Reciprocating Air Compressors – How They Work
Air Compressors are generally of two types –positive displacement or dynamic. The former can be further classified into reciprocating, rotary screw, and sliding vane. Of these the most common is the reciprocating compressor and it is the type most often used by do-it-yourselfers, contractors, and other craftsmen.
The air pump of a reciprocating air compressor works like an internal combustion engine. It is equipped with a piston, a connecting rod, crankshaft, cylinder, and valve head. Unlike the engine, however, it is the crankshaft that drives the piston. It is, in turn, powered either by an electric or gas motor. Most compressors have an air tank that holds air at a pre-determined pressure.
Air compression begins with the downward motion of the piston inside the cylinder. This creates a vacuum inside allowing outside air to push the air inlet valve and enter the said cylinder. On its upward movement, the air is compressed and it shuts the inlet valve while at the same time opening the discharge valve. This air goes into the tank where it is stored. With more downward and upward movements of the piston, air is accumulated in the tank thereby rising in pressure.
When a pre-set upper limit pressure is reached, a pressure switch turns the motor and the pump off. On the other hand, when air in the tank is depleted and pressure falls to a pre-determined lower limit, the pressure switch automatically activates the motor thus filling up the tank again.
Often, air tools need only a fraction of the maximum air pressure stored in the tanks. This necessitates the installation of a regulator to match the air output from the tank with the requirements of individual air tools. Gauges are included before and after the regulator. The former indicates air pressure in the tank, while the latter shows the pressure of the air going into the air hose and eventually to the air tools.