Scroll Compressors: Working Principle, Types & Choosing The Right One

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.

Choosing a scroll compressor ultimately depends on the size, flow and quality requirements of your application. Before choosing any type of scroll compressor, it is important to figure out the correct size and technology for your compressed air needs, starting with whether you need an oil-free or lubricated compressor. For higher capacity and flow, it is possible to choose units with two or four scroll compressor elements in one housing. However, it may be more economical in some cases to go for a single large compressor rather than teaming up several scroll compressors to produce sufficient flow. 

The scroll compressor has many advantages due to its simplified yet efficient design. With fewer components than reciprocating compressors, it ensures a high level of operational reliability and requires hardly any maintenance. Many leading industrial applications go for the scroll compressor because it meets all the basic requirements of a general-purpose compressor. Whereas oil-injected screw compressors may be more efficient in large industrial applications with larger volume demands, scroll compressors are still widely used in food, refrigeration, air-conditioning, and transportation industries.

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.