ABB drives save Tata Steel £250,000 on fume extraction 29 November 2012

The Aldwarke Bloom Caster complex in Rotherham, South Yorkshire, is set to save £250,000 a year, following the installation of variable-speed drives on its fume extraction system.

Completed by ABB system integrator Drives and Automation for Tata Steel, the project involved replacing fixed-speed direct-on-line electric motors with low voltage motors, controlled by four ABB low harmonic variable-speed drives.

ABB provided two 400kW and two 570kW variable-speed drives as well as transformers, a Form 4 distribution panel and inverter cubicles. Electrical and mechanical installation, plant room ventilation and integration of a PLC /SCADA with the existing plant control system was carried out by Drives and Automation.

The extraction plant is used to remove fumes produced by the two casting machines and two ladle arc furnaces in the plant complex, which are then passed through a filter system.

Ben Holroyde, planning project engineer for the Aldwarke Bloom Caster, says that the original installation used four 3.3kV motors: two 650kW and two 410kW. The two large motors were used as the primary extraction motors, with the smaller motors providing additional extraction as required.

"Due to motor limitations, the fans were restricted to four starts per hour, as additional starts would risk damaging the windings," explains Holroyde.

"Due to the starting restrictions, the motors would be forced to run-on for 15 minutes, even if demand for extraction was reduced. This obviously wasted a lot of energy."

In addition to the motor 'run-on' issues, several of the motors suffered multiple failures. "We estimate we were spending around £3,000 a year in motor repairs," says Holroyde, "and although not excessive for these types of motors, the downtime was becoming a major problem."

Holroyde says that each failure took up to six weeks to rectify, during which the plant had to cut back on production to stay within environmental limits of fume and dust levels.

Also, because the motors were 3.3kV, maintenance required special permits to work.

The company aimed to save in the region of £240,000 a year on energy costs by matching the speed of the motors to the dust extraction demand. "We also anticipated that using variable-speed drives would cut maintenance by reducing wear and tear on the motors, and strain on the ductwork – as well as making for a less noisy environment," says Holroyde.

Brian Tinham

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