What is RCM (Reliability Centered Maintenance)?
Reliability centered maintenance (RCM) is a methodology that aims to maintain system functionality using cost-effective maintenance strategies. Preventative maintenance (PM) is often used interchangeably with RCM, however the key difference between the two is RCM aims to be efficient and minimize costs by being selective in its application.
A RCM maintenance program is cost-effective because it identifies system functions and associated assets most critical for a system to achieve its business objectives. Essential assets are targeted, their failure modes identified, and effective maintenance strategies adopted to improve the reliability of the system as a whole.
Instead of a single strategy, reliability centered maintenance is the optimal combination of reactive, predictive, condition-based, and proactive maintenance. The advantage comes not from using these maintenance strategies independently, but by integrating them based on asset Criticality and Failure Modes. Smaller assets that are non-critical are replaced with reactive maintenance while assets with random failure patterns or PM induced failures are maintained with condition based maintenance. This piecemeal approach applied on a per asset basis minimizes life-cycle costs.
RCM Assessment Criteria
Currently, reliability centered maintenance is defined by SAE JA1011, Evaluation Criteria for Reliability-Centered Maintenance (RCM) Processes. The minimum criteria for RCM processes begins by asking seven questions:
- What are the functions and associated performance standards of the asset?
Before determining what must be done to ensure an asset continues its function, we first must identify the functions of each asset and ensure it is capable of performing its functional expectations.
- In what ways can it fail to fulfil its functions?
Functional failures need to be identified, followed by the events that can cause assets to go into a failed state.
- What are the failure modes for each functional failure?
After all operational failures are identified, the next step is to classify all possible causes for each failure. These are defined as failure modes and are identified, along with their effects, through a Failure Modes and Effects Analysis (FMEA).
- What happens when each failure occurs?
Next, failure effects must be identified and listed when each failure mode arises. Questions to consider include: what damage is triggered by the failure or in what ways does the failure present a hazard to the environment or safety?
- In what way does each failure matter?
Step five classifies the consequences for each failure mode. The RCM assessment categorizes consequences into four groupings: operational consequences, non-operational consequences, safety and environmental consequences, and finally, hidden failure consequences.
- What can be done to predict or prevent each failure?
Determine what preventative maintenance tasks are available and cost-effective to schedule.
- What should be done if a suitable proactive task cannot be found?
If no maintenance tasks are available to preserve asset function, alternative options, such as asset replacement or redesign, must be employed.