An Introduction to Screw Compressors

Screw compressors are a cornerstone of modern industrial compressed air systems, offering a reliable and efficient way to compress air using a rotary positive-displacement mechanism.

Unlike other compressor types, a rotary screw air compressor has two interlocking rotors to compress air smoothly and continuously, making it ideal for industrial applications.

Our screw compressor range is extensive, available in both fixed speed and variable speed drive (VSD) configurations to suit everything from small workshops to large-scale manufacturing operations. There is a screw compressor model designed to meet your needs, ensuring reliable compressed air for any industrial environment.

With low maintenance requirements and high efficiency, screw compressors deliver consistent performance and are engineered for continuous operation.  

Why Choose Screw Compressors?

A rotary screw air compressor is a machine that uses the principle of rotation to compress atmospheric air, because of this, screw compressors are also known as rotary compressors.

Screw compressors are a great choice for industrial applications in Manufacturing, Engineering, and Distribution facilities, especially as these machines have the ability to run continuously. Examples of applications that can be powered by rotary screw compressors include:

  • Food processing
  • Packaging machines
  • Metal cutting
  • Cooling and heating

Screw compressors are available in a variety of units with different capacities, making it easy to match the right model to your specific operational requirements.

Even for the applications above, choosing whether to opt for a screw compressor really comes down to your specific needs, which is why Direct Air offers expert recommendations and bespoke solutions. We’ll help you select the right screw compressor for each specific application to ensure optimal performance and efficiency.

 

How Does a Screw Compressor Work?

A rotary screw air compressor works by drawing air in and compressing it between the male and female rotors as they revolve in opposite directions. As the space between the rotors narrows the air is compressed, resulting in compressed air that is positively displaced out of the outlet. Screw compressors are capable of producing high-quality compressed air at various pressures to meet industrial needs.

This cycle repeats until the rotor reaches maximum speed, at which pressure inside the machine will be at its maximum point to provide that continuous supply of compressed air that so many industries require. The air delivery capacity is often measured in CFM (cubic feet per minute) or m3/min, which is a key performance indicator for these compressors.

Screw compressors can be single stage, meaning air is pushed from only one end of the chamber to the other. Therefore, multi-stage screw compressors compress air from both ends of the chamber simultaneously, as they are able to change direction. These compressors produce a consistent and reliable airflow for demanding applications.

Advantages of a Screw Compressor

Screw compressors offer key benefits such as energy efficiency, low noise, durability, reliable long-term performance and operational flexibility, making them a preferred choice for many industrial applications.

Durable – Rotary screw air compressors have a considerably long lifespan compared to other types of air compressors, and their durability ensures reliable long-term performance even in demanding environments.

Low noise – Due to the smooth movement of the rotating shaft, rotary screw compressors operate quieter than other compressor types. This makes the compressors ideal for facilities where employees are working near to the compressed air system, as it acknowledges health and safety factors.

High demand – Rotary screw air compressors are built for continuous operation, running 24/7 at a lower temperature so overheating isn’t an issue. Therefore, these compressors can meet consistently high demands as there’s no delay in waiting for the receiver tank to fill up, meaning air can be used right away.

Energy efficient – As an energy-efficient screw air compressor is less likely to overheat, less heat is produced and wasted into the atmosphere, supporting both lower running costs and long-term reliability.

 

Screw Compressors vs Piston Compressors

In comparison to pistons, screw compressors do not have rods, valves, pistons, and other parts that pulsate during the compression of the air. Therefore, screw compressors operate a lot smoother than piston compressors and due to no thudding sounds from these moving parts the noise level is significantly reduced.

Also due to the relatively low number of mechanical parts and continual, smooth rotation of the central screw shaft, screw compressors have little wear and tear. This means that the risk of a machine break-down is much lower, contributing to their overall cost effectiveness by reducing both energy consumption and maintenance costs.

Things to consider with Screw Compressors

Despite screw compressors being an excellent solution for many applications, there are some things to consider…

The screw compressor’s advanced design compared to the pulsating, noise generating mechanisms of other compressor types means that this of course comes at a price. Therefore, you’ll often find that screw compressors come at a higher price than their piston counterparts. However, many modern screw compressors are designed for easy installation, reducing setup time and complexity.

As this compressor type is designed to function in a continual motion, intermittent loads and regular stopping and starting aren’t ideal for screw compressors.

Although the reduced moving parts in compressors mean reduced wear and tear, if something does require repairing it can often be more complicated. Some systems offer a combined design, integrating components like tanks and dryers for greater convenience. 

This is where our qualified Direct Air Service & Maintenance engineers are on hand to step in and help!

Oil-Lubricated Screw Compressors

Lubricated screw compressors, also known as oil-injected screw compressors, use oil in the chamber where air is compressed to cool and lubricate the compressor as this helps form a seal and dampen noise levels.

Proper oil management in these compressors helps minimise leakage during compression, which improves overall efficiency. Some oil-lubricated screw compressors also utilise a gear drive system to ensure reliable and efficient operation.

These types of compressors can be ideal for applications where the compressed air doesn’t come into direct contact with an end product that is consumable.

Oil-Free Screw Compressors

Alternatively, if your compressed air is coming into direct contact with your consumable end product, oil free compressors can be a smart choice. This would be most apparent in Food & Beverage and Pharmaceutical production industries. For added versatility in workshop environments, screw compressors can also be configured as tank mounted units, also known as air stations.

Whether you opt for an oil-lubricated or oil-free screw compressor, don’t forget that the connecting compressed air treatment is a vital requirement to complete your system. Dryers, filtration systems, and condensate management solutions are available to complement screw compressors and create a complete compressed air system. Not sure which model is right for your business? Request a free quote and our team will recommend the right compressor from our full range.