A complete guide to the scroll compressor

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To understand the different types and technologies of compressors, we first need to understand the two basic principles of compressing air. These are dynamic and displacement compression. In this article, we talk about the scroll compressor. This is a type of displacement compressor with wide applications in air-conditioning and refrigeration systems, heat pumps, and cars. 

What are scroll compressors?

the scroll compressor, a graphic of the inside

A scroll compressor, also known as a spiral compressor and a scroll pump, is a type of positive-displacement compressor. It works through the internal compression of air or gas. Scroll compressors can be oil-lubricated or oil-free. The latter is best suited for applications where there is a need for clean, dry air quality without any oil contamination in the compression chamber.

Watch the video to learn more!

Scroll compressor working principle

How do scroll compressors work?

Scroll compressors use two spiral-shaped scrolls to compress air. One scroll remains fixed, while the other moves in an orbiting motion around the center of the stationary scroll. As the scrolls rotate, the orbiting scroll draws air through the inlet, compressing and pushing it towards the center. Finally, the compressed air is released through the outlet.

These machines consist of two spiral-shaped scroll elements that are bolted together. They include a stationary scroll and an orbiting scroll driven by a motor. The scrolls oscillate in a continuous motion without any metal-to-metal contact while the air is compressed into increasingly smaller volumes in crescent-shaped air pockets.

Let’s dive a bit deeper to understand the mechanism of displacement compression in scroll air compressors. The orbiting scroll is driven by a short-stroke crankshaft and runs eccentrically around the center of the fixed scroll. The movement of the orbiting scroll creates suction, which draws the air in from the inlet opening. This is located at the top of the element housing.

Air or gas that is captured in air pockets between the two scrolls is gradually compressed while moving toward the center of the housing. The outlet port and non-return valve are found here. Compressed and pressurized gas is discharged from the outlet port at the center of the assembly. The non-return valve, or check valve, prevents the backflow of gas or refrigerant.

The 180° rotation or phase displacement provides the radial stability of the scroll element. Since the compression chamber becomes increasingly smaller while air or gas is compressed, this is usually called internal compression. During this process, leakage is minimized. This is because the pressure difference in the air pockets is lower than the pressure difference between the inlet and outlet.


Similar to internal compression in a screw compressor, the amount of internal compression is determined by the discharge port. Due to the unique design of the discharge port, the scroll air compressor can compress more air or gas while using minimal power.

Compared to other compressors, these machines attain the highest efficiency level by volume. This is because there are no pistons to compress the gas.


The noise emission of a scroll air compressor is significantly lower than other compressors. The complete compression cycle takes 2.5 turns, including the suction, compression, and discharge revolution phases. These occur simultaneously while providing a constant flow of pulsation-free air.

The scroll air compressor offers smooth and vibration-free operations thanks to its scroll element. It hardly has any torque variation compared to a piston compressor. The simple design of the scroll air compressor contains only one moving part. This makes it highly reliable and quieter than equivalent piston and rotary screw compressors.

Modular vs. digital scroll compressors

Modular scroll compressor

  • Scroll compressors with variable flow technology incorporate the benefits and flexibility of a modular system. They utilize two to four compressor modules integrated into one canopy.
  • Additionally, the Elektronikon® controller continuously monitors the status of each element and starts and stops the compression elements. This ensures that the compressed air output matches the air demand.
  • Moreover, the perfect air quality and user-friendliness of these units guarantee a superior production process.

Digital scroll compressor

  • On the other hand, the digital scroll compressor has a mechanical design. This machine matches the output of the compressor to the cooling requirements of the complete process.
  • The digital scroll compressor is mainly used in refrigeration and air-conditioning systems. They ensure precise temperature control in these applications. When temperatures are kept stable during the transportation of food, for example, this results in better food quality.

Why choose a scroll compressor?

Choosing a scroll air compressor ultimately depends on the size, flow, and quality requirements of your application. Before choosing any type of compressor, it is important to figure out the correct size and technology for your needs. You'll also want to determine if you need an oil-free or lubricated compressor. This will be based on your air quality requirements.

For higher capacity and flow, it is possible to choose units with two or four scroll compressor elements in one housing. It may be more economical to go for a single large compressor than to use several machines.

As pointed out in this article, the scroll air compressor offers many advantages. This is due to its simplified and efficient design.

✔ With fewer components than reciprocating compressors, they ensure a high level of operational reliability.

✔ In addition, these machines require minimal maintenance.

Many leading industrial applications can utilize scroll compressors. This is due to how they meet the basic requirements of a general-purpose compressor. As mentioned above, scroll compressors are widely used in the food, refrigeration, air-conditioning, and transportation industries. That being said, oil-injected screw compressors may be more efficient in large industrial applications with larger volume demands.


We're here to help

We hope this guide provides a good overview of whether or not a scroll compressor makes sense for your needs. If you'd like more information, feel free to get in touch. Our team is happy to point you in the right direction.

Read more on scroll compressors

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