Paddle, Ribbon, or Hybrid: Does It Really Matter?

Feb 24, 2016

 

You bet. In fact, this is the most important decision you’ll make. Paddle-style agitators are specially designed to scoop, lift, and tumble in a gentle but thorough mixing action, and are ideal for mixing solids or liquids of various particle size, density, and viscosity. While being mixed, the material travels in a three-dimensional figure 8 pattern. The material is constantly being pulled from the ends of the mixer to the middle of the figure 8 where the most aggressive mixing is taking place. Another benefit of paddle mixers is that they are able to work effectively when filled to as little as 20% of rated capacity, thus allowing flexibility of batch sizes. Paddle-style agitators also allow easier access for cleaning between batches.

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Double ribbon mixers are capable of performing a variety of mixing operations. These agitators are excellent for free-flowing materials that are of like size, shape, and density. In mixes with small agglomerates, the greater shearing action of a ribbon mixer can also be beneficial. Ribbon mixers are designed for thorough end-to-end mixing with inner spirals pushing product away from the discharge, while the outer flightings pull material back toward the discharge opening. Each helix spiral is positioned 180 degrees out of phase. Here, the mixing action occurs by scrubbing the material back and forth across itself. The additional flighting of a double ribbon provides twice the mixing action of a single ribbon mixer. A continuous ribbon is preferred over a segmented ribbon as the inner and outer flights form a continuous helix from the end-plate to the discharge. Segmented ribbons only span from spoke to spoke causing gaps in the flighting which interrupts product flow and creates pockets of stagnant material.

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Hybrid agitators combine the tumble action of paddles with the rolling pattern of ribbons to create a double reversing effect. These agitators are especially effective with materials that tend to mound in the center of the mixer, thus creating a more even product level throughout the mixer. This type of agitator can be configured with either paddles or a ribbon on the inside or outside depending on the application.

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While accurate mix times are truly application specific, regardless of agitator selection, the general rule of thumb is an average blend time between 3-7 minutes (after the last ingredient is added), depending on the volume being mixed. Choosing the correct agitator configuration for your application is crucial for optimizing your blend, minimizing your mix time, and ensuring effective evacuation at discharge.



Category: General

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