Explosion-safe Milling System for API

Small Particles and High Safety

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The solution which was discussed in meetings and implemented by Frewitt is comprised of different elements, which together ensure the explosion-safe conveyance, dosing, milling and filling of the product. A level sensor is placed in the feed funnel of the vacuum conveyor, monitoring product feed and regulates it in order to ensure a continuous process. In order to keep the milling chamber temperature at a constant, cool temperature: the milling housing is equipped with a water-cooled system. The temperature of the milling chamber, as well as the drive bearings, is constantly monitored.


The oxygen concentration level, with a programmed threshold of three percent, is monitored from the product feed to the final filling of the milled product. The alarm threshold of three percent is programmed, and held constant under the pre-set value of three percent. This maintains the milling chamber at Atex II G/D (Zone 0/20) and the area of the milling head at Atex II 2G/D (Zone 1/21).


Monitoring and regulating the exhaust air ensures that the product is not heated, hence allowing for a constant, high throughput. The Profi-Clean 250 system, equipped with an H13 filter, prevents even the finest dust or powder leakage from the system. The filter is continuously cleaned by an efficient, blow-back system.

Bag-changings is done with special attention. When the bag reaches the prescribed weight; a valve stops the product flow. The remaining nitrogen is aspirated from the bag. Thereafter, the Profi-Bant bag holder is disengaged, the filled bag removed, and a replacement bag is installed. The system remains inerted during the bag exchange.

Saving Raw Material

This inerting design is not only technically complete (fulfilling GMP standards, Atex guidelines and all rules of the country-specific Institution of Quality), it also has considerable economic advantages. Continuous monitoring of oxygen contents reduces the use of nitrogen, a very expensive raw material, to a minimum.

* The author is Regional Sales Manager at Frewitt, Granges-Paccot/Switzerland.