How to Troubleshoot Abnormal Unloading in Screw Compressors? Fault Diagnosis + Resolution Steps

Oil-injected screw air compressors are widely used in industrial applications. Load/unload malfunctions can cause frequent equipment startups and shutdowns, pressure fluctuations, and negatively impact production efficiency and equipment lifespan. Below is a streamlined analysis of common faults and corresponding solutions:

I. Core Principles of the Load/Unload System

Loading Mechanism: When system pressure drops to the lower limit, the pressure switch/sensor triggers an instruction to open the intake valve. The rotors compress air and deliver it to the consumption end.

Unloading Mechanism: When pressure reaches the upper limit, the intake valve closes. The equipment operates under no-load conditions, maintaining only rotor rotation to reduce energy consumption.

Pressure Regulation: Precise control of the pressure range is achieved by setting upper and lower limits. High-end models feature PID regulation for stable air supply pressure.

II. Core Causes of Load/Unload Failures

Sensor Component Failure: Oxidation of pressure switch contacts or sensor chip drift causes signal distortion; high temperatures, humidity, dust, and oil accelerate performance degradation, affecting sensitivity.

Intake Valve Malfunction: Carbon deposits and contaminants cause piston sticking or spring fatigue; damaged solenoid coils or loose wiring prevent normal valve operation, accounting for 35% of related failures.

Control System Failures: PLC module malfunctions or loose solder joints on circuit boards causing command errors; improper parameter settings or algorithm flaws leading to inaccurate control.

Pipe Leaks: Aging flange gaskets, loose joints, or corroded/perforated pipes. A 1mm² leak results in annual gas loss of approximately 15,000 m³, forcing frequent equipment loading.

Mechanical wear: Prolonged operation of intake valve stems and pressure switch microswitch mechanisms increases clearance gaps and surface abrasion, causing response delays or incomplete actuation.

III. Fault Diagnosis and Solutions

Sensor system maintenance: Calibrate pressure switches/sensors quarterly using high-precision calibrators with error ≤±1%; install protective covers, regularly clean sensing surfaces, and apply anti-corrosion treatment when necessary.

Intake Valve Repair: Disassemble and clean carbon deposits/oil residue; inspect seal surface wear and grind for restoration. Perform airtightness testing and dynamic opening/closing verification post-assembly to ensure response compliance.

Control System Diagnosis: Use multimeters and oscilloscopes to inspect PLC signals and circuit board parameters; replace damaged components. Verify program logic, optimize control algorithms, and update to stable versions.

Pipeline Leak Remediation: Locate leaks using ultrasonic leak detectors, verify with leak detection fluid; repair minor leaks with sealant, replace severely damaged pipes, reinforce threaded connections with anti-loosening adhesive.

Mechanical Component Maintenance: Measure critical part dimensions, replace worn valve stems and plugs exceeding tolerance limits; lubricate moving parts with high-temperature grease to ensure smooth operation.