What this is
What does MTBF actually measure?
What does MTBF actually measure?
Mean time between failures is total operating hours divided by the number of failures in a period, for a single asset or a class of similar assets. It is a rate, not a guarantee — an asset can run well past its MTBF and fail the next hour. Its value comes from comparing periods against each other, not from the figure in isolation.
Why does this review exist separately from a failure report?
An equipment failure report captures one event. An MTBF review aggregates a period of events into a rate, checks whether that rate is improving or worsening against the previous period, and decides whether the trend justifies a reliability intervention. It is analysis of a pattern, not a record of an incident.
What is the difference between MTBF and MTTR here?
MTBF measures how often an asset fails; MTTR measures how long it takes to get it back into service once it has. Both feed availability. A site can hold a healthy MTBF and still run poor availability if MTTR is long, so the review carries both figures side by side rather than MTBF alone.
Scope
When is a mtbf review required?
This review aggregates failure data into a trend. It is not the place to investigate a single failure, decide a maintenance strategy, or record a repair — those live in the neighbouring templates this one draws its inputs from.
Use this template when
- The reporting period covered by this review has closed, or a trigger event (a repeat failure, a bad actor) has forced an out-of-cycle look
- A new record is needed; each one gets its own ID in the form MTBF-2026-000
- You are running the Reliability and Predictive Maintenance programme and this quarterly review is one of its scheduled steps
- You need to decide whether a declining trend on an asset justifies raising a bad actor report or a CAPA
- A linked record needs this one to exist, such as a PM Optimization Review citing the measured intervals behind an interval change
Do not use it for
- Equipment Failure Report, which records a single failure event as it happens, not a rolling rate across a period.
- Equipment FMEA, which works through how an asset could fail, what the effect would be and how likely it is to be detected, ahead of any actual failure data.
- Reliability Centred Maintenance Study, which decides the maintenance strategy for each failure mode once this review or an FMEA has identified where the problem sits.
- PM Optimization Review, which uses this review's MTBF figures as an input but is deciding task frequency, not failure rate.
- Anything outside KnowMaintain, which belongs in the workspace that owns that process
Compliance mapping
Which ISO 14224 requirements does this satisfy?
ISO 14224 governs how reliability data is classified and collected so that failure rates are comparable across assets, sites and time; the fields below map to the parts of that framework this review depends on.
| Clause | Requirement | Where it lands |
|---|---|---|
| ISO 14224 Cl. 4 — equipment taxonomy and boundary | The asset or class under review must be identified against a consistent equipment boundary before a failure rate means anything. | Assets reviewed |
| ISO 14224 Cl. 5 — failure and maintenance data collection | Failure counts feeding the rate must come from recorded failure events, not estimate or memory. | Assets reviewed |
| ISO 14224 Cl. 6 — time-related reliability data | Operating hours behind the MTBF calculation should be metered, not assumed, for the figure to be defensible. | Interpretation |
| ISO 14224 Cl. 6 — reliability performance parameters | MTBF and MTTR are reported as a pair, since either alone under-represents availability. | Assets reviewed |
| ISO 14224 Cl. 7 — data presentation and trending | A single period's figure is compared against the prior period to establish direction, not read in isolation. | Assets reviewed |
| ISO 14224 Annex — failure mode classification | The dominant failure mode driving the rate is classified against a standard taxonomy so patterns can be compared across assets. | Assets reviewed |
What it does not cover
- An MTBF figure with no trend direction recorded, which tells a reader nothing about whether the asset is heading toward failure or away from it.
- Operating hours marked assumed rather than metered, which means the MTBF calculated from them is a decorative number, not a reliability finding.
- A declining asset with no bad actor report and no action raised, which lets a known problem asset roll into the next quarter unaddressed.
- Availability percent reported without MTTR alongside it, which hides whether a healthy failure rate is being undone by slow repairs.
- A blended MTBF across an asset class with dissimilar duty or design, which masks the one unit that is actually degrading behind the average of the others.
Global
MTBF Review requirements by country
MTBF as a metric is not itself a legal instrument, but the reliability data standard behind it, and the industries that lean on it hardest, differ enough by region and sector to change how the review should be run.
ISO 14224
The template's own basis standard
ISO 14224 defines the equipment classes, failure modes and time-related data this review depends on; sites outside oil and gas can still adopt it, but should expect to adapt the taxonomy to their own asset types.
OSHA process safety management, 29 CFR 1910.119, and FDA food-contact equipment rules
Drives why a declining MTBF on safety- or hygiene-critical assets can't just be logged and left
Where the asset sits in a safety-critical or food-contact system, a worsening trend feeds directly into process safety or sanitation risk assessments, not just a maintenance backlog.
EN 13306 (maintenance terminology) alongside ISO 14224
Sets the terminology many EU sites expect this review to align to
EN 13306 defines MTBF, availability and related terms in a way most European reliability teams already use; aligning field labels to it avoids a translation gap between this review and the plant's own KPIs.
How to complete it
How to complete a mtbf review, step by step
Filling in the numeric fields is mechanical. The defensibility of the review rests on four judgement calls a reliability engineer has to make deliberately, not default through.
An estimated or assumed hours figure produces an MTBF that looks precise but isn't. Mark it honestly — 'Estimated' or 'Assumed' — rather than letting a guess pass as data; a reviewer downstream needs to know how much weight the number can bear.
Reviewing 'MTBF' across a mixed class of old and new, or duty-cycle-different assets, produces an average that hides the one unit degrading. Split the review by class before trusting the blended figure.
A first review has no prior period to compare against, so 'Stable' or 'Improving' is a guess dressed as a finding. Flag it as a baseline period rather than asserting a trend that doesn't exist yet.
The review exists to trigger intervention, not just to log a number. An asset marked declining with no bad actor report and no CAPA reference is a review that identified a problem and then did nothing with it.
What auditors find
Most common mtbf review findings
The failure modes that repeat across MTBF reviews sit less in the arithmetic and more in what gets skipped around it.
| Finding | Clause | What fixes it |
|---|---|---|
| MTBF reported with no comparison to a prior period | ISO 14224 Cl. 7 | Require the previous period's figure and a trend direction before the review can close; a first review is flagged as a baseline instead. |
| Operating hours marked assumed, MTBF still treated as fact | ISO 14224 Cl. 6 | Route any review with assumed or estimated hours to a lower confidence rating and flag metering as an action item. |
| A declining asset closed with no action raised | Site reliability procedure | Make Action Required mandatory wherever Trend Direction is Worsening, not left to reviewer discretion. |
| MTBF blended across a mixed equipment class | ISO 14224 Cl. 4 | Split review rows by a consistent equipment sub-class before calculating a class-level rate. |
| Bad actors identified but no bad actor report reference recorded | Site reliability procedure | Cross-check Bad Actors Identified against Bad Actor Report Raised before sign-off; a mismatch blocks closure. |
| Availability percent reported with no MTTR figure alongside it | ISO 14224 Cl. 6 | Make MTTR Hours mandatory wherever Availability Percent is entered, since one without the other misrepresents uptime. |
Case in point
Case in point: the pump that looked fine on paper
A packing-line pump held an MTBF of 1,600 hours for three straight quarters, comfortably above the site's 1,200-hour target, and every review closed it as stable. The operating hours behind the figure, though, were marked assumed — nobody had fitted a run-hour meter, so the reliability engineer was working from the maintenance planner's estimate of shift utilisation.
When the pump failed twice in six weeks, a root cause analysis found the real operating hours were roughly 40% higher than assumed, meaning the true MTBF had already dropped below 1,000 hours two quarters earlier. The review process wasn't wrong to run quarterly; it was wrong to let an assumed hours figure carry the same weight as a metered one without saying so.
The template
The template, field by field
The form exactly as it installs. Every field, option, score and conditional rule is editable, and the links to other templates come with it.
4 sections
- Reference
- MNT-051
- Archetype
- Review
- Record ID
- MTBF-2026-000
- Scoring
- Hours between failures
- Direction
- High is good
- Singleton
- No
- Basis
- ISO 14224
- Links
- Links Asset, Failure records
- Tags
- Reliability, Analysis
- Sections
- 4
- Fields
- 43
- Follow up fields
- 3
- Repeating sections
- 1
- Links out
- 4
Header
11 fieldsReview ID*
Auto sequence. Format MTBF-2026-000.
The record's own ID. Other templates point at this value.
Status*
Drives who this goes to next.
- Planned2 pts
- In progress2 pts
- Complete3 pts
- Deferred0 pts
- Open0 pts
- Closed3 pts
- Overdue0 pts
Date and Time*
Raised By*
Site*
Site ID*
Format SITE-000.
Links to FDN-001 Site ID
Area
The area within the site.
Exact Location
Drop a pin for anything hard to find.
Period From*
Period To*
Scope*
Single asset, asset class, line or whole site.
Assets reviewed
Repeats11 fieldsAsset*
Asset ID*
Format AST-0000.
Links to FDN-002 Asset ID
Operating Hours*
Failures*
MTBF Hours*
Total Repair Hours
MTTR Hours*
Availability Percent*
Previous Period MTBF
Trend Direction*
- Improving3 pts
- Stable2 pts
- Worsening0 pts
Dominant Failure Mode
Related records
1 fieldFMEA ID
The failure modes these intervals were measured against.
Links to MNT-049 Assessment ID
Interpretation
20 fieldsDirection Beats Absolute Value
MTBF numbers are only meaningful against your own history. A machine at 900 hours and climbing is in better shape than one at 1,400 and falling.
Assets Improving*
Assets Stable*
Assets Declining*
Site MTBF
Site Availability Percent*
Availability Target
Data Quality Adequate*
MTBF calculated from incomplete failure records is a decorative number.
- Yes3 pts
- Partly1 pt
- No0 pts
Operating Hours Accurate*
- Metered3 pts
- Estimated1 pt
- Assumed0 pts
Bad Actors Identified*
Bad Actor Report Raised
Action Required*
Raise the action record, then enter its reference here.
- No2 pts
- Yes0 pts
Priority
- High0 pts
- Medium1 pt
- Low3 pts
CAPA ID
Format CAPA-2026-00000.
Links to FDN-014 CAPA ID
Action Owner
Next Review Due*
Reliability*
Signature*
Maintenance Manager*
Second Signature*
MNT-051 · record IDs look like MTBF-2026-000 · Links Asset, Failure records
Open in KnowellaRun it with agents
From a document you fill in to a programme that runs itself
The arithmetic behind MTBF is simple. What actually slips is keeping the operating-hours data honest, catching a declining asset before it rolls into a fourth quarter unaddressed, and connecting the finding to the report or study that should follow it.
Holds the MTBF review library against your asset register, flags any review built on assumed or estimated operating hours, and keeps the trend history connected across quarters.
Picks up any declining trend on a safety-critical asset and checks whether it should be feeding a risk assessment rather than sitting as a maintenance line item.
Rolls site-level availability and MTBF trends into the operations view, so a declining reliability picture shows up next to the production numbers it affects.
Coordinates the crew, rolls completion and exceptions into one view, and holds every write for your approval before it touches a record.
This template lives in KnowMaintain — asset maintenance. Work orders, planned maintenance, calibration, reliability and shutdowns.
Meet KnowMaintain→Glossary
MTBF Review definitions and key terms
- MTBF
- Mean time between failures — total operating hours divided by the number of failures, for a defined asset or asset class over a period.
- MTTR
- Mean time to repair — the average time an asset spends out of service being fixed, once a failure has occurred.
- Availability
- The proportion of scheduled time an asset is actually able to run, driven by both MTBF and MTTR together.
- Bad actor
- An asset whose failure rate, cost or downtime impact is disproportionately high relative to its peers, usually flagged for targeted intervention.
- Equipment class
- A group of assets with comparable design, duty and failure behaviour, used as the unit against which reliability data is aggregated and compared.
FAQ
Frequently asked questions about mtbf review
What is the MTBF review template based on?+
It is built against ISO 14224, the reliability and maintenance data standard that defines equipment classes, failure modes and time-related data used to calculate rates like MTBF consistently across assets and sites.
What sections does the MTBF review contain?+
Four sections: Header, Assets reviewed, Related records, Interpretation. Together they hold 43 fields, 30 of which are required, with the assets reviewed section repeating for each asset in scope.
How often is an MTBF review raised?+
Quarterly by default, plus any trigger event such as a repeat failure or a newly identified bad actor. Each record gets an ID in the form MTBF-2026-000 so it can be traced and referenced from other records.
Why does trend direction matter more than the MTBF number itself?+
MTBF only has meaning against its own history. An asset at 900 hours and climbing is in better shape than one at 1,400 and falling, because the trend shows whether the failure rate is heading toward or away from trouble.
What happens when data quality is marked inadequate?+
The review still runs, but its findings carry a lower confidence rating. A worsening trend calculated from incomplete failure records or assumed operating hours shouldn't be treated with the same weight as one built on metered, complete data.
Can the MTBF review template be changed?+
Yes. Every field, option, score and conditional rule is editable, and the links to other templates come with it. Most teams install it as it is, run it for a cycle, then adjust the equipment classes and scope to match their own asset register.
Keep going
Related templates and programmes
Industries this is written for
Programmes this belongs to
Used together in Reliability and Predictive Maintenance
Root Cause Analysis
Finds out why something happened rather than who was involved
Equipment Failure Report
Records that an asset has failed and stopped or degraded production
Failure Mode Record
Records how an asset failed, using standard failure mode codes rather than free text
Repair Record
Records what was actually done to fix the asset, including parts replaced and settings changed
Temporary Repair Record
Records a repair that is not permanent, with an expiry date and a plan for the proper fix
Repeat Failure Review
Reviews an asset that has failed the same way more than once
More in Reliability
Equipment FMEA
Works through how an asset could fail, what the effect would be and how likely it is to be detected
Reliability Centred Maintenance Study
Decides the right maintenance strategy for each failure mode, from run to failure through to condition monitoring
PM Optimization Review
Reviews whether preventive tasks are set at the right frequency, using actual failure and finding data
Root Cause Failure Analysis Trigger
Decides whether a failure warrants a full investigation, based on cost, safety and repeat history
Spares Criticality Review
Decides which spare parts must be held on site based on lead time and asset criticality
Written and reviewed by
Siddarth Singh
Founder & Chief Executive Officer, Knowella
Certified Safety Professional and industrial and systems engineer with more than a decade inside food supply chain, freight and manufacturing operations. This page was written against the current text of the standards it cites, not against secondary summaries of them.
- Certified Safety Professional (CSP), Board of Certified Safety Professionals
- MBA, University of Chicago Booth School of Business
- MS and BS, The Ohio State University, Industrial and Systems Engineering
- Six Sigma Black Belt
Sources and last review. Reviewed 16 August 2026 against:
- ISO 14224 — Petroleum, petrochemical and natural gas industries: collection and exchange of reliability and maintenance data for equipment
- EN 13306 — Maintenance terminology
- 29 CFR 1910.119 — OSHA Process Safety Management of Highly Hazardous Chemicals
This page is general guidance, not legal advice. Confirm requirements with your jurisdiction’s regulator.