An $800-million supplier of specialty chemicals hit a manufacturing snag that became a blessing in disguise. The company, International Specialty Products, Wayne, NJ, which provides chemicals for pharmaceutical, photographic, personal care, agricultural, and coating and polymer products, found that one of its raw materials used to make an ingredient for a hair spray product was not flowing smoothly. By switching to a pneumatically powered vacuum conveyer system, however, ISP not only solved its flow problem but also was able to charge bulk bags quickly and safely in an oxygen-free inert atmosphere and maintain a high level of cleanliness in the plant.
ISP received the material in bulk bags and wanted to load it directly into its process vessel. Unlike a high-granularity material, however, this was a fine powder that tended to form "rat holes" in the bulk bag, keeping the material from feeding easily into the process vessel. According to Fran Minnock, a 12-year veteran in ISP's process engineering and quality assurance department, the company also wanted to rethink the way it was "charging," or loading, this raw material as a way to eliminate dust. "We needed to control the dust that the material generated into the production atmosphere, improve efficiency, and accomplish this in an oxygen-free atmosphere," said Minnock.
To meet these multiple challenges, ISP evaluated several approaches including screw and vacuum conveyors. In the end, it turned to a vacuum conveyor system consisting of an air-driven vacuum conveyor, pneumatic controller, and bulk bag unloader. The conveyor moved the raw material safely and quietly. "This approach met our most important criteria – that it was a complete and cost-effective system," says Minnock. In addition, "the fact that we could remotely mount the bulk bag unloader away from the actual conveyor appealed to us."
The time savings, as well as the reduction in labor, was dramatic. In addition, the entire manufacturing process became far more efficient. Previously, three people had to charge 23 bags, moving them manually into a vessel, lifting them up onto a hoist, and holding them over a manway. In all, it took a total of 10 hours to prepare the batch for the reactor. With the new conveyor equipment, however, that process was decreased by more than 50 percent to four hours.
In evaluating the system, one major benefit was ISP's ability to test the flow of its product under real-life conditions using both the conveyor vendor's fully equipped test facility as well as a unit at the production site. The use of the test facility let ISP run a wide variety of materials to assess their conveying characteristics – and identify any possible challenges – over varying configurations. "There's no doubt that the use of a testing facility as well as testing unit at the site was a strong selling point for us," said Minnock. "It was not enough for us to see some theoretical equations on a blackboard. We needed to see how our process would work in the plant."
To solve its problem, ISP selected the C-Series 33 vacuum conveyor from PIAB Inc., Hingham, MA. The system has a modular design that let ISP adapt it to its specific needs. In addition, the conveyor's stainless steel design had hygienic (USDA and 3-A accepted) and corrosion-resistant characteristics needed for this application. Because the conveyor is made of stainless steel, it is both corrosion-resistant and easy to clean.
The vacuum pump is the heart of the vacuum conveying system. The pump is driven by compressed air and features high flow rates and a deep vacuum, down to 27 in.-Hg. Thanks to a unique design, the compressed air pump maximizes efficiency, keeping overall energy consumption low. The pump also produces minimal noise – just 72 dB(A) to 76 dB(A). Also, because the vacuum conveyors are powered pneumatically, not electrically, the need for an explosion-proof electrical rating – an expensive proposition – is eliminated. And because the conveyor has only a few moving parts, routine maintenance and downtime are minimized.
In the manufacturing process that produces the hairspray ingredient, the bulk bag unloader is positioned under the hanging bulk bag, with the spout of the bulk bag attached to the unloader. The bulk bag unloader, a simple, fully contained unit for the unloading of bulk bags, works in conjunction with the compressed air-driven vacuum conveyor. It, too, is constructed of stainless steel. With the bulk bag elevated above the station, the spout of the bag is attached before it is untied to an inflatable pneumatic seal, making a totally dust-tight connection. This eliminates the need for glove boxes, doors, enclosures, or a dust connection. The bulk bag unloader is also easily disassembled for periodic cleaning.
The feed assembly features a nitrogen-fluidized cone to keep the product flowing towards the feed point. The nitrogen serves two purposes: it fluidizes the powder and it keeps the atmosphere for the transport piping inert and explosion-proof. The entire feed assembly is mounted on a large pneumatic cylinder.
If rat holes form in the bulk bag, the cylinder extends, lifting the feed assembly up into the bag, breaking up the bridges in the material, and allowing fresh material to flow toward the feed point. The cylinder can either be raised and lowered manually or configured to cycle up and down automatically.
More information is available by contacting PIAB USA Inc., 65 Sharp St., Hingham, MA 02043, calling 800-321-7422, or visiting www.piab.com.
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