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Pumpable emulsions (INNOVEX UG) – making underground blasting safer

Mining at great depths - the standard for South African mines - places inherent safety risks on miners who have to cope with arduous working conditions and narrow reef stopes whilst handling explosives. But, says BME, the increasing acceptance of pumpable emulsions in the deep mining environment, is literally showing ‘light at the end of the tunnel’.

BME

The major safety benefit of this new technology, says Selwyn Pearton, Research and Development Manager of BME, is that under the current explosives regulations, approved by the Department of Mineral Resources and incorporated into the Mine Health and Safety Act, pumpable emulsions are not classified as explosives until they are sensitised at the underground workplace.

The reprieve from class 1.1 explosive regulations marks a new era in the onerous storage, transport and control of explosives. The major benefits are safety, productivity and operational profitability – all derived from the fact that, until the charging process is undertaken at a face, that the emulsion is officially classified as a class 5.1 oxidiser.

As with many other developments in the mining industry, pumpable emulsions have undergone several transitions to meet the demands of present-day mining. At the top of the BME pumpable emulsion development list, says Pearton, was always safety. Ease of use ran a close second and saw BME introducing several innovations into their emulsion product.  

“The major benefits of pumpable emulsions begin on surface where handling, logistics and storage are simplified as a result of the 5.1 oxidiser classification. Unlike cartridges, which are pre-sensitised explosives, emulsions are not pre-sensitised and do not require storage in dedicated magazine facilities,” says Pearton.

Moving the emulsion safely through the shaft provides a second benefit. “Pumpable emulsions can be moved down vertical shafts at will without the shaft having to be closed to men and materials during shaft head deliveries. Movement of men and equipment continues uninterrupted producing immediate operational savings and aiding profitability.

“It is underground that they come into their own. The emulsion can either be moved underground in bulk and stored awaiting use - where they are impervious to environmental conditions such as high-moisture levels - or simply carried to the workface daily by miners within ‘backpacks’ weighing just 20 kilograms.

“Without the new Portable charging unit developed for use with BMEs range of Megapump emulsions, the emulsion cannot be sensitised to form an explosive and cannot be detonated. Ease of operation is assisted by the fail-safe controls and vast reductions in the size and weight of charging unit.

BME believe that the transition of pumpable emulsion explosives from the open-cast environment into underground operations and particularly those with confined, narrow stope environments was part of a natural progression brought about by demands for a new approach to safe, deep level mining in South Africa.

The ultimate advantage of the new technology lies in the fact that specific quantities of product can be delivered through smaller pumps in extremely cramped conditions.

“With miners being able to individually carry individual pumping units into a stope, operational flexibility has become greatly enhanced. BME’s Megapump emulsion packed in individual rucksacks weighing approximately 20 kilograms can be used to charge the panel whilst sensitiser - the key to the system - is added from its own container controlled by the responsible person,” notes Pearton.

Turning to the other advantages of pumpable emulsions against ‘traditional’ explosives, Pearton says these include:

  • The portable pump weighs just 14kg and can be moved and operated in confined spaces with ease, whilst emulsion and sensitiser are transported separately. Emulsion and sensitiser containers are connected to the pump through specially designed couplers designed to prevent the ingress of grit and rock particles into the pump, thereby increasing the robustness and reliability of the pump.
  • Pumpable emulsion has a higher velocity of detonation than Anfo. Fragmentation is improved and damage to side walls and hanging walls is reduced.
  • Complete coupling of emulsion within the blasthole result in an increased concentration of explosive energy at the base of the blasthole as well as an increase in the efficiency of shock wave transmission into the rock mass. These characteristics contribute to an improvement in the advance achieved.
  • Over-break is significantly reduced. With emulsion explosives, less over-break means that secondary costs involved in transport of rock through the shaft system and beneficiation process are reduced.
  • Without the sensitising agent, the emulsion and pump are unusable. Control is therefore simplified as a single container of sensitising agent weighing 2 kilograms is sufficient to charge a complete panel. This sensitiser container is the responsibility of the responsible person thereby providing a means for the control of the system.
  • Anfo is not water resistant. In the event of seepage in a wet mine, Anfo dissolves and bad blasts will result together with damage to the environment.
  • Emulsions are suitable for use in wet holes as they are able to displace the water when charged into a wet hole.

“There is no doubt, that pumpable emulsion systems are presently at the forefront of safe and cost effective blasting technology throughout the mining industry,’ Pearton concludes.