Gearboxes ideal for wet, dry cooling towers

20th November 2020

Industrial equipment provider BMG’s electromechanical team plays an important role in the dependable operation of wet and dry cooling towers in the mining sector, through the supply and support of many power generation components, including Hansen gearboxes.

“Hansen units, which have been designed by Sumitomo Drive Technologies, in accordance with global Cooling Technology Institute (CTI) specifications, are manufactured especially for wet cooling towers (WCT) and air-cooled condensers (ACC),” says BMG’s Sumitomo national product manager Rob Green, adding that the Hansen M4 and P4 series are locally-renowned for dependable operation and extended service life in arduous conditions.

“The company is currently introducing the new M5 series to the local market for use in dry and wet cooling towers in mines throughout Africa.”

He adds that, Hansen P4 right angle vertical shaft-up units WCTs are available in 11 sizes, from Z to H and as 2 stage units in ratios of 3.55:1 to 22.4:1, with ratings up to 100 kNm.

The internal mechanically-driven pump has been specially adapted for low operating speeds and to withstand wind-milling conditions.

There is increased distance between the propeller and the high-speed input shaft to reduce vibrations and there is extended bearing span on low-speed shaft bearings. Bearings have been carefully selected to withstand high axial loads.

Green points out that the application-specific and designed Hansen gearboxes are coated with corrosion-resistant paint for added protection in wet and humid environments.

The housing has suitably machined ports to facilitate external piping that enables effective oil drainage and allows easy maintenance. 

“Owing to the importance of the regulation of the cooling tower, ACCs are subjected to frequent starts and stops of the system. Precise control of factors such as temperature and pressure, from the condenser to the boilers, is critical for the efficient functioning of this closed system,” Green says.

In addition, during starting sequences, it is crucial that the gearbox can withstand high startup torques of up to more than three times the nominal torque of the motor, or higher.

BMG’s ‘dry’ Hansen M4 compact gear units for ACCs, are known for efficient performance and long service life in arduous operating conditions. This series is available from BMG in six size units, from DA to FX, as 2 stage units in ratios from 9:1 to 25:1.

Green explains that the internal backstop is situated in the International Electrotechnical Commission or National Electrical Manufacturers Association motor size lantern housings, for effortless installation and removal. The addition of an internal cooling fan in the lantern is also possible and can assist in ensuring that the compact gearbox remains within an adequate thermal operating limit.

New to the Hansen range, is the recently launched M5CT range, which comprises right angle vertical gearboxes that have been further developed for cooling technology.

This series, with high resistance in corrosive and extreme humidity environments, has a proven design, maximum load capacity, minimum losses and quiet operation. M5CT units are also compliant with stringent CTI specifications.

“Features of these new units include a rigid housing design that can withstand peak loads, which is enhanced by cooling fins with flexible cooling options. The well-balanced design and advanced micro geometry of the gear results in an optimised pressure distribution that absorbs high shock loads,” Green says.

Further, the system offers smooth transition of high forces from the centre bore to the mounting feet, which are positioned concentric to the low-speed shaft.

For increased dynamic stability, there is an extended bearing span with heavy-duty roller bearings, specifically selected to handle the high axial thrust loads on the output shaft.

An effective sealing system designed to keep the oil in, and dirt out, significantly reduces maintenance requirements. The dedicated lubrication system does not require monitoring, Green notes.

The new M5 range has been designed for easy replacement of the existing P4 cooling tower range and to match the footprint or shaft height, without excessive installation adaptations.

BMG’s integrated engineering solutions service to the mining sector, encompass a complete electromechanical capability, which includes a customised product design, product selection, commissioning support and ongoing technical back-up, Green concludes.