What Is a Piston Compressor?

A piston compressor, which is often called a reciprocating compressor is a machine for compressing gases that operates in much the same way as a piston internal combustion engine, but without the explosive ignition of fuel. Outside power, often provided by another engine is used to operate the machine. A piston compressor uses pistons enclosed in cylinders, usually with at least two valves for the intake and output of gases. The gas is taken into the cylinder, compressed by the cylinder and then expelled under pressure. These machines can be used for the compression of a number of different gases which may also be used in several ways, including, but not limited to, the operation of pneumatic tools, machinery, or instrumentation systems or for storage in pressurized tanks.

In basic design, a piston compressor resembles an internal combustion engine without the fuel delivery and ignition systems. One or more pistons enclosed in cylinders are connected to a camshaft, which is turned by an outside power source, usually a diesel engine, although electric motors or other types of power can also be used. As the camshaft turns, it causes the pistons to move back and forth within the cylinders, which are sealed except for the intake and outflow valves. The camshaft is designed to move the pistons in a specific pattern to allow for a continuous expulsion of compressed gas, each piston performing its compression stroke one after the other.

The operation of the individual cylinders is fairly simple. As the piston is drawn outward from the cylinder, an intake valve opens, drawing gas into the interior of the cylinder. When the piston reaches its maximum travel distance on the intake stroke, the intake valve closes, and the piston begins its compression stroke. This serves to compress the gas contained within the cylinder, and when the piston has reached its maximum travel on this stroke, the exhaust valve opens and the compressed gas is expelled into some type of closed, pressurized system for further use or storage. At this point, the exhaust valve closes and the cycle begins again.

Designs for piston compressors can vary substantially from one another. They can be fairly simple, with as few as one cylinder or they may have many. The number of valves per cylinder can vary as well with some having only one valve for both intake and exhaust. Exterior systems provide for the diversion of intake and exhaust in machines of this type. A piston compressor may have multiple valves per cylinder as well.

Applications for these machines are numerous. The use of compressed air for pneumatic tools, instrumentation, and other machinery is very common, for example. Gases may include others besides air, such as nitrogen, hydrogen, oxygen, or gaseous hydrocarbons. They may be used directly from the compressor or stored in pressurized tanks for further use.