Description of Operation
How does a Vertical Cone Screw Mixer compare?
Ribbon blenders and vertical cone screw blenders are found in many plants, and in many ways they perform a similar function on the process line. But the differences in their design - and in the advantages they offer - are far more important than their similarities.
Of course, one very important difference to consider is price. The ribbon blender is generally less expensive than a vertical cone screw blender of comparable capacity. So, in practical terms, you should determine whether you application requires a vertical cone screw blender in order to achieve the product quality and processing efficiency that you need.
To decide which type of blender will work more efficiently in your application, ask yourself these questions.
- How much room is available on your plant floor? Before we even start talking about your blending needs, you can answer the first important question with a tape measure. If floor space is tight, you may have to go up - with a vertical blender - since a vertical blender requires a much smaller footprint. If overhead space is limited, you may be forced to use a horizontal ribbon blender, which allows you to use a low-profile loading system. A multi-level operation is generally unnecessary.
- Does the friability of your product require gentle blending? If so, you will probably need a vertical cone screw blender. The blending action of mixing screw is extremely gentle.
- Is complete discharge essential? The cone screw blender gives you virtually 100% discharge through the lower cone. Even the best ribbon blenders fall short.
- How tight is your budget for power? Since the cone screw blender consumer 25-30% more power, over long blending cycles this can add up.
- Is contamination a critical risk? With a packing gland in the product zone, the ribbon blender always poses a great threat of contamination. New seal designs have reduced the risk dramatically, but if your application requires the best protection available, you will have to switch to a cone screw blender.
- Is your product heat sensitive? The blending action of a ribbon generates more heat than that of a mixing screw. In the cone screw blender, heat is also more easily removed with thermal jacketing.
- Will you always operate with the blender at least half full? If you need the flexibility to operate with smaller batches, choose the cone screw blender. Because of the geometry of the cone, this blender can operate efficiently with batches as small as 10% of blender capacity. The ribbon blender generally requires a minimum of 40-50% capacity.
- How fast do you want to finish the batch? A fast blending cycle is not always the most important concern, but it is always a factor you should consider carefully. Cone screw blenders are usually about 30% faster than ribbon blenders in similar applications.
- Are you concerned about blending accuracy? The ribbon blender and cone screw blender both produce a well-blended product. But the cone screw blender will virtually always produce a more homogenous blend in given blending cycle. The difference is not critical in all industries, but if you want to get as close as possible to perfection, you will probably need a cone screw blender. If accuracy is critical, be sure to test the blender in your manufacturer’s laboratory before you buy it – to prove that it can deliver the product quality you need.
- Will you need complete cleaning between batches? The cone screw blender is easier to clean, especially since you will never have to disassemble a packing gland in the product zone. Just make sure that the cone screw blender you select does not require a bearing at the lower end of the screw. A screw supported entirely from the top end will give you faster, more thorough discharge, easier cleaning, and fewer maintenance headaches.
Blender Selection: A Case In Point
At a major Urethane manufacturer, a international leader in the production of thermoplastic polyurethane film, blending is a crucial process step before resin, colorants and lubricants can be fed into an extruder. Consistency and throughput are critical, since demand for polyurethane film is soaring. A hot product in the plastics industry, polyurethane film is fast replacing polyethylene and polypropylene film in manufacturing such products as greenhouse glazing, rain coats and sporting gear, seals and gaskets, and fuel cell linings.
Following a recent plant expansion, the company now runs ten process lines - including the only line in the world that produces 120” ultra-wide film. A ribbon blender on each line feeds a high speed extruder, and together they produce hundreds of unique formulations for customers worldwide.
They change products constantly, so they have to clean each blender three or four times a day. This company switched to a ribbon blender design that allowed fast discharge and easy cleaning.
To select a ribbon blender, you have to look closely at the small details in design and construction. With a short blending cycle and a product that is not particularly shear-sensitive and does not require vacuum, there was no need to consider a switch to a cone screw blender. But floor space in the plant was still an important consideration.
This client was concerned about the space that would be required by the horizontal blenders. But they found that the Ross ribbon blender is actually more compact that the blenders they were replacing. A right-angle gear drive gives it a small footprint. And since the drive is not a separate stand alone unit, it is easy to move and maintain.