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FEATURE DRIVES, CONTROLS & TRANSMISSIONS


HIGH EFFICIENCY MOTORS save thousands on energy costs


A fume extraction system at a steel works is saving £570,000 a year on energy costs thanks to the installation of variable speed drives and high efficiency motors from ABB


A


fume extraction system at a steel works is saving £570,000 a year on


energy costs thanks to the installation of variable speed drives (VSDs) and high efficiency motors from ABB. The contract involved the supply of services and solutions from across the ABB group and coordination with a number of other subcontractors. Tata Steel’s Aldwarke melting shop in Rotherham, South Yorkshire produces 750,000 tonnes of steel a year. The main extraction system of the


machine shop was identified by the company as being an area where significant savings could be made. This consists of five main extraction fans which draw the fumes from the shop via a system of dampers and vanes. These fumes are then sent to the bag filter plant for removal of dust particles. The common duct pressure was originally controlled to maintain a suction pressure of 21 mBar using input vanes to the main extraction fans operating at a fixed speed. The fans were driven by direct- on-line, fixed speed, 3.3 kV, 1.2 MW, 740 rpm, water-cooled motors. With no capacity to match speed to demand these motors represented a heavy drain on the plant’s electrical supply. “Tata Steel is committed to sustainable


solutions to cut energy use,” explains department engineer Andy Burgar. “The size of these fans meant they were


22 MARCH 2014 | FACTORY EQUIPMENT


significant energy users costing us around £1.5 million a year to run. Our internal calculation showed that we could conceivably save hundreds of thousands of pounds a year on energy, cutting CO2 production by 6000 tonnes.” Although the motors had suffered few


failures, maintenance was a challenge because of the special certification needed for servicing 3.3 kV equipment.


TOTAL SOLUTION Tata Steel chose ABB to supply a complete solution for the melting shop. This included the supply and installation of five 690 V regenerative drives with active front-end supply units and five 1200 kW, 6-pole, air-cooled motors. “We evaluated the limited number of


suppliers on our database for this contract based on their ability to manage a project of this size and their company’s proven track record,” continues Burgar. “We took references and ABB satisfied all our criteria.” In addition ABB supplied two high performance pressure transmitters with remote diaphragms along with numerous services including project management and engineering, provision of documentation and modifications to existing third party PLC equipment and software code. Further services supplied were removal of the old AC motors, mechanical installation of the ABB


Tata Steel’s extraction system saves £570,000 a year on energy costs with ABB variable-speed drives and high efficiency motors


motors, drives and control equipment, supply and installation of cables and terminations and commissioning of the drives and control modifications. The use of VSDs allows the company to


have far better control of the fan system. ABB adjusted the control loop to allow the VSDs to match the needs of the system. For example, the melting shop has a certain level of ambient fumes. When another furnace is tapped, fumes increase in volume when hot metal is poured. To account for these dynamic changes the pressure control logic was adjusted and the associated control loop retuned to allow for the difference in response between vane control and motor variable-speed control. “The major challenge was keeping the


fans working throughout the project,”explains Ken Hughes, project manager for ABB. “The extraction system works around the clock for six days a week and needs at least four of the five fans to be working at all times. This required very close liaison with the customer so we could fit in our installation and commissioning work with the shutdowns in the plant. Flexible planning of our activities was essential.”


ABB


T: 01925 741 111 www.abb.com


Enter 318 / FACTORYEQUIPMENT


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