Multidrive AC control weaves success story
"Building from scratch gives you the opportunity to think about everything you want to accomplish in terms of efficiency and operation," noted Amin. The polypropylene fiber extrusion equipment, which takes up half of the facility, was set up first - both as a source of raw material supply internally, and for producing fiber to sell to other nonwoven manufacturers. The resin, extruded in a number of colors, is stockpiled for standard fabric production, with specialty fibers produced on a custom order basis.ASF also pioneered an industry first for electrical integration and control of its new production lines. Working alongside systems integrator Electric Systems Integrator, LLC (Chattanooga, TN), ASF elected to install a combination of PC control and multidrive ac motor control for seamless operation of all processes from the carding system to the winder. The two lines installed are, to date, the largest and first production lines in the nonwoven industry to be built this way, with the multidrive featuring a true, common dc bus.
Why this control configuration? "Because it optimizes throughput, increases operational reliability - fewer power devices are required in a multidrive, utilizes all regenerated energy, and reduces inventory costs of spare parts dramatically," said Mike Mauney, director of business development, ESI. "It is a cost-effective solution for an industry that utilizes machinery and processes that generate significant inertia and regenerative energy."
While the common dc bus multidrive features a total of 43 ABB (Zurich, Switzerland) ac motor drives (ranging from 3 to 200 hp) to provide progressive draw control for the production machinery, a standalone configuration of 16 standard ABB drives operate the motors of ASF's opening and blending process.
The multidrive operation is controlled from the master operator console. Changes in control made from the console automatically cascade downstream process to process; or changes can be made to individual machines. The feed station is controlled from a PC located inside the enclosure protecting the drives.
Driver comfort
With no a/c in the building, keeping the PCs and the drives properly ventilated was another major concern from the outset of the project. ASF nonwovens plant manager, Troy Ash said that individual a/c units were considered for the three cabinets that house the drives, but that concept was cost prohibitive. With the assistance of Michael Heating and Air (Athens, GA), ASF selected a 5,000-ton Carrier cooling unit."The cost was a lot less with the big unit because we haven't expanded yet, but we're only using half the capacity of the 5,000-ton unit. So we can actually branch off a duplicate line of the one that we have and still be able to cool it, so it was a lot cheaper to buy the one unit instead of smaller units," Ash said.
The three cabinets, which range in size from 6 ft high by 3 ft wide by 8 ft long to 6 ft high by 3 ft wide by 75 ft long, were built on top of iron frames with vents at the top, for additional cooling.
Since the Carrier unit is suspended about 25 to 30 ft above the production floor to maximize floor space, Ash said that running the ventilation piping from the unit for the cabinets was no easy task. "When you're running the piping from all the way up there to the ground and from 150 ft away, the system is pretty complex as far as the branches it has and the length it has to travel," he noted.
Ash reports that despite sometimes torrid summer days, the factory (which now employs 75 people) has experienced "no faults because of the drives being overheated."
With state-of-the-art drives being protected by a solid hvac system, the machinery is set up so that it can exploit its optimum operational capabilities allowing expansion, going forward, into fiber blending, fabric coloration, and fabric slitting to virtually any size. Factory management expects to add 40 more employees over the next three years, and ASF seems poised to initiate more new ideas in its pursuit of maximizing up time and optimizing throughput of very high-quality fabrics.
