Recommissioning a compressed-air system to restore performance

When does a compressed-air system need recommissioning?

Few systems fail suddenly. More often, performance slips a little each year until the plant is using far more power for the same production, or users complain of low pressure even though more compressors are running. Common triggers are:

• Rising electricity use or specific power with no matching rise in production.
• Repeated low-pressure complaints from particular machines or areas.
• New production lines, extra shifts or faster machine cycles added since the system was designed.
• Recurring high-temperature trips, especially in summer.
• Compressors spending long periods running unloaded.
• Wet air, oil carry-over or unstable dew point.
• Controls running in manual or with sequencers bypassed.
• A major equipment change, such as a new compressor or dryer, added without system review.

Recommissioning, routine service and replacement are different

Performance problems often come from leaks, restrictions, controls, ventilation or changed demand rather than from the compressors themselves. Recommissioning should come before any decision to replace, so that new equipment is not bought to feed waste.

Recover the design intent and record what has changed

Start by collecting what the system was designed to do: equipment schedules, layouts, piping drawings, control descriptions, pressure targets, air-quality requirements and the original commissioning records, if any exist. Then record what has changed since: machines added or removed, pipe extensions, dryer replacements, new shifts, pressure increases and control modifications.

Before touching anything, freeze the current configuration. Record every compressor setpoint, sequencer setting, dryer mode, filter arrangement, receiver isolation, zone regulator setting and bypass position. Back up controller settings and take photos of displays. Recommissioning must be reversible if a change causes an unexpected problem.

Walkdown: what to look for on site

A careful walkdown of the whole system often reveals more than any single measurement. Look in particular for temporary fixes that became permanent:

• Compressor-room doors propped open for cooling.
• Dryers bypassed or filters removed after a pressure-drop complaint.
• Compressors running in manual mode with sequencers disabled.
• Setpoints raised to cure a single machine’s problem.
• Temporary hoses, tees and connections still in use.
• Alarms silenced or disabled.
• Drain valves left cracked open to clear water.
• Idle lines left pressurised and leaking.

Also check equipment condition: cooler cleanliness, filter differential pressures, separator condition, drains, oil condition, and the compressor-room environment, including intake air temperature, hot-air recirculation and dust. In Telangana and Andhra Pradesh, dust and summer heat foul coolers quickly, and many high-temperature trips trace back to a dirty cooler or a recirculating room.

Measure the system as it really runs

Measurement turns opinions into facts. A recommissioning survey typically logs, on the same time base:

• Pressure at the compressor discharge, after treatment and at critical users.
• Total system flow, where a flow meter can be fitted.
• Power or current of each compressor, with load and unload states.
• Dryer dew point at operating flow.
• Room and intake temperatures under full load.
• Non-production flow, measured with production stopped, which is mostly leakage.

From these, calculate the station’s specific power in kW per m³/min and compare it with what the machines should achieve. Our power and flow logging page explains the method.

How do you restore compressed-air system performance?

1. Repair leaks, starting with the largest, and isolate idle areas when not in use.
2. Remove restrictions: change loaded filter elements, open partly closed valves, replace undersized hoses and couplings.
3. Restore treatment: reinstate bypassed dryers and filters, repair drains, confirm dew point.
4. Correct the room: clean coolers, fix ventilation and stop hot-air recirculation.
5. Service the compressors where the survey shows worn separators, poor oil condition or blocked intake filters.
6. Reset pressure to the lowest value that maintains critical users, in small trial steps.
7. Retune compressor bands or the sequencer so machines do not overlap and unloaded running is reduced.
8. Re-enable alarms and safety functions that had been bypassed.
9. Re-measure under the same conditions as the baseline.

Each correction should be checked before the next, so you know which action produced which result.

Typical drift and what restores it

Restoring controls, sequencing and air quality

Control drift is one of the costliest and least visible problems. Over time, each compressor’s load and unload pressures are adjusted separately, often by different people, until the bands overlap. Several machines then run part-loaded or unloaded at once, and the plant sits at a higher average pressure than it needs. A sequencer may have been bypassed after a single fault and never reinstated.

Restoring control starts with a clear pressure hierarchy: one target band for the station, with each machine’s settings arranged so the base machines stay loaded and only one machine trims. Where a variable-speed machine is fitted, check that it really is the trim machine and that its speed range suits the demand. Confirm that a safe fallback exists if the sequencer fails, so the plant does not lose air. Our master compressor control page explains this coordination.

Air quality needs the same discipline. Confirm the required ISO 8573-1 class at the critical users, then check that each dryer achieves its expected pressure dew point at actual operating flow and inlet temperature. A refrigerated dryer typically delivers a pressure dew point around +3 °C when it is within its rating; a desiccant dryer is chosen for lower dew points such as −20 °C or −40 °C. Replace filter elements by differential pressure and service life, not by appearance.

Verify, freeze and keep it stable

After corrections, repeat the measurements over a comparable production period and compare with the baseline: pressure at critical users, total flow, non-production flow, specific power, dew point and temperatures. Report each improvement separately and note any change in production that might affect the comparison.

Then freeze the accepted configuration. Record final setpoints, control settings and valve positions, and make them part of routine checks. Set triggers for the next review, such as a rise in specific power, a return of low-pressure complaints, a new production line or a major equipment change. A planned preventive maintenance programme and regular leak surveys keep the system from drifting again.

How Reddy Compressors helps

Reddy Compressors, from our office at Tarnaka, Secunderabad, recommissions compressed-air systems for plants across Telangana and Andhra Pradesh, and supports projects elsewhere in India where feasible. We work on all major brands, including ELGi, Atlas Copco, Ingersoll Rand, KAESER and Chicago Pneumatic, as an independent multi-brand specialist, not an authorised dealer, with over 20 service engineers and technicians. We have tie-ups with all major and reputed brands.

• Site walkdown, configuration record and measurement of pressure, flow, power and dew point.
• Leak surveys, repair support and isolation of idle areas.
• Compressor and dryer service, cooler cleaning and drain replacement.
• Pressure reduction trials and retuning of compressor controls and sequencers.
• Supply of spares, filters, drains, receivers and, where justified, new or used compressors.
• Rental compressors from our own fleet if a machine must be taken out for overhaul.
• AMC support to keep the restored settings and condition in place.

What to send us

• Make, model and age of each compressor and dryer, with nameplate photos.
• Current setpoints and any sequencer settings.
• A description of the symptoms and when they occur.
• Any changes to the plant since the system was installed.
• Recent electricity use or running-hour readings, if available.
• A layout or photos of the compressor room and main header.

Frequently asked questions

Why is my compressed-air system using more power than before?

The usual causes are growing leaks, pressure raised over time, more unloaded running, fouled coolers and loaded filters. None of these looks like a breakdown, so they build up unnoticed. Measure pressure, flow and power together, and check non-production flow with production stopped. That shows how much of the increase is waste and how much is genuine new demand.

What is compressed-air system recommissioning?

Recommissioning is a structured review and restoration of an existing compressed-air system. It records the current configuration, measures pressure, flow, power and air quality, finds where performance has drifted, fixes physical causes such as leaks and restrictions, resets controls and verifies the result. Unlike routine service, it looks at the whole system rather than individual machines.

Should I replace my compressors if pressure is low?

Not before the system has been checked. Low pressure is often caused by leaks, loaded filters, restrictive piping, bypassed receivers or poor control settings rather than by the compressors. Replacing machines without fixing these means the new equipment feeds the same waste. Recommissioning shows whether real capacity is short and, if so, how much is needed.

How often should a compressed-air system be reviewed?

Review the system whenever specific power rises noticeably, low-pressure complaints return, production changes significantly or major equipment is added or replaced. Leak surveys should be done regularly between full reviews because leaks return steadily. Keeping a recorded baseline of pressure, flow and power after each review makes it easy to see when the next one is due.

Can recommissioning be done without stopping production?

Most of it can. Walkdowns, logging and many corrections, such as filter changes, control retuning and pressure trials, are done while the plant runs. Some leak repairs, valve changes and tie-ins need short isolations, which can be planned for breaks or weekends. A rental compressor can cover demand if a machine has to be taken out for longer service.

Why does my compressor keep tripping on high temperature in summer?

Typical causes are dirty coolers, hot exhaust air recirculating to the intake, poor room ventilation, low oil level or a faulty thermostatic valve. High ambient heat and dust in Indian summers make these worse. Check intake air temperature under full load, clean the cooler and correct ventilation before assuming the compressor is faulty.

Related pages

• Compressed-air system audit and benchmarking
• Measurement, verification and energy performance
• Leak detection and air-loss management
• Pressure optimisation and artificial demand
• Rotary screw compressor service
• Compressor AMC