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

Scroll compressors consist of two spiral-shaped scroll elements that are bolted together: a stationary scroll and an orbiting scroll driven by a motor. The process of compressing air in a scroll compressor involves several steps:

1. Oscillation: The scrolls oscillate in a continuous motion without metal-to-metal contact, compressing air in crescent-shaped pockets.
2. Orbiting Scroll Motion: The orbiting scroll, driven by a short-stroke crankshaft, moves eccentrically around the fixed scroll, creating suction that draws air in from the inlet at the top of the housing.
3. Compression: Air captured in pockets between the scrolls is gradually compressed as it moves toward the center.
4. Discharge: Compressed air is discharged from the outlet port at the center, where a non-return valve prevents backflow.
5. Stability: The 180° phase displacement provides radial stability, and the internal compression minimizes leakage due to lower pressure differences between air pockets.

By following these steps, scroll compressors achieve efficient and reliable air compression.

When most people think of air compressors, they probably imagine a bulky and loud machine. Scroll compressors are pretty much the opposite of that. They are oil-free, compact and relatively silent compared to other types of compressors.

Thanks to the simple design of the scroll compressor with only one moving part, this type of compressor is highly reliable and quieter compared to the piston and rotary screw compressor. This makes them perfect for sensitive working environments, like a dentist’s office. Another advantage of scroll compressors is energy efficiency. 

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.

Selecting a scroll air compressor involves considering several factors: size, flow, and air quality requirements.

Determine Needs:

• Size & Technology: Identify the correct size and technology for your application.
• Air Quality: Decide between an oil-free or lubricated compressor based on air quality needs.

Capacity & Flow:

• For higher capacity and flow, units with multiple scroll elements (two or four) can be chosen.
• It may be more economical to use a single large compressor instead of multiple smaller ones.

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.

• Laboratories & Research: Instrument calibration, sample analysis, and environmental control in cleanrooms.
• Medical & Healthcare: Providing clean air for ventilators and incubators, powering surgical tools, and assisting in breathing during surgery.
• Food & Beverage: Food packaging and vacuum sealing, meat processing, and carbonation.
• Electronics: Parts cleaning, maintaining cleanroom environments, and preventing moisture and corrosion in precision assembly.

There is an abundance of applications for quiet and energy-efficient compressors that produce absolutely clean air. Take the SF scroll compressor series from Atlas Copco, which has been a leader in this field for more than 60 years. Its unique characteristics make it ideal for many manufacturing processes for which clean, oil-free compressed air is a prerequisite. That is why the SF is the preferred choice for sensitive indoor environments, like hospitals but also labs, breweries, bakeries, dairy farms, electronics manufacturing, and even lens production.

The SF series features a capacity range of 1.9 to 7.6 l/s (4.03 to 16.10 cfm), a maximum working pressure of 10 bar (145 psi), and a dew point performance as low as 2°C/36°F. Its air-cooled scroll element ensures efficiency, reliability, and durability, while the premium efficiency IE3 class motor lowers energy consumption. Most importantly, the SF series produces absolutely clean air.

Atlas Copco’s oil-free compressors, certified ISO 8573-1 Class 0, set a new standard in air quality, exceeding testing requirements. These features make the SF series indispensable in maintaining a pleasant and hygienic environment in dentist offices, contributing to a less unpleasant visit for patients.

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.