When is a failure really closed?
A breakdown is not closed when the compressor restarts. It is closed when the cause is understood, the risk is controlled and recurrence has been shown to stop. Many plants replace the failed part, reset the alarm and move on, only to see the same trip return in the next hot spell or production peak. Each repeat costs downtime, emergency call-outs, parts and often a rental machine.
Formal failure analysis is not about blame. It is a method for preserving evidence, reconstructing what happened, and fixing the conditions that allowed it. It feeds back into maintenance, reliability, design and purchasing. For first-response fault finding see breakdown diagnostics and fault triage; this page covers what to do once the immediate recovery is done.
Which events deserve a formal investigation?
Not every alarm needs a full study. Agree in advance which events trigger one, using your site’s safety, production and quality priorities. Typical triggers:
- Loss of air to a critical process or production stop.
- The same compressor tripping repeatedly on the same fault.
- An air-quality excursion: water, oil or particles reaching product or instruments.
- A thermal event: high discharge temperature trips, oil degradation, fire or smoke.
- Airend, motor or major component failure.
- Control or sequencing failure leaving the plant short of air with machines available.
- Any event with a safety consequence, such as hose whip or a pressure-equipment failure.
First steps: stabilise and preserve evidence
Restore safe conditions and essential supply first. If needed, start standby machines or bring in a rental compressor. Then protect the evidence, because recovery actions can erase the causal sequence.
- Photograph the compressor, controller display, valve positions, hoses and temporary connections before changing anything.
- Download or photograph the controller fault log, alarm history and trends.
- Record setpoints, sequence state, bypasses and overrides as found.
- Keep failed parts, filters, separator elements and an oil sample, labelled with date and machine.
- Note what operators saw, heard and did, in their own words, as soon as possible.
- Avoid repeated resets; each reset can overwrite the log and stress damaged components.
Building the timeline
A factual timeline is the backbone of the analysis. Include enough data before the event to show developing conditions, and enough after to understand the recovery. Sequence alarms, pressure, flow, power, temperatures, machine states, operator actions and production events on one time axis.
Label each entry as measured, observed, reported, inferred or unknown. This simple discipline stops assumptions becoming “facts” in the final report. Check that the clocks on different controllers and data loggers agree, because a few minutes of difference can reverse the apparent order of events.
Top event, initiating event and safeguards
Three questions structure the analysis:
- Top event. What consequence are we analysing? For example, loss of pressure at the packing line, or a high-temperature trip on compressor 2.
- Initiating event. What first changed or failed? For example, a cooling fan stopped, a thermostatic valve stuck, or a large new user started.
- Safeguards. What should have prevented escalation? Alarms, standby capacity, storage, sequencing, treatment redundancy, isolation and procedures.
A minor initiating fault becomes a major outage when the protection or recovery layers do not work. A standby compressor that would not start, a sequencer left in manual, or an alarm that had been disabled are often more important findings than the original fault.
How do you find the root cause of a compressor failure?
Separate the levels of cause:
| Level | Meaning | Example |
|---|---|---|
| Immediate cause | The direct physical condition that produced the event | Discharge temperature exceeded the trip setting |
| Underlying cause | The condition that allowed the immediate cause | Oil cooler fouled with dust and oil mist |
| Contributing causes | Other conditions that combined with it | Ambient above 45 °C, poor room ventilation, peak production |
| Root cause | The deepest actionable cause, supported by evidence, whose correction materially reduces recurrence | No cooler cleaning task in the maintenance plan; hot-air recirculation in the room |
| Latent condition | A hidden weakness waiting for a trigger | Standby machine never test-run; no spare fan motor |
Root cause is rarely the first failed component. A fan motor can fail because of dust, poor supply voltage, vibration or wrong specification. Stopping at “replaced motor” misses the driver. Tools such as five-whys, fault trees and cause-and-effect diagrams help, provided every branch is tested against evidence. Our page on root-cause analysis and corrective action covers these tools.
Common failure patterns in Indian plants
| Event | Frequent causes found | Evidence to check |
|---|---|---|
| High discharge temperature trip | Fouled cooler, low oil level, stuck thermostatic valve, blocked ventilation, high ambient | Trend of discharge temperature against ambient, cooler condition, oil level and grade |
| Oil carry-over into the network | Failed separator element, blocked scavenge line, wrong oil, overfilling, low minimum pressure | Separator differential pressure, oil consumption, scavenge flow, oil sample |
| Water in air lines | Dryer stopped or bypassed, failed drains, overloaded dryer in monsoon or summer | Dryer dew point, drain operation, bypass valve position |
| Motor overload or electrical trip | Low or unbalanced voltage, worn bearings, high discharge pressure, starter faults | Supply voltage, current trend, insulation and bearing condition |
| Airend seizure or noise | Oil starvation, degraded oil, bearing wear, contamination through intake | Oil analysis, bearing condition, intake filter history |
| Plant pressure collapse with machines available | Sequencer fault, pressure-sensor failure, conflicting setpoints, large new user | Control logs, sensor calibration, demand trend |
For oil-injected screw compressors, normal discharge temperature is typically about 75–95 °C. A slow upward trend over weeks is a warning that a cooler or thermostatic valve needs attention well before the trip.
Corrective action that actually prevents recurrence
Corrective actions should address the root and contributing causes, not only the failed part. Rank them by how strongly they control the risk:
- Eliminate the condition, for example redesign ventilation to stop hot-air recirculation.
- Engineer a safeguard, for example add standby capacity, storage or a dew-point alarm.
- Improve maintenance, for example add cooler cleaning before summer and condition checks.
- Improve procedures and training, for example a standby start test each week.
- Repair the failed component with the correct, verified part.
Give every action an owner, a date and an acceptance test. Where a human action contributed, ask why it seemed necessary at the time and what information or controls were missing. Describe decisions and conditions factually and avoid blame language; people report problems more openly when they are not punished for them.
Verifying the fix and sharing the learning
Verification proves that recurrence has stopped. Define the evidence before closing: for a temperature trip, discharge temperature through the next hot season; for oil carry-over, oil consumption and downstream filter condition over several service intervals. Close the investigation only when that evidence is in.
Then share what was learned. Update the maintenance plan, the spare-parts list, standard operating procedures, purchasing specifications and training material. Check whether the same weakness exists on similar machines elsewhere in the plant or at other sites. Keep a register of investigations so repeat patterns, often called bad actors, become visible. See reliability, availability and resilience.
How Reddy Compressors helps
Our team of over 20 service engineers and technicians, based at Tarnaka, Secunderabad, attends breakdowns and investigations across Telangana and Andhra Pradesh. We are an independent multi-brand specialist, so we work on ELGi, Atlas Copco, Ingersoll Rand, KAESER, Chicago Pneumatic and other makes, without being an authorised dealer of any brand.
- Breakdown attendance, fault finding and evidence capture at the first visit.
- Inspection of failed components, coolers, separators and airends, with specialist processes arranged where needed.
- Correct spare parts identified from the nameplate, serial number and old part, with fit confirmed before quoting.
- Rental compressors from our own fleet to restore supply while the investigation and repair proceed.
- Service and AMC plans updated with the corrective actions; see compressor AMC.
Call +91 99590 60718 or +91 92468 88812, or email reddycompressors@gmail.com.
What to send us
- Compressor make, model, serial number and a nameplate photo.
- Photos of the controller fault log and alarm history.
- A short description of what happened, when, and what was done.
- Running hours and the last service date.
- Photos of failed parts, oil condition and the compressor room.
- Whether the event has happened before.
Frequently asked questions
Why does my air compressor keep tripping on high temperature?
Repeated high-temperature trips usually come from poor cooling: a fouled oil cooler, low oil level, a stuck thermostatic valve, a failed fan or hot air recirculating in the compressor room. Hot summer ambients make it worse. Compare discharge temperature with ambient over time, check the cooler and ventilation, and fix the cause rather than raising the trip setting.
What is root cause analysis for an air compressor?
It is a structured way to find the deepest actionable cause of a failure, supported by evidence. It separates the immediate cause, such as a trip, from the conditions that allowed it, such as missing maintenance or poor ventilation. Fixing the root cause, not only replacing the failed part, is what stops the same breakdown returning.
What evidence should I keep after a compressor breakdown?
Photograph the controller display and fault log before resetting. Keep the failed parts, filters and an oil sample, labelled with date and machine. Record setpoints, valve positions and any bypasses as found, and note what operators observed. This evidence often shows the real cause, and it is lost quickly once repair begins.
Why is there oil in my compressed air lines?
Oil carry-over in an oil-injected compressor is commonly caused by a failed or damaged separator element, a blocked scavenge line, overfilling, the wrong oil or the compressor running below its minimum pressure. Check separator differential pressure, oil consumption and scavenge flow. Downstream filters should also be inspected, because once oil reaches the network it needs cleaning out.
How do I stop the same compressor failure happening again?
Find the root and contributing causes, then choose actions that remove the condition or add a reliable safeguard, not just replace the part. Give each action an owner and a date. Define how you will prove recurrence has stopped, such as temperature trends through the next summer, and close the case only when that evidence is in.
Should we rent a compressor while the failure is investigated?
If the failed machine supports critical production and there is no standby, a rental compressor can restore supply while the cause is investigated and the repair is done properly. Rushing a repair to restart quickly often destroys evidence and leads to repeat failures. Match the rental unit’s flow, pressure and air quality to your duty.
Related pages
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.