Lafarge has achieved 100 per cent reliability of its cement kiln pre-heater fans, following the installation of two 1.8 MW ABB drives, according to a report by Process Engineer magazine.
Lafarge Cement’s plant at Hope in Derbyshire produces 1.2Mt of cement a year. 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, says: “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, and asked ABB to tender. ABB won the contract. “We had knowledge of ABB’s drives from our plant in Le Havre and so had built up a good relationship with the company. A new position was established for the drive equipment to reduce the dust problems and Lafarge worked closely with ABB to minimise installation time and potential problems,” says Bramley.
Two 1.8 MW ACS1000 medium voltage drives from ABB were proposed to meet Lafarge’s needs.
Jon Clews of ABB says: “We proposed medium voltage drives because of the distance from the drives to the motors, some 200 metres, for a number of reasons. 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, with the drives pre-mounted and pre-wired to save time on site.
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 environment of the Peak District National Park.