As mining operations increasingly look to optimise energy use, Zest WEG rotating machines manager Fanie Steyn suggests a more holistic approach toward fan system efficiency in mine ventilation.

While South African fan manufacturing companies design the most efficient fan solutions worldwide and have made significant progress in optimising mine ventilation systems, motor sizing and increased efficiencies could offer the last mile in savings.

“Mine ventilation systems are critical in all underground mining operations as these dilute and remove gas, dust and heat and supply clean air. These systems also account for a large percentage of energy consumption on mines,” he tells Mining Weekly.

Fans, which were historically left to run for hours, consuming a large amount of energy, were switched on and off as needed as part of a demand-side management strategy a few years ago.

However, this was not most efficient way to conserve energy and the mines realised that more efficient fans were needed instead to conserve energy, with newly designed fans systems yielding savings in the region of 20% to 30%.

Motor efficiencies were not considered to initially form part of the system at the time as it only generated additional savings of 1% to 3%, depending on motor size, so standard off the shelf motors were kept as part of the fan design, instead of introducing higher efficiency motors, he explains.

However, even installing the most efficient motor coupled with the highest efficiency fan does not always guarantee maximum fan optimisation: there is a need to look at reducing the size of the motors.

“We believe that there is a need to consider the application and all the components as a whole system instead of separated parts, and by doing that there is an opportunity for the designers to look at different fan/motor combinations,” says Steyn.

“As electricity gets more expensive year after year, currently at just over R1 per kilowatt hour in an industrial setting, any small saving now yields a huge nett effect on the bottom line.”

The next step to extract further cost savings will be to review the optimisation of the motor fitted to the fan.

“In many instances, a standard motor with standard ratings is selected when a better option would be to size the electric motor for the process to yield maximum efficiency at the required duty point,” he says highlighting that the motors could be smaller, more efficient and sized for increased performance, ultimately contributing to the total fan system efficiency.

Smaller and lighter motors are also cheaper to produce and, with the resultant reduced frame, the relevant mounting brackets could also be much lighter.

In line with this, Zest WEG’s newly configured design of the WEG W22 Pad mount motor offers a number of advantages.

With the WEG W22 Pad mount motor, the frame size and weight of the motor can be reduced by up to 100 kg in a typical underground fan, which is an important consideration as the motor is the heaviest component inside the fan system, Steyn explains.

This could also contribute to the fan system flow rate, he says, as further restrictions are removed from the air stream as the motor frame itself is smaller.

“An important advantage of the WEG W22 Pad mount motor is its greater air over rating which ensures increased performance and avoids unnecessary oversizing of the motor,” Steyn comments, noting that with the air over ratings, the same motor could provide an additional 15% output if the minimum air speed could be maintained over the motor fins.

“The newly designed W22 Pad mount fan motors are well received in industry and could benefit both the fan manufacturers and end-users with regards to cost, robustness and energy savings.”

In addition, the motors are available from stock, which means there is no lead time wait for the order.