Why a structured breakdown response matters
When a compressor stops, production pressure pushes everyone towards the reset button. Resetting a trip without understanding it is the most common way a minor fault becomes a major failure. A screw element that tripped on high temperature and is restarted three times can seize; a motor that tripped on overload and is forced back on can burn a winding.
A good breakdown response has three goals, in this order: keep people safe, get the plant the air it needs, and fix the real cause so the fault does not return. These goals sometimes pull in different directions. A rental machine or a standby compressor can restore air while the failed unit is diagnosed properly, rather than rushed.
It also helps to remember that many compressor trips start outside the compressor. Low supply voltage, a hot compressor room, a closed isolation valve, a choked dryer or filter, a failed drain or a sudden jump in plant demand can all make a healthy machine alarm. The diagnosis must look at the whole air system when the evidence points there.
First actions when the compressor stops
Before anyone opens a panel or loosens a fitting, follow a short, disciplined sequence. It takes minutes and saves hours.
- Make it safe. Isolate electrical supply with lock-out and tag-out, close the discharge isolation valve and let the package depressurise fully. Oil-flooded screw machines hold hot oil under pressure in the separator vessel; never open a filler cap or oil line on a pressurised or hot machine.
- Record the controller display. Photograph the fault code, alarm history, running hours, loaded hours and the last recorded pressures and temperatures before the controller is reset or powered down.
- Note the operating context. What was the machine doing when it stopped: starting, loading, running fully loaded, unloading? What was the ambient temperature? Did another machine or a large air user start at the same time?
- Talk to the operator. Unusual noise, smell, smoke, oil mist at points of use or repeated earlier trips are valuable clues that never appear on the controller.
- Do a visual walk-round. Look for oil leaks, burnt smell at the starter, a broken or slipping belt, blocked cooler fins, a flooded drain or a tripped breaker upstream.
- Decide on air continuity. If the plant cannot wait, bring a standby compressor online or arrange a temporary rental while the diagnosis continues.
Only after these steps should the team attempt a controlled restart, and only if the likely cause is understood and judged safe to test.
Common compressor faults: symptom, likely cause and what to check
The table below summarises the faults we see most often on oil-flooded rotary screw and reciprocating compressors in Indian plants. It is a starting point for triage, not a replacement for the manufacturer’s service manual for your specific model.
| Symptom | Likely causes | What to check first |
|---|---|---|
| High discharge or element temperature trip | Blocked oil cooler or aftercooler, low oil level, faulty thermostatic valve, clogged oil filter, hot or poorly ventilated room, failed cooling fan | Oil level when cold, cooler fin condition, room temperature and hot-air recirculation, fan rotation, thermostatic valve operation, oil filter age |
| Motor overload or electrical trip | Low or unbalanced supply voltage, single phasing, failed contactor, high starting load, seized bearing or element, wrong overload setting | Phase voltages and balance, contactor contacts, star-delta timer, insulation resistance, free rotation of element by hand with power isolated |
| Runs but does not build pressure | Inlet valve stuck closed, failed loading solenoid, blocked air filter, large leak or open drain, separator or minimum pressure valve fault | Load signal at solenoid, inlet valve movement, air filter restriction, downstream valves and leaks, pressure at package versus plant header |
| Low pressure at points of use but normal at compressor | Choked dryer or line filter, undersized or long piping, closed or partly open valve, high leakage, demand growth | Pressure drop across each filter and dryer, header pressure at several points, recent added air users |
| Oil carry-over into the air line | Failed or saturated air/oil separator, blocked scavenge line, overfilled oil, running at too low pressure, wrong oil | Separator differential pressure, scavenge line and orifice, oil level, operating pressure versus design, oil grade and condition |
| Safety valve lifting | Pressure switch or transducer fault, failed unloading, blocked separator, valve set too close to working pressure | Controller set points, transducer reading against a calibrated gauge, unload operation, separator differential pressure |
| Abnormal noise or vibration | Bearing wear, coupling or belt misalignment, loose mounting, damaged valves (reciprocating), element damage | Belt tension and alignment, coupling condition, mounting bolts, vibration trend if available, valve plates on piston machines |
| Frequent load/unload cycling | Undersized receiver, narrow pressure band, leaking check valve, sensor fault, oversized compressor for demand | Receiver volume, pressure band settings, cycle count, check valve leakage when unloaded |
| Water in the air line | Failed condensate drain, dryer stopped or bypassed, dryer overloaded by high inlet temperature, missing drain on receiver | Drain operation at aftercooler, receiver and filters, dryer status and dew-point indicator, dryer inlet temperature |
How we triage a breakdown
Triage means sorting the possible causes by likelihood and by the cost of being wrong, then testing them in a sensible order. We work from the outside in: utilities and system first, then package controls, then the mechanical heart of the machine.
1. Rule out the external causes
We check supply voltage at the incoming terminals, compressor room temperature and ventilation, the state of downstream valves, dryers and filters, and whether demand has changed. A surprising share of high-temperature trips in summer turn out to be hot-air recirculation in a closed room rather than a fault inside the package.
2. Verify the controls and sensors
A temperature probe or pressure transducer that has drifted can trip a healthy machine or, worse, fail to protect a sick one. We compare controller readings against independent instruments, check solenoid and contactor operation and review the alarm history for patterns.
3. Test the mechanical and fluid systems
Only then do we move into the oil circuit, cooling circuit, separator, inlet valve, minimum pressure valve, drive train and compression element. On a screw machine this may include checking oil condition, thermostatic valve operation, separator differential pressure and whether the element turns freely. On a piston machine it includes valves, rings, unloaders and crankcase oil.
4. Separate the symptom from the mechanism
A high-temperature trip is a symptom. The mechanism might be a fouled cooler, a stuck thermostatic valve or simply low oil. Replacing the temperature sensor because it raised the alarm fixes nothing. We aim to name the mechanism and the evidence that supports it before we fit parts.
Getting air back: restore, repair or replace
Once the cause is clear, the decision is how to get the plant running at acceptable risk and cost. There are usually three paths.
| Path | When it fits | Watch-outs |
|---|---|---|
| On-site repair | Cause confirmed, parts available, repair within field capability (valves, sensors, coolers, filters, separators, belts, contactors) | Confirm part fit from nameplate before fitting; verify performance after restart |
| Temporary air plus workshop repair | Element, motor or major component damage; parts lead time; plant cannot stop | Size the rental for actual demand and pressure; plan hose and electrical connection |
| Overhaul or replacement | Repeated failures, worn element, high running hours, poor efficiency, obsolete parts | Compare overhaul cost and residual life against a new or refurbished machine |
Temporary air is often the cheapest decision a plant makes during a breakdown. A diesel or electric rental machine can carry the load while the failed compressor is repaired properly, rather than patched under pressure and returned to service with the root cause still present.
Verifying the repair before handing back
A compressor that restarts has not necessarily been fixed. Before we hand a machine back, we check that it performs as it should under real load.
- Runs through several load and unload cycles without alarms.
- Discharge and element temperatures settle within the manufacturer’s normal range at full load.
- Delivers rated pressure at the package and acceptable pressure at the plant header.
- Motor current is balanced across phases and within nameplate values.
- No oil, air or water leaks; drains discharge correctly; dryer is running.
- Controller set points, safety valve and protective trips are correct and active.
- The fault, cause, parts fitted and readings are recorded for the maintenance history.
Preventing the next breakdown
Most breakdowns are announced in advance. Rising discharge temperature over weeks, increasing separator differential pressure, more frequent cycling or a slowly climbing motor current are all early warnings. A short weekly log of pressures, temperatures and running hours, kept by the operator, catches many of these trends.
After any significant breakdown, we recommend a short review: what failed, why, what the warning signs were and what change to the maintenance plan would catch it earlier. Common changes include shorter cooler cleaning intervals in dusty plants, better room ventilation, regular drain checks and a defined stock of critical spares for high-criticality machines.
For plants that cannot tolerate unplanned stops, a planned preventive maintenance programme or an annual maintenance contract, combined with a clear standby or rental plan, is usually the most effective protection.
How Reddy Compressors helps
Reddy Compressors has supported industry from Secunderabad since 2002. We are an independent, multi-brand specialist working on Atlas Copco, Ingersoll Rand, ELGi, KAESER, Chicago Pneumatic, Gardner Denver, Sullair, Doosan, Kirloskar, Bobcat and many other makes. We are not an authorised distributor for these brands. We have tie-ups with all major and reputed brands.
For a breakdown, our engineers carry out on-site diagnosis and repair, identify and supply spare parts, and handle overhauls where the damage is more serious. Spare parts are identified from your machine’s make, model, serial number, nameplate or the old part, and fit is confirmed before we quote. If the plant cannot wait, we can arrange rental compressors from 50 to 2,000 cfm and 2 to 30 bar, diesel or electric, to keep production running while the repair is done properly.
Our service teams cover the whole of Telangana and Andhra Pradesh, and we supply compressors, rentals and spare parts across India.
What to send us
- Make, model and serial number, ideally a photo of the nameplate.
- Photo of the controller display showing the fault code and alarm history.
- Running hours and the date of the last service.
- A short description of what happened and what the operator noticed.
- Your required pressure and approximate air demand, if temporary air may be needed.
- Site location and a contact person on site.
Frequently asked questions
Why does my screw compressor keep tripping on high temperature?
The most common causes are a blocked oil cooler, low oil level, a faulty thermostatic valve, a clogged oil filter or a hot compressor room with poor ventilation. Check the oil level when the machine is cold, clean the cooler fins, confirm the cooling fan runs in the right direction and make sure hot exhaust air is not recirculating into the intake. If these are fine, the thermostatic valve and temperature sensor need testing.
Is it safe to reset a compressor alarm and restart it?
Only once you understand why it tripped. A single reset to observe the fault can be acceptable if nothing is visibly wrong, but repeated resets on high temperature or motor overload can seize the element or damage the motor. Photograph the fault code and alarm history first, check the obvious causes such as oil level, voltage and room temperature, and call a service engineer if the trip returns.
Why is my air compressor running but not building pressure?
Usually the machine is not loading, or the air it makes is escaping. Check whether the inlet valve opens on a load signal, whether the loading solenoid is energised, and whether the air filter is badly blocked. Then look downstream for an open drain, a burst hose, a large leak or a valve left open. On piston compressors, worn valves or rings can also reduce output significantly.
What causes oil in the compressed air line?
On oil-flooded screw compressors, oil carry-over usually comes from a failed or saturated air/oil separator element, a blocked scavenge line, an overfilled oil sump or running the machine well below its design pressure. Using the wrong oil grade can also cause foaming. Check separator differential pressure, clean the scavenge orifice and verify the oil level. Persistent carry-over needs prompt attention because it contaminates dryers, filters and the product.
Should I repair my old compressor or replace it after a major breakdown?
Compare the full repair or overhaul cost with the machine’s remaining useful life, its energy efficiency and the availability of parts. A well-maintained machine with a single failed component is normally worth repairing. Repeated failures, a worn compression element, very high running hours or discontinued parts often favour a new or refurbished replacement. An engineer’s inspection report gives you the facts to decide.
Can I get a rental compressor while mine is being repaired?
Yes. Temporary air is a common way to keep production running during a breakdown repair or overhaul. Tell us your working pressure, approximate air demand in cfm, whether diesel or electric suits the site, and how the rental will connect to your header. Sizing the rental for real demand rather than the nameplate of the failed machine avoids paying for more capacity than you need.
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Technical content reviewed by D. Srinivas Reddy, Managing Partner and service engineer, Reddy Compressors. Last updated 7 November 2026. How our engineering content is reviewed.