Air compressors are machines that compress and direct air for industrial applications. Small-scale devices are designed for pneumatic tools such as grinders, drills and nail guns. Manufacturing-scale products are used to drive punching and stamping equipment, power robotic tools, and convey parts. Air compressors that are designed for direct-use applications such as sandblasting and spray painting are also available. There are three basic types of air compressors: reciprocating, rotary screw, and centrifugal. Reciprocating air compressors use pistons to compress the contents of an air cylinder and force them into a storage tank. These piston-driven air compressors are designed for intermittent use. Rotary screw air compressors use twin screws instead of pistons to pressurize air. They are designed for continuous use and have a rated duty cycle of 100%. Centrifugal air compressors are turbine engines that use rotating blades to produce high pressures. Typically, these air compressors are used in power generation and large-scale industrial applications.
Selecting air compressors requires an understanding of specifications and requirements such as air quality, temperature, power source, size, and mobility. Some air compressors are equipped with driers (dry compressors) which remove the condensation that is created during compression. Others include coolers that lower the temperature of the compressed air. Air compressors with paper or polyester filters that remove oil, dust, vapors, and other debris are also available. Oil-free air is especially important in applications such as food processing and semi-conductor manufacturing, where as little as one part per billion (ppb) of oil is unacceptable. Smaller air compressors are usually powered by gasoline, diesel fuel, or single-phase electricity. Larger, commercial and industrial units often use three-phase power at 208 V, 230 V, or 460 V. In terms of mobility, portable air compressors feature wheel, casters, or self-contained trailers. Vertical air compressors are designed for fixed mounting and require less floor space.
Pressure, air flow, efficiency, and operating costs are important parameters for air compressors. Air pressure is usually measured in pounds per square inch (psi). Air flow is usually measured in standard cubic feet per minute (SCFM). Reciprocating air compressors can achieve air flows of up to 100 CFM. Rotary air compressors can reach 1500 CFM with a single stage and up to 2500 CFM with two stages. Centrifugal air compressors operate at levels greater than 1000 CFM. With regard to air compressor efficiency, the Compressed Air and Gas Institute (CAGI) has developed a standard set of test criteria. Suppliers of air compressors can provide a CAGI data sheet with information about horsepower, efficiency, and expected energy consumption.
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