Reliability Centered Maintenance (RCM) 101

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

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.

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.

Implementing RCM

Implementing a reliability centered maintenance program begins by taking the seven questions asked during the RCM assessment and categorizing them into three phases. These phases are: prioritization, evaluation, and results.

Prioritization Phase
The first phase determines priority and targets equipment with the highest probability of failure or largest consequences of failure. Deciding asset criticality and defining what equipment performs crucial system functions is the focus of phase one.

Analysis Phase
Phase two consists of conducting the RCM study and can be broken down into three parts. First, functional failures need to be identified and defined. Next, effects of the failures are evaluated. How does this failure affect the overall system or safety? The final step is identifying failure modes. Often, FMEA will be used to uncover failure modes.

Results Phase
After prioritizing and analyzing, the final phase is acting on the information acquired. This stage focuses on identifying areas for improvement and updating maintenance tasks or asset design. Actions can include preventative maintenance techniques to mitigate risk of failure or proactively preventing failures.

Conclusion: Why you should consider RCM solutions

The biggest benefit of a RCM program is cost reduction through efficient maintenance techniques. Companies that successfully implement RCM see reduced maintenance and resource costs as well as increases in equipment availability. Because criticality is determined through FMEA, a greater understanding of risk levels and consequences are established and limited resources can then be focused on assets that if failed, would cause the most disruption.

The results of RCM services has very real consequences for a business’ bottom line. In their book, Maintenance, Replacement, and Reliability: Theory and Applications, Jardine and Tsang found that implementing RCM saved a utility company up to 40 percent on maintenance costs. An effective RCM program isn’t achieved overnight and requires strategic planning and industry expertise.