Full clean-in-place features for powder air classifier mill

Meeting the increasing demands from the pharmaceutical industry for full clean-in-place capability, the new Mikro ACM CIP air classifier mill made its first public appearance on Hosokawa Micron's stand at last month's Solidex exhibition in Harrogate.

The basic mill is a high-speed impact pulveriser with an integral dynamic classifier, capable of ultra-fine grinding of many materials to d97=10micron. Material fed into the mill is reduced in size by impact with a high-speed rotor, from where the ground material is entrained in the air flow through the mill and carried to the classifier wheel. Oversize particles are recycled to the grinding zone, while `on spec' material passes through the classifier and is conveyed to the Pulsaire dust collector as the finished product.

All that is fairly standard for an air classifier mill. But what makes the new mill different is its innovative CIP design. This allows the mill to be filled with water, special cleaning fluids and even some organic solvents. In conventionally designed mills CIP can be a problem because the rotating parts inside the mill need to have their bearing assemblies sealed against any ingress of cleaning fluids that may damage the bearings. Hosokawa, however, has designed a sealing system to overcome this problem.

The sealing system is inoperative during mill operation but is activated during the CIP operation. The fluid inside the mill can even be agitated for better cleaning.