A clean concept for a tablet press

Gerd Hüffmann explains how to prevent contamination by means of a clean design 

 With the increasing potency of today’s drugs, the quest to ensure perfect clean ability and avoidance of any chance for product contamination is becoming more important than ever.

For a tablet press this requires the execution of a clean engineering concept to: avoid contamination in the process; ensure easy and thorough clean- ability; and prevent chances for cross-contamination. How can this be achieved?

Contamination in the compression process is avoided – or at least considerably reduced – by limiting the area exposed to pharmaceutical product by keeping the compression area as compact as possible.

Great care has to be taken to ensure that there is no product dust migration to technical areas of the compression machine, as these will be difficult to clean once contaminated. This is best ensured by a hermetic separation of the compression chamber from the technical sectors of  the tablet press.

This can be achieved by a seamless base plate and a well- functioning seal between such plate and the rotating die-table.

Punch bellows, preferably of closed design, will prevent the punch shafts from being exposed to product and ensure that no product residue will find its way into the punch guides.

An adequate dust extraction system, with proper functional monitoring, will ensure that there is no powder built-up in the compression area. At the same time, well-sealed doors and tablet chute, the later ideally fitted with dust tight tri- clamps, ensure that there is no dust exposure to the tableting room.

Thorough cleanability is ensured and potential cross contamination prevented via several considerations. Firstly, easy to clean surfaces of mirror polished stainless steel are required, with the total avoidance of angles and a ‘curved edge design’ with a radius of not less than 50mm in the product contact area.

Next, all product contact parts have to be easily removable, preferably to be cleaned off-line in an automated washing system. This also applies to die tables/turrets, which are ideally interchangeable, leaving a minimal area for manual cleaning after removal from the press.

A ready, clean set of product contact parts (and die table) to be re-installed for the next product will conveniently reduce cleaning and change over time.

Finally, closed punch bellows ensure that there is no chance of product residue built-up in sections of the turret, from where it would be difficult to remove.

Once all these features have been thoroughly incorporated into the design of a tablet press, a truly clean tablet press concept has been realised.

Gerd Hüffmann is with Romaco Kilian.

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