With rising costs and slimmer profit margins, now more than ever manufacturers need to make sure that everything in their production lines is working effectively. Mixing equipment is one area of processing that can dramatically improve manufacturing times, product quality and profitability. In some cases, a mixer may be able to undertake the mixing task perfectly well, but another could achieve the same or better results in half the time. So what are some of the different types of mixing equipment available and what do they do?

What is a High Shear Mixer?

High shear mixers are designed not only to move product around a vessel, but to actively process it. In simple terms, shear means to cut. By applying intense mechanical and hydraulic shear, these mixers can rapidly disperse powders, emulsify liquids, reduce particle or droplet size, dissolve solids and create smooth, stable, homogeneous products. This is achieved by utilising specialised rotor/stator technology to generate extremely high shear rates.

The rotor part of the workhead creates a powerful suction effect that continuously draws materials into it. Centrifugal force then drives materials towards the periphery of the workhead where they are subjected to a milling action in the precision machined clearance between the ends of the rotor blades and inner wall of stator.  This is followed by intense high shear as the materials are forced, at high velocity, out through the perforations in the stator and circulated into the main body of the mix. The materials expelled from the head are projected radially at high speed towards the sides of the mixing vessel. At the same time, fresh material is continually drawn into the workhead maintaining the mixing cycle. The effect of the horizontal (radial) expulsion and suction into the head is to set up a circulation pattern that minimizes aeration caused by the disturbance of the liquid’s surface.

A single Silverson high shear mixer can replace multiple pieces of conventional equipment, delivering faster, cleaner and more consistent results.

Laboratory Stirrers and High Speed Dispersers vs. High Shear Rotor/Stator Mixers

Laboratory stirrers come in a wide variety of forms, but, like their production equivalents, their use is limited to duties such as maintaining uniformity in the vessel, promoting heat transfer, simple blending and dissolving tasks etc.  At the other end of the scale, high speed dispersers offer high shear mixing and can be used for more complex mixing applications such as the formation of emulsions and disintegration of solids. However, the high speeds of 25,000 rpm or more at which these mixers operate cannot be replicated on a production scale, meaning products produced in the laboratory cannot be scaled-up without the need for additional R&D work.

Silverson Laboratory mixers run at slower speeds, but there is a direct correlation of rotor tip speed between laboratory and production scale mixers, making scale-up a relatively easy process. All Silverson rotor/stator mixers come with a range of interchangeable workheads, giving manufacturers more versatility and allowing one mixer to be used for several mixing applications.

Conventional Agitators vs. Batch Mixers

Agitators are one of the most common types of mixers and there are many designs available covering a wide viscosity range. These mixers are normally scalable from the laboratory to larger batch sizes. An agitator is ideal for maintaining in-tank movement and for ensuring uniformity in the tank and for promoting heat transfer in jacketed vessels. These mixers can be used for dispersing powders but powder addition must be carefully controlled as once agglomerates have formed in the mix, these low shear devices are unable to break them down. Even after a long mixing time a filtration stage may be needed to remove agglomerates remaining in the mix. Not only does this add to processing time, but also increases processing costs as full yield of expensive raw material would not be achieved.

Silverson in-tank Batch mixers facilitate rapid and thorough dispersion, significantly reducing mixing times and enhancing overall production efficiency. The efficient dispersion process ensures that all powder particles are fully hydrated, maximizing the utilization of raw materials and minimizing formulation discrepancies. By dispersing agglomerates rather than filtering them out, high shear mixers maximize product yield and reduce waste, resulting in cost savings and improved efficiency.

Static Mixers and Inline Agitators vs. In-Line Mixers

Static mixers are made up of a series of baffles within a section of pipeline, designed to disrupt the flow of product.  They have to be pump fed and their main application is simple liquid/liquid blending. In-Line agitators, which as the name suggests, comprise an impeller mounted within a chamber in the pipeline, are similar in their application – and as with their in-tank counterparts, the low shear nature of this type of mixer means that their application is limited to simple blending of like-viscosity fluids.

For more demanding duties such as blending liquids of differing viscosities, emulsifying, dissolving or disintegrating solids, high shear is required and, where a high shear In-Line mixer is used in place of a static mixer it can replace both the static mixer and feed pump. Silverson In-Line mixers are self-pumping and incorporate the same rotor/stator workhead as in-tank models. All Silverson interchangeable workheads are machined with close clearances between the rotor and stator, resulting in low droplet sizes and significant particle size reduction making these mixers suitable for producing emulsions, dispersing powdered ingredients into liquid and disintegrating solids.

The High Shear Advantage

Traditional mixers have their place in the manufacturing process but are limited in what they can do and the results they can achieve. Silverson High Shear mixers can:

• Cut processing time by up to 90% compared to conventional agitation meaning more batches per shift and no additional capital equipment.
• Create stable emulsions with uniform droplet size and zero phase separation, batch-after-batch.
• Maximise yield of ingredients. Pectin, xanthan gum, starch, and other gums and thickeners can be incorporated completely at ambient temperature, eliminating filtration steps, reducing ingredient waste, and improving product quality.
• Handle high viscosity mixes and effortless blend liquids of varying viscosities
• Eliminate costly heating cycles as dissolving and incorporation of other ingredients can be done at ambient temperature.
• Incorporate powders with less dust and waste. Silverson’s high shear powder/liquid mixers draw ingredients directly into the liquid stream, minimising airborne dust and ingredient loss whilst preventing floating “rafts” and pockets of unmixed materials.
• Disintegrate and suspend solids. Low micron milling and uniform suspensions in a single operation.
• Achieve results in R&D that can easily be replicated at full production scale.

For nearly eighty years, Silverson Machines has worked closely with food and beverage manufacturers to solve their mixing problems. We are confident that high shear mixing can revolutionise your mixing process. Get in touch today to arrange a trial and see the results for yourself.

You can view the entire range of Silverson High Shear Mixing equipment on the Silverson website.

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