In a highly specialised application for a power station’s dry cooling towers in southern Africa, SEW-EURODRIVE’s MACC-series air cooled condenser units have come to the rescue. The customer had experienced frequent failures on a competitor product, compromising the towers’ vital cooling functions. The success of the MACC units has now led to a second order.
Recently installed in a power station, 24 of SEW-EURODRIVE’s MACC-Series two-stage gear units for air cooled condensers are ensuring adequate air movement to cool circulating water so that power generation can continue.
This cooling function had become a challenge for the power station when the previously installed competitor products had repeatedly failed unexpectedly. SEW-EURODRIVE had installed these MACC units over the past few years, and their reliable operation has led to a request to supply several additional units. According to SEW-EURODRIVE Business Development Representative Quintin Bianchina, the design is specific to this demanding application.
“Comprising a gearbox and long output shaft that attaches to a fan via a hub, these MACC units also boast a thicker, more rigid cast iron housing than a standard gearbox,” explains Bianchina. “The radial and axial loads transmitted by the fan are substantial, requiring a suitable design that will withstand these forces.”
With the fan in operation, there is both upward and downward thrust as well as forces to the left and right. The flat topography and climatic conditions around the power station also exacerbate the situation, especially on hot days when air moves rapidly up the cooling towers. The gearbox, bearings and shaft must be designed and manufactured to accommodate these forces while continuing to operate reliably.
“This application is, in fact, so challenging that the customers’ existing equipment was not coping with the demands,” he says. “We were able to offer our world class engineering solutions to develop the MACC09 model – the largest version in this range – which has proved fit for purpose under these arduous conditions.”
The noise levels are an additional factor in this application, and the quiet MACC units ensure that they do not exceed maximum limits; the customer monitors the noise to check compliance. Heat build-up in the gearbox must also be dissipated, so the design includes cooling ribs to increase the surface area. This design enhances the cooling significantly on the gear units. SEW-EURODRIVE also offers a low noise axial cooling fan as an option, for enhanced thermal improvements.
Another vital aspect of the SEW-EURODRIVE’s MACC’s features is the maintenance safety brake on the high speed input section of the gearbox. This can be applied to bring the fan safely and easily to a standstill under wind milling conditions when maintenance is required.
“Due to their size, these fans do not otherwise stop turning once they start – due to the natural upward airflow into the cooling tower,” he says.
Since SEW-EURODRIVE has recently built a new and expanded facility at Aeroton in Gauteng, the assembly of these MACC units can be done locally. Enlarged stockholdings of components means that the turnaround time will be drastically reduced.
“Rather than the usual 30+ weeks to import this equipment, we expect to assemble and deliver these in batches within 8 to 12 weeks,” says Bianchina. The MACC series is designed and tested by SEW-EURODRIVE’s centre of excellence for these products in Finland.
On behalf of SEW-EURODRIVE South Africa
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