Gas compressor

From Wikipedia, the free encyclopedia

A gas compressor is a mechanical device that increases the pressure of a gas by reducing its volume. Compression of a gas naturally increases its temperature.

Compressors are closely related 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, whereas the main result of a pump raising the pressure of a liquid is to allow the liquid to be transported elsewhere.

Air Compressor designs


* Reciprocating compressors—uses pistons driven by a crankshaft. They are both stationary and portable, can be single or multi-staged, and can be driven by electric motors or internal combustion engines. Small reciprocating compressors from 5 to 30 HP are commonly seen in automotive applications and are typically for intermittent duty. Larger reciprocating compressors up to 1000 HP are still commonly found in large industrial applications, but their numbers are declining as they are replaced by less costly rotary screw compressors. Discharge pressures can range from low pressure to very high pressure (>5000 psi or 35 MPa).


screw * Rotary screw compressors—uses two meshed rotating positive-displacement helical screws to force the gas into a smaller space. These are usually for continuous, commercial and industrial applications and are both stationary and portable. Their application can be from 5 hp (3.7 kW) to over 500 hp (375 kW) and from low pressure to very high pressure (>1200 psi or 8.3 MPa).


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* Oil-Free Rotary screw compressors—Developed especially for applications demanding the highest levels of purity, such as pharmaceutical production, food processing and critical electronics, Absolute class. Absolutely class zero. Make decades of experience in oil-free compressed air for critical applications work for you.



* VSD (Variable Speed Drive) Rotary screw compressors— offers a constant supply of compressed air, regardless of fluctuating demands.

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The benefits of variable speed drive (VSD) are widely recognized. VSD compressors simply measure the system pressure and maintain a constant delivery pressure within a narrow pressure band (about +/- 1.5 psi. By varying the speed of the drive motor, the VSD can supply the exact air capacity required so, as the air demand decreases, the VSD will lower the air delivery and electrical power consumption. This leads to greater energy savings, as every 2 psi reduction yields a 1% decrease in power consumption. Integrated VSD packages offer benefits beyond energy savings, including less regular maintenance, lower risk of current damage and longer lasting machinery.



* Low Pressure Rotary Screw Compressors - Blowers—reduces energy costs by an average of 30% when compared to lobe technology. ZS blowers provide a continuous and reliable supply of 100% oil-free air – certified according to ISO 8573-1 CLASS 0 (2010). Integrating the proven benefits of screw technology, the ZS range will cut your energy costs by an average of 30% when compared to lobe technology.



* Scroll compressor—similar to a rotary screw device, this one includes two interleaved spiral-shaped scrolls to compress a gas. The SF and SF+ ranges of oil-free scroll air compressors unite Atlas Copco’s vast experience and knowledge in a class-leading package. Whereas the SF range includes a standard pneumatic controller, the SF+ range boasts the high-end Elektronikon® controller. Reliable and compact, they both answer your demands through innovative technologies and supreme energy efficiency without compromising on quality.



Staged compression

Since compression generates heat, the compressed air is to be cooled between stages making the compression less adiabatic and more isothermal. The inter-stage coolers cause condensation meaning water separators with drain valves are present. The compressor flywheel may drive a cooling fan.

For instance in a typical diving compressor, the air is compressed in three stages. If each stage has a compression ratio of 7 to 1, the compressor can output 343 times atmospheric pressure (7 x 7 x 7 = 343).

Prime movers

There are many options for the "prime mover" or motor which powers the compressor:

* gas turbines power the axial and centrifugal flow compressors that are part of jet engines
* steam turbines or water turbines are possible for large compressors
* electric motors are cheap and quiet for static compressors. Small motors suitable for domestic electrical supplies use single phase alternating current. Larger motors can only be used where an industrial electrical three phase alternating current supply is available.
* diesel engines or petrol engines are suitable for portable compressors and support compressors used as superchargers from their own crankshaft power. They use exhaust gas energy to power turbochargers


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