The pump impeller 

is the most important part of the pump because of its size, shape and speed

Determines pump capacity in all conditions. Butterfly type with simple conical blade

And with a single cap, it is usually used in small industries. 

The blade with a simple blade can also have two caps

Another type of impeller has a curved or radial blade. These impellers are often 

used to transport materials including solid masses

Or large suspended particles are used, giving the pumped material more speed.