Why a repaired leak is not a permanently removed loss
Leak campaigns usually end with a satisfying number: so many tags raised, so many closed. A few months later the compressors are running as hard as before. The leaks were real, the repairs were real, but many did not last. Push-in fittings work loose under vibration, quick couplings wear, hoses crack in heat, drains stick open again and new leaks appear where work was done in a hurry.
The dashboard adds the dimension most leak registers miss: time. It follows each verified repair into later operating periods and answers one management question:
“Of the repairs that have reached their follow-up date, how many were checked properly, how many still pass, and what is happening to the rest?”
A repair that has not been revisited is not automatically failed, but neither is it proven to have lasted. Keeping those three groups separate is the core of the tool.
What the dashboard calculates
| Measure | Calculation | What it tells you |
|---|---|---|
| Eligible repairs | Verified repairs whose follow-up date has passed | The population that should have been re-checked |
| Inspection coverage | Re-checked ÷ eligible | How much of the evidence actually exists |
| Persistence rate | Still passing ÷ re-checked | How well repairs last, on inspected items only |
| Recurrence rate | Leaking again ÷ re-checked | How often the same point fails again |
| Unknown status | Eligible but not re-checked | The size of the evidence gap |
| Residual leak flow | Sum of estimated flow from recurred and new leaks | Air still being lost, in m³/min or cfm |
| Recurrence by mechanism | Recurrences grouped by component and cause | Where to change parts, methods or specifications |
A headline such as “95% of repairs successful” means little without the coverage beside it. If only 30% of eligible repairs were re-checked, the persistence figure describes a small and possibly unrepresentative sample.
Inputs: what each record needs
Persistence analysis depends on a clean link between the original leak and every later visit. Each record should hold:
- A unique leak identity and tag number that survives re-tagging
- Location: area, line, machine and exact point
- Component type: coupling, push-in fitting, hose, flange, valve stem, regulator, drain, cylinder seal, filter bowl
- Original estimated leak size, from ultrasonic reading or flow estimate, with the method used
- Repair date, action taken and parts used
- Initial verification: who checked, how, at what pressure
- Follow-up dates and result of each re-check: pass, recurred, replaced by a new leak nearby, or not inspected
- Cause of recurrence, where known
Re-checks must be made at comparable system pressure with the same detection method. An ultrasonic survey at 6 bar on a Sunday cannot be fairly compared with one at 7.5 bar during full production.
Method: building follow-up groups
The dashboard uses cohorts – groups of repairs completed in the same period – so that recent and old repairs are not mixed.
- Group repairs by the month or campaign in which they were verified.
- Set follow-up points suited to your plant, for example one, three, six and twelve months after repair. There is no universally correct interval; vibration, heat and the quality of fittings decide it.
- Count the eligible population at each follow-up point.
- Record outcomes as pass, recurred or not inspected.
- Calculate coverage and persistence separately for each cohort.
- Classify recurrences by component and cause.
- Compare with station data – flow, unloaded running and energy – to see whether persistent repairs are actually reducing compressor load.
Worked example
A textile mill in Andhra Pradesh completes a leak campaign and verifies 120 repairs in one month. Six months later:
- Eligible repairs: 120
- Re-checked: 90, so coverage is 90 ÷ 120 = 75%
- Still passing: 72, so persistence is 72 ÷ 90 = 80%
- Recurred: 18, so recurrence is 20% of inspected repairs
- Unknown: 30 repairs not yet inspected
Of the 18 recurrences, 11 are quick couplings on loom feed drops and 4 are push-in fittings on vibrating frames. The recurred leaks are estimated at about 0.9 m³/min in total. The useful conclusion is not “80% success” but “quick couplings on loom drops are failing repeatedly; change the coupling type and re-check the remaining 30 repairs”. That is the information a maintenance manager can act on.
Common recurrence mechanisms and fixes
| Component | Typical cause of recurrence | Lasting correction |
|---|---|---|
| Quick couplings | Wear from frequent connection, dirt, cheap seals | Better-quality couplings, dust caps, fewer disconnections |
| Push-in fittings | Vibration, tube cut at an angle, scored tube | Square-cut tube, support clips, threaded fittings on vibrating machines |
| Hoses | Heat, oil, UV and abrasion; wrong rating | Correct hose grade, routing away from hot surfaces |
| Threaded joints | Poor sealing, over-tightening, corrosion | Correct sealant, re-make with new fittings |
| Condensate drains | Timer drains set open too long, stuck float drains | Zero-loss level-sensing drains, scheduled cleaning |
| Regulators and FRLs | Diaphragm wear, cracked bowls | Replace kits on a schedule, protect bowls |
| Cylinder and valve seals | Wear, contaminated or wet air | Improve air treatment, replace seals with the right material |
If the same component fails again and again, it should be passed to bad-actor analysis rather than repaired a third time in the same way.
How to read the dashboard
- Low coverage means the evidence is weak; schedule re-checks before drawing conclusions.
- High persistence but rising station flow means new leaks are appearing elsewhere, or demand has grown. Repairs alone cannot hold the line without regular surveys.
- Falling flow but unchanged energy often means the compressors are unloading rather than stopping or slowing. Check controls, sequencing and receiver storage.
- Clustered recurrences in one area point to a design or installation problem, not just maintenance.
Limits of the dashboard
The dashboard tracks evidence; it does not detect leaks or estimate their size by itself. Its flow figures are only as good as the survey method used. It does not set tariffs or emissions factors, and it does not guarantee that energy will fall – that depends on how the compressors respond to lower demand. Energy savings should be confirmed against an adjusted baseline, and any cost or carbon value calculated separately with your own inputs.
Setting up the dashboard in practice
Most plants already hold the raw material for a persistence dashboard in job cards, survey reports and maintenance software. The work is mainly in linking records consistently.
- Fix the identity rule. Give every leak point a permanent identity based on its location, so that a later leak at the same coupling is recognised as a recurrence rather than a new item.
- Standardise outcomes. Use a short, fixed list: pass, recurred, new leak nearby, component removed, not inspected.
- Agree the re-check method. Use the same detection method, at a comparable header pressure and production state, for every follow-up.
- Assign responsibility. Name who carries out re-checks and who reviews the dashboard each month.
- Review with the station data. Put the dashboard beside compressor loaded hours, flow and energy at the same monthly meeting, so that repairs and supply-side results are discussed together.
A simple spreadsheet is enough to start. What matters is that each repair can be traced from detection through every later inspection without relying on one person’s memory.
Where re-checks are scarce, prioritise the repairs that matter most: the largest original leaks, points on critical machines and component types that have recurred before. Inspecting those first gives the most useful evidence for the least effort, and the remaining repairs can follow in the next routine survey. Record the order of priority, so that coverage figures are read in context.
How Reddy Compressors helps
Reddy Compressors, based at Tarnaka, Secunderabad, carries out leak detection, repair support, re-surveys and full compressed-air audits for plants across Telangana and Andhra Pradesh. Our audits follow the ISO 11011 method, although we do not issue conformity certificates. Because we service and supply all major compressor brands as an independent specialist, we can also follow the result through to the compressor room: adjusting pressure bands, correcting sequencing, replacing faulty drains and checking that lower demand is actually turning into lower kWh. Where a supply-side change needs temporary cover, our own rental fleet can keep the plant running.
What to send us
- Your existing leak register or survey report, in any format
- Dates of past leak campaigns and repairs
- Compressor makes, models, pressures and running hours
- Any flow, power or energy data from the compressor station
- Plant layout or line list showing the main air users
Frequently asked questions
How long do compressed air leak repairs usually last?
It varies widely with the component, vibration, heat and repair quality. A properly re-made threaded joint can last years, while a worn quick coupling on a frequently used drop may leak again within weeks. That is why repairs should be re-checked at planned intervals and recurrence recorded by component type, rather than assuming every closed tag stays closed.
Why do compressed air leaks keep coming back?
Most recurring leaks come from the same few causes: poor-quality quick couplings, push-in fittings on vibrating machines, hoses near hot surfaces, stuck drains and joints re-made with the wrong sealant. Repeating the same repair gives the same result. Changing the component type, supporting the pipework and improving air treatment usually stops the cycle.
What is inspection coverage in a leak repair programme?
Inspection coverage is the share of repairs due for follow-up that were actually re-checked. It shows how much evidence supports the persistence figure. If only a third of eligible repairs were inspected, a high persistence rate may be misleading. Good dashboards always report coverage beside persistence and list the uninspected repairs separately.
How often should a factory carry out a compressed air leak survey?
There is no single correct interval. Many plants survey at least once or twice a year and re-check recent repairs in between, while plants with heavy vibration, frequent line changes or large networks benefit from more frequent checks. The persistence dashboard itself helps set the interval: if recurrences rise quickly, survey more often.
Why did energy not fall after we fixed the leaks?
Lower air demand reduces energy only if the compressors respond. Fixed-speed machines that unload but keep running still draw significant power, and poorly set pressure bands can keep extra machines on line. Check controls, sequencing and receiver storage, and compare energy against an adjusted baseline rather than last month’s bill.
Can Reddy Compressors re-survey leaks we repaired earlier?
Yes. Our engineers can re-survey previously repaired points with the same method and comparable system pressure, update your register with pass or recurrence results and identify repeat offenders. We work on sites across Telangana and Andhra Pradesh from our Secunderabad office and can follow the work through to compressor controls and energy checks.
Related pages
Calculators and worked examples
These tools give indicative figures for screening, comparison and for preparing an enquiry. They run in your browser and send nothing. No prices or tariffs are assumed: enter your own to see costs. Efficiencies and other figures shown are example values: replace them with your own. Results are not a performance guarantee or a design certificate; final selection is confirmed by a service engineer against the machine data sheet and the site.
Leak repair persistence
The worked example below shows the method with fixed numbers. Turn on JavaScript to change the inputs.
Worked example
Inputs
- Number of eligible repairs (follow-up date passed): 120
- Number of repairs re-checked: 90
- Number of repairs still passing: 72
- Number of repairs leaking again (recurred): 18
- Number of recurrences in the most frequent component group: 11
- Estimated flow of recurred leaks (m³/min): 0.9
- Estimated flow of new leaks found nearby (m³/min): 0
- Specific power (kW per m³/min): 7
- Running hours per year: 6000
Result
- Inspection coverage: 75 % (90 of 120)
- Persistence rate: 80 % of re-checked repairs still pass
- Recurrence rate: 20 % of re-checked repairs leak again
- Other outcomes among re-checked: 0 repairs (neither passing nor recurred)
- Unknown status: 30 eligible repairs not yet re-checked
- Persistence range over all eligible: 60–85 % (all unknowns failed – all unknowns passed)
- Most frequent component group: 61.1 % of recurrences (11 of 18)
- Residual leak flow: 0.9 m³/min (32 cfm)
- Compressor power for residual leaks: 6.3 kW
- Energy per year: 37,800 kWh
- Cost per year: Enter your electricity tariff (cost per kWh) above
Method. Coverage = re-checked ÷ eligible. Persistence = still passing ÷ re-checked; recurrence = leaking again ÷ re-checked (inspected items only). Unknown = eligible − re-checked. The persistence range assumes every unknown repair failed (low) or passed (high), each over all eligible repairs. Residual flow = estimated flow of recurred leaks + new leaks nearby; power = flow × specific power. Other outcomes = re-checked − passing − recurred (for example component removed). Default: the page example (120 eligible, 90 re-checked, 72 passing, 18 recurred, 11 of them quick couplings, 0.9 m³/min).
What to take from it. Report coverage beside persistence. A high persistence figure from a low coverage describes a small, possibly unrepresentative sample.
Technical content reviewed by D. Srinivas Reddy, Managing Partner and service engineer, Reddy Compressors. Last updated 17 October 2026. How our engineering content is reviewed.