Lafarge cements reliability with drives
24 November 2008
UK cement manufacturer, Lafarge Cement has boosted reliability of its cement kiln pre-heater fans with ABB drives. The two 1.8MW drives were installed at the company’s Hope, UK plant which produced 1.2 million tonnes of cement a year.
Drive installation: Lafarge cement has improved reliability
The plant was suffering reliability problems on the pre-heaters due to the obsolete slip-ring motors and control system used to drive the fans. Unscheduled stoppages were affecting the company’s ability to meet its production targets. Many of these problems were caused by dust ingress due to the location of the drive equipment. Additionally, the fans needed 1.8 MW to reach the required output but the slip-ring motors could only supply 1.6 MW, resulting in the process failing to reach its designed airflow.
Mark Bramley, electrical engineer for the Hope plant, said: ‘The original drive suppliers were now unable to give Lafarge reliable support for the equipment due to its age and lack of trained engineers, this left the Works’ engineering team with sole responsibility for problem solving on the drive.’
Lafarge decided to find a replacement for the two slip-ring motors, one for each of the company’s pre-heaters. Two 1.8 MW ACS1000 medium voltage drives were proposed.
Jon Clews of ABB proposed the medium voltage drives for ‘ a number of reasons’.
He said: ‘Volt drop is less of a problem at medium voltage levels and with the output waveform of the ACS1000 being sinusoidal, voltage reflections do not occur. At low voltage, the cable would have a larger diameter, adding expense and weight and also making the cables more difficult to route. With medium voltage drives, these problems are significantly reduced.’
ABB also supplied ABB HXR high voltage motors, which include seals on the bearings designed to prevent the ingress of dust.
Another measure designed to counter the dusty atmosphere was the provision by ABB of containers to house the equipment. Based on a similar design to shipping containers, they incorporate a ventilation system, heating and lighting.
One enclosure houses the drives, another the transformer. Because the transformer is an oil-filled type, this container incorporates a bund well which is capable of containing leaks and preventing oil from contaminating the surrounding environment of the Peak District National Park.
Lafarge says the drives offer them better control of the speed of the pre-heater fans.
‘With the old system, we were always limited by the turndown range,’ said Bramley. ‘The drives could only run down to around 475 rpm. The ABB drives can run at 100 rpm, which is useful as we can start the fans before we need them without affecting our kiln warm up procedures. This allows the engineers to check the operation of the running fan and reduces the operators work load during the critical initial kiln feeding procedure when the fan speed is increased to 600 rpm.’
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