When it comes to pulverising and milling hard, crystalline or fibrous products, there is often no alternative to the hammermill. As long as only unproblematic solid materials are required to pass through a mill of this type, there is nothing to worry about. However, if potentially explosive products also have to be processed, conventional design measures must be complemented by additional safety precautions.
The Frewitt MFH-6 hammermill combines a number of quality features: a high surface rating of Ra ^0.8 µm, weld seams with a top finish, rotor mounting on one side with direct, gearless transmission of power from the motor to the axis. As well as allowing access to the rotor and sieve simply by opening the front cover, this also reduces heat build-up compared to systems mounted on both sides. Even extremely heat-sensitive products can be processed without any problems. The milling chamber is manufactured from high-grade stainless steel (AISI-316L), which is a further advantage as regards safety and ergonomics. The surface design prevents product adhesion, and cleaning the system is both 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. In the model in question, a pressure wave-proof rotary paddle feeder measures the raw product supply 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. Apart from passive explosion protection, there is also an active option where the milling chamber is rendered inert by the use of 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. The product is metered by means of an adjustable 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 crys- talline products or to the blade side for fibrous products. Any grain size can thus be achieved with the cutting or milling process – another good selling point of this multi-use system. In addition to the pres-sure surge resistance of 10 bar, this hammermill offers several important benefits:
- Simple cleaning (easier removal of the sieve/rotor; interior cable)
- No product adhesion (surfaces minimised through organic curves)
- Stand-alone function; easy to integrate into facilities
- Irrigated lip seal (for air or nitrogen)
Proven in practical duty
A leading international pharmaceutical company and a Swiss food producer are just two of the customers who installed the pressure wave-proof MFH-6 hammermill in their manufacturing facilities last year – precisely because of these safety and quality features.
Explosion and pressure wave-proof systems were specified by the pharmaceutical group throughout all of its processing cycles. The mill is connected to a melt extruder, meaning that an extremely 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 pos-sible.
Frewitt originally developed its hammermills to meet the very high demands laid down by the pharmaceutical industry. In the meantime, the modular safety design is attracting increasingly strong interest from food producers as, apart from delivering increased bulk density – leading to streamlined logistics and lower transport costs – and improved product solubility, it also provides higher safety levels when handl-ing products that constitute an explosion hazard. Only a few months after a leading Swiss manufacturer of milk powder and proteins had installed an MFH-15 hammermill and experienced extremely good results with this equipment at its production site, the milling system was retrofitted with a pressure wave-proof system in the MFH-6 series. Due to the higher bulk density, the changeover cycles for the end packs are now substantially shorter, bringing down handling and transport costs.
Frewitt SA info@frewitt.com www.frewitt.com
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