Safer Milling A New Hammer Mill from Frewitt Resists Pressure Shocks up to 10 bar

Editor: Doris Neukirchen

The new MFH-6 pressure shock resistant hammer mill from Frewitt Ltd provides size reduction to meet the highest standards of quality and safety. For milling products where there is a risk of dust explosions, the machine can withstand internal explosion pressures of up to 10 bar. The improved safety, operating comfort and production quality have prompted two companies in the pharmaceutical and food sectors respectively to install the new hammer mill.

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The MHF-6 pressure shock resistant hammer mill is a modular design that can be integrated into any production line, says Frewitt. (Pictures: Frewitt)
The MHF-6 pressure shock resistant hammer mill is a modular design that can be integrated into any production line, says Frewitt. (Pictures: Frewitt)
( Archiv: Vogel Business Media )

Wherever hard, crystalline or fibrous substances must be reduced to fine powders, the Frewitt MFH-6 hammer mill is ideal for the job. The mill uses a single side-mounted rotor fitted with knives or hammers, depending on the texture of the original material and the result required. For pharmaceutical industry applications, the rotor can be supplied ground and polished. The inlet product feeder is connected directly to the mill by a Tri-Clamp flange, creating a tightly closed system that makes product contamination impossible. The MFH-6 hammer mill is a modular unit that can be integrated into any inline configuration.

No heat generation

The construction, surface finish and user-friendliness of the MFH-6 all display the quality users have come to expect from this Swiss manufacturer. An outstanding characteristic is the single side-mounted rotor with its direct, automatic power transmission. This arrangement allows easy access to the rotor and sieve when the front cover is opened.


Heat generation is much less than with double side-mounted rotor mills, so heat-sensitive products can be processed without problems. On request, the MFH-6 can also be fitted with a cooling system.

The one-piece sizing chamber is made from 316L stainless steel with a surface finish of Ra ≤ 0.8 µm and a minimum of polished welds in contact with the product. The smooth surface prevents product adhesion and ensures quick and easy cleaning. All seals are made from FFDA-approved low-friction synthetic materials such as silicone and PTFE.

Pressure shock resistance

Like Frewitt’s larger MFH-15 mill, the pressure shock resistant version of the MFH-6 has ATEX approval. Its pressure shock resistance of 10 bar g ensures that production areas are protected from explosions. The paddle wheel that introduces feed material to the milling chamber and removes the product is designed to resist explosion overpressures, with an inertia that ensures that pressure does not propagate upstream or downstream of the mill.

As well as passive explosion resistance, the mill can be protected by nitrogen blanketing. This allow the system to be certified for category 1G (zone 0) as well as 1D (zone 20).

Success in pharma and food

A leading international pharmaceutical company and a Swiss food company have both equipped their production plants with the MFH-6 pressure shock resistant hammer mill.

The pharmaceutical company normally specifies explosion-proof systems for all its production processes. The mill is positioned at the end of a melt extruder, from where a rotary feeder transfers the extremely hard product into the mill. To keep the proportion of fines low, the mill uses the side of the rotor equipped with knives. The client appreciates the good accessibility of the sieve and the rotor for cleaning. After successful validation, the mill went into production at the beginning of January 2007.

The ease of cleaning and explosion resistance of the MFH-15 have also attracted the attention of food manufacturers. A leading Swiss producer of milk powder and proteins has upgraded its production plants to use the new mill. Apart from the increase in safety, the company appreciates the fact that the milled product has a significantly higher bulk density than was achieved using the original mills. This means that product collection containers have to be changed less frequently, and also reduces transport costs.