Milling System How pharmaceutical manufacturer could fulfill Atex in grinding processes

Author / Editor: Roy Housh* / M.A. Manja Wühr

Milling products is one matter. Finely milling products in compliance with Atex to a particle size of 75 µm is another. In order to ensure perfect Atex compliance when finely milling different products, all the conditions have to be in concert.

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Challenge, which has been taken up – milling sugar in compliance with Atex to a particle size of 75µm.
Challenge, which has been taken up – milling sugar in compliance with Atex to a particle size of 75µm.
( © Coprid - Fotolia)

A French pharmaceutical manufacturer had already validated a system to finely mill crystal sugar (saccharose), however they were missing the final aspect. Atex compliance. Never had they realized that they would have to take such an arduous path and have it done by other suppliers. Crystal sugar was originally milled with a vibrating-sieve machine, and sequentially manually filled. In order to simplify the process and make it safer; a hammer mill was purchased from one of Frewitt’s competitors. The product to be milled was fed via a pneumatic conveyor, and thereafter manually filled.


The system worked perfectly albeit required considerable manual handling. The validation results were satisfactory, but they stumbled at the step of Atex compliance evaluation. Realizing the existing system could not comply to Atex standards, they initiated a search for an alternative solution.

A process expert from Frewitt visited the pharmaceutical manufacturer in order to obtain important, on-site information, to analyze the existing system, the process and finally the product. The existing process did not need to be completely revised, instead, the same product could be finely milled with the same sieve execution and the same parameter settings, notably the identical rotor tip speed. Following this conclusion, various Frewitt milling processes were tried. The customer decided to entrust his fine milling to the Hammerwitt, as it achieved the same results as the competitor’s hammer mill, while providing significant improvements in the granulometry and throughput.

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