Reliability-Centred Maintenance: a structured method that examines the consequence of each failure mode and selects the maintenance task that suits it and is worth its cost. SAE JA1011 and JA1012 define its criteria and give guidance.

Is predictive maintenance right for every asset?

No. There must be a measurable symptom before failure, the P-F interval must be long enough for the measurement interval, and monitoring must cost less than the failure. Otherwise time-based maintenance or run to failure may fit better.

What is the P-F interval?

The time between the first measurable symptom of a failure and the loss of function. For condition monitoring the measurement interval should, by a common rule of thumb, be about half of it or shorter.

What does hidden failure mean?

A failure nobody notices during normal operation; usually the failure of a protective or standby function (safety valve, alarm, standby pump) that only has consequences when another failure occurs. The remedy is a regular failure-finding test.

When is run to failure acceptable?

When the failure carries no safety or environmental risk, production impact and repair cost are low, and the preventive task would cost more than the failure. Spare parts and a repair method should be kept ready.

Maintenance Strategy Selector — predictive, preventive or run to failure? RCM logic

Equipment name (optional)Used when adding to the list, for example "Pump P-101".

Consequence of the failure

Choose the most severe one.

Production impact

Production or service loss per failure.

Repair cost

Parts, labour and external service per failure; pick on your own scale.

Failure likelihood

How often this failure mode occurs, from your maintenance records; an example scale, adapt it to your own risk matrix.

Failure pattern

Do failures increase with the age or usage of the equipment?

Is there a measurable symptom before the failure?

A change you can monitor, such as vibration, temperature, oil condition, current, pressure or sound.

Is the P-F interval long enough for your measurement interval?

P-F interval: the time between the symptom first appearing and the failure occurring. If the measurement interval is about half of it or shorter, the symptom is caught before failure.

Monitoring cost compared with failure cost

Compare the cost of sensors, inspection rounds and analysis with the total cost of the failure.

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Recommended strategy

Condition monitoring / predictive maintenance

Measure the symptom (vibration, temperature, oil analysis, current and so on) and intervene in a planned way when a threshold is crossed. The measurement interval should be about half the P-F interval or shorter.

Reasons

The failure affects production: maintenance cost is weighed against the lost output.
There is a measurable symptom before the failure.
The P-F interval is long enough for the measurement interval: the symptom can be caught before failure and a planned intervention made.
Monitoring costs less than the failure: condition monitoring is economic.

Criticality

Severity: 4
Likelihood: 3
Score: 12
Class: High

5×5 criticality matrix: the number in each cell is severity × likelihood
	Severity
	1	2	3	4	5
5	5	10	15	20	25
4	4	8	12	16	20
3	3	6	9	this asset: 12	15
2	2	4	6	8	10
1	1	2	3	4	5

↑ Likelihood

Simplified first assessment; it does not replace a full RCM analysis.

This tool is a simple decision flow inspired by RCM logic (SAE JA1011/JA1012); it does not replace a full RCM analysis, in which a team works out functions, functional failures and failure modes. The criticality bands are examples; adapt them to your own risk matrix.

Let's assess which strategy could be backed with data for your critical equipment.

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Equipment list

No equipment added yet. You can assess several assets and collect them in one table.

01

How to use it

A
Choose the consequence of the failure; mark production impact, repair cost and failure likelihood on your own scale.
B
Answer the failure pattern, the measurable precursor, whether the P-F interval is adequate and the monitoring cost.
C
Read the recommended strategy, the reasons and the position in the criticality matrix; add the asset to the list and download it as CSV.

02

RCM decision logic in brief

Reliability-Centred Maintenance (RCM) asks for each failure mode: what is the consequence, and is there a maintenance task that can prevent it and is worth its cost? If the consequence is safety or environmental, the task must reduce the risk to an acceptable level; for economic consequences only, the task must cost less than the failure.

The flow in this tool is as follows. If the failure is hidden (a protective function), a failure-finding test is chosen. If there is a measurable symptom before failure and the P-F interval is adequate for the measurement interval, condition monitoring is chosen. Otherwise wear-related failures lead to time-based maintenance, and random failures lead to run to failure or redesign depending on the consequence.

The flow is only a small part of a full RCM study. In a real analysis functions, functional failures, failure modes and their effects are worked out by a team; this tool gives a quick first pointer for a single failure mode.

03

The P-F interval and the measurement interval

The time between a failure starting to show a symptom (potential failure, P) and losing its function (functional failure, F) is the P-F interval. For condition monitoring to work, measurements must be taken more often than that; a common rule of thumb is to keep the measurement interval at about half the P-F interval or shorter, so that you can expect to see the symptom at least once with enough time left to act.

If the interval is in the order of minutes, or you cannot measure often (access, cost, safety), condition monitoring is not reliable for that failure mode. Sensors that measure continuously often remove this limit, which is why sensor coverage is decisive in predictive maintenance projects.

04

How to read the criticality matrix

The criticality score is severity times likelihood (1-25). In this tool severity is 5 for safety and environmental impact, and otherwise the larger of production impact and repair cost; a hidden failure is taken as at least 3, because the real consequence comes from multiple failures.

The score bands (1-4 low, 5-9 medium, 10-15 high, 16-25 critical) are examples. If your organisation has its own risk matrix, use that. The score helps rank maintenance budget and priorities: for critical equipment, investment in monitoring and redundancy; for low-class equipment, run to failure is usually more appropriate.

FAQ

What is RCM?: Reliability-Centred Maintenance: a structured method that examines the consequence of each failure mode and selects the maintenance task that suits it and is worth its cost. SAE JA1011 and JA1012 define its criteria and give guidance.
Is predictive maintenance right for every asset?: No. There must be a measurable symptom before failure, the P-F interval must be long enough for the measurement interval, and monitoring must cost less than the failure. Otherwise time-based maintenance or run to failure may fit better.
What is the P-F interval?: The time between the first measurable symptom of a failure and the loss of function. For condition monitoring the measurement interval should, by a common rule of thumb, be about half of it or shorter.
What does hidden failure mean?: A failure nobody notices during normal operation; usually the failure of a protective or standby function (safety valve, alarm, standby pump) that only has consequences when another failure occurs. The remedy is a regular failure-finding test.
When is run to failure acceptable?: When the failure carries no safety or environmental risk, production impact and repair cost are low, and the preventive task would cost more than the failure. Spare parts and a repair method should be kept ready.

Back the strategy with data

Let's assess which symptoms can be measured on your critical equipment and where predictive maintenance pays off.

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