Positive Displacement Pumps

There are many types of positive displacement pumps. Examples: Reciprocating, Rotary and Diaphragm.

In a positive displacement pump a certain quantity of liquid is drawn into the pump and the same quantity is forced out of the pump. This causes actual displacement of the liquid. This is the reason why the discharge side must be ready to accept the liquid, otherwise serious damage will occur. For example, if the discharge valve of a positive displacement pump is not open, it will lead to serious damage.

Reciprocating Pumps

A reciprocating pump consists of the following key elements:

• Has one or more cylinders
• A piston is provided for each of the cylinders
• A prime mover designed to rotate the shaft
• An "eccentric"
• A pump shaft and inlet/outlet valves.

The "eccentric" and other components are provided to convert the circular motion of the prime mover into lateral movement - which enables a pump piston to move forward and backward.

In the following section we provide brief information about the basic functions of a reciprocating pump.