- Compressing air is one way to store energy.moteur image by berdoulat jerome from Fotolia.com
A compressor turns electrical or gas energy into stored energy in the form of compressed air. Hydraulic systems work with liquids, usually oil or water, and pneumatic systems work with gases, almost always air. One of the chief advantages of pneumatic systems over hydraulic systems is gases can be easily compressed--and stored--while liquids are very hard to compress. Another advantage is air is free and readily available.
- The tank is the most predominant feature of an air processor. It is where the compressed air is stored. It must have a one-way valve, aka a check valve, that lets air into the tank and prevents it from escaping along the same path. The primary job of the air compressor is putting more air in the tank. The tank must also have some way of letting compressed air out of the tank to be used for powering pneumatic devices. The egress valve can be much more complicated--sometimes there are multiple egress valves of different diameters, because some systems need to use compressed air at different pressures. Tanks usually have some protective system to ensure they vent air if the pressure is becoming dangerously high.
- The engine of an air compressor can be either gas or electric. Gas engines are preferred for some outdoor uses where there is no reliable source of electricity. The engines can be two types: piston or blade. Piston engines, often called positive displacement compressors, use gas or electric power to rotate a crankshaft that causes a piston to pump blocks of air into the tank--virtually the exact opposite of how pistons function in an internal combustion engine. The check valves that prevent back flow are located over the piston heads and are open during the compression stroke and closed during the retraction stroke. Some large industrial air compressors use spinning blades, like a compressor pump, to force air into the tank.
Valves, Gauges and Fittings
- Air compressors must have elaborate valves, gauges and fittings for safety and to get the compressed air where it needs to be. The most obvious of these is the check valve between the engine and the tank, but there are usually both check valves and other valves between the tank and the output. One of these may be a manual or automatic valve that is closed when there is a breach in the system, so the compressed air in the tank is saved from escaping. There is almost always a pressure valve on the tank to ensure the pressure does not become dangerously high--this valve is also useful so you know when the pressure is high enough to use. In better systems, too much pressure will automatically shut off the engine.