by unlikely events, non-predictable acts of nature, etc. will usually receive no action provided their risk (combination of severity and frequency) is trivial (or at least acceptable). When the risk of such failure is very high, an RCM program encourages, and sometimes mandates the user to consider changing something which will reduce the risk to an acceptable level.
The result is a maintenance program that focuses resources on those items that would have the most impact on the ‘bottom line’ if they were to fail.