Make the Most of Equipment Testing Opportunities

As plants become more sophisticated and reliant on automated systems, process engineers are tasked with collecting more information to justify capital expenditure, all while being faced with a greater number of suitable technologies than ever were available. In the case of mixing and blending equipment, it has become imperative to more accurately predict cycle time, energy consumption, labor cost, end product quality, yield, even loading, discharge, and cleaning times. In the push to stay competitive, equipment selection has become a less simple matter.
    Perhaps with the exception of off-the-shelf propeller mixers, most mixers and blenders today must be viewed as “custom” equipment because many of their features – from motor size and speed range to material of construction and inlet/outlet ports – are now typically tailored to best serve a particular application.
    For the above reasons, it is easy to see why simulation testing is an invaluable tool when purchasing new equipment. From working with similar formulations in the past, experienced mixer manufacturers can point to one or more machines that would be most suitable to test. More often than not, there are several ways to successfully mix or blend a particular product. Empirical testing using actual raw materials allows you to narrow down the selection to one best technology that matches your technical needs as well as business goals. When upgrading or scaling up an existing process, keep an open mind to test mixers or blenders you have not used or considered before. Testing enables you to reevaluate if inherited equipment and procedures are still efficient.
     What specific information can you expect to take away from a mixing demonstration? The most important ones are usually those that you cannot easily calculate or predict. Just a few examples:
* The product’s flow characteristics when mixed by a particular style agitator across its speed range. Which speeds produce vigorous flow without splashing, excessive foaming or generating too much heat? Is the power draw within limits at all times?
* How long it takes for powders to completely wet-out or dissolve. Is it better to add solids through a charging port continuously as the mixer is running? Or in increments which requires stopping the agitator and opening the mixer?
* The energy required to generate dispersion. Parameters such as power consumption, run time and agitator speed are important determining factors.
* How the batch behaves as vacuum is being pulled (watch out for changes in volume and/or composition).
* How long it takes to heat or cool the product with the aid of agitation. Is heating/cooling a potential bottleneck?
* Completeness of discharge and cleanability. What is the best way to quickly transfer product out of the mixer? How much cleaning would be required in between batches?

    Mixer demonstrations and simulations at a manufacturer’s testing facility are easy to arrange and generally free of charge. Simply shipping your raw materials and sending detailed instructions is one option but in most cases, it’s best to attend the mixing trial yourself along with other key personnel or decision makers who intimately know the product. Your expertise on the characteristics and properties of the specific formulation will boost the trial’s chances of success. In addition, you could observe how the mixer is operated, learn useful techniques and identify any potential issues. To obtain reliable data for scale-up, a good rule of thumb is to test on a mixer no smaller than 10% of the capacity you are looking to eventually purchase.
    Alternatively, testing may be performed in your own lab or plant using rental equipment. Rental arrangements vary from one supplier to the next but usually, for a small fraction of the true equipment cost, you can fully test the mixer in your own production floor for a flexible period of time. Certain programs credit a significant portion of trial/rental fees towards the purchase price of a same or larger capacity mixer. Ask about these credit terms and any free consignment period that may apply.
    Ken Langhorn is technical director at Charles Ross & Son Co. (Hauppauge, NY). He has published many articles on mixing and blending technology. Formerly an R&D specialist at Ross, he holds multiple patents for innovations in high-shear and high-viscosity mixing. As manager of the Ross Test & Development Center, he oversees a large program of testing and process optimization for customers, along with operations in the company’s adjacent analytical laboratory. He can be reached at [email protected].

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