Centrifugal Water Pumps

Centrifugal Pumps are normally single impeller type pumps and are widely used in water transfer. As a general rule they deliver a large amount of water at a relatively low pressure. A centrifugal pump is of very simple design. The only moving part is an impeller attached to a shaft that is driven by the motor.

The two main parts of the pump are the impeller and diffuser. Water enters the eye of the impeller and is thrown out by centrifugal force. As water leaves the eye of the impeller, a low pressure area is created causing more liquid to flow toward the inlet because of atmospheric pressure and centrifugal force.

Velocity is developed as the liquid flows through the impeller while it is turning at high speeds on the shaft. The liquid velocity is collected by the diffuser or volute and converted to pressure by specially designed passageways that direct the flow to discharge into the piping system; or, on to another impeller stage for further increasing of pressure.

The head or pressure that a pump will develop is in direct relation to the impeller diameter, the number of impellers, the eye or inlet opening size, and how much velocity is developed from the speed of the shaft rotation. Capacity is determined by the exit width of the impeller All of these factors affect the horsepower size of the motor to be used; the more water to be pumped or pressure to be developed, the more energy is needed. A centrifugal pump is not positive acting. As the depth of water increases, it pumps less and less water. For these reasons it is important to select a centrifugal pump that is designed to do a particular pumping job. For higher pressures or greater lifts, two or more impellers are commonly used; or, a jet is added to assist the impellers in raising the pressure.