AEL Mining Services, a pioneer and leader in development and manufacturing of electronic detonators, recently completed a successful trial blast using the DigitShot Plus electronic initiating system at Optimum coal mine, situated some 40 km east of Middelburg in the Mpumalanga Province. The Digishot Plus system is the latest technology electronic delay detonator available today. The current Smartdet system in use at the mine has certain limitations which were addressed in the development of the new system. With the current system, logging cannot commence until after the Mobile Manufacturing Units (MMU) have left the bench (to prevent damage to the surface harness wire). With the new Digishot Plus system, logging of the holes can start while the MMUs are still busy charging resulting in less downtime for the earth moving equipment such as loaders and draglines.
On 6 May 2010, a trial block on the Kwagga section, consisting of 345 holes with an average depth of 36 m, was allocated to AEL for a trial blast. Johan Duvenhage, AEL’s Regional Manager, Eastern Operations, of Coal Southern Africa, commented, “This block was broken down into decks presenting some challenges. AEL charged it up with its new E-Series MMUs, which are manufactured locally for South African mining conditions. These MMUs have an efficient charge speed of explosives down the hole and have the capacity to carry a 20 t payload on mine.
“We initiated the blast on 22nd May 2010 using the DigiShot Plus system. Through this system, we tagged and assigned locations to each detonator at any time during the charging process, allowing miners to log the entire blast pattern before the MMUs left the bench. However, due to mining regulations, the MMUs were forced to only pump up to a certain distance from the drill rig before they had to stop. Despite the challenge posed by these regulations, the MMUs managed to pump an average of 80 t per MMU per day on site.”
The AEL DigiShot Plus system is designed to set a blast off remotely, meaning that the blast can be set off in a range of 3.5 km with direct line of site. The mine was impressed with the new electronic system and realises the benefits in terms of risk and connecting time reduction. By setting off the blasts remotely, it has a much clearer view of the area being blasted, thus an additional safety measure. The mine is also able to clear the area without the risk of damaging any connecting wires from the Bench box to the blasting area which in turn also provides cost saving opportunities to the customer.
The timing of the block can also be uploaded onto the Bench box beforehand, thereby saving even more time. By following this process, there is no risk of damage to the harness wire and the miner is in full control of the blast pattern. During the blast, time on the bench was significantly reduced, resulting in an efficiency improvement of the blasting process as well as the related earth moving equipment.
From a post blast analysis done a significant improvement in fragmentation uniformity and size distribution was noted. Contributing factors to the improved results was the combination of the AEL Mining Services SD135E bulk formulation and the Digishot Plus electronic detonator system.
“This was the largest blast ever done with the DigiShot Plus system to date. Negotiations are currently under way between mine personnel and AEL Mining Services to discuss a service offering on how we believe we could further contribute to the operation, with clear and proved benefits to the customer,” concluded Duvenhage.