ABB drives improve reliability of pre-heater fans

An ABB Automation Tech (Drives and Motors) product story

Edited by the Engineeringtalk editorial team Nov 25, 2008

Lafarge Cement has achieved 100 per cent reliability of its cement kiln pre-heater fans following the installation of two 1.8MW ACS1000 medium voltage ABB drives.

Lafarge Cement's plant at Hope in Derbyshire produces 1.2 million tonnes 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 1.8MW to reach the required output but the slip-ring motors could only supply 1.6MW, resulting in the process failing to reach its designed airflow.

'The original drive suppliers were unable to give Lafarge reliable support for the equipment due to its age and lack of trained engineers, which left the engineering team with sole responsibility for problem solving on the drive,' said Mark Bramley, electrical engineer for the Hope plant.

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.

'We had knowledge of ABB drives from our plant in Le Havre and so had built up a good relationship with the company,' said Bramley.

'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.' Two 1.8MW ACS1000 medium voltage drives from ABB were proposed to meet Lafarge's needs.

'We proposed medium voltage drives because of the distance from the drives to the motors, some 200m, for a number of reasons,' said Jon Clews of ABB.

'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.

As the transformer is an oil-filled type, this container incorporates a bund well that is capable of containing leaks and preventing oil from contaminating the environment.

As well as reliability, the ABB drives also give Lafarge 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 475rpm.

'The ABB drives can run at 100rpm, 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 600rpm.' The ABB drives have achieved 100 per cent reliability, with the first one operating without fail since November 2006.

Bramley sees the installation of the ABB drives as a considerable step forward in reducing downtime and helping Hope Works to meet its production targets.