Compressors exposed to abrasive dust, such as those used in mining environments, could become increasingly inefficient and fail, owing to internal damage caused by clogged and compromised intake filters, notes RTS Africa Engineering MD Ian Fraser.

Additionally, opencast mine dust frequently enters dragline machinery spaces and operator cabins, while the grid floors in many blast-hole drill-rigs’ grid floors allow dust to enter into the cabin, compromising machinery, which affects wear life and performance, and creates health risks.

Fraser notes that, through innovative and solutions-focused application engineering, RTS Africa spin filters are able to address these and other dust problems.

“It’s become almost standard for mining companies to use spin filtration as a means of achieving effective dust extraction from the air intake filters of compressors, and for the direct ventilation of variable-speed drives (VSDs) using back channel cooling.

“VSDs used to use expensive air-conditioning systems for cooling – expensive from a capital and operational perspective. Spin filters supply clean air directly into the VSDs, enabling them to continue operating in hot conditions . . . spin filters have become the standard application control rooms,” Fraser explains.

To this end, RTS Africa is already a preferred supplier to several of Southern Africa’s largest mining groups, with RTS spin filters frequently specified by part number.

More recently, the company installed spin filters on blasthole drill rigs at a large South African platinum mine. “The filters maintain the positive pressure inside the cabin, [which] prevents the ingress of dust very effectively,” says Fraser.

Spin filters are frequently used to keep dust out of compressors, and to cool and provide dust ingress protection for VSDs.

Spin filters consist of a module comprising a cyclone-shaped tube through which air is propelled down or drawn. On entering the tube, the air is induced to spin using fixed vanes, and particulate matter moves to the outside of the vortex, while clean air exits through the centre of the vortex through a central orifice. Dust-laden air exits through the outer circumference of the vortex, from which it is either vented back into the atmosphere or directed to a recollection system such as a drop-out box.

The spin filter can remove 98% of particulate matter that is 15 μm in size and larger, 93% of particulate matter that is 10 μm, and 80% of matter that is 5 μm.

Additionally, while it is not its core function, the spin filter can be used for occupational health and safety applications. In this case, it could act as a primary filter, in association with a secondary filter capable of eliminating particles 1 µm and smaller, thereby preventing occupational health diseases.

Journey to Date

Fraser explains that spin filters were initially only used for large air-conditioning intake systems in the US. “[But that RTS Africa] could see huge applications in industry and mining – and, as we went along, we developed more application engineered systems and, to address our clients’ toughest mining, industrial and manufacturing dust extraction challenges . . . we’ve truly made this technology our own, and we believe that we have taken it further than anyone else in the world.”

Fraser says the initial uptake of RTS Africa’s flagship product was slow, specifically because of the instability and uncertainty surrounding South Africa in the early 1990s. Fraser explains that, rather than expand capital on protecting assets, companies preferred to take a wait-and-see approach and replace equipment once it failed.

In the early 2000s, as soon as it was evident that the country had stabilised and once companies were more certain of their futures and ties to South Africa, the first mining application of spin filtration was implemented by RTS in an underground operation in Rustenburg, in the North West.

Further, Fraser points out that, while uncertainty has returned to a lesser degree, the ‘maintenance mindset’ has shifted, and companies – specifically in the mining sector – are now focused on life cycle extension, return on investment and reducing maintenance costs, which presents opportunities for other innovative applications of spin filtration.

He explains that, while the initial upfront cost is more than that of conventional air filtration, spin filters do not need to be cleaned or replaced, thereby eliminating the operational and labour costs associated with maintaining the conventional system.

“A spin filter can be installed and left alone for ten, fifteen, or even twenty years without any maintenance.”

He adds that there have been enquiries from original-equipment manufacturers regarding the use of spin filters on VSD and in control rooms in the Middle East, and northern Africa.