Impeller Selection Guide
Our selection guide will help you answer some common
questions so you can choose the appropriate impeller for
your needs.
What factors are important when choosing an Impeller?
Stirring for mixing, emulsifying or solid suspension have different requirements, that certain impeller types meet better than others. Now that you have chosen the right overhead stirrer, it is time to find the impeller for that stirrer. Impellers come in various shapes, sizes, and materials.
The one you choose will depend on several factors, such as the viscosity of your sample, the size of the vessel, the desired outcome of your application and the nature of the material you are using. There are PTFE coated options available in case the sample material reacts with the impeller.
One more important factor to consider is the desired flow pattern that will be created with the impeller. The main types that can be created are axial, radial and tangential flow, as illustrated below.
Axial Flow
The fluid is moved from top to bottom in the tank and is ideal for stratification or solid suspension. Shearing force tends to be lower, but the flow is stronger than with radial flow.
Radial Flow
The liquid is moved sideways and then either up or down before flowing back to the centre. Shear force is higher, but the flow rate is lower compared to axial flow. Radial flow is often used for high shear applications such as liquid-gas dispersion and emulsification.
Tangential Flow
The fluid is moved horizontally around the vessel as with a paddle. Tangential flow is most suitable for mixing high-viscosity materials. Shear force is low and there is little vertical flow.
Impeller types can create different stirring motions and as such different impellers can be used to accomplish different tasks more effectively. The table below shows the most common types of impeller design and their importance for different applications.
Type of Impeller | Image | Flow | Application |
|---|---|---|---|
Straight |  | Radial |
|
Propeller |  | Axial |
|
Turbine |  | Radial |
|
Anchor |  | Tangential |
|
Centrifugal |  | Axial |
|
Dissolving |  | Radial |
|