## What is a semi closed impeller?

Semi-Closed impellers have a back wall that adds strength to the impeller. Semi-closed impellers are usually used with liquids or products that have solids. Reduced efficiency is a common problem with semi-closed impellers, but the ability to pass solids is an important trade-off.

### What is the most efficient pump design?

Positive displacement pumps are able to handle variations in pressure, flow and viscosity and remain efficient, unlike centrifugal pumps which do not operate well off the centre of their curve.

Why we use semi open impeller?

Semi-open impellers have a back-wall shroud that adds mechanical strength to the vanes, whilst remaining open on the other side. They are somewhat of a middle ground between open and closed impellers in terms of efficiency and NPSHr, making them suited to medium sized pumps with a small amount of soft solids.

How do you choose an impeller type?

The size of vessel used for mixing will determine the diameter of the impeller. A general rule of thumb for axial or radial flow patterns is the diameter of the impeller be ⅓ of the vessel’s diameter, so a 10 cm beaker would require approximately 3 cm impeller.

## How do you measure a closed impeller?

The trick is to measure the radius and multiply it by 2 to get the diameter. Measure the outer most tip of the blade to the center of the bore to obtain the radius. Therefore, a propeller or impeller that measures a radius of 3” from the tip of the blade to the center of the bore will have a diameter of 6”.

### How is impeller type selected?

Impeller flow designs can take on three distinct types: axial, radial, and mixed. Because centrifugal pumps are also classified in this manner, the impeller selection depends upon matching the pump’s flow characteristic to that of the impeller. Axial flow impellers move media parallel to the impeller.

Which pump has maximum efficiency?

The centrifugal pump converts mechanical energy into hydraulic energy (flow, velocity and pressure), and the AC motor converts electrical energy into mechanical energy. Many medium and larger centrifugal pumps offer efficiencies of 75 to 93 percent and even the smaller ones usually fall into the 50 to 70 percent range.