Figure 1 – Two Master Magnets Electro Magnets installed side by side at West Burton Power Station
On behalf of EDF Energy, Alstom Power has purchased and installed two (2) Master Magnets oil cooled in-line Electro Overband Magnets at the coal-fired West Burton Power Station located on the River Trent near Gainsborough, Lincolnshire, UK. The Electro Overband Magnets remove tramp metal contamination from the coal to prevent damage to processing equipment and conveyor belts.
Alstom Power employs some 3,500 people in the UK and is responsible for the maintenance, refurbishment and operation of many of the country’s existing power plants. As part of the Alstom Power continued maintenance plan, it was decided to replace the existing Electro Magnets that had been installed when the West Burton Power Station was built in 1968. The coal-fired West Burton Power Station provides electricity for around 2 million people generated by using four 500 megawatt English Electric turbo generators.
When the power station was built in 1968, the Electro Overband Magnets were originally supplied by the Birmingham based company Rapid Magnetics and the manufacturing drawings were produced by Geoff Worley, a young draftsman just starting his career in engineering. Ten years after the commissioning of the West Burton Power Station, in 1978, Geoff founded Master Magnets Ltd. Also based in Birmingham, Master Magnets has become one of the world’s leading designers and manufacturers of Magnetic Separation equipment, especially for coal handling, mining, mineral processing and recycling.
The Heavy-Duty Electro Overband Magnet is the most powerful suspended magnetic separator in the Mastermag range. The magnetic field is generated by an electric current being passed through an aluminium coil that is wound around a steel pole piece and a thick steel back plate is used to project the magnetic field downwards towards the conveyed coal. Any magnetically susceptible tramp metal such as steel angle, large steel bolts, etc, which is conveyed in the coal, moves into the magnetic field where it becomes attracted and lifted up out of the feed material, towards the face of the magnet. A self-cleaning belt system revolves around the Electro Magnet to remove and discharge the captured metal into a separate chute.
For optimum performance the magnetic coil needs to be kept cool and this is achieved by filling the steel box, which houses the coil, with oil. Convection currents within the oil then transfer the heat away from the coil to be dissipated through the sides of the housing.
Master Magnets has a wide range of Electro Overband Magnet designs, with the largest weighing 35 tonnes and spanning over 2 metres wide and in the past two years they have designed and manufactured over 60 Electro Overband Magnets for installation in plants worldwide. Due to the high magnetic strength, the Electro Overband Magnet is able to work at an increased distance above the conveyor (the operating gap), enabling the extraction of ferrous metal from even deep troughed conveyors.
Figure 2 – One of the Master Magnets Electro Magnets installed over the head pulley of the conveyor at West Burton Power Station.
On receiving the enquiry, the Master Magnets team of Adrian Coleman (Managing Director), Mark Baker (Engineer) and Dave Lahiffe (Works Manager) went to site to survey the installation. The conveyors over which the Electro Overbands were to be positioned were both 1,350mm wide and running at approximately 2.3 m/sec each transporting up to 1,500 TPH of coal. Both the magnets were positioned in-line over a non-magnetic head pulley to enable the best level of tramp metal separation as the coal begins to open up and splay as it discharges the conveyor and falls in a natural trajectory down into a collection chute.
Alstom Power placed the order for the two (2) oil-cooled in-line Electro Overband Magnets (model 100 OCW 40). The magnet system of each unit is 1400mm square and 700mm high and the complete system including the discharge conveyor, pulleys and frame weighs 6 tonnes. The coil wattage is 8kW and this produces 20,000 force index at the required 350mm operating gap (the distance between the face of the magnet and the conveyor belt).
The Electro Overband Magnets were installed by Alstom in September 2014 during a scheduled maintenance shutdown.
Master Magnets Managing Director, Adrian Coleman explained the significance of the order:
“We have worked hard in developing a reputation as a world leader in the design and manufacture of magnetic separators including the Electro Overband Magnets and all from our manufacturing facility in Redditch. When we found the link between our founder Geoff and the original magnets at West Burton, we felt it would be very fitting if we ended up designing and supplying the replacements.”