Reprinted with permission from Pharmaceutical Processing magazine, September 1996 issue.
Sturtevant, Inc., manufacturers of the Sanitary Design Micronizer® (SDM) has continued to develop the only USDA-DAIRY accepted jet mill by custom engineering solutions for its customers. By working to solve special application problems, Sturtevant continues to advance the sanitary design features of the SDM to meet the stringent industry needs. Originally, Sturtevant engineered the stainless steel SDM especially for the pharmaceutical industry in response to a customer request.
Inside the SDM, compressed air creates a vortex within which feed material is reduced to low- to sub-micron ranges by particle-on-particle impact, a process free of media contamination or heat generation. The SDM features hand disassembly in minutes and complete accessibility for sterilizing. To assure that the equipment would meet the highest industry standards. Sturtevant worked within USDA guidelines which support and utilize established 3-A sanitary standards and 3-A accepted practices. In this way, the SDMs sanitary designs and fabrications were certain to meet equipment requirements at the up front end, whereas, FDA process approval would by subject to approval only after the installation had been made. Sanitary features include the use of quick-release clamps, FDA-accepted O-rings and gasket seal materials to eliminate dust leakage, continuous welds, and machined and polished surfaces. This development process assures optimal sanitary design.
A customer-impacted development on the Sanitary Design Micronizer came about when a company needed to reduce exposure to highly toxic pharmaceutical in their just-ground phase. The operation was to take place in a "glove box" environment to protect operators from exposure to hazardous grinding dust.
By going one step further, Sturtevant engineered a solution that further protects operators and improves post operation clean-up. In standard jet mill design, the unground materials fed to the mill inlet through an unsealed opening. Eventually, dusting in the area would build-up and potentially contaminate the glove box as well as present a hazard during clean-up.
Sturtevant engineers solved the problem by designing a four-way cross attachment from the feeder to the mill inlet. The top of the assembly is fitted with a sight glass to view the feed stream. A filter breather was mounted on the remaining connection. This assembly allowed the venturi to breathe, but contained dusting to assure safe operation - even if the mill puffed.
Another valuable SDM development brought even greater flexibility. A "toll grinder" who grinds, pulverizes and blends materials on contract, approached Sturtevant for help. A jet mill typically exhausts into a cyclone and filter bag configuration. This type of discharge is not efficient since the best cyclones will not collect 100% of the micronized product, thereby losing valuable ultrafines.
By working jointly with a dust collector manufacturer, Sturtevant sought to create a sanitarydust/product collector that would replace the SDM cyclone and exhaust bag. The dust collector was designed for either bags or cartridges, according to customer preferences or installation requirements. Like the SDM, the collector was designed to disassemble without tools.
The portion of the dust collector that functioned as the discharge hopper clamped to a removable sample container that could be immediately sealed and ready for delivery. The collector exhaust fan was fitted with a discharge HEPA filter. This new, enclosed grinding system made the collection and delivery of the ground product safe and efficient, and operators were now free to monitor the process throughout. Moreover, the tremendous expense associated with losing product from the discharge bag was eliminated. For another customer, Sturtevant later designed the filter bag section with sealing covers for safe transfer to a separate room where the filter bags could be removed and cleaned.