Mixing blades (or impellers as they are most commonly referred to), make or break industrial mixing. They are pivotal to liquid mixing because they allow the right flow to be executed. In this blog, we have classified mixing blades into 3 major categories: low shear, medium shear, and high shear. It is important to understand these three categories because each impeller accomplishes a particular type of flow. Understanding the why of their shape and design can be crucial to choosing the right mixing blade for the application. Mixing blades can differ greatly due to differing diameter, horsepower, type of shear, and RPMs. Now let’s explore the three categories of mixing blades.
Mixer Direct’s low shear impellers are designed with the intention of imparting motion to the mix while utilizing the least amount of energy possible. For this to occur, our low shear mixing blades are designed specifically for low drag and smooth flow. A helpful example of this would be to picture a large stainless steel tank filled with a mixed product that needs to be kept stable while preventing any separation by rotating it over periodically. This is an ideal application for a low shear impeller.
The Hydrofoil is a high-efficiency impeller. This low shear mixing blade offers the greatest pumping per horsepower. It is comprised of 3 blades and is constructed with 316 stainless steel. The hydrofoil is a great fit for a broad amount of applications and is often more economical in larger sizes than a propeller.
Propellers (Left Handed and Right handed)
Durable and efficient are two words that accurately describe the propeller. With its three-blade design, the propeller is a principal choice in low shear mixing blades. Propellers are durable because they are solid 316L which offer the maximum amount of corrosion resistance in a variety of mixing environments. This mixing blade comes standard as a left handed impeller, which means it pumps in a downward direction when it is rotated clockwise. However, it can also be found in a right-handed design. The right-hand design allows for the liquid being mixing to pump in an upward direction when rotated clockwise. The propeller is prevalently used in chemical, coatings, pharmaceutical, and construction industries.
Steep Pitch Impellers
The steep pitch impeller is a propeller that produces additional flow with the same diameter a propeller would with the exception of steeper pitch design. This mixing blade is also 316L for corrosion resistance and is primarily utilized with a left handed design that pumps in a downward direction while it is rotated clockwise.
Medium Shear Mixing Blades
Mixer Direct’s medium shear mixing blades are the perfect choice for the middle ground of mixing found between low and high shear applications. Medium shear mixing blades are meant for mixing moderately viscous materials that do not require high shear dispersion, but require more shear and movement than a low shear application. Medium shear mixing blades can often be found in use in the food industry, distilling, and where tote mixing applies.
Radial Flow Turbine
Radial flow turbines are designed to generate a radial flow that changes position away from the impeller itself and outwardly to the walls of the mixing container or tank. These mixing blades are constructed with 304 stainless steel, but can also be fabricated in 316LSS. The radial flow turbine differs from the axial flow turbine in that it has a higher horsepower draw. One application the radial flow turbine excels in is gas dispersion.
Axial Flow Turbine
The axial flow turbine is the staple when it comes to classic medium shear impellers. This mixing blade is designed to generate axial flow which breaks up clumped materials while being able to handle the introduction of other ingredients to the mix. This mixing blade is designed with a pitched 45 degree angle to produce a localized shear area. The axial flow turbine can also be found with a reduced blade width design. An RBW axial flow turbine is designed for mixing high viscosity products that require a maintained velocity as materials are shifted away from the axial flow turbine. These mixing blades are constructed with 304 stainless steel, but can also be fabricated in 316LSS.
Folding impellers are compactly designed to fit through smaller openings in closed containers. The folded design allows for the necessary mixing power of a large impeller to be allowed entry for sufficient agitation. Although the mixing blade must be folded for entry into the mixing container, the folding impeller opens up as the mixer is turned on. These mixing blades are perfect for mixing in an IBC Tote or a 55 Gallon drum. The folding impellers all stainless construction provides durability and the ability to be easily cleaned. These mixing blades are constructed with 304 stainless steel, but can also be fabricated in 316LSS.
High Shear Mixing Blades
Mixer Direct’s high shear mixing blades are designed for shear force.The forte of the high-shear line is the dispersion or fast breakdown of solids. The high shear mixing blades can be categorized into three grades: high flow dispersion, dispersion blades, and ultra shear dispersion.High shear mixing blades are optimized for high RPMs which are required for a fast breakdown of materials. Each of these three categories of high shear mixing blades produces differing levels of ability to reduce particles in the mixing process. All three types of high shear mixing blades are constructed with 304 stainless steel, but can also be fabricated in 316LSS.
High Flow Dispersion Blades
The high flow dispersion blades are designed for outward flow to overcome common problems related to achieving sufficient fluid motion for complete uniformity. Each HFD blade is geometrically designed with integrated axial flow blades for extra flow in mixing higher viscosity materials.
The dispersion blade is designed for outward flow and reduction of particles in the mix.
Ultra Shear Dispersion Blade
The ultra shear dispersion blade is designed for outward flow and increased reduction of particles.
All of the aforementioned classification of mixing blades are available in laboratory sizes as well. Each mixing blade can be optimized for the laboratory setting and can be customized in a variety of way. Customization options can include geometry, finishes, and specialized coatings.