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How Do Low Pressure Screw Compressors Work?

Low pressure screw compressors are designed to deliver large volumes of air at pressures typically below 1.5 bar(g). They’re used in industries like wastewater treatment, pneumatic conveying, and fermentation—where high flow and low pressure are more efficient than traditional compressed air systems.

 

Core Principle: Rotary Compression

At the heart of the system are two interlocking helical rotors—one male, one female. As they rotate, air is drawn into the compression chamber. The rotors trap the air between their lobes and the casing, gradually reducing the volume as the rotors turn. This mechanical action compresses the air without the need for pistons or valves.

Unlike high-pressure compressors, low pressure screw compressors are optimized for volume rather than force. They operate at lower speeds and temperatures, which reduces wear and energy consumption.

Why Use Screw Technology for Low Pressure?

Screw compressors offer continuous, pulse-free airflow. That’s a major advantage over reciprocating compressors, which deliver air in bursts. The screw design also allows for oil-free or oil-injected configurations depending on the application.

In low pressure systems, screw compressors are more energy-efficient than throttling high-pressure air down to a lower pressure. This direct generation of low-pressure air avoids waste and improves system reliability.

Key Components

  • Air End: The rotor housing where compression occurs.
  • Drive System: Typically a motor and gearbox or direct drive.
  • Cooling System: Maintains optimal operating temperature.
  • Control System: Regulates pressure, monitors performance, and protects against overload.

Efficiency Considerations

Energy savings come from matching the compressor output to the actual demand. Variable speed drives (VSDs) are often used to adjust rotor speed in real time. This minimizes energy waste during low-demand periods.

Additionally, low pressure screw compressors are often integrated into broader control systems that optimize performance across multiple machines.

Maintenance and Reliability

Fewer moving parts mean lower maintenance. There are no valves to wear out, and the oil-injected models benefit from internal lubrication. Regular checks focus on filters, oil levels (if applicable), and rotor condition.

 

Common Applications

  • Aeration in wastewater treatment
  • Fluidization in cement and chemical industries
  • Fermentation processes in food and beverage
  • Pneumatic conveying of powders and granules

FAQs

Low pressure models operate below 1.5 bar(g) and are optimized for high flow. High pressure models go up to 13 bar(g) or more and are used for tools, packaging, and general plant air.