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At the heart of the process

Design features increase the safety of hammermills
At the heart of the process

At the heart of the process
Paddle wheels upstream and downstream of the milling chamber of the MFH-6 hammermill provide explosion protection
When it comes to pulverising and milling hard, crystalline or fibrous products, there is often no alternative to the hammermill. Putting unproblematic solid matter through a hammermill is fairly straightforward, but when products that constitute an explosion hazard have to be processed, conventional design measures are no longer sufficient to guarantee safety because the rotor speed in the hammermill is a few percent higher than in other sizing systems.

The MFH-6 hammermill from Frewitt combines a high surface rating of Ra #0.8 µm with weld seams with a top finish. A further excellent feature of the MFH-6 is the rotor mounted on one side with direct, gearless transmission of power from the motor to the axis. Apart from the desired access to the rotor and sieve simply by opening the front cover, there is little heat build-up from the two systems mounted one each side. As a result, even very heat-sensitive products can be processed without any problems. The milling chamber consists of high-grade stainless steel (AISI-316L), which is a further benefit in terms of safety and ergonomics. The surface design prevents prod-uct adhesion and makes cleaning the system much quicker and easier. All the seals are made of FDA-compliant synthetic materials such as silicone and polyurethane (PTFE).

The Frewitt pressure wave-proof hammermill is certified according to the EU Atex explosion protection standard. On the model in question, a pressure wave-proof rotary paddle feeder measures the supply of raw product and the discharge of the sized material. Thanks to the inertia of the rotary paddle feeder, the entire sizing system resists pressure up to 10 bar, even in this critical part of the sizing process. In addition to passive explosion protection, there is also an active option that involves rendering the milling chamber inert using nitrogen.
The mill material hits the hammer side of the rotor when it enters the milling chamber and is milled into a fine-grained end product. This product is measured via a regulatable rotary paddle feeder and transported to the milling chamber, where it reaches a controlled level before the dust-free milling process begins. The rotor can be turned to the hammer side for milling hard or crystalline products or to the blade side for fibrous products. Any grain size can thus be achieved with the cutting or milling process – another advantage of this multi-purpose system.
The hammermill offers many more convenient features in addition to the pressure surge resistance of 10 bar: it is easy to clean and there is no product adhesion because of the surface.
Use in practice
In the last year, a leading international pharmaceutical company and a Swiss food producer were just two of the numerous customers to install the pressure wave-proof MFH-6 hammermill in their production facilities – precisely because of these safety and quality features.
The pharmaceutical company specified explosion and pressure wave-proof systems throughout all of its processing cycles. The mill is connected to a melt extruder, meaning that a very hard substance can be transported to the milling system in doses via a rotary paddle feeder. The blade side of the rotor is used to make the fine particle fraction as small as possible.
Frewitt developed its hammermills for the very high demands of the pharmaceutical industry. The modular safety design is also attracting ever stronger interest from food producers as – apart from delivering increased bulk density, leading to streamlined logistics and lower transport costs, plus improved product solubility – it also provides higher safety levels for handling products that constitute an explosion hazard. Only a few months after a leading Swiss producer of milk powder and proteins installed a MFH-15 hammermill and reported very good results at the production site, the machine was retrofitted with a pressure wave-proof milling system from the MFH-6 series. The changeover cycles of the end packs can be greatly reduced owing to the higher bulk density, bringing down handling and transport costs.
Hall 3.1, Booth K22
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