The 7 RCM Questions Explained with Practical Examples

Introduction

The seven questions of RCM form the backbone of the methodology. Every RCM analysis, regardless of the asset or industry, follows this same logical sequence. Understanding these questions—and how to answer them properly—is essential for anyone conducting or participating in RCM analysis.

In this article, we'll examine each question in detail, with practical examples drawn from common industrial equipment. By the end, you'll have a solid grasp of how to apply RCM thinking to any asset.

The Seven Questions at a Glance

Before diving deep, here are the seven questions:

1. 1.What are the functions and associated performance standards?
2. 2.In what ways can it fail to fulfil its functions?
3. 3.What causes each functional failure?
4. 4.What happens when each failure occurs?
5. 5.In what way does each failure matter?
6. 6.What should be done to predict or prevent each failure?
7. 7.What should be done if no proactive task is appropriate?

Now let's examine each one.

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Question 1: What Are the Functions?

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

This question establishes what we're trying to preserve. Before we can prevent failure, we must define success.

Primary vs Secondary Functions

Primary functions are why the asset exists. They're the main reason it was installed. Secondary functions are additional expectations. These typically include:

• •Safety/environmental containment
• •Control and indication
• •Comfort and appearance
• •Structural integrity
• •Efficiency
• •Compliance

The Importance of Performance Standards

Functions must be quantified. "The pump pumps water" is not useful. "The pump transfers cooling water at 150 L/min minimum at 4 bar to the heat exchanger" is actionable.

Without performance standards, you can't determine whether something has failed or is deteriorating.

Practical Example: Centrifugal Cooling Water Pump

Operating Context: Provides cooling water to heat exchangers in a chemical process. Runs 24/7. Redundant pump available (standby). Primary Function:

• •Transfer cooling water from the reservoir to heat exchangers at a minimum flow rate of 200 L/min at 5 bar discharge pressure

Secondary Functions:

• •Contain the cooling water (no leaks exceeding 10 mL/hour)
• •Allow flow to be isolated when required
• •Indicate running status to the control room
• •Operate without vibration exceeding 4 mm/s RMS at the bearings
• •Consume no more than 15 kW electrical power
• •Comply with noise limits (<85 dB at 1m)

Notice how each function is specific and measurable. This clarity is essential for the questions that follow.

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Question 2: How Can It Fail?

"In what ways can it fail to fulfil its functions?" A functional failure is the inability of an asset to fulfil a function to a standard acceptable to the user. Each function typically has at least two functional failures:

• •Complete loss of function
• •Partial loss or degradation of function

Practical Example: Cooling Water Pump

For the function "Transfer cooling water at 200 L/min at 5 bar": For the function "Contain the cooling water (leaks <10 mL/hour)": Each function gets examined for ways it can fail. This ensures comprehensive coverage.

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Question 3: What Causes Each Failure?

"What causes each functional failure?"

These are the failure modes—the specific events that can cause the functional failure. This is where the analysis gets technical.

What is a Failure Mode?

A failure mode is a single event that causes a functional failure. Good failure modes are:

• •Reasonably likely to occur: Not purely theoretical
• •At an appropriate level of detail: Specific enough to select maintenance, not so detailed it's impractical
• •Single events: Not combinations of failures

Example: Failure Modes for "Unable to transfer any water"

For functional failure A1 (unable to transfer any water), failure modes might include:

Level of Detail

The right level of detail allows you to select appropriate maintenance. Consider:

Too vague: "Motor fails" — Which part? What maintenance would address this? About right: "Motor bearing fails due to wear" — Can address with vibration monitoring or greasing Too detailed: "Motor drive-end bearing inner race fails due to subsurface fatigue initiating at machining marks" — More detail than needed for maintenance selection

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Question 4: What Happens When It Fails?

"What happens when each failure occurs?"

Failure effects describe what happens when the failure mode occurs. This information is used later to assess consequences and evaluate maintenance options.

What to Include in Failure Effects

A good failure effect description includes:

1. 1.Evidence of failure: What indicates it has happened?
2. 2.Safety/environmental impact: Any hazards created?
3. 3.Operational impact: Effect on production, quality, service?
4. 4.Secondary damage: Does the failure damage other equipment?
5. 5.Corrective action: What's needed to restore function?

Practical Example: Motor Bearing Seized

Failure Mode: Motor bearing seized Failure Effect:

"High-pitched squealing noise heard from motor for 1-2 minutes before motor stops. Control room receives motor trip alarm. Standby pump starts automatically. No safety hazard. Production continues on standby pump. Repair requires motor removal to workshop for bearing replacement (2x 6205-2RS bearings, £40). Estimated repair time 4 hours with two fitters. Motor may need rewinding if operated while seized (additional £800 and 2 weeks if sent away)."

Notice this effect tells us:

• •There's warning before complete failure (opportunity for condition monitoring)
• •It's not safety-critical (standby available)
• •The consequence is primarily repair cost
• •Early detection saves significant money

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Question 5: In What Way Does It Matter?

"In what way does each failure matter?"

This question assesses the consequences of each failure mode. RCM categorises consequences into four types, which directly influence what maintenance (if any) is appropriate.

Consequence Categories

Hidden failures: The failure is not evident to the operating crew under normal circumstances. Examples include:

• •Standby equipment that's not running
• •Safety devices (relief valves, trips, alarms)
• •Protective systems

Safety/environmental consequences: The failure could injure someone or breach environmental regulations. Operational consequences: The failure affects output, product quality, customer service, or operating costs (beyond repair cost). Non-operational consequences: The failure only involves the direct cost of repair.

Why Consequences Matter

Consequences drive maintenance selection:

• •Hidden failures require failure-finding tasks to detect degradation
• •Safety/environmental consequences justify more expensive maintenance
• •Operational consequences may justify proactive maintenance if it's cost-effective
• •Non-operational consequences often mean run-to-failure is acceptable

Practical Example: Pump Seal Failure

Failure Mode: Mechanical seal failure Consequence Assessment: Is the failure evident under normal operating conditions? Yes — seal leak is visible during routine rounds. Does the failure cause a safety or environmental hazard? No — cooling water is non-hazardous, contained in drip tray. Does the failure affect operations? Marginally — increased seal water consumption (~£5/week). Pump continues operating. Consequence category: Non-operational

This means the failure can potentially be allowed to occur, provided repair cost is reasonable and there's no secondary damage.

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Question 6: What Should Be Done?

"What should be done to predict or prevent each failure?"

Now we select proactive maintenance tasks. RCM recognises three types of proactive tasks:

Scheduled On-Condition Tasks

These tasks detect the potential failure before functional failure occurs, giving time to intervene.

Requirements:

• •There must be a detectable potential failure condition
• •There must be a consistent interval between potential and functional failure (P-F interval)
• •The task interval must be less than the P-F interval
• •It must be practical to do the task at that interval

Examples:

• •Vibration monitoring (detects bearing wear)
• •Thermography (detects electrical hotspots)
• •Oil analysis (detects wear particles)
• •Visual inspection (detects leaks, corrosion)

Scheduled Restoration Tasks

These tasks restore the asset's original capability at fixed intervals.

Requirements:

• •There must be an identifiable age at which wear-out begins
• •Most items must survive to that age
• •The task must restore original capability

Examples:

• •Bearing replacement at fixed hours
• •Pump impeller restoration
• •Filter element replacement

Scheduled Discard Tasks

These tasks replace items at fixed intervals regardless of condition.

Requirements:

• •There must be an identifiable wear-out age
• •Most items must survive to that age
• •Running to failure is unacceptable

Examples:

• •Safety relief valve replacement
• •Seal replacement
• •Belt replacement

Practical Example: Motor Bearing Failure

Failure Mode: Motor bearing wear leading to seizure Task Selection: Can we detect potential failure? Yes — vibration increase, temperature rise, noise change What's the P-F interval? Typically 1-3 months from first detectable vibration change to failure Is it practical to monitor at less than that interval? Yes — monthly vibration readings are practical Selected Task: Monthly vibration monitoring (portable analyser), alarm at 4mm/s, action at 7mm/s Alternative Considered: Scheduled bearing replacement at 4 years Why not selected: Bearings show random failure pattern; 30% fail before 4 years, some last 10+ years. On-condition is more effective.

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Question 7: What If No Task Works?

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

When no proactive task is technically feasible and worth doing, RCM provides three default actions:

Failure-Finding Tasks

For hidden failures only. Periodic checks to determine if something has already failed.

Example: Weekly functional test of emergency shutdown system

Redesign

Change something to eliminate the failure mode or reduce its consequences.

Example: Add redundancy, install better materials, modify operating procedures

Run to Failure (No Scheduled Maintenance)

Accept the consequences and fix it when it breaks.

Requirements:

• •The failure must have no safety or environmental consequences
• •The failure must be evident
• •The cost of repair must be acceptable
• •No secondary damage must result

Example: Let indicator lights burn out and replace on failure (evident, low consequence, no secondary damage)

Default Action Selection

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Putting It All Together

Let's trace one complete failure mode through all seven questions:

Asset: Air-Operated Control Valve

Q1 — Function: Regulate flow of process fluid from 0-100% proportional to 4-20mA signal, fail-closed on air loss Q2 — Functional Failure: Unable to regulate flow proportional to signal Q3 — Failure Mode: Positioner feedback linkage disconnected Q4 — Failure Effect: "Valve drives to fully open or closed regardless of control signal. Control room operator notices flow deviation alarm within 5 minutes. Manual control can be established via handwheel. Process upset may result in batch quality issue (£5,000 value). Reconnecting linkage takes 30 minutes, one technician." Q5 — Consequence: Evident, no safety impact, operational consequence (batch quality risk) Q6 — Proactive Task: On-condition task: Weekly visual inspection during rounds to check linkage integrity and tightness. Tighten if loose. Time: 2 minutes. Q7 — Default Action: N/A — proactive task identified

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Key Takeaways

• •Question 1 establishes what we're protecting — functions must be specific and quantified
• •Question 2 identifies how functions can be lost — both complete and partial failure
• •Question 3 determines what causes failures — at a level allowing maintenance selection
• •Question 4 describes the evidence and impact — essential for consequence assessment
• •Question 5 categorises consequences — this drives maintenance selection
• •Question 6 selects proactive tasks — only if applicable AND worth doing
• •Question 7 provides defaults — failure-finding, redesign, or run-to-failure

The seven questions form a rigorous logic that ensures maintenance is justified, appropriate, and focused on preserving function rather than just "maintaining equipment."

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Want to apply these questions to your equipment? Our RCM FMEA Template Pack guides you through each question systematically. Or explore our FMEA step-by-step guide for detailed instructions on documenting your analysis.