Nic Michel is General Manager, North America for Pharma Technology Inc., designs and manufactures specialty dedusters, metal detecting devices and loading systems for tablet- and capsule-producing machinery.

The two primary methods are vertical vibration and concurrent airflow techniques.

Vertical spiral designs account for the vast majority of dedusters sold in the North American and European pharmaceutical marketplace. Simpler horizontal vibration dedusting unit are still in use but the technology has become becoming obsolete over the last decade.

With vertical dedusting, tablets are vibrated up a stainless steel or polymer spiral by a combination of electromagnets and spring blades positioned at the spiral’s base. Dust extraction ports are placed at regular intervals along the spiral, either in the form of slots perforated directly in the central extraction column, suction channels under sections of the spiral with perforations or in the most advanced units in the formal of a continuous circular channel at the circumference of the spiral. By increasing the residence time of tablets in the deduster and tumbling them in a variety of positions while vibration conveys them upward, tablets are exposed to dust-clearing vacuums at multiple points.

Compressed air jets are also used on high efficiency models to help the deduster run cleaner for longer (several days) without cleaning. The compressed air jets push residual dust away from the center of the spiral towards the dust extraction channels and help flip tablets from one side to the other to help ensure even dedusting and deburring.

Dedusters equipped with circumferential dust extraction channel and radial compressed air jets have been proven to dramatically improve process times and yields: namely, more powder being dedusted from tablets at a higher conveying speed. Residual powder is rapidly and efficiently eliminated through a continuous extraction channel on the spiral’s outside circumference. This design helps prevent the residual powder saturation common at the bottom in stainless steel units, ensuring high dedusting efficiency for lengthier periods, and reducing the need for mid-batch cleaning.

In 2009, a design using high-tech polymer materials was introduced. Instead of a continuous stainless steel spiral encased in a stainless and Plexiglass hood, with dust extraction coming from a central tube, the new spiral was comprised of high-pressure molded, FDA-accepted Tritan polymer segments. The concept, called PharmaFlex, features stacked segments that automatically encase the spiral, eliminating the need for an external hood.