What is Reliability Centered Maintenance?

A Definition of Reliability Centered Maintenance

Introduction
Reliability Centered Maintenance grew from studies carried out during the development of the Boeing 747. This work showed that the failure modes of aircraft components are random dominated. At this time aircraft maintenance was based predominately on flying hours, therefore, a new method of maintaining aircraft was considered appropriate. The Reliability Centered Maintenance approach assumes no prior knowledge of the components, a so-called zero-based or first principles approach. Each component in the aircraft was systematically analyzed to identify their failure modes and appropriate maintenance tasks were then assigned. Asking seven questions about each asset carries out this analysis.

Seven Basic Questions
1 What are the functions and associated performance standards of the asset in its present operating context?

Functions are categorized as follows:
On Line Functions that are in use continuously or at such frequency that personnel will be continuously aware of their state.
Standby Functions that are under the supervision of operations personnel but are used so infrequently that a special check is required to identify (hidden) failures that have occurred.

2 In what ways does it fail to fulfill its functions (failure mode)?
The failure modes to be considered are:
Failures that have previously occurred on the equipment or similar machines.
Possible failures that have not occurred before but could have serious consequences.
Failure modes for which preventive maintenance has already been applied in order to prevent failure.

3 What causes each failure?
Each potential failure must be investigated to identify every possible cause. Maintenance actions are then put in place to tackle the causes and not the symptoms of a failure. This stage of Reliability Centered Maintenance must be controlled as time can be wasted investigating unlikely causes of failure.

4 What happens when each functional failure occurs?
It is necessary to understand the consequences of each functional failure to determine if any preventative maintenance is actually required.

5 In what way does each failure matter?
Once the failure consequences have been identified, they are categorized, which will aid in the determination of an appropriate maintenance task.

6 What can be done to prevent each failure?
The characteristics of the individual failure mode will determine which one of the four maintenance strategies will be chosen

7 What should be done if a suitable preventative task cannot be found? (default tasks)
An obvious maintenance task may not exist for some failure modes. Reliability Centered Maintenance provides a detailed decision tree to ensure the correct type of maintenance task is selected for each failure mode.

Implementing Reliability Centered Maintenance
Reliability Centered Maintenance can be implemented through the setting up of cross-section review groups who will work through the above 'seven questions' to develop the maintenance requirements for specified assets. The zero-based approach necessitates a high degree of understanding of the asset being analyzed. If the necessary skills do not exist within the company external specialists may be invited to join the group to discuss specific problem areas. Each review group will be chaired by a facilitator who will control the flow of information, ensuring it is recorded on specific Reliability Centered Maintenance worksheets. The group will work together to answer the first four of the 'seven questions'. The Reliability Centered Maintenance Information Worksheets are used to record the answers to these questions:

- Function of the asset
- Functional failure
- Failure mode
- Failure effect
The next stage of Reliability Centered Maintenance considers the final three of the 'seven questions' to evaluate the consequences of the failures and based on the consequences, identify appropriated maintenance tasks. The Reliability Centered Maintenance Decision Tree is used in this task. The output from the groups will be Reliability Centered Maintenance Decision Worksheets detailing:

- Item or component
- Proposed task
- Periodicity
- Trade
It is then the responsibility of maintenance and production management to introduce these revised tasks to the factory floor employees.



adapted from Patrick Barry and Tony Doyle: Maintenance Techniques and Analysis

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