How to Service Your Rotary Screw Air Compressor

rstom036
Jun 9
4 min read

Rotary screw air compressors are among the most reliable and efficient tools for supplying compressed air in industrial and commercial environments. Their continuous-duty operation and energy efficiency make them ideal for demanding applications. However, just like any mechanical system, a rotary screw air compressor requires regular maintenance to ensure optimal performance, energy efficiency, and long-term reliability. Neglecting routine service can lead to costly repairs, downtime, and premature equipment failure.

This essay outlines a complete guide to servicing your rotary screw air compressor, focusing on the key components involved, recommended maintenance intervals, tools needed, and essential safety precautions.

Understanding Rotary Screw Air Compressor Operation

Before diving into service procedures, it's essential to understand how a rotary screw air compressor works. Unlike piston compressors, which compress air using a reciprocating piston, rotary screw compressors use two interlocking helical rotors (screws) to compress air as it moves through a sealed chamber. These compressors are typically oil-injected, meaning oil is used to lubricate the rotors, cool the air, and seal gaps for efficient compression.

This design makes them ideal for continuous operation but also means that the system must be kept clean, cool, and properly lubricated. Servicing your compressor ensures these operating conditions are maintained.

Key Components to Service

Air Filter
Oil Filter
Air-Oil Separator
Compressor Oil
Cooling System
Drive Belts or Couplings
Control Panel and Sensors
Drain Valves and Moisture Separators

Each of these components plays a vital role in the performance and longevity of your compressor.

Routine Maintenance Schedule

Maintenance Task	Interval
Check oil level	Daily or every 8 hours
Inspect air filter	Weekly
Drain condensate from tank	Daily
Change oil	Every 1,000–2,000 hours
Replace oil filter	Every 1,000–2,000 hours
Replace air filter	Every 1,000 hours
Change air-oil separator	Every 2,000–4,000 hours
Inspect belts or couplings	Monthly
Inspect electrical connections	Monthly
Clean cooler	Every 2,000 hours

Always follow the specific recommendations outlined in your compressor's service manual.

Step-by-Step Guide to Servicing a Rotary Screw Compressor

1. Safety First

Before performing any maintenance:

Turn off the compressor and disconnect it from its power source.
Allow the unit to cool down completely.
Depressurize the system by opening the drain valve and ensuring all internal pressure is released.
Wear safety gear including gloves and safety glasses.

2. Change the Oil

Rotary screw compressors rely on oil for cooling, sealing, and lubrication. Dirty or degraded oil will cause premature wear.

Steps:

Locate the oil drain plug and place a container beneath it.
Open the plug and allow oil to drain completely.
Replace the plug and remove the oil fill cap.
Refill the compressor with the recommended compressor oil to the specified level.
Replace the oil fill cap securely.

3. Replace the Oil Filter

The oil filter traps contaminants to protect the compressor’s internal components.

Steps:

Unscrew the old filter (use an oil filter wrench if necessary).
Clean the filter mount surface.
Apply a thin layer of oil to the gasket of the new filter.
Screw the new filter into place by hand until tight, then give it a slight additional turn.

4. Replace the Air Filter

A clean air filter ensures that only clean air enters the compression chamber, protecting internal parts.

Steps:

Open the air filter housing.
Remove the old air filter.
Clean any accumulated dust or debris inside the housing.
Insert the new filter and close the housing securely.

5. Replace the Air-Oil Separator

This component separates the compressed air from the oil mist. A clogged separator increases oil carryover and operating pressure.

Steps:

Locate the separator tank.
Carefully remove the top cover or access panel.
Remove the old separator element (this may require loosening bolts or fittings).
Clean the surrounding area thoroughly.
Install the new separator and secure it according to manufacturer instructions.

6. Inspect and Tighten Belts or Couplings

Drive belts or shaft couplings transfer power from the motor to the compressor unit.

Steps:

Inspect belts for signs of wear, cracks, or slack.
Adjust tension if needed or replace worn belts.
If using a direct-drive coupling, check for alignment and wear on flexible elements.

7. Inspect the Cooler and Clean

A blocked cooler reduces the efficiency of heat dissipation, leading to overheating.

Steps:

Inspect the external fins of the oil cooler and aftercooler.
Use compressed air to blow dust and debris off the surfaces (blow air opposite to the direction of airflow).
If buildup is severe, use a degreasing agent and rinse with low-pressure water. Allow it to dry completely before use.

8. Drain Condensate and Inspect Moisture Traps

Water accumulation can lead to corrosion and poor air quality.

Steps:

Open the tank drain valve and let any moisture escape.
Inspect and clean automatic drain valves or inline moisture separators.
Make sure drains are functioning correctly to avoid manual buildup.

9. Test Safety Shutdown Systems

Most rotary screw compressors are equipped with thermal and pressure protection systems.

Steps:

Use the control panel to check alarm history.
Test safety shutdown features (like high-temp shutoff).
Ensure that pressure and temperature sensors are responding accurately.

10. Record the Maintenance

Always document:

Hours of operation at the time of service
What components were replaced or inspected
Any abnormalities found

Maintaining a detailed log helps with future troubleshooting and warranty validation.

Final Inspection and Restart

Once all service tasks are complete:

Reconnect the power supply.
Start the compressor and monitor for abnormal noise, vibration, or pressure spikes.
Watch the control panel for warnings or errors.
Check for any signs of oil or air leaks.

Allow the unit to run for 10–15 minutes and observe temperature and pressure readings to ensure proper operation.

Conclusion

Properly servicing your rotary screw air compressor is essential for maintaining performance, ensuring safety, and avoiding expensive repairs. Though rotary screw units are designed for long-term reliability, their complexity means that overlooking maintenance—especially oil changes, air/oil separator replacement, and filter servicing—can quickly result in failures or inefficiencies.

By following a structured maintenance schedule, using quality replacement parts, and inspecting key components regularly, you ensure your air compressor continues to deliver clean, dry, and pressurized air efficiently. Whether you’re a shop owner, plant manager, or technician, investing the time to service your equipment will pay off in uptime, reduced repair costs, and better overall system performance.