The main function of an impeller is to increase or decrease the flow of liquid, vapor or gas in the mixer at your production facility. This is the reason why these impellers are available in the market with different kind of mechanisms designed for different industries as well. They also come in different sizes and shapes; thus it is significant for you to be aware about which one is the right impeller for you based on its application.
Here is a simple criteria based on which you can decide which impeller to choose. Let’s have a look at the methodology:
Firstly you need to know the purpose of deploying an impeller. What would be its usage? To what extent will it be subjected to wear and tear? During the process will it be exposed to any dangerous or corrosive materials?
You need to have concrete answers to all of the above questions in order to take the right decision. Based on your requirements, you would have alternatives to choose from, as each impeller style has its own function. You will also be able to select based on sizes and other specifications, for instance an open or a closed design.
A closed impeller consists of wear rings, which usually require maintenance, while the open ones have less chances to clog; hence some manual adjustments might be made.
Once you’re sure about the application of the impeller, you need to know about the flow pattern that will be inculcated in the process.
So for example, an axial flow is appropriate for heat transfers, liquid-liquid blending, etc. This type of flow is suitable for a lesser shear and an efficient pumping rate. It is generally considered to have a pitched blade turbine, but it can also be a radial flow with respect to certain dimensions.
Radial flow on the other hand has a higher shear as compared to axial. It is suitable for applications like gas-liquid dispersion which is also called emulsion mixing. Such flows can be introduced with the usage of crossed blades. The speed of shearing can be customized and controlled depending on how fine you want the emulsions and dispersions of the pigments. For a radial flow, saw tooth impellers are recommended.
Lastly, if your application is based on high viscous substances, then the flow pattern would be a tangential one. This would require an anchor or a square blade.
3. Vessel Diameter
The next step is to figure out the impeller’s diameter. This depends on the type of flow pattern you require and the vessel’s diameter. Generally, for the radial and the axial flow, impeller’s diameter is one third of the vessel’s diameter.
It is acclaimed to have a diameter of 70% less than the diameter of the vessel, for an axial impeller, so that the circulation path cannot be hindered by any means. On the other hand, the percentage increases from 70% to 90% in case of anchor impellers.
Viscosity of the material is important to consider while choosing an impeller. For lower viscosities which are closer to water like consistency, a prop impeller is recommended. As for higher viscosities and thicker substances, a pitched blade turbine or a vertical blade turbine is appropriate. Anchor and square blades are used when the viscosity is extremely high.
Next criteria is to decide about the material of the impeller. Generally, manufacturers use stainless steel, as it known to be anti-corrosion, anti-contamination, anti-heat and resistant to chemical reactions; thus it is durable and reliable than any other material. This material is also hygiene friendly, as the cleanliness is extremely convenient.
Iron, Titanium, Bronze, Nickel Alloys, etc. are some of the other options available for material of the impeller. In order to make the impellers even long lasting, additional coatings and finishing material are used, specifically when the application is that of a high pressure.
After all the functional factors, one needs to see the feasibility of the impeller with respect to the cost associated with it. Impeller’s cost is not one time. Depending on their durability, they also require maintenance from time to time.
Thus, it is indispensable to choose an impeller with low maintenance costs but productive at the same time. Compromising on the costs in the first installment could cost you in the long term, so take the decision wisely and practically, because you don’t want your production to stop even for a second for replacement, fixing or maintenance purposes.
Special applications require special impeller styles with respect to the consistency of the material and the vessel size.
So if your production requires impellers for narrow necked flasks or vessels then collapsible impellers would be an appropriate option for you
On the other hand, if your product is very thick or viscous and requires to be scrapped from the walls of the vessel then anchor impellers are the perfect fit for you, as they would easily clean your vessel walls and would not let your material to waste at all.
Based on the criteria and requirements mentioned above, you’ll be able to find the perfect impeller for your product. Although, sometimes even after applying the above mentioned methodology and after considering each dimension of the impeller, you might be not be able to find the perfect fit. In that case, customized options are also available, which could make your life easier and your production up to the mark.
So don’t hesitate to get in touch with us, if you’re still confused which impeller would be the right fit for you.