Why commissioning is a test, not a ceremony
Most compressed-air problems that surface in the first year of a plant were present on the day of handover and were not looked for. The dryer that cannot hold its dew point in August was undersized for the ambient on the day it was installed. The far-end machine that starves at shift start was starving at handover, but nobody measured pressure at the tool under load. The receiver without a relief certificate was uncertified from delivery. The compressor that trips every June afternoon was short-circuiting its own hot exhaust from the first week, because the louvers were never checked against the heat-rejection figure.
Commissioning is the one moment when the installer, the owner and the service engineer are all present, the system is new, and nothing has yet been blamed on “age”. A proper commissioning record is also the baseline that every later service visit and every warranty discussion refers back to. Without it, there is no “before”.
The six rules that come before any test
These are not formalities; each one exists because somebody was hurt or a vessel failed when it was ignored.
- Never exceed the lowest rating in the system. A 13 bar compressor connected to a 10 bar receiver is a 10 bar system. Hoses, fittings and filters all have ratings; the lowest one governs the test pressure.
- Never defeat, block or isolate overpressure protection to complete a test. If a test cannot be done with the safety valves in service, it is the test that is wrong.
- Electrical energisation, high-voltage work and protective-device testing are for authorised, competent people using approved methods. Not the mechanical fitter, not the site electrician on his own say-so.
- Apply the site’s lockout-tagout, stored-energy release, mechanical isolation, confined-space and permit-to-work requirements. Compressed air stays stored after the machine stops; a receiver at 7 bar is energy, not an empty tank.
- An unchecked item is not a pass. It is recorded as Not Tested, with the reason, or Not Applicable, with the engineering justification. A blank box is a failure of the record, not evidence of a pass.
- Use calibrated instruments within their range, and record the uncertainty where it affects the decision. A ±2% gauge cannot prove a 1% acceptance tolerance.
The record: One sheet per checkpoint
Every checkpoint is recorded on the same sheet so that two installations, or the same installation five years apart, can be compared line by line. The sheet holds: the asset, location and serial; the approved reference and revision; the test date, inspector and witness; the instrument, its calibration and uncertainty; the operating conditions and load during the test; the measured result or observation; the acceptance limit; the result (PASS, FAIL, Not Tested, Not Applicable); the evidence reference (photo, trend, certificate); any nonconformity, corrective action and retest; and the signatures. PASS requires sufficient evidence. FAIL opens a tracked nonconformity. Not Tested means the dossier is incomplete. Not Applicable needs a written technical reason.
The forty checkpoints, in ten sections
Section 1 – Equipment identity, specification and documentation
| Checkpoint | What is done | Accepted when | The clue that something is wrong |
|---|---|---|---|
| 1. Manufacturer, model, serial and nameplate | Photograph every plate (compressor, motor or engine, receiver, dryer); reconcile with the purchase order and the as-built register | Every identity matches the approved configuration; any difference is formally dispositioned | Wrong model delivered; a receiver with no traceable plate; an obsolete nameplate on a “new” machine |
| 2. Rated airflow, pressure, power and operating conditions | Record the pressure basis, the free-air-delivery reference conditions, the motor or engine rating, altitude and temperature limits; compare with the duty | The machine meets the approved duty at site conditions, with any derating written down | Displacement quoted as if it were free air delivery; no allowance for a 45 °C compressor room |
| 3. Drawings, manuals, certificates and datasheets | Compare the general arrangement, P&ID, single-line diagram, wiring, manual and certificates with the current design index | Current, controlled, legible documents are on site | A superseded drawing; a missing statutory record for the receiver |
| 4. Deviations from the approved specification | Give each deviation an identifier, a risk assessment, a disposition and an approval route | Every material deviation assessed; safety-critical differences resolved before release | Substitutions agreed on the phone and never written down |
Section 2 – Installation, supports, ventilation and access
| Checkpoint | What is done | Accepted when | The clue that something is wrong |
|---|---|---|---|
| 5. Foundations, mounting, anchoring and vibration | Inspect base, grout, anchors, isolation and alignment; measure vibration under stated conditions where the design requires it | Matches the approved installation and the manufacturer’s limits | Soft foot; a pipe nozzle carrying the machine’s weight; loose anchors |
| 6. Inlet and discharge ventilation | Inspect the air paths for recirculation, check louvers and ducts, record ambient and room temperature under load | Measured airflow and temperatures meet the design | Hot exhaust short-circuiting to the intake; louvers blocked by a stores rack |
| 7. Cooling clearances, service access and lifting | Demonstrate that filters, the airend and the motor can actually be removed; check lift points and clearances | Manufacturer’s minimum clearances and safe maintenance routes exist | The door opens but the separator cartridge cannot come out |
| 8. Piping supports, expansion and connections | Walk the pipe: supports, flexible sections, isolation valves, drains, expansion provision, nozzle alignment | Conforms to drawings; every component is pressure-rated | An unsupported header; a rigid pipe bridging the machine’s vibration to the building |
Section 3 – Electrical and mechanical protection
| Checkpoint | What is done | Accepted when | The clue that something is wrong |
|---|---|---|---|
| 9. Electrical supply, earthing and protective devices | Authorised inspection of supply, phase rotation, earth continuity, device settings and ratings | Approved electrical design and the required tests are satisfied | Breaker set wrong; the wrong cable type on a VSD machine |
| 10. Motor protection, emergency stops and interlocks | Simulate approved inputs by safe methods; log expected and actual trips, resets and alarms | Every mandatory protective function responds as designed | The alarm sounds but the machine does not stop |
| 11. Guards, couplings and rotating-equipment protection | Inspect guards, couplings, fasteners and interlocked access | All required guards secure and working | A missing coupling guard; an exposed belt drive |
| 12. Electrical inspection and test evidence | Compile insulation, continuity and protection test evidence with the method and any exclusions | Signed records meet the applicable criteria | Insulation tested through a connected controller |
Section 4 – Pressure protection
| Checkpoint | What is done | Accepted when | The clue that something is wrong |
|---|---|---|---|
| 13. Pressure-equipment ratings and statutory records | Match maximum allowable working pressure, service, temperature, certificates and inspection obligations to every pressure boundary | Every component is suitable for its design pressure and service | An unrated receiver; a vessel certified for a different service |
| 14. Relief-device identity, set pressure and capacity | Match tag, set pressure, certified capacity, fluid and certification to the approved relief basis | Device and capacity meet the overpressure assessment | A valve of the right size but the wrong certified capacity |
| 15. Relief-device installation and discharge | Check orientation, isolation, back-pressure and the discharge path | Installed as the relief design requires | An outlet pointing at a walkway; a valve that can be isolated from its vessel |
| 16. Protection testing or certification | Verify valid certification or an approved test record; never force overpressure in service to “see it lift” | Documented compliance with the specified requirement | An in-situ lift test done by raising system pressure |
Section 5 – Operating pressure and airflow
| Checkpoint | What is done | Accepted when | The clue that something is wrong |
|---|---|---|---|
| 17. Discharge pressure under representative demand | Log pressure at the outlet and at the critical points during normal and peak loads | Results satisfy the limits, with uncertainty considered | A single reading taken with the plant idle |
| 18. Delivered airflow | Measure with a suitable, calibrated method; record pressure, temperature, calibration and the flow basis | Measured capacity meets the contractual tolerance on the stated basis | Actual flow compared with free air delivery as if they were the same |
| 19. Pressure stability through transients | Trend compressor and point-of-use pressure through load changes and control transitions | Stability and recovery meet the criteria | A ten-minute test that never saw the shift-start peak |
| 20. Comparison with the acceptance requirements | Compare each measured result with its limit, uncertainty and correction basis | All mandatory performance gates pass or are formally dispositioned | The acceptance limit quietly changed after the test |
Section 6 – Air-treatment performance
| Checkpoint | What is done | Accepted when | The clue that something is wrong |
|---|---|---|---|
| 21. Dryer performance and pressure dew point | Measure dew point at the defined location, load and stabilised state | Verified dew point meets the application | Sensor fitted upstream of the dryer, or downstream of a dead leg |
| 22. Filter installation and differential pressure | Confirm type, grade, flow direction, element condition and differential pressure | Correct grade installed; pressure loss within budget | The wrong element grade in the right housing |
| 23. Condensate drainage and disposal | Inspect traps, automatic drains, collection and the disposal route | Drains work; condensate handling meets the site’s environmental procedure | A drain stuck closed, flooding the receiver; a drain stuck open, wasting air |
| 24. Particle, water and oil purity | Sample and analyse for each required contaminant at the specified point, against the ISO 8573-1 class the process needs | Required class proven where it matters | “Oil-free compressor” taken to mean oil-free air at the point of use |
Section 7 – Control sequencing and alarms
| Checkpoint | What is done | Accepted when | The clue that something is wrong |
|---|---|---|---|
| 25. Load/unload, start/stop or VSD control | Trend setpoints, speed or load state, timers and pressure response | Transitions match the approved control narrative | Rapid cycling; instability at minimum speed |
| 26. Multi-compressor sequencing | Exercise lead, lag, trim and standby logic under safe demand scenarios | Sequencing and standby response meet the design | Two machines unloaded at the same time while pressure falls |
| 27. Alarms, shutdowns and permissives | Safe input simulation; record each response and reset | Every required action and annunciation confirmed | A bypassed trip left active after commissioning |
| 28. Sensor readings, settings and event recording | Compare readings with references; record the configuration and event timestamps | Sensors and logs within tolerance | Setpoints changed during commissioning and never documented |
Section 8 – Leakage and distribution pressure losses
| Checkpoint | What is done | Accepted when | The clue that something is wrong |
|---|---|---|---|
| 29. Leak survey | Survey accessible piping, joints, valves and connections at representative pressure; tag and photograph | Leakage within target, or defects in the action register | Leaks behind panels “not accessible” and therefore ignored |
| 30. Pressure loss across treatment and distribution | Simultaneous upstream and downstream readings at known demand, section by section | Each section and the total within the pressure-drop budget | Readings taken an hour apart at different loads |
| 31. Pressure at critical points of use under load | Measure at the equipment inlet during its real operating cycle | Minimum required pressure achieved where the work happens | Pressure read at the regulator with the tool idle |
| 32. Corrective actions for restrictions and leaks | Assign owner, method, retest and evidence | All release-blocking defects closed and retested | “Repaired” recorded with no retest |
Section 9 – Operator training and maintenance handover
| Checkpoint | What is done | Accepted when | The clue that something is wrong |
|---|---|---|---|
| 33. Normal operation and shutdown training | Demonstrate start, daily checks, alarm interpretation and shutdown; attendance and competence recorded | The required people are trained and the evidence accepted | The day shift was trained; the night shift was not |
| 34. Emergency procedures and safe isolation | Demonstrate emergency roles, isolation and residual-pressure release under controlled conditions | Procedures understood and demonstrated | Pressure still trapped between two closed valves after “isolation” |
| 35. Preventive-maintenance schedule and consumables | Map tasks to hours, time and conditions; name the kits and the responsibility | A complete, equipment-specific plan issued | A generic schedule overriding the manufacturer’s intervals |
| 36. Manuals, contacts and spare-parts information | Verify as-built manuals, serial-specific parts list, warranty terms and support contacts | Complete package acknowledged in writing | A parts manual for the previous revision of the machine |
Section 10 – Final acceptance evidence and unresolved defects
| Checkpoint | What is done | Accepted when | The clue that something is wrong |
|---|---|---|---|
| 37. Signed inspection and test records | Cross-check every mandatory inspection, calibration, test and approval against the index | All evidence traceable and complete | The flow test record is missing from the dossier |
| 38. Outstanding defects, severity, owners and deadlines | Classify safety, performance, operational and documentary defects with owners | No unresolved release-blocking issue; other items controlled | A safety defect labelled “cosmetic” |
| 39. Closure evidence for pre-operation defects | Review the correction, repeat the affected tests, record the witness | Objective evidence supports closure | Closed by an email saying “done” |
| 40. Authorised acceptance signatures and limitations | Issue the recommendation with limitations and residual actions; obtain the designated signatures | Only the authorised decision-maker signs, after the mandatory gates | An editorial approval mistaken for plant acceptance |
The measurements behind the checkpoints
Airflow and pressure. Every flow figure must carry its basis: free air delivery at stated inlet conditions, actual volume at the measured conditions, or standard volume at a defined reference. The sheet records the meter type, range and accuracy, the straight pipe run before it, the data interval, the production state and the correction method. Figures on different bases are never compared directly; a catalogue displacement is not a delivered flow. The FAD and reference-condition conversion tool and the compressor performance acceptance worksheet do this arithmetic.
The pump-up estimate. For a receiver-based system with negligible leakage, filling a known volume from one absolute pressure to another in a measured time gives an approximate free-air delivery: flow ≈ V × (P2 − P1) ÷ (P_ref × t). A 500-litre receiver taken from 4 to 7 bar gauge in 90 seconds has had roughly 0.5 × 3 = 1.5 m³ of free air added, about 1.0 m³/min, or 35 cfm. It is a diagnostic estimate, sensitive to temperature, connected volume and the compressor’s controls; it is not a certified capacity test, and for screw machines with integrated receivers and modern controls an instrumented flow test is the right method.
Ventilation. The preliminary air needed to remove the heat a compressor rejects is V = Q ÷ (ρ × cp × ΔT): the manufacturer’s heat-rejection figure, the air density at site, and the allowable room temperature rise. Add the other heat sources in the room, allow for louver and duct losses, check the fan curve, and look for recirculation. Then measure the room temperature under load on a hot afternoon, because the calculation is only a prediction. The compressor room ventilation worksheet does the arithmetic.
The pressure-drop budget. The sections are the same on every job: compressor to dryer, the treatment train, the main header, the critical branch, the tool hose. Each gets an upstream and downstream reading at the same moment and a known load, a measured loss, a budgeted loss and a disposition. The pressure budget builder and the pipe network pressure drop calculator build the budget; the walk-down proves it.
The cause-and-effect matrix. For each initiating condition (high temperature, motor protection, low pressure, emergency stop, sensor fault) the matrix records the expected alarm, the expected protective response, the observed response, whether the reset was verified, and the result. It is the single document that proves the machine will protect itself when nobody is watching.
What is different on Indian sites
The checklist is universal; the failure modes are local. Compressor rooms at 45 °C with louvers facing the afternoon sun; dust loading that halves the intake filter interval; a monsoon that defeats a dryer sized on a European ambient; electrical supplies with voltage sag at shift start that trip motor protection set to the nameplate; receivers from a previous installation with no traceable certificate; and site crews who are experienced but have never been shown the isolation sequence for this machine. Checkpoints 6, 9, 13, 21, 23 and 34 are the ones that most often come back FAIL on a first commissioning here, and the ones a Reddy Compressors service engineer looks at first.
Commissioning a rental tie-in or a relocated machine
The forty checkpoints scale. For a rental machine tied into a plant for a shutdown, the identity, protection, pressure-and-flow, control and training sections still apply, compressed into a day; the commissioning and acceptance page in the rental section shows the short form. For a machine relocated from one plant to another, the installation, electrical and pressure-protection sections are done again in full, because the foundation, the supply and the receiver are all new to the machine; the asset relocation and recommissioning guide explains why “it worked at the old site” proves nothing.
What we do, and what needs the manufacturer or the authority
Reddy Compressors commissions the compressors, dryers, receivers and distribution we supply, hire or relocate, and carries out commissioning assessments on installations by others: the inspections, measurements, functional tests, training and dossier above, by our service engineers with calibrated instruments. Three things sit outside that scope and are said so in writing: statutory certification of pressure vessels and relief devices, which is the competent authority’s; manufacturer-authorised procedures for engineered-to-order, high-voltage and hazardous-area packages, which need the manufacturer’s model-specific documentation; and clause-by-clause compliance declarations against standards, which need the current licensed text and an independent reviewer. The centrifugal service boundary page describes the same honest boundary for high-speed machinery.
How Reddy Compressors helps
Commissioning of new, used, refurbished and rental compressors and air-treatment equipment across Telangana and Andhra Pradesh; commissioning assessments and baseline measurement on existing installations; the forty-checkpoint record as a document you keep; more than 20 service engineers and technicians; independent of any manufacturer since 2002.
What to send us
- What is being installed or tied in (make, model, pressure, flow) and where
- Whether it is a new installation, a relocation or a rental tie-in, and the date
- The duty: pressure and flow at the point of use, hours, air-quality requirement
- Drawings, datasheets and receiver certificates you have; WhatsApp 99590 60718
Frequently asked questions
Do you issue a commissioning certificate?
We issue the commissioning record: the forty checkpoint sheets, the measurement annexes, the cause-and-effect matrix, the defect register and an acceptance recommendation with its limitations, signed by our service engineer and your witness. Statutory certification of vessels and relief devices comes from the competent authority, not from us.
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Short explainers on this topic
Slide-by-slide engineering explainers from Reddy Compressors. More in the video library.
How long does commissioning take?
A single screw compressor with a dryer and receiver in a prepared room is usually a day for the inspections and functional tests plus a load run; a multi-compressor station with sequencing, air-quality sampling and training takes two to three days. Air-quality laboratory results follow separately.
Can you commission a machine we bought elsewhere?
Yes. The checklist does not care who supplied the machine. We will need the manufacturer’s manual and datasheet for the model.
What if a checkpoint fails?
It becomes a numbered nonconformity with a severity, an owner and a deadline. Release-blocking items (safety, pressure protection, electrical protection) are closed and retested before the machine goes into service; other items are tracked to closure.
Is a pump-up test enough to prove capacity?
No. It is a useful diagnostic estimate for receiver-based piston systems. Contractual capacity needs an instrumented flow measurement on a stated basis.
Do you train our operators?
Yes; training the people who will run the machine, including the night shift, is checkpoints 33 and 34, and it is recorded.
Related pages
- Compressor performance acceptance worksheet
- Rental commissioning and acceptance
- Asset relocation and recommissioning
- Safety, isolation and permit to work
- Compressor room ventilation worksheet
- Pressure budget builder
- Compressor controls and sequencing
- Compressor pump-up test and capacity check
- Industrial air compressor selection guide
Technical content reviewed by D. Srinivas Reddy, Managing Partner and service engineer, Reddy Compressors. Last updated 4 November 2026. How our engineering content is reviewed.