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The Civil and Marine Middlesbrough plant has saved money and reduced noise and maintenance requirements following Control Techniques’ variable-speed drive technology.

At the plant, blast-furnace slag – otherwise a waste product from iron production – is ground into a fine powder called ground granulated blast-furnace slag (GGBS).

This is used to enhance the properties of concrete, replacing between 20 per cent and 80 per cent of the normal Portland cement.

Excessive wear-and-tear on dampers in particular prompted an examination of alternative means of control of the air flow that extracts the highly abrasive fine powder from the ball mill and Sepol separator.

Rob Thwaites, electrical engineer and assistant works manager at the plant, said: ’As neither fan operated at full speed, we also saw an opportunity for energy-savings.

’We brought in Control Techniques, which calculated likely savings and predicted that the drive for the Sepol separator would have a payback of seven months, while the ball mill would pay for itself in nine.

’The calculations have proved to be accurate and we have made precisely the savings that Control Techniques predicted.’
The Sepol separator is driven by a 200kW motor running at 71-75 per cent of full speed.

With the original damper, its energy consumption was 146kWh.

Now, under inverter control using a CT Unidrive SPM drive, this has been reduced to 61 kWh, giving a saving of 85kWh.

Total savings on the two installations resulted in a GBP700 per week reduction in the power bill.

Thwaites added: ’A further benefit we hadn’t anticipated is the reduction in noise, which makes the plant much more comfortable for operators.

’We also anticipate that fan motors and bearings will last longer and require less maintenance.’ Further Control Techniques Unidrive SP AC drives have been installed on the pre-grinders, which has resulted in an overall increase in throughput from 50 to 70 tonnes of GGBS per hour, enhancing the energy efficiency of the plant by reducing the energy consumed per ton of output produced.

Control Techniques recommends that any higher power installation operating a pump or fan, where the output is throttled using a valve or damper, should be reviewed closely, to see how the energy consumption could be reduced using VSD control.

Control Techniques

Control Techniques, an Emerson Industrial Automation company, is a world leader in the design, production and marketing of electronic variable speed drives for the control of electric motors. Our strategy is to concentrate on delivering drives and servo products that enhance the productivity of our customers’ machines and processes.

We operate through a global network of drive and application centres that both distribute product and add value by building our drive products into custom designed systems and by offering the highest levels of customer service.

Our Control Techniques drive centres also provide us with invaluable feedback and market intelligence so that we can further improve our products and service. This customer focused strategy will enable us to continue to grow profitably.

Our competitive edge is based on our unique focus on drives, our strength in research and development, our investment low-cost manufacturing and an effective worldwide marketing strategy.

Emerson Industrial Automation, a business of Emerson, is a global technology provider that enables productivity, efficiency and quality gains for customers across a spectrum of industries. Our products include alternators, electric motors and drives, electrical distribution devices and mechanical power transmission, fluid automation and ultrasonic joining solutions. Visit our website for more details.

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