page_title: Compressor
section_title: Rolling piston
hierarchical_section_title: Compressor / Types / Positive displacement / Rolling piston
caption_attribution_description: Deutsch: Schematische Darstellung eines Rollkolbenverdichters
context_page_description: A compressor is a mechanical device that increases the pressure of a gas by reducing its volume. An air compressor is a specific type of gas compressor.
  Compressors are similar to pumps: both increase the pressure on a fluid and both can transport the fluid through a pipe. As gases are compressible, the compressor also reduces the volume of a gas. Liquids are relatively incompressible; while some can be compressed, the main action of a pump is to pressurize and transport liquids.
  Many compressors can be staged, that is, the fluid is compressed several times in steps or stages, to increase discharge pressure. Often, the second stage is physically smaller than the primary stage, to accommodate the already compressed gas. Each stage further compresses the gas and increases pressure. Those that are powered by an electric motor can also be controlled using a VFD or power inverter, however many compressors can only work at certain speeds, since they may include built-in oil pumps. The oil pumps are connected to the same shaft that drives the compressor and forces oil into the compressor and motor bearings.
context_section_description: The Rolling piston in a rolling piston style compressor plays the part of a partition between the vane and the rotor. Rolling piston forces gas against a stationary vane.
  2 of these compressors can be mounted on the same shaft to increase capacity and reduce vibration and noise. A design without a spring is known as a swing compressor.
  In refrigeration and air conditioning, this type of compressor is also known as a rotary compressor, with rotary screw compressors being also known simply as screw compressors.
  It offers higher efficiency than reciprocating compressors due to less losses from the clearance volume between the piston and the compressor casing, its 40% to 50% smaller and lighter for a given capacity (which can impact material and shipping costs when used in a product), causes less vibration, has fewer components and is more reliable than a reciprocating compressor. But its structure does not allow capacities beyond 5 refrigeration tons, is less reliable than other compressor types, and is less efficient than other compressor types due to losses from the clearance volume.
caption: Rolling piston compressor
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