The biggest combined force driving the adoption of hydropower equip-ment in the underground mining industry – specifically in gold and platinum mines – is the need to move away from using compressed air and an understanding by industry that it must do so, hydropower specialist Hydro Power Equipment (HPE) innovation manager Peter Fraser tells Mining Weekly.
He says using hydropower has several benefits, compared with using compressed-air equipment, in the underground mining environment.
“Hydropower equipment is energy efficient because of the intrinsic efficiency of the posi-tive displacement of water hydraulics and the absence of leaks. It also has lower operating costs, as localised hydropower systems feeding a local network of small bore pipes on a half-level stope are noted as the lowest cost method to power all the operations required for conventional mining,” Fraser says.
Hydropower drilling has higher penetration rates than compressed air drilling, which allows for a quicker task and, subsequently, a reduction in the risk of a lost blast and of unnecessary exposure time of drill operators on the face.
“Compliance with noise and other environ-mental requirements is yet another driving factor behind the adoption of hydropower in the platinum and gold mining industry,” he notes.
Fraser adds that hydropowered drilling rigs have achieved mainstream acceptance in man-free box-hole development and in flat-end development and hydro stoping, which uses either centralised or localised hydrosystems.
Other applications for hydropower in underground platinum mines include the establishment of hydropowered box-hole chutes, roof bolting and stope cleaning.
Hydropower benefits large- and small-scale mining operations, he notes.
The technology enables small mines to move steadily away from using inefficient compressed air. “For example, a new section in the mine could be developed as a stand-alone localised hydropower operation, while the compressed-air operation can be main-tained for the existing operation,” Fraser explains.
Meanwhile, the implementation of hydro- power at a mainly compressed-air operation means that mines could cherry-pick hydro-power solutions most suited to their needs while maintaining the compressed air equipment.
The modular approach of the hydropower equipment allows it to be applied to most conventional narrow-stope South African mines and is especially well suited to deep and hot mines as the water provides cooling and power to the point of use.
Fraser notes that, without hydropower, it would, therefore, be difficult to mine in challenging conditions, owing to the high virgin rock temperatures associated with the depths at which platinum miners, such as Northam Platinum, are currently mining.
In deep mines, ventilation is also limited, owing to the small size of the tunnels, which are typically 3.2 m wide and 3.5 m high, and hydropower provides cooling in addition to that which can be transported by ventilation.
Further, unlike diesel-powered equipment, hydropower pollutes neither the air, nor the ore in underground mines and it does not reduce recovery in the plant, as the spilling of hydraulic oil is eliminated.
Fraser points out that, when originally conceived, hydropower was seen as a centralised service, delivering cooling and power for mining operations in a mine-wide reticulation system, where the pressure was generated by the hydrostatic head available from the depth of the mine.
However, the development of hydropower over the last 12 years has mainly been driven by low air pressures at the extremities of existing mines and safety concerns about hand-held development giving rise to pumped systems, specifically in micro systems con- sisting of a flat-end rig with a loader, or in localised systems powering a half-level stoping operation.
Fraser says that over 100 flat-end develop-ment systems are in operation and are sup-ported with HPE’s maintenance contracts.
New Developments
Rapid and safe development of box holes has been made possible by the fast, accurate and straight drilling achieved with water-powered drilling systems manufacturer Wassara’s in-the-hole hammers mounted on the HPE long-hole rig.
Other developments at HPE include the development of reef boring and long-hole stoping mining methods and equipment.
The advantage of these developments is a reduction in ore dilution and in support needs. They also aim to improve safety, as no persons are required to enter the stopes.
These mining methods have been used for ore passes and vent raises and to create media holes for drains, cables and pipes.
Meanwhile, HPE received an order for ten high-pressure valve stations in July, to be installed at JSE-listed Anglo American Platinum’s Dishaba mine, situated between the towns of Northam and Thabazimbi, in Limpopo.
The mine is situated on the north-western limb of the Bushveld Complex and comprises one vertical shaft, one raise bore and four decline shafts.
Dishaba mines on the Merensky and the Upper Group 2 reef horizons. The operating depth for the current workings is between 130 m and 1 250 m below surface.
The valve stations reduce the pressure of the incoming water to the 12 bars of pressure required for mine service water.