Screw air compressors are critical power equipment in industrial applications, and their stable operation is essential for productivity. However, overload trips (current overloads) during operation can lead to unexpected shutdowns or even equipment damage. Based on practical engineering experience, this article systematically analyzes common causes of overload trips and provides targeted solutions to help users quickly diagnose issues and restore operations.

 

Root Causes of Overload Trips

Overload trips occur when the motor current exceeds the rated value, triggering protective shutdowns. The root causes fall into two categories: electrical system abnormalities and excessive mechanical load, with specific manifestations as follows:

 

1. Abnormal Power Supply Voltage

Symptoms: Voltage drops (e.g., below 90% of the rated voltage) cause a surge in motor current.
Common Scenarios: Grid fluctuations, undersized power cables, or long-distance power supply lines.

 

2. Excessive Discharge Pressure

Symptoms: Discharge pressure exceeds the rated value (due to incorrect settings or sudden drops in downstream air demand), forcing the motor to operate under overload.
Common Scenarios: Faulty pressure sensors, malfunctioning pressure valves, or blocked pipelines.

 

3. Electrical Circuit and Component Failures

Symptoms: Loose connections, damaged wiring, or eroded contactor terminals leading to abnormal current fluctuations.
Common Scenarios: Loose terminals caused by prolonged vibration, or aged contactors not replaced in time.

 

4. Mechanical Failures in the Compressor Unit

Symptoms: Increased rotational resistance in the compressor host, caused by:

50. Carbon Deposits on Rotors: Carbonized lubricant adhering to rotor surfaces, increasing friction.
50. Foreign Object Ingestion: Dust or metal debris entering rotor gaps, risking rotor seizure.
50. Bearing Wear: Damaged bearings causing rotor misalignment and friction.

 

5. Clogged Oil-Gas Separator

Symptoms: Blocked separator filter elements elevate internal resistance, increasing compressor load.
Common Scenarios: Overused filters or substandard lubricant quality.

 

Troubleshooting and Resolution Workflow

 

Step 1: Inspect the Electrical System

1 , Check Power Supply Voltage

50. Use a multimeter to measure input voltage, ensuring stability within the rated range (e.g., 380V ±5%).
50. Solution: Install a voltage stabilizer or upgrade power supply lines.

2, Verify Wiring and Contactors

50. Tighten all electrical terminals to eliminate loose connections.
50. Disassemble and clean contactors, replacing severely eroded contacts.

 

Step 2: Validate Discharge Pressure Settings

1, Calibrate Pressure Sensors and Controllers

50. Ensure discharge pressure settings do not exceed the compressor’s rated pressure (e.g., 0.8 MPa).
50. Solution: Recalibrate sensors and inspect pressure relief valves for proper operation.

2, Inspect Downstream Air Systems

50. Check for pipeline blockages or accidentally closed valves causing pressure buildup.

 

Step 3: Diagnose Mechanical Systems

1, Perform Manual Rotation Test

Disconnect power and manually rotate the compressor coupling. If resistance is abnormal, proceed with disassembly:

50. Carbon Deposits: Clean rotors with specialized solvents and replace with high-quality lubricant.
50. Foreign Objects: Clean the compressor chamber and inspect air intake filters for damage.
50. Bearing Failure: Replace bearings and realign rotor concentricity.

2, Test Oil-Gas Separator

50. Monitor the differential pressure gauge. If pressure exceeds 0.1 MPa, replace the filter immediately.
50. Preventive Tip: Replace filters regularly (recommended every 2,000–4,000 hours) using OEM parts.

 

Preventive Maintenance Recommendations

 

1, Electrical System

Inspect terminal tightness monthly; replace aged contactors annually.
Install voltage monitoring devices for real-time alerts on abnormalities.

 

2, Mechanical System

Lubricant Management: Replace oil strictly per schedule (e.g., every 2,000 hours) using low-carbon, oxidation-resistant lubricants.
Air Filtration: Clean intake filters every 500 hours to prevent dust ingress.

 

3, Smart Monitoring

Integrate IoT sensors to track real-time parameters (current, pressure, temperature) for early fault detection.

 

Conclusion

Overload trips are common in screw compressors but require a systematic approach combining electrical and mechanical diagnostics. By following the standardized workflow (electrical → pressure → mechanical), users can swiftly identify and resolve issues. More importantly, establishing a preventive maintenance program minimizes downtime and ensures long-term reliability.