DM30 II: Redesign of the Low Pressure DM30 Hole Drill

The island of Kalimantan has approximately 70% of Indonesia’s drills operating in the coal industry, thus representing the country’s major blasthole market. Larger models used for blasthole drilling include the Atlas Copco DML and DM45 rigs. With the launch of the new DM30 II, Atlas Copco provides new option in blasthole drill rigs in the 7 ⅞-inch hole class for miners. The DM30 II is the redesign of the low-pressure DM30.

DM3011 Mid-sized rig by Atlas Copco.

Key Advantages of DM30 II

In the coal region of Kalimantan, the DM30 II has been taking on the DM45, maintaining its production and tonnage at similar properties. According to Jerry Murthi, second generation owner of Nariki Minex Sejati, the DM30 II enables the company to drill larger holes and suitably sized patterns yet much smaller holes when required, thanks to the mid-sized rig’s 7 ⅞-inch capability. Operating at about 15 mine properties, Nariki has larger drills, and many DM45 rigs, but virtually never requires a 9 inch or larger hole.

Jerry Murthi. Second generation owner of Nariki Minex Sejati drilling organisation.

Murthi also informed that the smaller drill also helps the company’s customers in planning. The company mostly drills 7-8-8 or 8-8-9 bench and pattern and the maneuverability of the DM30 II provides the capability to the company to meet the requirements of the mine engineers. The configuration of the DM30 II and the DM45 is listed in Tables 1 and 2.

Table 1. DM30 II Configuration.

Table 2. DM45 Configuration.

Role of DM30 II in Prima Sarana Gemilang (PSG) Mine in Indonesia

Although the PSG mine opened two years before, the first drill rigs were brought to the mine in recent time. Before beginning the drilling at the mine, ripping to crumble the sandstone and claystone formation is assessed. The formation has the hardness, which leads to more productive excavation with less wear on the excavation equipment during blasting. Ripping generated only 25-30% of the output of blasting and drilling per hour.

The formation ruptures well with an 8- or 9-meter burden and 9- to 10-meter spacing. Drill and Blast Supervisors Jos Bernadus Manulang and Handik Setiawan were told that they are still fine-tuning the pattern depending on the variations of the two pits in clay or sandstone rock. They are challenged with a layer of coral in Pit 1 that reduces productivity from an average 56m/h down to 40m/h. Drilling with the DM30 II yields an average of 48m/h in Pit 2.

For comparison, the nearby Buma Binungan mine reaches 63m/h in the mostly sandstone formation with its Atlas Copco DM45. Although the penetration rate is more, the associated costs are also higher with the larger drill. The DM30 II is equipped with a 29.7m³/min (1050cfm), 7.5bar (110psi) compressor, while that parent DM30 design features a 900cfm compressor and the DM45 features a 34.0m³/min (1200cfm), 7.5 bar (110psi) compressor.

At PSG, eight seams are mined, with a coral stratum encountered in Pit 1 at the third seam from the highest elevation. Drilling is typically performed during a 10-hour period each day, with round-the-clock mining operations in two shifts. With benches of 8m high in both pints, the coal sits on a 30-degree incline in seams with a thickness range of 5-30m. The coal in Pit 2 operates at 5,800kcal, while Pit 1 is at 6,000kcal. The coal in Pit 2 is lower in quality, but the seams are usually thicker and more convenient to mine.

Conclusion

In a month, PSG generates 700,000 tonnes of coal from Pit 1 and 300,000 tonnes from Pit 2, yielding a stripping ratio of 7 to 1. Mining began at an elevation of 90m over the seal level and is presently at 20m ASL. Exploration is progressing to estimate the total depth of the coal formation, with a third pit scheduled in the future. Possessing the DM30 II drill rig is advantageous to the mine as it provides more options due to its size.

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This information has been sourced, reviewed and adapted from materials provided by Atlas Copco.

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