Air Supply UK: Specialist Compressed Air Engineers

Published: 30/05/2022

Rotary screw vs rotary vane compressor: choosing the right air compressor

When choosing an air compressor for any application, it’s important to understand how it will meet the needs of your business. Two common air compressors you can choose from are rotary screw compressors and rotary vane compressors. 

Both air compressors were developed around the same time and they’re designed to produce the same end result but they do differ slightly so it’s important to be aware of the differences and which is best for your application. 

We’ll take a look in more detail in this guide.

What is a rotary vane air compressor? 

A rotary vane compressor is made up of a rotor inside a cylindrical housing and the rotor has slots for the vanes. As the rotor moves, the vanes are thrown out by centrifugal force until they touch the housing. As the air enters the compressor, it is trapped between the vanes and the volume of trapped air becomes gradually reduced as the rotor turns. This compressed air exits the outlet to power the processes it’s required for. 

Benefits of a rotary vane air compressor 

The key benefits of a rotary vane air compressor include: 

  • Simple design with few moving parts 
  • Low initial costs 
  • Long life expectancy 
  • Easy to maintain 
  • Compact 

What is a rotary screw compressor? 

Rotary screw compressors are made up of two helical screws, or rotors. The rotors rotate towards each other in opposite directions and compress the air between them as they turn. The air becomes trapped between the two rotors which reduces the volume of the trapped air and results in compressed air that can be used within a wide range of applications. 

If you’d like to know more about how a rotary screw air compressor works, please read our guide. 

Benefits of a rotary screw air compressor 

The benefits of rotary screw air compressors include: 

  • Energy efficient and cost effective 
  • Larger capacity than other types of compressor 
  • 100% duty cycle 
  • Long lasting 

How do rotary screw and rotary vane compressors compare? 

There are a few key ways in which these two compressors differ and knowing the differences can help you to choose the right compressor for your application. 

Energy efficiency 

Energy efficiency is a key factor for many businesses and industrial applications. An inefficient air compressor can affect the bottom line and cause unwanted ongoing maintenance costs. 

Rotary Vane air compressors 

This type of air compressor has very minimal internal air leakage which makes them more energy efficient than other types of air compressor. Lubrication inside the compressor means the rotor vanes stay in contact with the cylinder surface constantly so the air seal is nearly perfect. 

Rotary Screw air compressors 

Rotary screw compressors have a ‘blow hole’ which contributes to internal air leakage and will never be completely eliminated which makes rotary screw air compressors less energy efficient than rotary vane compressors. 

To compensate for this leakage, screw compressors run at high speeds. On the other hand, vane compressors operate at low speeds which leads to lower power consumption. 

A compressor that operates efficiently has minimal air leakage because losing air during compression means lost energy. If internal leakages are kept to a minimum, the volumetric efficiency of the air compressor is increased which reduces the power required to deliver a unit of compressed air. 

Performance 

Both rotary vane and rotary screw air compressors are designed to run continuously. This makes them the perfect solution for highly demanding industrial or manufacturing environments that need long term and high volumes of air. 

Longevity and maintenance 

If a rotary vane air compressor is looked after properly, the operating life can be unlimited. Some air compressors can last for up to 100,000 hours without experiencing any wear. However, it’s important to have your compressor regularly serviced to make sure it operates properly throughout its lifetime. 

Screw compressors can run for up to 20,000 hours but will need roller bearings to be replaced after this time to continue operating at full capacity. 

The compressor you choose will depend on the needs of your business and the maintenance you can provide on a regular basis to keep the compressor running as well as you need it to. 

Whilst rotary screw air compressors may not operate as long as rotary vane compressors, they offer better energy saving qualities. Rotary screw compressors produce less heat than other compressors which helps to reduce the costs of maintenance and provides optimum performance throughout the lifetime of the compressor. 

If you’d like more information on how a rotary screw air compressor could benefit your application, please contact our expert team.

 

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