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ZR/ZT oil-free rotary screw compressor

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Rotary screw air compressor

Rotary screw air compressors

Explore our complete range of rotary screw air compressors for every application. When shopping with us, you'll benefit from the knowledge of our team of compressed air experts to find the right equipment for your needs.

Rotary screw compressors are designed for a wide range of users across various industries and applications. They are powered by two counter-rotating screws that compress air as it moves through the compressor.

These units are designed for continuous use, capable of operating 24 hours a day, 7 days a week. They are known for their quiet operation, with noise levels around 60 dBA, and their efficiency in producing compressed air. This type of compressors are more efficient and have a longer lifespan compared to piston compressors, making them a great long-term investment for many industries.

Rotary screw compressors for sale

Compressors are used by a wide range of industries and businesses. Atlas Copco specifically designed these all-rounders to suit your needs effectively.

Selecting an appropriate screw compressor involves a careful assessment of various factors: 

  1. Determine the air demand 
  2. Select the appropriate capacity, expressed in terms of cubic feet per minute (CFM) or liters per second (L/s)
  3. Consider the operating pressure range, compressor energy efficiency, reliability, and maintenance requirements is vital.
  4. Opt for a backup compressor to maintain uninterrupted production during scheduled maintenance for critical applications.

Different types of air compressors

Rotary air compressors come in two primary versions: oil-flooded and oil-free, with options for fixed speed, dual-speed or variable speed drive operation.

Oil-lubricated screw air compressors

Oil-lubricated compressors inject oil into the compression chamber, which cools and lubricates the compressor element, helps to remove the heat of compression, and minimizes leakage. These compressors are chosen for their continuous operation capability, low oil carryover, and minimal capacity loss over time. They are suitable for a wide range of industrial purposes.

Explore Atlas Copco's range of Oil-lubricated Screw Compressors

Oil-free screw air compressors

Oil-free compressors do not use oil in the process, making them ideal for sensitive industrial applications where air purity is critical, such as in the food and beverage or pharmaceutical industries. These compressors still use lubricants for other processes, like motor cooling, but some variants use water as an alternative lubricant. Oil-free types are known for their reliability, efficiency, and ability to deliver the highest air purity at the lowest TCO.

What are the benefits of a rotary screw air compressor?

Top rotary screw compressors offer several advantages that make them a preferred choice for continuous, workplace, and industrial use.

These are the main benefits of rotary screw air compressors: 

  • Reliability and 100% Duty Cycle: They can operate continuously at temperatures up to 46 degrees Celsius without adverse effects, which is crucial for manufacturing environments where a stopped compressor can impact production.
  • Energy Efficiency: VSD compressors, such as our GA VSDs, are capable of achieving energy reductions of up to 60% over conventional fixed-speed designs, thanks to advanced features like interior permanent magnet motor drive and inverter systems. Dual-speed compressors like the GA FLX can save up to 20% compared to traditional fixed-speed compressors.
  • Low Noise and Small Footprint: Rotary screw compressors operate at low sound levels and have a compact design, making them suitable for workplace installations.
  • Versatility: With a wide range of options available (2.2-500 kW), these types of compressors are designed to provide everything you need. 

What is the working principle of a rotary compressor?

The basic working principle, also called the twin screw compressor principle, is that the male and female rotors rotate in opposite directions. This draws air in between them. As air progresses along with the rotors, the decrease of space between them and their housing leads to air compression. To generate compressed air, the electric motor uses energy to produce power. To maintain air quality, a filter removes contaminants from the compressed air before it is delivered to the pneumatic system or application. The compressed air is then displaced to the outlet.


Although they belong to the same class, rotary screw compressors are more complex than piston compressors. The speed of the rotors in rotary screw compressors is optimized. This is to minimize both mechanical losses, caused by heat generated at very high speeds, and volumetric losses, resulting from air loss at very low speeds during compression. 

Male and female rotors

Difference between types of rotary screw air compressors

GA oil-injected screw compressors series: These compressors are known for their outstanding performance, high productivity, and low cost of ownership, even in harsh environments. They are suitable for continuous operation and come with integrated refrigerated dryers for some models.

Oil-free screw air compressors ZR & ZT (VSD): These compressors are designed for efficiency, safety, and reliability at the lowest TCO. 

This range of oil-free compressors guarantees dry, quality air with a smaller footprint and integrated drum dryer. They are ISO Class 0 certified, meaning they are 100% oil-free, and are suitable for industries that require clean, oil-free air, such as food and beverage, medical, and pharmaceutical.

Variable Speed compressors (VSD): VSD technology is ideal for operations where demand for compressed air fluctuates. These compressors adjust their operating speed to match air production to demand in real-time, offering energy savings of up to 60% compared to traditional fixed-speed compressors.

Oil-lubricated screw compressor G (VSD) series: The G series compressors provide reliable high-quality air and are designed to avoid costly downtime and production delays, even in the harshest conditions. They are available in a range from 2 to 250 kW.

Need help choosing the best compressor? Contact us for more information.