Book companion resource · Worksheet
Mean Time to Repair (MTTR) in Plant Maintenance
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Measure the whole clock. Then break it.
Mean time to repair (MTTR) is the average time it takes to get a failed asset back in service, from the moment the failure is reported to the moment the asset runs again. In plant maintenance, the hands-on repair is often the smallest part of that time. The rest is waiting: for a technician, for a diagnosis, for parts.
- The MTTR formula and a worked calculation.
- The five clocks inside every repair, and how to time them.
- Target bands for critical assets.
- The worksheet below, printable as a PDF: clock breakdown, repair kits, response protocol, diagnostic aids, shift coverage and a 90-day tracker.
The MTTR formula
MTTR = total repair downtime ÷ number of repair events
Repair downtime for one event runs from failure notification to the asset back in service. Count unplanned repairs only, not planned PMs. Use the same start and stop points every month, or the trend means nothing.
The worksheet's clock runs one step further, to work order closure, so a slow close-out shows up too. When you report MTTR as a KPI next to availability, stop at return to service, the definition in Fix the System, Chapter 4, and keep the closure minutes as their own number.
A worked MTTR calculation
Original fictional scenario. Created for this page to show the arithmetic. It is not a real plant or a real result.
A packaging line logs four breakdowns in a month. They took 1.5 hours, 2 hours, 3.5 hours and 9 hours from the call to the line running again.
Total repair downtime is 16 hours. Divided by 4 events, MTTR is 4 hours.
Three of the four repairs finished well under 4 hours. One 9-hour event pulled the average up to the edge of the target. Before anyone works on the average, the team opens that one event and breaks its clock.
Calculate MTTR per asset, or per failure mode on your critical assets, as well as for the plant. A belt change and a gearbox rebuild do not belong in one average.
Break the clock: the five parts of MTTR
A work order records a start time and an end time. Everything in between is invisible. Part 1 of the worksheet splits each long repair into five components, in minutes:
- Response
- Failure reported (alarm, call or report) to a technician on site with the work order.
- Diagnosis
- Technician on site to failure mode confirmed and repair scope defined.
- Parts retrieval
- Diagnosis done to every part needed in hand at the job.
- Repair
- Parts in hand to the asset restored and running.
- Closure
- Repair done to the work order closed in the CMMS with the notes filled in.
Take your five longest repairs from the last three months. Rebuild each timeline from the alarm log, radio calls, storeroom records and the technician's memory. Average each component. The largest one is the first thing to fix. Do not try to fix all five at once.
From the book: the bearing at 2:17 AM
Story from Fix the System, Chapter 24.
A motor failed at 2:17 in the morning. The night technician diagnosed it in fourteen minutes: inboard bearing, same as always. The CMMS showed three bearings in stock. The bin was empty.
He checked nearby bins, called the day shift lead, searched the back of the shop and finally called the vendor's emergency line. The bearing arrived at 6:28. He installed it in ninety-one minutes.
The work order recorded just under six hours of downtime. The repair itself took less than two.
When the manager and the technician broke the clock on the five longest repairs of the quarter, hands-on repair averaged eighty-eight minutes. Everything else averaged four hours and forty-five minutes. The repair was 24% of MTTR. Waiting was 76%.
“So what we're actually measuring,” the technician said, “is how long it takes to get set up to fix it.”
In that plant, parts retrieval was the largest component. In yours it may be diagnosis, access, permits or restart checks. Fix the largest one you can show with evidence.
MTTR targets for critical assets
| MTTR on critical assets | Band | What to do |
|---|---|---|
| Under 2 hours | World class | Sustain it with kit audits and shift coverage. |
| 2 to 4 hours | Target range | Close the remaining parts and coverage gaps. |
| 4 to 8 hours | Recovering | Find the largest clock component and fix that one. |
| Over 8 hours | Act now | Build repair kits and break the clock on every long event. |
These are the working bands from Fix the System, Chapters 4 and 24. Set asset-specific targets where consequence, access and failure mode differ. One plant-wide number hides those differences.
How to bring MTTR down
- Break the clock on your five longest repairs and find the largest component.
- Build repair kits for your five most common breakdowns on critical assets: verified parts, special tools, the printed job plan and the lockout procedure, in one labeled box near the asset. Check the parts physically, not from the CMMS.
- Set a response standard, for example a technician on site with the work order and kit within 20 minutes, and write down who gets called next if nobody answers.
- Write a one-page diagnostic aid for each top failure mode: the three most likely causes in order, and the two-minute check for each.
- Cross-train until at least two technicians per shift can do each repair on their own. Watching a repair does not count.
- Run a repair-versus-replace review when two years of repairs pass 50% of an asset's replacement value.
Questions planners ask
- How do you calculate MTTR?
- Add up the downtime of every unplanned repair in the period, from the failure report to the asset back in service. Divide by the number of repairs. Four repairs that took 16 hours in total give an MTTR of 4 hours.
- Does MTTR include waiting for parts?
- Yes. The clock runs from the failure report to the asset running again, so waiting for a technician, a diagnosis or a part all count. That is the useful part: in many plants the waiting is longer than the repair.
- What is a good MTTR for maintenance?
- On critical assets, under 4 hours is the target in Fix the System, under 2 hours is world class, and over 8 hours means act now. Compare each asset with its own history before you compare it with another plant.
- What is the difference between MTTR and MTBF?
- MTBF, mean time between failures, is how long an asset runs between breakdowns. MTTR is how long each breakdown keeps it down. Together they set availability: MTBF ÷ (MTBF + MTTR). Lower MTTR raises availability even when failures happen just as often. For the MTBF formula and a calculator, see MTBF and MTTF.
- Should you push technicians to repair faster?
- No. Pressure on the repair itself tends to produce rushed close-outs and repeat failures. Remove the waiting around the repair instead: kits, a response path, diagnostic aids and shift coverage.
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The PDF remains the blank worksheet. This web guide is excluded from printing so it does not add pages to the form.
Break repair events into clock components, identify the dominant delay, and track repair kit readiness and technician coverage for critical failure modes.
Companion to: Fix the System, Chapter 24. Who uses it: the maintenance manager, planner, and shift lead. When to use: at the start of the MTTR Reduction playbook, then monthly on any event exceeding 4 hours.
Plant / Asset Group: _______________________ Date: _______________________ Completed by: _______________________
PART 1 — Clock Breakdown: Last 5 High-MTTR Events
For each event, reconstruct the time sequence from failure notification to WO closure. Record each component in minutes.
| Event | Asset | Failure Mode | Response (min) | Diagnosis (min) | Parts Retrieval (min) | Repair (min) | Closure (min) | Total MTTR (min) |
|---|---|---|---|---|---|---|---|---|
| 1 | ||||||||
| 2 | ||||||||
| 3 | ||||||||
| 4 | ||||||||
| 5 | ||||||||
| Average |
Clock Component Definitions:
- Response — Failure notification (alarm, call, report) to technician physically on-site with WO.
- Diagnosis — Technician on-site to failure mode confirmed (root cause identified, repair scope defined).
- Parts Retrieval — Diagnosis complete to all required parts physically in hand at the job site.
- Repair — Parts in hand to asset restored and functional.
- Closure — Repair complete to WO closed in CMMS with all required information entered.
Dominant Component (highest average): _______________________
This is the first thing to fix. Do not address all components simultaneously.
PART 2 — Repair Kit Inventory
For each of the top 5 critical breakdown scenarios, assess the current repair kit state.
A repair kit is: a physical case or shelf section containing verified parts, specialized tools, the printed job plan, and the LOTO procedure for one specific breakdown scenario. Staged near the asset or in a designated emergency repair area. Not a CMMS parts list.
| Kit # | Asset | Failure Mode | Kit Exists? | Parts Verified (Physical)? | Job Plan Included? | LOTO Procedure Included? | Staged Location | Last Verified Date | Last Used / Restocked |
|---|---|---|---|---|---|---|---|---|---|
| 1 | ☐ Yes ☐ No | ☐ Yes ☐ No | ☐ Yes ☐ No | ☐ Yes ☐ No | |||||
| 2 | ☐ Yes ☐ No | ☐ Yes ☐ No | ☐ Yes ☐ No | ☐ Yes ☐ No | |||||
| 3 | ☐ Yes ☐ No | ☐ Yes ☐ No | ☐ Yes ☐ No | ☐ Yes ☐ No | |||||
| 4 | ☐ Yes ☐ No | ☐ Yes ☐ No | ☐ Yes ☐ No | ☐ Yes ☐ No | |||||
| 5 | ☐ Yes ☐ No | ☐ Yes ☐ No | ☐ Yes ☐ No | ☐ Yes ☐ No |
Rule: Parts in a kit must be physically verified — not confirmed from the CMMS. A kit built from a CMMS list that has not been physically checked may contain wrong specifications or missing items. Verify before sealing. Audit every 90 days.
Kits missing or incomplete: _______ Action owner: _______________________ Target completion: _______________________
PART 3 — Response Time and Escalation Protocol
Document the current response chain for each shift and verify it is functional.
Response Time Target: Technician on-site with WO and repair kit within _______ minutes of failure notification on critical assets.
| Shift | On-Call Technician | Contact Method | Response Time Standard | Escalation Contact (if no answer) | Escalation Method | Last Tested |
|---|---|---|---|---|---|---|
| Day | ☐ Phone ☐ Radio ☐ Pager | ___ min | ||||
| Afternoon | ☐ Phone ☐ Radio ☐ Pager | ___ min | ||||
| Night | ☐ Phone ☐ Radio ☐ Pager | ___ min | ||||
| Weekend Day | ☐ Phone ☐ Radio ☐ Pager | ___ min | ||||
| Weekend Night | ☐ Phone ☐ Radio ☐ Pager | ___ min |
Gaps identified: _______________________________________________
PART 4 — Diagnostic Aids Assessment
For each top failure mode, verify a one-page diagnostic aid exists.
A diagnostic aid is: a one-page fault tree or diagnostic sequence listing the three most likely causes in frequency order and the two-minute check that identifies each. Different from a job plan — the job plan tells you how to fix it; the diagnostic aid tells you what it is.
| Failure Mode | Asset | Diagnostic Aid Exists? | Last Updated | Cause 1 | Cause 2 | Cause 3 | Action if Missing |
|---|---|---|---|---|---|---|---|
| ☐ Yes ☐ No | |||||||
| ☐ Yes ☐ No | |||||||
| ☐ Yes ☐ No | |||||||
| ☐ Yes ☐ No | |||||||
| ☐ Yes ☐ No |
To write a diagnostic aid: Interview the most experienced technician for each failure mode. Ask: "When you hear this alarm / see this symptom, what's the first thing you check, and what are you looking for?" The three answers become the fault tree branches. Keep it to one page. Laminate it and store it in the repair kit.
PART 5 — Technician Coverage Matrix
Identify coverage gaps for each critical failure mode across shifts.
Target: Minimum 2 technicians per shift who can execute the repair independently (not just assist).
| Failure Mode | Asset | Day Shift | Afternoon | Night | Weekend | Gap Shifts | Cross-Train Plan |
|---|---|---|---|---|---|---|---|
Cross-training is complete when: the technician executes the repair independently using the job plan, with the experienced tech available but not directing. Document the date of independent completion below.
| Technician | Failure Mode | Completed Training Date | Independent Repair Date | Verified By |
|---|---|---|---|---|
PART 6 — Repair-vs-Replace Tracker
For assets with high repair frequency or cost, track cumulative two-year repair cost against replacement value.
Threshold: If 2-year accumulated repair cost exceeds 50% of replacement value, conduct a formal repair-vs-replace analysis.
| Asset | Replacement Value | Repair Events (2 yr) | Cumulative Repair Cost (2 yr) | Ratio (%) | Action |
|---|---|---|---|---|---|
| ☐ Continue repairing ☐ RVR analysis needed | |||||
| ☐ Continue repairing ☐ RVR analysis needed | |||||
| ☐ Continue repairing ☐ RVR analysis needed | |||||
| ☐ Continue repairing ☐ RVR analysis needed | |||||
| ☐ Continue repairing ☐ RVR analysis needed |
Note: The 50% threshold is a prompt for the conversation, not an automatic replacement decision. Factors that may justify continued repair: replacement lead time, capital budget cycle, production impact of extended changeover. Document the decision and rationale regardless of outcome.
PART 7 — 90-Day MTTR Tracker
| Week | Critical Asset Events | Total MTTR Hours | Avg MTTR (hrs) | Avg Parts Retrieval (min) | Avg Response Time (min) | Repair Kits Used | Kits Restocked? |
|---|---|---|---|---|---|---|---|
| Week 1 | ☐ | ||||||
| Week 2 | ☐ | ||||||
| Week 3 | ☐ | ||||||
| Week 4 | ☐ | ||||||
| Week 5 | ☐ | ||||||
| Week 6 | ☐ | ||||||
| Week 7 | ☐ | ||||||
| Week 8 | ☐ | ||||||
| Week 9 | ☐ | ||||||
| Week 10 | ☐ | ||||||
| Week 11 | ☐ | ||||||
| Week 12 | ☐ | ||||||
| Week 13 | ☐ |
Benchmarks:
- MTTR >8h: Action threshold. Build repair kits and break the clock immediately.
- MTTR 4–8h: Recovering. Identify dominant clock component and address.
- MTTR 2–4h: Target range. Focus on remaining parts retrieval and coverage gaps.
- MTTR <2h: World-class. Sustain through kit audits and coverage maintenance.
From Fix the System by Ivan Getov. Companion to Chapter 24: Playbook 10 — MTTR Reduction. getov.xyz/toolkit/fix-the-system/ch24/mttr-clock-analysis. Free. No email required.