One of Europe’s leading tyre manufacturing plants has installed a new cooling tower for process water – and cut its annual energy consumption by 1,500MWh. Key to the savings is the close speed control of fans and pumps, using AC drives from Control Techniques, matching supply with demand and reducing the cooling plant power consumption, when idling, to about that of a domestic kettle.
This project, recently completed at Michelin’s Dundee plant, was driven from inception by project manager Mike Barklie who identified that efficiency improvements in recent years had reduced demand for cooling water which meant that the existing plant was over-sized. “I measured actual cooling requirements and realised that there were further potential savings to be made by putting in variable-speed drives to match the supply of cooling water to demand,” he says. “It was a major investment, but we have achieved a tremendously successful result that has a return on investment of less than three years.”
Control Techniques drives are the drive of choice throughout Michelin plants worldwide. There are already several hundred drives installed on production lines, stirrers, extruders, pumps and fans throughout the Dundee factory alone, which has an output capacity of some 24,000 car tyres a day for the worldwide market. Considerable investment at the plant is boosting production output and creating new jobs. This latest project reflects Michelin’s commitment to the environment and its drive to save energy wherever possible.
The new SPX Marley high-efficiency cooling tower has two 30kW cooling fans for the dual 300m3 cells and there are six large pumps – three 22kW pumps for the hot water to the tower and three 90kW, 4.4 bar pumps to return the chilled water back to the factory. All fans and pumps are fitted with Control Techniques Commander SK AC drives, each of which receives a speed reference from the controlling PLC system that monitors pressure, temperature (of cooled water), levels in the cooling water sumps etc and which also produces trend predictions.
The fans in the cooling tower are designated as main and standby, the drive for the standby only starting when the demand on the main fan drive exceeds 60 per cent. On minimum speed, which is one fan at 40 per cent of full speed, the power demand is just 2.5kW – described by Barklie as ‘the same as an electric kettle’ – some 87.5kW less than the old cooling tower. The average consumption per hour has now dropped from 242kW to just 66kW over all the pumps and fans associated with the water cooling system – a saving of 186kW per hour – or over 4MWh per day.
The Commander SK range of general purpose drives – 0.25 to 132kW – has been designed as a simple, compact, cost-effective AC motor speed controller that delivers performance with simplicity and ease of use. With all the parameters needed for 90 per cent of applications printed on the front of the drive, Commander SK ensures installation and commissioning are straight forward.
However, for more demanding applications, Commander SK can deliver advanced functionality at no added cost to the base drive itself. Plug-in options, dynamic performance, PLC functionality, feedback versatility and connectivity with all main industry networks ensures that, in more complex applications, Commander SK delivers much more than the average general purpose drive - giving users lower cost solutions and better productivity in their motor control applications.
In addition to supplying cooling water for production requirements, the new cooling plant at Michelin’s Dundee plant also supplies chilled water to the air handling units to cool the factory in the summer months. In the winter, the same system uses steam to provide space heating.
Michelin’s UK head office and commercial headquarters is in Stoke-on-Trent with tyre factories in Ballymena (bus and truck tyres) and Dundee (car tyres) as well as a truck tyre retreading factory in Stoke-on-Trent. Its Dundee factory exports its car tyres all over the world and continues to expand with growing demand. In 2006, the Dundee plant was the first Michelin plant in the world to embrace wind energy with two wind turbine generators helping the factory to reduce its environmental impact and energy bills.
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