What is RCM? A Complete Guide for Maintenance Professionals

Introduction

Reliability Centred Maintenance (RCM) is a structured methodology for determining the maintenance requirements of physical assets in their operating context. If you've worked in maintenance or reliability engineering, you've likely heard the term thrown around—but what does it actually mean, and why does it matter?

In this comprehensive guide, we'll explore everything you need to know about RCM: where it came from, how it works, and how you can apply it to improve reliability and reduce maintenance costs in your organisation.

A Brief History of RCM

The Aviation Origins

RCM didn't emerge from a factory floor or a university research lab. It was born out of necessity in the commercial aviation industry during the 1960s.

At that time, the prevailing maintenance philosophy was simple: the older something gets, the more likely it is to fail. Therefore, preventive maintenance meant overhauling or replacing components at fixed intervals. The problem? Aircraft were becoming increasingly complex, and this approach was becoming prohibitively expensive.

In 1960, the Federal Aviation Administration (FAA) established a task force with representatives from the airlines to re-examine maintenance practices. What they discovered challenged fundamental assumptions about equipment failure.

The MSG Process

The task force developed what became known as Maintenance Steering Group (MSG) logic—a decision-based approach to determining maintenance requirements. This evolved through several iterations:

•MSG-1 (1968): Applied to the Boeing 747
•MSG-2 (1970): Refined the logic further
•MSG-3 (1980): Still used in aviation today

The key insight was revolutionary: most equipment failure modes do not follow a predictable age-related pattern. In fact, their research showed that only about 11% of failures were age-related, while 89% were random.

From Aviation to Industry

In 1978, the US Department of Defense commissioned Stanley Nowlan and Howard Heap of United Airlines to document the methodology. Their report, "Reliability-Centered Maintenance," became the foundation for modern RCM.

John Moubray later adapted these principles for general industry in his landmark book "RCM II" (1991), which remains the definitive reference for practitioners. His work made RCM accessible beyond aviation, applying it to manufacturing, utilities, and process industries.

What is RCM? A Definition

At its core, RCM is a process used to determine what must be done to ensure that any physical asset continues to fulfil its intended functions in its present operating context.

Let's break that down:

•"What must be done" — We're determining maintenance requirements, not assuming them
•"Physical asset" — Equipment, systems, infrastructure—things that can fail
•"Intended functions" — Not just "keep it running," but what it needs to actually do
•"Operating context" — The specific environment and conditions where it operates

RCM is fundamentally about asking the right questions. It doesn't assume that maintenance is always the answer. Sometimes, the right response to a failure mode is to run the equipment to failure. Other times, it's to redesign the system entirely.

The Seven Questions of RCM

Every RCM analysis follows a structured questioning process. These seven questions form the backbone of the methodology:

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

Before you can preserve function, you must define it. This isn't just "the pump pumps water." It's specific: "Transfer cooling water at 150 litres per minute at 4 bar pressure from the reservoir to the heat exchanger."

Functions can be:

•Primary functions: The main reason the asset exists
•Secondary functions: Safety, containment, control, comfort, efficiency, environmental compliance, structural integrity

2. In what ways can it fail to fulfil its functions?

A functional failure is the inability to fulfil a function to a standard acceptable to the user. For our pump example:

•Unable to transfer any water (complete failure)
•Unable to transfer water at 150 L/min (reduced capacity)
•Unable to maintain 4 bar pressure (performance degradation)

3. What causes each functional failure?

These are the failure modes—the specific events that lead to functional failure. For the pump:

•Impeller wear
•Seal failure
•Motor bearing failure
•Electrical fault in motor windings
•Coupling failure
•Blocked suction strainer

Good RCM analysis identifies failure modes at a level of detail that allows appropriate maintenance action.

4. What happens when each failure occurs?

Failure effects describe what happens when the failure mode occurs—the sequence of events. This includes:

•Evidence that the failure has occurred
•How it affects safety or the environment
•How it affects operations
•What physical damage results
•What must be done to repair it

5. In what way does each failure matter?

This question assesses failure consequences. RCM categorises these as:

•Hidden failure consequences: The failure isn't evident under normal conditions
•Safety and environmental consequences: Could hurt someone or breach regulations
•Operational consequences: Affects output, quality, customer service, or costs
•Non-operational consequences: Only involves the cost of repair

6. What should be done to predict or prevent each failure?

This is where we select proactive maintenance tasks:

•Scheduled restoration: Restore to original capability at fixed intervals
•Scheduled discard: Replace at fixed intervals
•Scheduled on-condition tasks: Check for potential failures (inspections, testing)

A task is only worth doing if it deals with the consequences of failure effectively and is worth doing compared to not doing it.

7. What should be done if a suitable proactive task cannot be found?

When no proactive task is appropriate or cost-effective:

•Failure-finding tasks: For hidden failures, periodic checks to determine if something has failed
•Redesign: Change the equipment or operating conditions
•Run to failure: Accept the consequences and fix it when it breaks

SAE JA1011: The RCM Standard

In 1999, the Society of Automotive Engineers published SAE JA1011, "Evaluation Criteria for Reliability-Centered Maintenance (RCM) Processes." This standard defines the minimum criteria any process must meet to be called "RCM."

Key Requirements

To comply with SAE JA1011, an RCM process must:

1.Define functions and performance standards in operating context
2.Determine how the asset can fail to fulfil its functions
3.Identify failure modes likely to cause each functional failure
4.Describe failure effects for each failure mode
5.Classify failure consequences
6.Select maintenance tasks that are applicable and effective
7.Address situations where no applicable task can be found

Why Compliance Matters

Many organisations claim to do "RCM" but are actually doing something else—perhaps equipment-based FMEA, or simplified PM optimisation. There's nothing wrong with these approaches for appropriate applications, but they're not RCM.

SAE JA1011 compliance matters because:

•It ensures rigour and consistency
•It provides a benchmark for auditing
•It gives credibility to your programme
•It ensures you're getting the full benefit of the methodology

Benefits of RCM

When properly implemented, RCM delivers significant benefits:

Improved Reliability

By understanding how equipment actually fails and selecting appropriate maintenance tasks, you address the real causes of failure rather than applying blanket PM schedules.

Reduced Maintenance Costs

Studies consistently show 40-70% reduction in routine maintenance costs. This comes from:

•Eliminating unnecessary time-based maintenance
•Extending intervals where justified
•Running appropriate items to failure
•Focusing resources on what matters

Better Safety

RCM explicitly addresses safety consequences. Hidden failures that could compromise safety systems are identified and managed through appropriate failure-finding tasks.

Knowledge Capture

The RCM process documents how equipment works, how it fails, and why maintenance is done. This knowledge often exists only in the heads of experienced personnel—RCM captures it systematically.

Regulatory Compliance

Many industries require documented justification for maintenance programmes. RCM provides an auditable process that satisfies regulators.

Key Takeaways

•RCM originated in aviation in the 1960s and was adapted for general industry by John Moubray
•It's a structured process based on seven questions about functions, failures, and consequences
•SAE JA1011 defines the minimum criteria for a genuine RCM process
•RCM is context-specific—the same equipment in different applications may need different maintenance strategies
•Benefits include improved reliability, reduced costs, better safety, and knowledge capture
•RCM is rigorous but practical—it's about doing the right maintenance, not more maintenance

Getting Started with RCM

If you're ready to implement RCM in your organisation, start with these steps:

1.Build understanding: Ensure key stakeholders understand what RCM is and isn't
2.Select a pilot asset: Choose something important but manageable
3.Assemble the right team: Include operators, maintainers, and engineers
4.Use proper tools: Our RCM FMEA Template Pack provides SAE JA1011 compliant worksheets
5.Document everything: The analysis is only valuable if it's recorded properly
6.Implement and review: Put the tasks into your CMMS and monitor results

RCM isn't a quick fix—it requires investment in training and time. But for critical assets where reliability matters, it's the most thorough and effective approach available.

Ready to start your RCM journey? Explore our RCM Starter Bundle for everything you need, or try our free RCM Decision Diagram tool to see the methodology in action.