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Wheels of steel turn energy into gold

ABB Limited (Group Headquarters) : 02 April, 2004  (Company News)
Over 1,000 MWh of energy is being saved each year at Magnetto-Topy's steel wheel manufacturing plant in Coventry, following the installation of seven ABB drives.
An additional spin-off is the significant reduction in pump noise, which will help the former Dunlop company meet new health and safety levels set at 80dbA. And all for a 23,000 investment that will pay back in just over one year.

Four of the drives, rated from 37 to 55 kW, are used on water pumps within four cooling towers. Two, 37 kW drives are used on filtration paint line pumps within the company's wheel paint line. A further 37 kW drive controls a compressor house pump. The drives are supplied by ABB Drives Alliance partner, Sentridge Control in Coventry.

The cooling tower drives have replaced star-delta switching which turned the pumps on or off. With this arrangement, the pumps were left running at full speed on 50Hz, regardless of production needs.

With the drives fitted, Magnetto-Topy is able to reduce the running speed on one pump, rated at 55 kW, to 35 Hz, resulting in a 53% energy saving. On three other pumps the running speed is reduced to between 40 to 45 Hz, reducing energy consumption between 33 and 46%.

Because of the risk of legionella bacteria spawning within the cooling towers, a continuous flow of water is essential. The drives have been tuned to between 35 to 45 Hz to ensure that there is sufficient water flow, regardless of production levels.

Pump house noise is reduced by an average of 10 per cent by operating the drive at a higher switching frequency. Using this switching frequency, the motors are perceived to be operating silently, because the sensitivity of human hearing decreases rapidly above 15 kHz.

The company is the UK's only producer of steel wheels, with the capacity to manufacture 90,000 each week, primarily for Nissan UK, Peugeot in UK and France, Vauxhall, Opel, LDV, MGRover and Land Rover.

It presently produces up to 100,000 wheels each week. According to Dave Pound, Operations Manager, the electricity costs alone needed to make each wheel is estimated at 14p. The energy reduction saves at least 1p off the electricity costs for each wheel. 'That may not sound much, but when we are producing so many wheels and with pressure on to reduce overheads, then 1p per wheel mounts up to a tidy sum.'

One of the overhead costs under scrutiny is the maintenance budget. 'Apart from energy saving, the drives bring a much greater reliability to our process. Star-delta starting stresses the motor, whereas with variable speed drives, smooth starting has a direct impact on maintenance costs,' says Phil Smith, Maintenance Services Administrator. 'Pumps will run longer as they are running slower and with less vibration. Now the reliability of the drives means I rarely go near the system.'

Keeping up to date with the demands of the environmental system, ISO 14001 is a key factor in choosing variable speed drives. In addition, Magnetto-Topy aims to claim its Climate Change Levy (CCL) allowance, for which it needs a 10% saving over 10 years. 'We are on target to achieve it this year,' says Pound. 'We won't have to buy carbon permits this year'.

Magnetto-Topy is now looking at PID control, which could result in a further 10,000 per year in energy saving. Proportional-Integral-Derivative, which is fitted as standard to ABB drives, allows the process control to accurately maintain a setpoint by adjusting the control outputs.

Proportioning control continuously adjusts the output dependent on the relative positions of the process temperature and the setpoint. PID control is commonly used in today's controls arena. These functions, allow for the precise control of difficult processes.

However, with Magnetto-Topy, Sentridge faced a common hurdle that it experiences with most customers that are new to drives: persuading the company that the investment would repay itself in one year. 'I must take a dozen phone calls a week from someone offering to save me money,' says Pound. 'Naturally you become cynical. But here was a company that was prepared to prove the cost savings without me having to spend a single penny.'

Sentridge has developed a portable drive trial unit, which it temporarily installs on site to measure the actual saving. 'Even though the theory of energy saving and therefore the massive cost saving is well documented, people find them so incredible that they want to see before they believe. Our trial unit brings the proof,' explains Sentridge's Paul Wooldridge, who installed the unit along with Magnetto-Topy's engineers.

'The trial unit is as much for the benefit of the financial guys who are not engineers and would not be expected to understand the energy saving theory curves,' says Pound. 'We also did not know why different pumps were running at different pressures and what effect that would have on the plant. We wanted to prove that we wouldn't waste money by trying to save money.'

But some two years before being able to wheel in this portable unit, Sentridge faced a further challenge. 'When Sentridge came to see us and said we could save you money, this was not one of our key tasks,' says Pound. 'We had to get 70,000 wheels out, as production was paramount. However, when production capacity dropped, the running costs did not drop and so we had to start looking at how to save money.'

Paul Stafford, Director of Drives at Sentridge concludes: 'In a time of economic uncertainty, costs saving procedures are usually implemented on the factory floor, therefore why not reduce long-term costs through energy conservation? We have proven that energy cost savings when implementing drives will payback in about one year. Installing a variable speed drive not only lowers energy bills and pays for itself, but also conserves the valuable energy we all need on a daily basis'.
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