Single stage and Multistage pump

• A single stage pump is one in which the total head is developed by a single impeller.
• A multistage pump has two or more impellers on a common shaft acting in series in a single casing.

Impeller

• May be either single or double suction type.
• In single suction, liquid enters the impeller from one side only.
• In double suction impeller, the liquid enters from both the sides.

Types of impeller

• Based on the water flow through the impeller and axis of rotation, they are 3 types

a) Radial flow : create a side-to-side fluid motion that produces high shear rates and a relatively low pumping number.

b) Mixed flow: water passes parallel to the axis of rotation.

c) Axial flow: It receives and discharge in same direction in the axis of rotation.

• Based on mechanical construction, it is 3 types:

a) Open impeller: Consists essentially of a series of vanes attached to a central hub and used to pump water having considerable number of small solids such as sand.

b) Semi-open impeller: Consists side wall one side only usually on the back. It can be used to pump water containing suspended sediments.

c) Closed impeller: Has side walls on both the sides and used to pump clean water.