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Basics on rotary screw compressor

Rotary screw air compressors are widely used in various industries due to their efficiency, reliability, and durability. 

A rotary screw compressor is an air compressor that uses two rotating screws or helical rotors to compress air or gas. The male and female rotors rotate in opposite directions, drawing air into the compressor and compressing it as the gap between the threads becomes smaller.

Screw compressors are preferred in professional and industrial applications due to their quiet operation, energy efficiency, and reliability even under continuous use.

In this blog, we will explore the working principle of rotary screw compressors, their components, their advantages and limitations compared to piston compressors, as well as their performance and maintenance aspects.

How Does a Rotary Screw Compressor Work?

A rotary screw compressor compresses air by using two meshing helical screws or rotors. The air is drawn in through a filter and an open inlet valve to the compressor element. As the rotors rotate, the volume of the air is reduced, resulting in an increase in pressure.

The compressed air then flows into a separator tank where most of the oil is separated out in oil-lubricated screw compressors. The separated oil can be reintroduced into the air-end or go through an oil cooler depending on its temperature.

In contrast, oil-free screw compressors use gears to control the timing between the two rotors, and there is no oil to lubricate, cool, or seal the chamber. This makes them less efficient and results in a lower maximum pressure compared to oil-lubricated compressors.

Oil-free compressors are useful when high air quality is required, such as in the pharmaceutical or food and beverage industries.

Rotary screw compressor working principle

What are the Main Components of a Rotary Screw Compressor?

The main components of a rotary screw compressor include:

  • Compressor element: The compressor element consists of two interlocking helical rotors that compress the intake air.
  • Drive motor: The drive motor powers the compressor element.
  • Air/oil separator: The air/oil separator separates most of the oil from the compressed air using centrifugal force.
  • Oil filter: The oil filter removes impurities from the oil.
  • Oil cooler: The oil cooler cools the oil before it enters the compressor element.
  • Thermostatic bypass valve: The thermostatic bypass valve allows oil to enter the compressor element when the valve opens at a specific temperature.
  • Oil stop valve: The oil stop valve prevents flooding of the compressor element via the oil.

How Does a Rotary Screw Compressor Compare to a Piston Compressor?

Rotary screw compressors have several advantages over piston compressors, including:

  • Higher capacity: Rotary screw compressors offer a constant air flow and higher capacity, making them ideal for industrial applications.
  • Continuous running: Unlike piston compressors, rotary screw compressors do not have valve systems, allowing them to operate at high air flow rates with a higher duty cycle which enables continuous running.
  • Lower maintenance: Rotary screw compressors have fewer moving parts than piston compressors, resulting in lower maintenance requirements.
  • Quieter operation: Rotary screw compressors operate more quietly than piston compressors, making them ideal for noise-sensitive environments.

However, rotary screw compressors also have some limitations, including:

  • Higher initial cost:  Rotary screw compressors are more expensive than piston compressors, since they have a longer lifespan and produce more air.
  • Oil-lubricated compressors require regular oil changes and maintenance. Despite the new design made the maintenance easier, rotary screw compressors are still a complex system and the help of a skilled technician is still highly valuable.

 

Performance and Maintenance Aspects of Rotary Screw Compressors

Rotary screw compressors require regular maintenance to ensure optimal performance and longevity. Some maintenance tasks include:

  • Regular oil changes and filter replacements for oil-lubricated compressors.

  • Cleaning or replacing air filters.

  • Checking and adjusting belts and pulleys.

  • Inspecting and cleaning coolers and heat exchangers.

  • Checking and adjusting the thermostatic bypass valve.

Proper maintenance can help prevent breakdowns, reduce energy consumption, and extend the life of the compressor. It is also important to choose the right size and type of compressor for your application to maximize efficiency and reduce energy costs and carbon footprint.

Common Questions

How does a rotary screw compressor work?

A rotary screw compressor compresses air by using two meshing helical screws or rotors. The air is drawn in through a filter and an open inlet valve to the compressor element. As the rotors rotate, the air volume is reduced, increasing pressure.

What are the main components of a rotary screw compressor?

The main components of a rotary screw compressor include the compressor element, drive motor, air/oil separator, oil filter, oil cooler, thermostatic bypass valve, and oil stop valve.

How does a rotary screw compressor compare to a piston compressor?

Rotary screw compressors have several advantages over piston compressors, including higher capacity, continuous running, lower maintenance, and quieter operation. However, they are also more expensive and less portable than piston compressors.

What are the advantages and limitations of rotary screw compressors?

The advantages of rotary screw compressors include higher capacity, continuous running, lower maintenance, and quieter operation. The limitations include higher initial cost, and regular maintenance requirements for oil-lubricated compressors.

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We offer a wide range of screw compressors to cater to various industries' needs. Our compressors are designed to be efficient, reliable, and durable. They ensure optimal performance and longevity. Contact us today to learn more about our products and services.

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