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Choosing the Right Mill System

Choosing the Right Mill System
16 Jun 2021  |
Industrial lump breakers, hammer mills, fine grinders and air classifying mills are just a few types of impact milling equipment utilized in particle size reduction applications.

Each one offers manufacturers a unique method to achieve the desired size reduction characteristics of their dry bulk solid materials. However, when it comes to determining which milling system is best suited for their products, manufacturers are often challenged by the variety of milling equipment available on the market. 

So how can the manufacturer narrow down the best type of equipment to use? In this blog we will discuss four critical topics to consider when making a selection. 

What is the Material, and What Are the Application Requirements?

When selecting a milling system, a material’s particle size requirement is often the first and best criteria to hone in on a particular method of size reduction.  A vast majority of applications call for the reduction of material particle size from 6 inches to sub-micron. Prater’s equipment selector can help manufacturers match an appropriate equipment solution to their desired particle size output.   

Which Machine Do I Need? 

After establishing the particle size goals for a product, a thorough review of the material’s properties is often required. Once this is known, Prater can advise manufacturers on which type of mill is best suited to achieve the manufacturer’s objectives for a particular application. 

For example, air classifying mills are best for materials that are less friable, challenging to grind, or have narrow particle distribution curve requirements. On the other hand, suppose the requirement is to reduce agglomerated material to improve product flow. In that case, lump breakers are designed to reduce natural agglomerations in material that has become compacted or densified, such as sugar, salt, resin, filter cake, and fertilizer. 

In short, before implementing a milling system to achieve the desired particle size reduction of a product, it is necessary to know the desired finished particle size and properties of the material.

Is It a Small Scale Process, or is the Plan to Scale Up?

When selecting a milling equipment solution, the scale of the equipment’s operation and its long-term purpose are factors to consider before making a purchase. Do you need a small machine for research and development or a larger machine for high-volume production? Keep in mind that each solution comes in a variety of sizes and can be configured most efficiently to match the scale of your operation.

For example, Prater’s model range of industrial hammer mills is available in sizes from 5 to 250 HP. When selecting an appropriate model, consider your current and future growth potential. While on one hand, a 30 HP mill may satisfy your long-term needs, the incremental spend on a slightly larger model may prove beneficial if near-term growth is projected. Just the same, purchasing one large system versus two or smaller systems may provide less flexibility for a processor whose business is to be modeled on the speed and efficiency of turning out customized, small-batch runs.  In summary, looking into a system’s scale beforehand can save time and money on the long-term use of a particle size reduction system.

Safety and Exposure: What Safety Mechanisms Might Be Needed?

Another consideration is to make sure the milling system is designed to limit occupational hazards related to processing the material or interacting with the equipment.

Manufacturers processing volatile compounds, combustible dust or APIs (Active Pharmaceutical Ingredients) should consider designs that minimize or eliminate exposure to the material, and which include appropriate technologies to prevent and control a dust explosion.  This process requires that owners complete a DHA (dust hazard analysis) of their materials. A DHA is used to identify where dust explosion or fire hazards may exist in an existing or new process and typically includes explosivity testing of the material by a third-party specialist. It will be less costly to design the system properly than retrofit it in the future.

Likewise, equipment safety is also essential. Ensure that rotating parts are properly guarded and look for access interlocks that are appropriate for the severity of the hazard associated with that access point. For example, air classifying mills and fine grinders come equipped with a fail-safe trapped key interlock that prevents unintended access until rotation of the equipment has ceased. 

What are Your Cleaning and Sanitation Requirements?

Material handling of food and pharmaceutical (or nutraceutical) products is an integral part of particle reduction systems. Milling equipment must be cleaned and sanitized regularly to comply with local, state, and federal regulations. 

Simplifying the cleaning process saves time during cleaning and/or changeovers. The system’s product-contact surfaces should be readily accessed and inspected to ensure thorough cleanliness. Therefore, look for milling system designs that offer easy cleaning solutions that reduce cleaning, changeover, and/or maintenance times. Access doors for quick inspections and cleaning, easy removal of endplate fasteners, internals that are on rails, or quick-release housing clamps in applications where sanitation is critical.

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Prater Industries, Inc. offers a wide range of equipment for particle size reduction, enlargement, feeding and separation such as hammermills, fine grinders, lump breakers, classifiers, rotary airlocks and valves, briquettors/compactors and more. All Prater equipment,...

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