Basic Knowledge of Screw Air Compressors_Suzhou Chanun Compressor Co., Ltd.

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Basic Knowledge of Screw Air Compressors

Release time:

2025-06-13

I. Core Structure and Operating Principle
A. Core Components of Screw Air Compressors
Screw air compressors are primarily built around a pair of intermeshing helical rotors, available in single-screw and twin-screw configurations.

Twin-screw: Composed of a male rotor (convex teeth) and a female rotor (concave teeth). The male rotor is driven by a motor, which in turn drives the female rotor in the opposite direction. The clearance between the rotors is only 5–10 microns, forming a sealed compression chamber.
Single-screw: Features one main screw meshed with two star wheels. This design offers more balanced force distribution and reduces noise by approximately 15 dB.

B. Power Transmission Methods

Belt Drive: Suitable for models below 22 kW. Uses pulleys to adjust speed ratios.
Direct Drive: Connects the motor and main unit via a coupling. Twin-screw models require an additional speed-increasing gear, allowing rotational speeds to reach tens of thousands of RPM.

C. Auxiliary Systems in Air Compressors
Includes components such as the oil-gas separator, cooler, and intelligent control system. The oil injection system provides lubrication, sealing, and cooling simultaneously, keeping the exhaust temperature below 80°C.

II. Working Process

Intake Phase
As the rotors rotate, the grooves open to the intake port, drawing in external air due to negative pressure. The air fills the entire groove space. When the rotor tips disengage from the intake port, the enclosed volume reaches its maximum (approximately 0.2–60 m³/min).

Compression Phase
The meshing surfaces gradually move toward the discharge end, and the enclosed chamber volume continuously decreases. The air pressure rises from atmospheric pressure to 0.8–1.3 MPa. Injected lubricating oil forms a thin film, absorbing compression heat and stabilizing the temperature between 75–95°C.

Discharge Phase
When the compression chamber connects with the exhaust port, the high-pressure oil-air mixture passes through an oil-gas separator. The purified air is then cooled by an aftercooler to within 15°C above ambient temperature before being discharged.

III. Advantages and Key Maintenance Points

Core Advantages

Reliability: No easily worn parts (e.g., piston rings, valves), with major overhauls required only every 40,000–80,000 hours.
High Energy Efficiency: 30% more energy-efficient than piston compressors; variable frequency models can further reduce energy consumption by 15%.
Adaptability: Forced air delivery ensures over 85% efficiency across a 70%–100% load range.

3. Key Points for Routine Maintenance

Filter Management:
- Air filter: Clean every 1,000 hours
- Oil filter: Replace every 2,000 hours
- Oil separator element: Service life around 4,000 hours
Oil Selection:
- Synthetic oil can last up to 8,000 hours
- Acid number should be maintained below 0.1 mgKOH/g

Fault Warning Indicators

Abnormal Temperature:
- If exhaust temperature exceeds 110°C, check for cooler fouling or oil line blockage.
Increased Vibration:
- If bearing wear or rotor misalignment exceeds 0.05 mm, calibration is required.