What commissioning is and why it matters
Installation puts the equipment in place. Commissioning proves that it works as a system under the conditions the plant will actually run in. Skipping or rushing it is one of the commonest reasons new compressors trip in their first summer, dryers pass water, or controls make machines fight one another.
A good commissioning process gives you three things:
- A safe system, with protections tested rather than assumed.
- Evidence that the agreed performance has been delivered.
- A baseline of readings against which future service can be judged.
Manufacturer start-up procedures, statutory pressure-vessel requirements and authorised electrical work always apply and remain specific to each project.
Agree acceptance criteria before start-up
If nobody has written down what “working” means, nobody can say when commissioning is finished. Agree the following with the supplier and the plant team before the first start:
| Item | Typical acceptance basis |
|---|---|
| Pressure | Minimum pressure at defined points of use under peak demand |
| Flow | Required flow at the stated pressure, without standby machines running |
| Air quality | ISO 8573-1 class for particles, water and oil; pressure dew point |
| Temperature | Discharge temperature within normal range at hottest expected ambient |
| Controls | Load, unload, sequencing and restart behaviour as described in the control narrative |
| Safety | Safety valves, shutdowns, emergency stops, guards and labels in place and tested |
| Energy | Baseline kW and specific power in kW per m³/min recorded |
| Documentation | As-built drawings, settings, manuals and maintenance plan handed over |
Completion gates before the first start
Commissioning should not begin until each completion gate has been closed:
- Mechanical: equipment level, supported and anchored, with access for maintenance; piping supported without strain on the compressor connections.
- Electrical: supply, cable size, earthing, protection settings, starter or VSD and control wiring checked by competent electrical personnel.
- Pressure system: receivers, piping and safety devices inspected and documented as required.
- Safety: guards, labels, isolation points and emergency stops complete.
- Housekeeping: debris, rags, temporary blanks and packing removed from piping and enclosures. Foreign material in a new header is a frequent cause of early filter and drain problems.
- Ventilation: room inlet and exhaust openings and ducts complete, so hot air does not recirculate.
Pre-start checks on the compressor
- Confirm oil level and grade, and that transit locks and packing are removed.
- Check belts or coupling alignment where applicable.
- Verify supply voltage and phase sequence, then bump-check rotation direction. Reverse rotation can damage a screw airend quickly.
- Check that the inlet filter is clean and correctly seated.
- Confirm all isolation valves are in the correct position and the discharge path is open.
- Check condensate drains are connected and their discharge goes to an oil–water separator for oil-injected systems.
- Review controller settings: load and unload pressure, maximum pressure, restart settings and any sequencer inputs.
First start and functional testing
The first start should be controlled and observed. Start unloaded where the control allows, listen for abnormal noise, check for leaks and watch temperatures and current. Then work through the functions:
- Load and unload across the pressure band, confirming the switching points.
- Response to a demand change: the compressor or VSD should follow without large pressure swings.
- Sequencing: in a multi-compressor system, check that machines start, stop and change roles as designed.
- Restart after power failure, if enabled.
- Dryer start-up and operation; drain cycling.
- Safety shutdowns: high discharge temperature, motor overload and other protections operate and are reported correctly. Test methods should follow the manufacturer’s procedure.
- Emergency stop and safety valve function.
Performance and air-quality testing
Functional tests prove that the system works. Performance tests prove that it does the job. Run the system at real production demand and, ideally, during the hottest part of the day.
| Reading | Where | What normal looks like |
|---|---|---|
| Discharge temperature | Compressor controller | Typically about 75–95 °C for an oil-injected screw |
| Pressure | Compressor discharge, after treatment, at critical users | Losses within the agreed pressure budget |
| Pressure dew point | Dryer outlet | Typically about +3 °C for a refrigerated dryer; −20 °C or −40 °C for desiccant |
| Filter pressure drop | Across each filter | Low on new elements; record as baseline |
| Motor current and kW | Starter or VSD | Within nameplate at full load |
| Load and unload hours | Controller | Sensible ratio for the machine’s role |
Where users need a defined ISO 8573-1 class, such as pharma, food or instrument air, measurement of particles, moisture and oil at the point of use may be required. Agree the method and who carries it out as part of the acceptance criteria.
Recording the baseline and handing over
The commissioning record becomes the reference for every future service visit. A useful handover pack includes:
- Commissioning checklist, signed, with all readings.
- Final controller, VSD, dryer and sequencer settings.
- As-built drawings and redlined changes made during installation.
- Manuals and spare-parts lists.
- Open items, with owners and dates.
- Maintenance plan and first service date.
- Basic operator training record: normal readings, alarms, safe isolation.
Commissioning a multi-compressor system
When several compressors share a header, commissioning must prove the system as a whole, not each machine on its own. Assign each compressor a role (base, trim or standby) and check that its pressure band or sequencer setting matches that role. Then test what happens when demand rises and falls, when the trim machine reaches full speed, and when a running machine trips. The standby unit should start automatically and pressure should recover within the agreed band. Record which machine runs how many loaded hours during the performance run, so later reviews can tell whether the control strategy is working as intended.
Common commissioning problems
| Problem | Likely cause | Fix |
|---|---|---|
| High temperature trip in the afternoon | Poor room ventilation or hot-air recirculation | Duct the cooler exhaust out; increase inlet openings |
| Water at users despite new dryer | Dryer bypass open, drain not working, piping debris | Check valve positions and drains; flush piping |
| Frequent load and unload | Narrow pressure band, small receiver | Adjust settings; add storage |
| Machines fighting | Overlapping pressure bands without sequencing | Set staggered bands or a central controller |
| Low pressure at far users | Undersized piping or restrictive fittings | Measure pressure profile; fix bottleneck |
Commissioning in Indian site conditions
A system commissioned in a cool month can behave very differently in a Hyderabad summer. If commissioning happens in winter, agree a follow-up check during the first hot season to confirm discharge temperature, dryer dew point and room temperature at peak ambient. Dust is another local factor: check intake filters and cooler fins soon after start-up on dusty sites, because construction debris and road dust load them quickly in the first weeks.
Power quality also deserves attention. Voltage dips, unbalance and harmonics can cause nuisance trips on motors and variable-speed drives. Recording supply voltage under load during commissioning helps separate supply problems from equipment faults later. For temporary or rental compressors, the same principles apply on a smaller scale: check hoses, couplings, fuel or power supply and safety devices before the unit takes production load.
How Reddy Compressors helps
Reddy Compressors, Tarnaka, Secunderabad, has served industry since 2002 as an independent multi-brand specialist. We commission compressors, dryers and complete systems that we supply, and we also carry out independent commissioning checks on equipment of Atlas Copco, Ingersoll Rand, ELGi, KAESER, Chicago Pneumatic, Gardner Denver, Sullair, Doosan, Kirloskar and other makes. We are not an authorised dealer of any brand. We have tie-ups with all major and reputed brands.
- Pre-start inspection of installation, piping, ventilation and drains.
- Controlled first start, functional and safety testing.
- Performance runs with recorded pressure, temperature, dew point and power readings.
- Handover records and a maintenance plan, with service or AMC to follow.
- Rental compressors from our own fleet if the plant needs air before the new system is accepted.
Our team of more than 20 service engineers and technicians covers Telangana and Andhra Pradesh, and we supply equipment and spares across India. Call +91 99590 60718 or +91 92468 88812.
What to send us
- Equipment list with make, model and nameplate photos.
- Installation layout or photos of the compressor room and piping.
- Required pressure, flow and air-quality class at the users.
- Electrical supply details and starter or VSD type.
- Planned start-up date and any production deadlines.
Frequently asked questions
What is the difference between installation and commissioning of a compressor?
Installation places and connects the equipment: foundations, piping, cabling and ventilation. Commissioning then proves that the installed system works safely and meets its duty. It includes pre-start checks, a controlled first start, functional and safety tests, performance runs at real demand, air-quality checks and a documented handover. A compressor that has been installed but not commissioned has not yet shown it can carry production.
What checks should be done before starting a new air compressor?
Confirm oil level, removal of transit locks, correct supply voltage and phase sequence, rotation direction, clean inlet filter, open discharge path and correct valve positions. Check drains, safety valve and emergency stop, and review controller settings. Make sure the room ventilation is complete and the piping is free of debris. Follow the manufacturer’s start-up procedure, which takes priority over any general checklist.
What should the discharge temperature be on a new screw compressor?
For a typical oil-injected screw compressor, normal discharge temperature is about 75–95 °C, depending on the machine, load and ambient. Record it during the hottest part of the day at full load as part of commissioning. A reading that climbs towards the shutdown limit on a new machine usually points to ventilation, hot-air recirculation or cooler airflow, which should be fixed before handover.
How do I test compressed-air quality after commissioning?
Start by recording the dryer’s pressure dew point and checking that drains and filters are working. Where users need a defined ISO 8573-1 class, measure particles, moisture and oil at the point of use with suitable instruments, using an agreed method. Do this after the piping has been flushed and the system has run for a period, so installation debris does not distort the result.
Who should sign off compressor commissioning?
The plant owner or their engineer should sign off, based on recorded readings against acceptance criteria agreed before start-up. The supplier or commissioning engineer signs the test records, and competent electrical and pressure-system personnel sign their parts. Open items should be listed with owners and target dates, so acceptance is clear and nothing important is left undefined.
Why does my new compressor keep loading and unloading?
Rapid load and unload cycling usually means the pressure band is too narrow for the receiver volume and demand pattern, or that two machines are reacting to the same pressure without coordination. Widen the band within what the users can tolerate, review receiver size, and set staggered pressure bands or use a sequencer. Frequent cycling wastes energy and wears valves and contactors.
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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.