4 Main Causes of High Temperature in Screw Air Compressors and How to Fix Them

In daily operation of a screw air compressor, high temperature is one of the most common and hidden faults.
When the discharge temperature exceeds 105°C (110°C for some models), the compressor will stop due to protection. Long-term high temperature can also cause serious damage.

High temperature can:

• Speed up lubricating oil oxidation

• Age seals and gaskets

• Cause rotor seizure and even air end failure

This article explains the main causes of high temperature, how to check them step by step, and how to prevent overheating.

1. Warning Signs and Risks of High Temperature

Before troubleshooting, you should know the common warning signs:

• “High discharge temperature” alarm on the controller

• Compressor housing feels very hot

• Lubricating oil turns dark quickly

• Abnormal noise on some machines

Long-term overheating causes serious problems:

• Oil life can be reduced by more than 50%

• Rubber seals age faster, causing oil and air leaks

• In extreme cases, the oil film between rotors breaks, metal contacts metal, and the air end can fail within hours

2. Four Main Causes of High Temperature (With Checks)

High temperature is usually caused by more than one factor.
Follow the order: easy first, complex later.

1) Cooling System Failure (Most Common Cause)

The cooling system controls compressor temperature.
There are air-cooled and water-cooled types.

Air-cooled compressors

Common problems: dirty radiator or fan failure.

Check steps:

1. Stop the machine and check the radiator.
   Dust and oil block heat dissipation.
   Clean it with compressed air from inside to outside.

2. Check if the fan is running.
   If not, check wiring or replace the fan motor.

3. If the fan runs but airflow is weak, the fan blades may be damaged.

Water-cooled compressors

Common problems: low water flow or blocked pipes.

Check steps:

1. Check inlet valve and water pressure (should be 0.2–0.4 MPa).

2. Check pipes for scale, especially in hard water areas. Clean if needed.

3. Flush the water cooler in reverse direction with clean water.

2) Lubricating Oil Problems

Lubricating oil removes heat and lubricates rotors.
Low oil level or bad oil often causes high temperature.

Check steps:

1. Stop the compressor and wait 10 minutes.
   Check oil level. It must be between MIN and MAX.

2. Check oil color.
   Black or brown oil means oxidation. Replace oil completely.

3. Check the oil filter.
   If pressure drop is over 0.15 MPa, replace the filter.

⚠️ Always use the same oil type and brand. Do not mix oils.

3) Oil-Air Separator Blockage

The oil-air separator removes oil from compressed air.
If it is blocked, internal pressure rises and temperature increases.

Check steps:

1. Check separator pressure difference on the controller.
   If it is over 0.2 MPa (or 0.18 MPa on some models), it is blocked.

2. Stop the machine and replace the separator element.

3. Check seals and gaskets to prevent air leakage.

4. Clean excess oil inside the oil tank if needed.

4) Environment and Load Problems

External factors are often ignored but very important.

Check steps:

1. Check compressor room temperature.
   It should be below 40°C. Improve ventilation if needed.

2. Keep the compressor away from heat sources like boilers or ovens.

3. Check operating load.
   Long-term operation above 90% capacity increases heat.
   Reduce air demand or add another compressor.

3. Daily Maintenance Tips to Prevent High Temperature

Prevention is better than repair. Build these habits:

1. Clean the cooling system regularly

   • Air-cooled: every 2 weeks

   • Water-cooled: clean water system every 3 months

2. Replace oil and filters on time

   • Mineral oil: every 2,000–3,000 hours

   • Synthetic oil: every 8,000–12,000 hours

   • Oil filter: every oil change

   • Oil-air separator: every two oil changes

3. Monitor discharge temperature daily
   If temperature rises 5–10°C higher than normal, check immediately.

Conclusion

High temperature in a screw air compressor is not a complex problem.
By checking in this order:

Cooling system → Lubricating oil → Oil-air separator → Environment,
most overheating issues can be solved quickly.

Good daily maintenance helps:

• Avoid unexpected shutdowns

• Extend compressor life

• Reduce operating costs