What a leakage programme must prove
Leaks are often the largest single waste in a compressed-air system, and they run every hour the network is pressurised, including nights and weekends. Finding them is the easy part. The value lies in turning a survey into repairs that actually lower the electricity the compressors use.
A good programme proves three separate things:
- The repaired component no longer leaks under normal service pressure.
- The affected zone or the whole system uses less air under comparable conditions.
- The compressor station uses less electricity while still supplying the required pressure, flow and air quality.
These are linked, but one does not prove the next. Replacing a coupling is maintenance activity. Rechecking it proves the fix. A flow measurement proves demand fell. Only power measurement proves the energy saving. Repairs can also release capacity or steady pressure even when compressor controls initially stop power falling as much as expected.
Set the boundary first
Decide which compressors, dryers, receivers, headers and production areas are included, and whether dryer, cooling-pump and other auxiliary power counts. Use the same boundary before and after.
Record the operating states that matter: production shifts, cleaning periods, weekends and shutdowns. A leak’s yearly cost depends on how long its branch stays pressurised, not just on factory working hours. A branch isolated every night leaks for far fewer hours than a header that stays live all week.
Agree the reporting question before any instruments go in. A maintenance manager may want to know how many leaks were closed; an energy manager wants kWh; a production head wants to know whether pressure at the far end of the line is now steadier. Each needs a different measurement, and choosing them at the start avoids arguments later about what the programme achieved.
Leaks, legitimate use and avoidable use
Not every hiss is a leak, and not every waste is a leak either. Sort findings into three groups:
- Leaks: air escaping through defects such as worn couplings, cracked hoses, failed seals, loose threads, damaged filter bowls and stuck drain valves.
- Legitimate use: air consumed by machines doing their job.
- Avoidable use: open blow-offs, air left on to idle machines, timer drains set to waste air, and excess pressure feeding unregulated users.
Avoidable use is tackled through controls and pressure; see artificial demand reduction. Keep it on a separate list so leak savings are not overstated.
Build a baseline you can repeat
The simplest baseline is a non-production test: with production stopped but the network pressurised, the air the compressors still supply is mostly leakage. Common ways to estimate it:
| Method | How it works | Limits |
|---|---|---|
| Flow meter at the station | Measures flow directly while the plant is idle and pressurised | Needs a suitable meter; includes any users left running |
| Load–unload timing | Leak flow is about compressor capacity × load time ÷ (load + unload time) | Only for fixed-speed load–unload machines; capacity must be the real FAD |
| Receiver pressure decay | With compressors off, time the pressure fall in a known system volume | System volume must be estimated well; pipes add to receiver volume |
| Power and flow logging in production | Gives the real station response across shifts | Leaks cannot be separated from use without the idle test |
Worked load–unload example: a compressor delivering 10 m³/min loads for 30 seconds and unloads for 70 seconds during an idle test. Leakage is about 10 × 30 ÷ 100 = 3 m³/min. This is an illustration; the real figure depends on the machine’s actual delivered air.
Repeat the baseline the same way after repairs, at the same pressure, so results are comparable. See leak detection and leak quantification and air-loss management.
Which leaks should be repaired first?
The biggest leak is not automatically first. Rank each finding on four factors:
- Estimated flow, at the operating pressure.
- Pressurised hours per year for that branch.
- Process consequence: a leak on a critical actuator or instrument line may matter more than its flow suggests.
- Repair effort: can it be fixed live with a simple part, or does it need a shutdown, isolation or a new component?
| Leak | Estimated flow | Pressurised hours | Relative yearly volume | Priority |
|---|---|---|---|---|
| A: large leak, standby branch | High | Low, isolated most of the time | Moderate | Schedule; consider isolating the branch |
| B: medium leak, production header | Medium | Continuous | High | Repair first |
| C: small leak, critical valve | Low | Continuous | Low | Repair early for reliability |
| D: cluster of small hose leaks | Low each | Shift hours | Moderate in total | Batch repair in one visit |
Plant hours and flow can be turned into estimated annual air volume and, using the station’s specific power, into estimated kWh. Treat these as planning estimates, not measured savings. The leakage cost scenario calculator helps with the arithmetic.
From survey finding to completed repair
- Tag each leak on site with a number, and record its location, component, estimated size and photo.
- Specify the repair: part, size, thread type and whether isolation is needed.
- Group repairs by area and by shutdown need to save labour.
- Carry out the repair with the right parts and sealing method, not tape over a cracked fitting.
- Recheck the repaired point at service pressure, with the same detection method, before closing the record.
- Remove the tag only after the recheck, and log the date and who verified it.
A repair register keeps this honest; see leak repair register and verification.
Turning less air into less power
Fewer leaks mean less demand, but the compressors must respond. A fixed-speed machine on load–unload control may simply unload for longer, still drawing a significant share of its loaded power while unloaded. A VSD machine or good sequencing turns lower demand into lower power more directly. Where several compressors run, the right outcome may be one machine switched off entirely.
After the repairs, review:
- Whether one compressor can now be shut down or moved to standby.
- Pressure settings: with less leakage, pressure drop falls and the station may run lower. As a typical figure, each bar of extra pressure costs about 7% more compressor power.
- Control bands, sequencer settings and unload timers.
- Receiver and storage use, to reduce short cycling.
Illustration: a station drawing 75 kW on average during an idle test falls to 50 kW after a repair campaign and control adjustment. Over 2,000 non-production hours a year, that is about 50,000 kWh. These are teaching figures; your result must be measured.
Keeping leaks from coming back
Leaks return as fittings wear, hoses age and new equipment is added. Without a routine, most of the gain fades. Practical steps:
- Re-survey on a fixed schedule, with more frequent checks in high-vibration or high-wear areas.
- Repeat the idle-flow test at the same pressure and compare with the baseline.
- Track leak flow as a key figure alongside specific power.
- Isolate unused branches and machines when not in use, with valves operators can reach.
- Specify good-quality couplings, hoses and drains for replacements.
- Train operators to report leaks and make reporting easy.
Our leak repair persistence dashboard shows one way to track this over time.
How Reddy Compressors helps
We carry out ultrasonic leak surveys with tagging and a repair register, idle-flow tests, and power and flow logging, as part of compressed-air audits following the ISO 11011 method. We do not issue conformity certificates; we give measured findings and an action list. Our technicians can carry out the repairs, recheck each one and then adjust compressor controls and pressure so lower demand becomes lower energy use.
As an independent multi-brand specialist, we service ELGi, Atlas Copco, Ingersoll Rand, KAESER, Chicago Pneumatic and other compressors, and supply their spares. Our office is at Tarnaka, Secunderabad, and our team of more than 20 service engineers and technicians covers Telangana and Andhra Pradesh. Leak checks can also be built into an AMC.
What to send us
- Compressor makes, models and pressure settings, with nameplate photos.
- Plant layout or a line diagram of the air network.
- Production hours, shifts and weekend pattern.
- Any earlier leak survey reports or tag lists.
- Electricity data or compressor running and loading hours.
Frequently asked questions
How do I find compressed air leaks in my factory?
Large leaks can be heard during quiet periods, and soapy water shows leaks on accessible joints. For a thorough survey, an ultrasonic leak detector picks up the high-frequency sound of escaping air even in a noisy plant. Survey the whole network, including drops, hoses, couplings, filter bowls, drains and machine connections, and tag each leak with its location and estimated size.
Does repairing every leak guarantee a lower electricity bill?
No. Repairs lower air demand, but the compressors must turn that into lower power. A load–unload machine may simply run unloaded for longer. Review controls, sequencing and pressure after repairs, and measure station power before and after under comparable conditions. Bills also move with production and weather, so measure the compressors directly.
Should the largest leak always be repaired first?
Not necessarily. Rank leaks by estimated flow, pressurised hours, process consequence and repair effort. A medium leak on a header that is live all week may waste more air than a large one on a branch isolated most of the time. A small leak on a critical valve may need fixing first for reliability.
Can an ultrasonic survey tell me my exact annual savings?
No. Ultrasonic tools locate leaks well and give an estimate of size, but the estimate depends on the instrument, distance, pressure and the leak’s shape. Use survey figures to plan and prioritise work. Prove the saving with idle-flow tests and compressor power measurement before and after repairs.
Why did air flow fall but power fall much less?
Usually because of compressor controls. A fixed-speed machine on load–unload control still draws a significant share of its power while unloaded, so lower demand gives a smaller power drop. Better sequencing, switching a machine off, a VSD trim compressor or more storage can recover more of the saving.
How often should a factory check for leaks again?
There is no single interval; it depends on how fast leaks return in your plant. Many plants re-survey several times a year, with high-vibration areas checked more often. Repeat the idle-flow test on the same basis and compare it with the baseline. If leakage climbs between surveys, shorten the interval.
Can the air saved from leaks run a new machine?
Often, yes. Capacity freed by leak repair can supply new demand and may delay buying another compressor. Confirm with flow and pressure measurements at peak production, and check that dryers, filters and pipes can carry the extra flow. Count this as deferred capital, not as an energy saving.
Related pages
Field guide
Leak reduction: Often the cheapest air you can buy
Leaks are compressed air you pay for and never use. In many plants they account for a large share of compressor output, and they run 24 hours a day whenever the system is pressurised.
Find them
- Weekend or shutdown test: with production stopped, note how often the compressor loads, or how fast receiver pressure falls. What it delivers then is mostly leakage.
- Ultrasonic detector: finds leaks you cannot hear in a noisy plant.
- Soap solution on accessible fittings.
Where they usually are
Quick couplings, hose connections, filter-regulator-lubricator units, drain valves stuck open, pipe threads, worn cylinder seals and tools left connected.
Make it stick
- Tag each leak, record its size estimate and location.
- Fix the biggest first; many need only a new fitting or seal.
- Re-test after repair and record the drop in demand.
- Repeat the survey regularly, because leaks return.
- Isolate idle areas and machines with valves when they are not working.
Use the leak cost calculator to put a figure on what your leaks cost each year.
What to send for a quotation
- Compressor make, model and rated power of each machine.
- Electricity tariff and annual running hours.
- Typical pressure at the compressor and at the furthest user.
- Any measurements you already have (power, flow, loaded hours).
Send it through find my part or the spare parts enquiry, or call +91 99590 60718 or +91 92468 88812.
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.
System leakage test: Load/unload timing, residual flow or pressure decay
Turn a non-production leakage test into a leakage flow, a share of compressor delivery, leak power and annual energy. Choose the method you used; only that method’s inputs are read. Optionally enter the result after repairs, or the measured station power before and after, to state the reduction.
The worked example below shows the method with fixed numbers. Turn on JavaScript to change the inputs.
Worked example
Inputs
- Test method: Load/unload timing (fixed-speed compressor)
- Compressor actual delivered air, FAD (m³/min): 10
- Load/unload: loaded time per cycle, averaged (s): 30
- Load/unload: unloaded time per cycle, averaged (s): 70
- Residual: measured flow with production stopped (m³/min): 5
- Residual: verified legitimate continuous users (m³/min): 1.2
- Decay: system volume, receivers plus pipework (m³): 5
- Decay: start pressure (bar g): 7
- Decay: end pressure (bar g): 6
- Decay: time for the pressure fall (s): 60
- Atmospheric pressure (bar a): 1.013
- System pressure during the test (bar g): 7.5
- Normal operating pressure to restate the result at (bar g): 7.5
- Leakage after repairs, same method and pressure (m³/min; 0 if not yet measured): 0
- Station specific power (kW per m³/min): 6.5
- Pressurised hours per year: 6000
- Optional: station power in the idle test before repairs (kW; 0 to skip): 0
- Optional: station power in the idle test after repairs (kW): 0
- Idle (non-production) hours per year for the measured power: 2000
Result
- Loaded share of the cycle: 30% T ÷ (T + t) = 30 ÷ 100 s
- Estimated leakage at the test pressure: 3 m³/min free air = 50 L/s = 105.9 cfm (load/unload)
- Leakage as a share of compressor delivery: 30% of 10 m³/min
- Leak power at the operating pressure: 19.5 kW at 6.5 kW per m³/min
- Leak energy per year: 1,17,000 kWh over 6,000 pressurised hours
- Leak energy cost per year: Enter your electricity tariff (cost per kWh) above
Method. Load/unload timing (fixed-speed load/unload compressor, production stopped, timed over several cycles): leakage ≈ FAD × T ÷ (T + t), with T the loaded and t the unloaded time per cycle. Residual flow (flow meter, production stopped): unexplained residual = measured residual flow − verified legitimate users (dryer purge, instrument air, drains); it is the figure to investigate, not automatically all leakage. Pressure decay (compressors stopped and isolated, no users): leakage in free air ≈ V × (p_start − p_end) ÷ (p_atm × time), with V the receiver plus pipework volume in m³, pressures in bar and time in minutes; the pressure difference is the same in gauge or absolute terms. Leak flow through an orifice rises roughly in proportion to upstream absolute pressure, so a result taken at one pressure is restated at the normal operating pressure by × (p_op + p_atm) ÷ (p_test + p_atm). Leak power = leakage × station specific power (kW per m³/min); annual energy = power × pressurised hours. The after-repair figure must come from the same method at the same pressure. The measured-power option gives (kW before − kW after) × idle hours, which is a measured saving, not an estimate. Money is shown only when you enter your own tariff.
What to take from it. Record the method, the pressure and the plant state with every result, so the next test is comparable. A lower leak flow saves energy only if the compressors then unload, slow down or stop.
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.