A piston pump is a device modeled after a small engine. Instead of using the cylinders to produce power, the piston pump uses its cylinders to pump air, liquid or a combination of the two. The typical set-up uses an electric or other type of motor that turns the piston pump's crankshaft via a belt and pulley configuration. As the pump turns, the cylinders force the air or liquid into a storage tank for use at a later time. Often made of cast iron, the piston pump is among the most durably designed pumps available.
Using pistons and piston rings much the same as those found in a gasoline engine, the piston pump operates in a similar manner to a small engine. As the piston is drawn down into the cylinder, air or liquid is sucked in through an intake valve. As the piston moves toward the top of the cylinder, the air or liquid is pushed out of an exhaust valve and into a reserve or storage tank. The typical piston pump contains a pressure switch that shuts the motor off once a predetermined amount of air pressure has been reached in the storage tank.
The size of the piston pump is usually determined by the size and number of cylinders that the pump contains, as well as the horsepower rating of the motor powering the pump. While the vast majority of pumps are powered by electric motors, many pumps are powered by gasoline, diesel and propane-powered engines. The design of the pump can be a straight up-and-down cylinder, a V-configured pump or a radial pump. The radial design pump is typically the most productive and pumps the greatest amount of material.
A negative aspect of the pump design is that a tremendous amount of heat is generated from the friction generated by the cylinders speeding up and down the cylinder walls. The byproduct of this heat is water condensation. When used to pump air, water is a detriment to most operations performed using the air compressor. In an effort to reduce the amount of water that is produced by piston-type pumps, water filters and traps are used both before and after the air is introduced to the storage tank.
An advantage to using a piston pump design is that the pumps recover air extremely fast. Many air tools, such as sanders and drills, use an exorbitant amount of air. If not for the design and capabilities of the piston pump, these tools could drain the entire reserve air supply.