1. Introduction

Pumps and fans move fluids or gas from one location to another. The fluid or gas is moved using a rotating set of blades that draw the fluid in, then push it out.

The construction of a pump or fan has some basic similarities. A rotating impeller is enclosed inside a specially shaped shell. Imagine the airflow being drawn into a hair dryer. Air is taken into the centre of the dryer and it is then pushed along the vanes of the impeller (fan blades) out through a nozzle.

The fluid will be forced to flow at a particular rate, ie the fluid will be pushed along by the pump.

2. A single pump system

For a fixed impeller diameter and speed, the pump has a predictable performance curve.

Where the pump operates on its performance curve will be determined by the characteristics of the system in which it is to work. The operating point is where the performance curve and the system curve cross.

The system curve represents all of the losses caused by friction due to the piping, elbows, valves and other physical components in the system.

The system curve is parabolic as its values are related to the square of the flow rate.