Different Types of Impellers

Impellers play a major role in determining the efficiency of your pump. They vary in diameter, material, number of vanes, and the size of their shroud (the protective back-wall). 

It’s important to know the different types of impellers there are to determine the right kind of pump for the product you're pumping. This will maximize flow rates, minimize energy consumption, and overall, your operation will be more efficient. Choosing the right impeller for your operation starts by understanding what you're pumping. Does the fluid have high or low viscosity? Does it contain visible solids? What's its chemical composition? From there, you can determine the best pump type suited for the fluid's profile, along with its given impeller type.

We currently carry pumps with four different types of impellers: open, semi-open, helicoidal, and flexible impellers. 

[Note: these impellers are NOT interchangeable.] 

Open Impellers 

Open impellers aren’t enclosed like a semi-open or closed impeller; instead, they have open vanes that are attached to a central hub. The open design allows for easy access to clean and maintain the impeller. They require a higher NPSH to operate, but are able to handle a higher degree of suspended solids and viscous products compared to semi-open impellers. This is due to the larger passage between the vanes, which reduces clogging. 

Open impellers are a type of impeller used in centrifugal pumps. We use open impellers in our C-Series, C+Series, CB+Series, SEN Series, and Microbrew 100 centrifugal pumps. 

Semi-open Impellers 

Semi-open impellers combine the design of both open and closed impellers. Like an open impeller, semi-open impellers have vanes attached to a central hub, but they also have a back-wall shroud like a closed impeller. The back-wall shroud adds mechanical strength to the vanes and directs the pumped material more efficiently. The shroud also determines the impeller’s speed. Do keep in mind that the clearance between the vanes and the pump casing needs to be small or else slippage may occur. The semi-open vanes allow for moderate suspended solids to be pumped efficiently. 

Semi-open impellers are a type of impeller commonly used in centrifugal pumps. Semi-open impellers are used on our QIM+ series centrifugal pumps. We pair these semi-open impellers with stators to create a shear effect on the product you're pumping. 

Helicoidal Impellers 

Helicoidal impellers are semi-open impellers with a long corkscrew shape design. This design allows it to handle larger suspended solids and higher viscosity products than both open and semi-open impellers. Solid particles are able to pass through without being damaged, and the pump won't become clogged. 

Helicoidal impellers are used on our RVN centrifugal pumps. 

Flexible Impellers 

The flexible impeller has vanes that remain in contact with the pump casing, trapping fluids that enter from the inlet and transporting them to the outlet. At the outlet, a flat spot in the casing forces the impeller vanes to compress, expelling trapped fluids. This action creates enough suction to allow this pump to self-prime and to lift fluids upward up to 15 feet. With this operating principle, and a lower rotational speed due to the impeller touching the casing, these pumps are low shear. 

Flexible neoprene impellers are a type of impeller used on a specific kind of positive displacement pump. We use this impeller on our RF Series pumps. 

Conclusion 

When you know the fluid profile that you're pumping, you can select the pump and impeller combination that best suits your needs. We provide pumps with four impeller types: open, semi-open, helicoidal, and flexible, each designed for a specific application. Choosing the right match for your product will increase flow rates, reduce energy consumption, and keep your operation running at maximum efficiency.