What is an air compressor? A compressor is an electronic device that reduces the pressure of the air or gas by lowering its volume. An air compressor uses one or more compressors to increase the pressure of gas or air, which usually comes from a different pressure source such as a truck air tank or an oil tank. An air compressor also can be a specifically designed device to increase the pressure of some liquid such as gasoline or diesel.
Compressors are divided into three types according to how they work: positive displacement compressors, which use pistons; positive displacement refrigerators, which use liquid refrigerants; and, negative displacement compressors, which use a sealed displacement cylinder. Positive displacement compressors have a chamber on the top where the compressed air is stored. The compressed air is compressed and forces its way through a baffle that allows the air to be vented to the floor. A negative displacement compressor has no chamber on top and the compressed air is discharged through a hose and into a different container than the one it is in.
Centrifugal air compressors are the most common type and use an impeller similar to a bicycle wheel. These are generally used in applications where there is a large pressure change, such as the pumping of air into a turbine. Centrifugal compressors work by forcing air through an impeller, which rotates it at a high-speed. Because of the high-speed nature of centrifugal compressors, they are often found in oil-lubricated and turbine engines.
A two-stage compressor operates in much the same way as a one-stage device. It begins with a lower compression volume than the end of the cycle. After the compressed air has passed through the cylinder, a second compression occurs. The second compression, called the final stage, pumps the remaining gas into the discharge nozzle. A two-stage air compressor has a lower maximum pressure than a one-stage air compressor, but both are useful for the same purposes.
In addition to the above, many newer air compressors also feature a safety release valve. In an emergency or during startup, the valve allows only clean, oxygenated air to enter the compressor tank. If dirty oxygenated air enters the tank, the compressor will fail immediately, and all stored compressed air will leak out into the atmosphere. To prevent this failure, it is imperative that you manually open the safety release valve. You should never do this while operating the engine.
A high pressure pump is commonly included in all air compressors, although some models may also contain a high-temperature booster. These devices are essential for operation under high temperatures. They maintain high temperatures, long after the original power source is turned off. When operating at high temperatures, the liquid refrigerant expands to a vapor, which expands into a gas when heated by the surrounding environment. This gas is very combustible and can severely injure the user.
Finally, there are both dynamic and centrifugal compressors. Both utilize a stored mechanical energy, usually in the form of kinetic energy or force, to move a fluid through a medium such as a pump. Centrifugal compressors are often used in mobile units, such as scooters, lawnmowers, or even snow blowers, because of their low center of gravity and excellent fuel efficiency.
Centrifugal air compressors are often attached to a rotary vane pump to provide continuous rotary power. They have the advantage that they require the least maintenance, although the pump must be replaced periodically. Dynamic compressors, which use a sealed oil reservoir, are most commonly used in construction and industrial applications. As their name implies, the compressor forces air through a sealed tube, which results in high pressure.
