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. The company says the design is specific to this demanding application.

The unit comprises a gearbox and long output shaft that attaches to a fan via a hub and has a thicker, more rigid cast iron housing than a standard gearbox. 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.

Noise levels are also a factor in this application, and the quiet MACC units ensure that they do not exceed maximum limits. 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. The company also offers a low noise axial cooling fan as an option, for enhanced thermal improvements.

Other features include a 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. The assembly of these MACC units can be done locally in the company’s new and expanded facility at Aeroton in Gauteng, and an enlarged stockholding of components reduces lead times significantly.