A revolution in deep level mining

How does the deep level mining industry meet the daunting challenges of greater productivity through faster face advancement whilst reducing energy consumption and minimising damage to the environment? It engages with Peterstow Aquapower.

From its factory in Swaziland, Peterstow Aquapower has developed a

closed-loop water hydraulic drilling system which penetrates rock faster than traditional pneumatic and hydraulic systems, uses substantially less energy and reduces the environmental impact of deep level mining operations.

The Peterstow rock drill is driven by an electric power pack which continually circulates a contained volume of ordinary tap water from a reservoir tank to the drill. Connected by two hoses, the drill and power pack can be positioned up to 130 metres from each other without any loss of performance. The water is pressurised inside the drill and this provides the power to turn the drill steel.

Apart from the electrical supply for the power pack and the water for the reservoir tank and flushing cuttings from the blast hole, the Peterstow system needs no other energy source.

This enables mines to power their rock drills without relying on the expensive and inefficient process of compressing air. Compressed air is conservatively estimated to account for more than 20% of a mine’s total energy consumption so eliminating it from the drilling element of its operations, results in substantially reduced energy demand and lower overall operating costs.

The closed-loop design consumes approximately 60% less water than existing water hydraulic systems and ensures a more efficient transfer of power to the drill. Unlike open-loop water hydraulic drills, the water is contained within the system and does not escape onto the stope floor,

This means that the high pressure water piping normally required to pump the water supply underground and remove the waste back to the surface for re-processing can be vastly reduced. Infrastructure of this type not only carries a high capital cost but it is expensive to maintain and also consumes large amounts of energy.

The power required for the pumping of water and the compression of air can account for up to 40% of a typical mine’s electricity usage. Installing Peterstow Aquapower’s drilling system therefore enables mines not only to meet their targets for reducing energy consumption but may be essential to maintaining full operations and bringing into production previously uneconomic ore bodies.

In recent extensive underground production trials in South Africa, Peterstow demonstrated drilling speeds double that of pneumatic drills and up to four times faster where the compressed air pressure was low.These faster penetration rates enable miners to complete a drill cycle in substantially less time and ensure a rock blast every day. Penetration rates of one metre per minute in UG2 and 670mm per minute in 500 MPA hard rock were achieved. Fewer lost blasts and faster face advance helps to increase overall productivity and extend the life of a mine.

A faster drilling cycle should result in less time spent by operators at the working face and reduce exposure to potentially dangerous conditions.

Peterstow’s drills also improve health and safety conditions for rock drill operators in a number of other ways. The water powered drills create no oil mist and minimal air borne dust, they eliminate the risk of injury from damaged air hoses and reduce the electric shock hazard. Peterstow Aquapower drills also comply with industry standards for noise reduction targets.

The Peterstow rock drill is designed to drill holes between 32mm and 38mm in diameter and normally between 1.0 metre and 3.5 metres deep. It has been primarily used in narrow reef stoping conditions but has also been successfully used to drill roof bolting holes up to 4.0 metres deep.

The system uses a 15 kW power pack which holds a reservoir tank of 35 litres. The water flows through the system at 47 litres per minute at a pressure of 110 bar.

Replacing 1000 rock drills with the Peterstow Aquapower water hydraulic solution would save 20 million tonnes of water a year, can reduce capital costs by up to $21,000,000 and drill up to four times faster than many existing technologies; something that can not and should not be ignored as energy utilisation, productivity requirements and environmental pressures demand bringing the mining industry into the 21st Century.