5 Considerations to Select a Ribbon Blender

batch mixing system ribbon mixer

The type and number of blenders you choose for your process will play an important role in how fast and how well your recipe is mixed. There are a number of different ways to customize your ribbon blender, and it can be difficult to choose the right model. Here’s a few factors that will help you choose the right ribbon blender for you ingredients and process.

5 Considerations to Customize and Select a Ribbon Blender

1. Size and Volume

Ribbon MixerThe volume and profile of the ribbon blender are the most important aspects to consider when selecting your ribbon blender. This will depend on the amount of material you are mixing, as well as the speed with which it must be mixed. In some cases, a very large blender might be suitable. In other cases, multiple smaller blenders can help you optimize the process. With multiple blenders, you can avoid a shut-down if something goes wrong, and you can also dramatically reduce the time needed to mix a batch.

The ribbon mixer should be filled to its swept volume to get the most efficient mix. The swept volume is the area occupied by the agitator. In order to get the best mix in the shortest amount of time the mixer profile is also important. The length of the mixer should not exceed 2.5 times the diameter of the agitator. Consider the length, width, height and volume of the vessel, as well as the agitator size, to customize your ribbon blender to the right size.

2. The Ribbon or Agitator Type

A ribbon mixer successfully mixes materials by agitating them with a corkscrew-like metal blade. The outer helix of the ribbon moves product in one direction, while the inner helix of the ribbon moves the material in the opposite direction. This movement of material from one end to the other provides a fast but gentle mixing action. If more shear is needed to change the ingredients’ characteristics, then the mixer can be run at a higher speed or other devices can be added to the mixer, such as high-speed choppers. Some types of materials may work better with a mixer that uses paddles for the agitators instead of ribbons. This can be true of ingredients that have a high liquid content or those that are sensitive to shear. Selecting the right ribbon or agitator type is important for customizing the right ribbon mixer, or another type of mixer. The type of agitator you will need will depend on your ingredients, as well as the mixing time and mixer profile.

The following factors can help you determine what type of agitator to use:

  • Shear: If you are working with dense or viscous materials, your agitator may need a higher degree of shear. The speed of the agitator and the tolerances between the mixer body and agitator can increase the amount of energy that goes into the mix. Generally, more shear will require more horsepower.
  • Friability: Contrastingly, if your materials might easily break as they’re being mixed, you might use a gentler agitator, such as a paddle mixer. Mixing at a lower speed will also help this process, which we’ll discuss later in the post.
  • Single or double ribbons: Using mixers with two sets of agitators will decrease the overall mix time required for the process.  These mixers use ribbons, paddles, or sometimes a combination of the two. Using double agitators will also increase the horsepower required.

3. Mixer Construction Materials and Finish

Ribbon mixers are made from both mild and stainless steel. The materials of construction will depend upon the ingredients that are being mixed and the how those ingredients are going to be used. For example, in the case of food-grade ingredients, the mixer should be stainless steel with special finishes so that it can be easily cleaned and sanitized. If the ingredients are corrosive, then stainless steel would also be a good choice, since mild steel would be dissolved by the ingredients over time. However, your materials or process may require other materials or finishes. If your materials are not susceptible to foodborne illnesses, these finishes might not be necessary.

Quite often, the exterior of the mixer or non-contact areas of the mixer can be made from mild steel and painted. The interior of the mixer is usually not painted, since it could contaminate the ingredients being mixed. A mixer can also be lined with a material to enhance it’s performance. This is typically seen when a material is abrasive and would prematurely wear out the interior parts. Or, if you are working with corrosive materials, another finish may be required. Your ribbon mixer can be customized with a range of materials, finishes and paint to suit your facility.

The following are popular materials and finishes in ribbon mixers:

  • Various weld finishes from standard welds to sanitary
  • Industrial enamel paint or epoxy paint
  • Stainless steel food grade
  • Abrasion resistant linings such as ceramic and UHMW plastic

4. Horsepower

Most ribbon mixers operate at around 20 RPMs, though mixers with dual agitators or wider ribbons will require more power. A general rule of thumb for medium-density material in a single-agitator ribbon blender is 10hp per ton of material being mixed. To select a mixer that is both effective and efficient, use a motor with the appropriate horsepower. The supplier of the mixer can help with motor sizing and type. Selecting a motor that is too powerful can mean adding extra expenses, but underestimating the motor power can mean that the mixer cannot be started under load.

5. Discharge Gate

How your ingredients exit the mixer is also important when customizing your ribbon blender. The cycle time and downstream processes will partly determine which ribbon blender is best. Some processes may require complete, immediate discharge. In this case, a full-length drop bottom discharge gate would be ideal. Other processes may require gradual discharge or a tighter seal, and a slide-gate may be better in these cases.

The most common types of discharge gates for your ribbon mixer are:

  • Drop bottom: A drop bottom discharge gate will fully release materials in the mixer immediately. Though these gates work quickly, getting a tight seal can be difficult, especially when working with fine powders. This quick discharge can cause dust to escape into the air, so proper venting of the mixer is needed.
  • Pneumatic Slide Gate: A slide gate will allow a set amount of material to escape, which can be helpful for measuring, batching, or bagging processes following mixing. These will also have a tight seal to prevent powder from escaping.
  • Multiple Slide Gates: If you are looking for a faster discharge rate as well as a tight seal, you can use multiple gates to speed up the process, while still preventing powders from escaping.

Choosing the right ribbon blender and customizing features to suit your process and materials means getting the perfect mix. With consistency and accuracy built into your process, you can eliminate many concerns and problems both upstream and downstream. Work with a supplier who can help you customize these features to suit your process and provide testing to ensure you have the right fit.