Updated 20.07.26
Condition-Based Maintenance (CBM maintenance) is one of the three core maintenance strategies used within reliability centred maintenance (RCM), also spelled reliability centered maintenance outside the UK. When applied correctly, CBM maintenance can transform how organisations manage assets, reduce costs, and improve uptime.
CBM maintenance offers the ability to:
- Minimise maintenance work; tasks are only performed when condition data indicates a need
- Minimise maintenance costs; resources are used efficiently with no unnecessary interventions
- Minimise planned downtime; maintenance is scheduled at the optimal time
- Minimise unplanned downtime; early fault detection helps prevent unexpected failures
- Minimise production disruption; maintenance becomes predictable and strategically planned
Because of these advantages, many organisations assume CBM maintenance should be applied everywhere. However, this is not the case, and understanding why is central to reliability centred maintenance.
What is the difference between RCM and CBM?
The difference is simple but frequently misunderstood:
- RCM (Reliability Centred Maintenance) is a decision-making framework. It analyses how each asset fails and the consequences of those failures, then selects the most appropriate maintenance strategy for each failure mode.
- CBM maintenance (Condition-Based Maintenance) is one of the strategies RCM can select. Work is carried out only when condition monitoring data shows it is needed.
In simple terms: RCM tells you what to do. CBM tells you how to do it, where it applies.
Why reliability centred maintenance isn’t always CBM
A key principle of reliability centred maintenance (RCM) is that not all failure modes are predictable or worth monitoring.
CBM maintenance relies on detecting potential failure conditions early enough to take action. But in some cases:
- There is no measurable warning signal
- Detection methods are not cost-effective
- Failures occur too quickly to respond
Example: Light Bulb Failure
A simple example is a domestic light bulb:
- It typically fails without warning
- There is no practical condition monitoring technique
- There are no significant consequences of failure
- There is no cost benefit to replacing it early
In this situation, CBM maintenance is not suitable. The most logical strategy is run-to-failure (breakdown maintenance).
This illustrates a critical idea:
The “best” maintenance strategy depends on the failure mode, not the asset itself.
Learn more about how to build a business case for predictive maintenance
How reliability centred maintenance (RCM) determines the right strategy
Reliability centred maintenance (RCM) is a structured decision-making process, formalised in the SAE JA1011 standard, used to determine the most appropriate maintenance approach for each failure mode.
Rather than defaulting to CBM maintenance, RCM ensures that:
- Maintenance is technically feasible
- Maintenance is cost-effective
- Risks are properly managed
The RCM process: 7 steps explained
The reliability centred maintenance methodology follows a structured sequence:
1. Define asset functions
Identify what the asset must do to perform successfully.
Example: A pump must deliver 100 L/min at 10 m head and contain fluid without leaks.
2. Define functional failures
Determine when the asset fails to meet its required function.
Example: The pump runs but cannot deliver the required flow rate.
3. Identify failure modes
List all possible causes of failure, such as:
- Blocked pipelines
- Worn impeller
- Loose belt tension
- Coupling failure
- Electrical faults
4. Analyse failure effects
Understand what happens when each failure occurs.
Example: A blocked line could reduce flow, disrupt production, and cause overheating or pressure build-up.
5. Assess failure consequences
Each failure mode is assessed in four categories:
- Hidden failures – not immediately detectable
- Safety/environmental consequences – risks to people or compliance
- Operational consequences – production loss or cost impact
- Non-operational consequences – minor inconvenience only
This structured analysis is commonly known as FMEA (Failure Modes and Effects Analysis) or FMECA (Failure Modes, Effects and Criticality Analysis).
6. Select the most appropriate maintenance strategy
For each failure mode, choose the approach that is both technically feasible and worth doing:
- CBM maintenance (condition-based), where a failure gives detectable warning
- Preventive maintenance (time-based), where failure probability increases predictably with age or usage
- Run-to-failure (breakdown maintenance), where consequences are minor and no cost-effective prediction exists
If no strategy adequately manages a serious risk, RCM may recommend redesigning the asset or system to remove the failure mode altogether.
7. Implement, measure and review
RCM is not a one-off exercise. Once strategies are in place, condition data, failure records and maintenance KPIs feed back into the analysis, so decisions improve continuously as real operating evidence accumulates.
Learn more about the 7 benefits of condition-based maintenance (is it really worth it?)
Where CBM maintenance fits within RCM
Only after completing the RCM analysis can you determine whether CBM maintenance is appropriate.
CBM maintenance is selected when:
- A failure has a detectable warning sign (P-F interval)
- Monitoring methods are technically feasible
- The approach is cost-effective
Examples where CBM maintenance works well include:
- Vibration monitoring for rotating equipment
- Oil analysis for lubrication systems
- Thermography for electrical systems
In these cases, CBM maintenance plays a critical role in predictive maintenance strategies and reliability improvement.
RCM vs CBM maintenance: key difference
- RCM (Reliability Centred Maintenance) → A decision-making framework
- CBM Maintenance → A maintenance strategy used within that framework
In simple terms:
RCM tells you what to do
CBM tells you how to do it (when applicable)
Frequently asked questions
CBM maintenance (Condition-Based Maintenance) is a maintenance strategy where work is carried out only when asset condition data indicates it is necessary.
Instead of following a fixed schedule, CBM maintenance uses techniques such as:
- Vibration analysis
- Oil analysis
- Thermography
- Ultrasound monitoring
This approach allows organisations to detect faults early, reduce unnecessary maintenance, and prevent unexpected failures. CBM maintenance is often considered a key part of a broader predictive maintenance strategy.
Reliability centred maintenance (RCM) is a structured process used to determine the most appropriate maintenance strategy for each asset based on how it fails and the consequences of those failures.
Rather than applying a single approach across all equipment, reliability centred maintenance evaluates:
- Asset functions
- Functional failures
- Failure modes
- Failure effects
- Failure consequences
Based on this analysis, RCM selects the most effective strategy, which may include:
- CBM maintenance (condition-based)
- Preventive maintenance (time-based)
- Run-to-failure (breakdown maintenance)
The goal of reliability centred maintenance is to optimise reliability while minimising cost and risk.
Yes. CBM maintenance is one of the maintenance strategies that a reliability centred maintenance analysis can select. RCM is the framework that decides where CBM should be applied; CBM is the strategy that delivers the monitoring and intervention on the assets where it adds value.
CBM maintenance should not be used when it is not technically feasible or cost-effective to detect a failure before it occurs.
This typically includes situations where:
- There is no measurable warning sign before failure
- The failure happens too quickly to allow intervention
- Monitoring methods are too expensive relative to the risk
- The consequences of failure are low or insignificant
For example, components like light bulbs often fail without warning and have minimal impact, making run-to-failure the most practical approach.
In reliability centred maintenance, CBM maintenance is only selected when it provides clear value and actionable insight.
Conclusion: using CBM maintenance effectively
CBM maintenance is powerful, but only when applied in the right context.
Reliability centred maintenance ensures that CBM is used where it delivers real value, rather than being applied blindly across all assets.
By combining structured analysis with targeted maintenance strategies, organisations can:
- Reduce costs
- Improve reliability
- Eliminate unnecessary maintenance
- Focus effort where it matters most
Ready to implement reliability centred maintenance?
Whether you’re starting from scratch or refining an existing strategy, a reliability centred maintenance (RCM) review can help you:
- Identify the right maintenance approach for each asset
- Apply CBM maintenance where it is most effective
- Improve reliability while reducing cost
Get in touch today to discuss how reliability centred maintenance could work for your organisation.