A gas compressor can be running normally one minute and sitting completely stopped the next.
The control screen may show a trip.
Production begins backing up.
Suction pressure changes.
Operators start getting calls.
The immediate temptation is to reset the machine and see whether it will run again.
That can be a mistake.
A compressor trip is usually the protection system telling you that something moved outside an acceptable operating condition. The shutdown may have protected the compressor from serious mechanical damage or prevented a process problem from becoming worse.
The useful question is not simply how to restart the compressor.
It is why the compressor shut down in the first place.
Why Do Gas Compressors Have So Many Shutdowns?
Gas compressors handle pressure, heat, moving machinery, lubrication, and sometimes liquid contamination.
A serious problem in any one of those areas can damage the machine quickly.
Protective systems therefore monitor conditions such as:
Lubricating oil pressure
Discharge temperature
Suction pressure
Discharge pressure
Vibration
Scrubber liquid level
Cooling conditions
Engine or motor condition
Cylinder lubrication
Speed
The exact shutdowns depend on the compressor package.
A small screw compressor at a production facility will not have exactly the same protection as a large reciprocating compressor station.
What Is the Difference Between an Alarm and a Trip?
An alarm tells the operator that something needs attention.
A trip takes action.
Suppose discharge temperature begins rising.
The system may first generate a high temperature alarm.
If temperature continues rising and reaches the shutdown setting, the compressor trips.
The alarm provides warning.
The shutdown protects equipment.
This distinction matters during troubleshooting because the first alarm may reveal what was going wrong before the machine stopped.
Why Does High Discharge Temperature Trip a Compressor?
Gas heats up when it is compressed.
A certain amount of temperature rise is normal.
Excessive temperature is not.
High discharge temperature can damage valves, packing, lubricants, seals, and other compressor components.
Reciprocating compressor manufacturers establish discharge temperature limits because prolonged operation at excessive temperature can reduce reliability.
Possible causes include:
High compression demand
Low suction pressure
High discharge pressure
High suction temperature
Leaking compressor valves
Poor cooling
Reduced efficiency
Gas composition changes
A compressor that repeatedly trips on high discharge temperature should not simply be restarted without checking why the temperature increased.
Why Does Low Suction Pressure Cause Problems?
A compressor needs gas at its suction.
If suction pressure falls, the machine may have to work across a more demanding pressure condition.
Low suction pressure can also indicate that upstream gas supply is restricted.
Possible causes include:
Declining well production
A closed or partially closed valve
A plugged filter
A restriction in gathering piping
Another compressor changing the system pressure
Hydrate formation
Liquid accumulation
A process upset upstream
If discharge pressure remains high while suction pressure falls, compressor loading and discharge temperature can become more difficult.
Why Would Suction Pressure Suddenly Drop?
Start by asking whether the compressor caused the low pressure or whether the low pressure came from upstream.
Check recent trends.
Did suction pressure fall before the trip?
Did flow decrease?
Was a valve moved?
Did another compressor start?
Did a gathering line shut in?
Were wells taken offline?
Did a filter differential pressure increase?
The timeline matters.
A pressure reading after the compressor has already stopped may not tell you what caused the trip.
Why Does High Discharge Pressure Trip a Compressor?
A compressor has maximum allowable operating conditions.
If discharge pressure becomes too high, mechanical loading can increase beyond acceptable limits.
High discharge pressure can result from:
A downstream valve being closed
High pipeline pressure
A restricted cooler
A blocked discharge line
A check valve problem
Downstream equipment being unavailable
A control valve failing toward a restrictive position
Another station changing pipeline conditions
The compressor may be perfectly healthy.
The problem may be downstream.
Why Is Low Lubricating Oil Pressure Serious?
Bearings and other moving components depend on lubrication.
If oil pressure disappears, metal surfaces can be damaged rapidly.
That is why low lubricating oil pressure is commonly a shutdown condition.
Possible causes include:
Low oil level
Pump problems
Oil filter restriction
Incorrect oil viscosity
A leak
Instrumentation failure
Temperature related viscosity changes
Internal wear
Some reciprocating compressor lubrication systems also monitor whether cylinder lubricant is actually moving through the distribution system.
A blocked lubrication point can initiate a shutdown.
Can Cold Weather Cause Low Oil Pressure Problems?
Cold weather can create several unusual lubrication conditions.
Oil becomes more viscous when it is cold.
A cold start may therefore create pressure and flow behavior that differs greatly from normal warm operation.
Heaters, thermostatic valves, filters, and warm up procedures can all become important.
Operators should compare the condition with the equipment manufacturer’s operating requirements rather than assuming cold oil is harmless.
Why Does a Compressor Trip on High Vibration?
Rotating and reciprocating machinery naturally produces some vibration.
The problem is abnormal vibration.
A significant increase can indicate:
Mechanical looseness
Misalignment
Bearing problems
Valve problems
Unbalance
Piping vibration
Foundation problems
Liquid entering the machine
Internal mechanical damage
Vibration protection can stop a machine before a developing problem becomes a major failure.
One isolated vibration reading should be interpreted carefully, but a sudden trend change deserves attention.
Can Liquid Cause a Compressor Trip?
Yes.
This is one of the most important process problems around gas compression.
Compressors are designed primarily to compress gas.
Liquid behaves very differently.
Large amounts of liquid entering a reciprocating compressor can produce severe forces because liquid does not compress easily.
Even smaller amounts can cause:
Valve damage
Cylinder problems
Unstable operation
Corrosion
Lubrication issues
Reduced performance
Suction scrubbers are installed partly to prevent this.
Why Does the Suction Scrubber Have a High Level Shutdown?
The scrubber removes liquids before gas reaches the compressor.
If the liquid level becomes too high, there is a risk that liquid will carry into the compressor suction.
A high level shutdown stops the compressor before that happens.
When the scrubber trips high, simply draining the vessel and restarting may not be enough.
Ask where the liquid came from.
Possible causes include:
Upstream separator carryover
Condensation
A liquid slug from the pipeline
A failed level controller
A blocked dump valve
A frozen liquid line
Unexpected production changes
The scrubber may be protecting you from another problem farther upstream.
Why Would More Liquid Suddenly Arrive at a Compressor?
Gas gathering systems can collect liquid in low areas.
Changes in gas velocity can move that liquid.
Pigging can also push accumulated liquid toward a facility.
Cold weather can increase hydrocarbon and water condensation.
An upstream separator upset can send liquid into the gas line.
A compressor may therefore trip even though nothing inside the compressor itself failed.
Why Do Compressor Coolers Matter?
Compression creates heat.
Aftercoolers and interstage coolers remove that heat.
Poor cooling can increase gas temperature and affect the next compression stage.
Cooling problems may involve:
Dirty exchanger surfaces
Low cooling water flow
Fan failure
Air cooler fouling
Blocked passages
High ambient temperature
Control problems
An apparently mechanical compressor trip can sometimes originate in a simple cooling problem.
Why Can Hot Weather Cause More Compressor Trips?
Air cooled equipment loses some cooling ability as outside air temperature rises.
Suction gas may also arrive hotter.
Higher suction temperature means the compressor begins with hotter gas before compression even occurs.
The final discharge temperature can therefore move closer to a trip setting.
A compressor that runs comfortably all winter may become temperature limited during hot afternoons.
Seasonal trends are useful clues.
Can a Bad Compressor Valve Cause High Temperature?
Yes.
Reciprocating compressors use suction and discharge valves to control gas movement through the cylinder.
A leaking valve allows gas to move when it should not.
That wastes compression work and can create abnormal heat.
Possible signs include:
Reduced capacity
Higher valve temperature
Higher discharge temperature
Unusual sound
Changing pressure behavior
Higher power use
Comparing temperatures between similar cylinders can sometimes help identify an abnormal valve.
Why Can a Compressor Trip After a Production Increase?
More gas does not always mean the compressor can simply process more gas.
Additional flow may increase:
Driver load
Cooling demand
Pressure drop
Scrubber loading
Discharge temperature
The compressor may reach a horsepower, temperature, speed, or pressure limit.
A field can therefore produce enough gas to overwhelm compression even when the compressor is mechanically healthy.
What Is Compressor Recycle?
Recycle sends some compressed gas back toward the suction side.
It can be used for capacity control, start up, or protection.
Centrifugal compressors use recycle as part of surge control.
Recycle can stabilize operation, but it also means the compressor is recompressing gas.
If recycle remains open unnecessarily, the machine can consume significant power without increasing useful export flow.
Can a Recycle Valve Problem Trip the Compressor?
Yes.
A recycle valve that fails to open when required can contribute to unstable operation on certain compressors.
A valve stuck open can reduce useful capacity.
A poorly controlled valve can create pressure and flow swings.
When a compressor behaves differently after maintenance on a recycle valve, that connection should not be ignored.
Why Do Compressors Trip on Electrical Problems?
Motor driven compressors depend on electrical protection.
Trips can involve:
Overcurrent
Motor winding temperature
Voltage problems
Ground faults
Motor bearing temperature
Drive problems
Variable frequency drive faults
The compressor process may be normal while the motor protection system is what actually stopped the machine.
Always identify which protection system initiated the trip.
Why Do Engine Driven Compressors Trip?
Gas engine driven packages add another machine to troubleshoot.
Possible engine related trips include:
Low engine oil pressure
High coolant temperature
Overspeed
Ignition problems
Fuel gas problems
Detonation
Air system problems
The compressor may stop because the driver stopped, not because the compressor reached a process shutdown.
Understanding which side initiated the shutdown saves time.
What Is a First Out Trip?
A major shutdown can generate many alarms.
Suppose low compressor oil pressure causes the machine to trip.
Once it stops, suction pressure rises, discharge flow disappears, temperatures change, valves move, and other alarms appear.
The first out indication identifies the original shutdown signal.
That is one of the first things an operator should check.
The last alarm on the screen is often not the cause.
Why Is Trend Data So Useful?
One snapshot tells you very little.
A trend can show the order of events.
Suppose the compressor trips on high discharge temperature.
Look backward.
Did suction pressure fall first?
Did discharge pressure rise?
Did cooler outlet temperature increase?
Did gas flow change?
Did ambient temperature rise?
Did valve temperature begin increasing?
The trip tells you where the machine reached its limit.
The trend helps tell you why.
Should You Immediately Reset a Compressor Trip?
Not unless the cause is understood and the applicable procedure allows restart.
Some trips are caused by temporary process changes.
Others indicate developing equipment failure.
Repeatedly resetting the machine can turn a small problem into an expensive one.
Protective shutdowns should never be bypassed simply to keep production moving.
Why Can a Compressor Restart and Run Normally After a Trip?
Because the shutdown itself changed the process.
When the compressor stops:
Flow falls.
Temperatures begin cooling.
Pressure conditions equalize.
Liquid may drain.
Driver load disappears.
The original trip condition can vanish.
That does not mean the problem is fixed.
An intermittent fault can be more difficult to diagnose precisely because everything looks normal by the time someone arrives.
What Should an Operator Record After a Trip?
Useful information includes the first out condition, suction pressure, discharge pressure, temperatures, gas flow, scrubber level, driver load, compressor speed, valve positions, weather conditions, and anything that changed immediately before the event.
Also record whether similar trips happened previously.
Repeated events often reveal a pattern.
Why Do Compressors Sometimes Trip at the Same Time Every Day?
A repeating schedule often points toward a repeating process condition.
Examples include:
Peak afternoon temperature
Daily production changes
Pipeline nomination changes
Liquid dumping cycles
Cooling limitations
Automatic equipment sequences
Instead of treating every trip as random, compare the time and operating conditions.
Patterns are valuable.
How Do You Troubleshoot a Compressor Trip Without Guessing?
Start with the first out trip.
Then ask which process variable moved toward the limit.
Look at trends before the shutdown.
Check upstream and downstream conditions.
Inspect the field equipment.
Compare current operation with normal values.
Only after that should you decide whether the problem is process related, mechanical, electrical, or instrumentation related.
Good troubleshooting eliminates possibilities instead of changing several things at once.
Frequently Asked Questions
Why does a gas compressor keep tripping?
Repeated trips can result from pressure problems, high temperature, low lubrication pressure, vibration, liquid carryover, cooling problems, driver faults, or instrumentation problems.
What should I check first after a compressor trip?
Check the first out indication and review process trends immediately before the shutdown.
Why does low suction pressure cause a compressor problem?
Lower suction pressure can increase the compression demand and may indicate an upstream restriction or declining gas supply.
Why does a compressor trip on high discharge temperature?
The gas or compressor components have reached a temperature protection limit. Causes can include demanding pressure conditions, poor cooling, hot suction gas, or compressor valve problems.
Why does a compressor scrubber trip on high level?
The shutdown protects the compressor from liquid carryover.
Can a compressor trip because of a separator problem?
Yes. An upstream separator upset can send liquid toward the compressor and eventually trigger scrubber or compressor protection.
Can hot weather cause compressor trips?
Yes. Higher ambient and suction temperatures can reduce cooling performance and increase discharge temperatures.
Can a failed compressor valve cause a trip?
Yes. Valve leakage can reduce efficiency and create excessive heat.
Why does a compressor run normally after being reset?
Stopping the machine can temporarily remove the condition that caused the trip. That does not prove the original problem is gone.
Should compressor shutdowns ever be bypassed?
Protective shutdowns should not be bypassed simply to maintain production. The cause needs to be understood and the proper operating procedure followed.
What is the best way to troubleshoot repeated compressor trips?
Trend the operating conditions before each trip and look for the variable that consistently changes first.