CONTRACT mining company at the Adaro mine near Tanjung in Kalimantan, PT Rahman Abdijaya, is one of two companies using the Atlas Copco DM45 rotary blasthole drill rig. Rahman has used other drills but operators say they prefer the easy operation of the DM45.

An Atlas Copco DM456 rotary blasthole drill rig in use at the Adaro coal mine in Kalimantan.
An Atlas Copco DM456 rotary blasthole drill rig in use at the Adaro coal mine in Kalimantan.

Adaro Mine produced 48 million tonnes of coal in 2012 and Rahman produced 6.5 million tonnes of that. There are three DM45 rigs working at the mine.

The coal seam sits on a slanting angle of 30 to 45 degrees and is about 7 metres thick with nine metres of overburden above it. As the overburden is pushed back from surface, the mine operates on a 7 metre-wide by 16 metre-high bench system. The coal body is mined to a depth of 10 metres and totals 146,645sqkm.

Rahman uses multiple Atlas Copco DM45 rigs in a systematic drilling operation. On average a three-rig team drills 100 to 120 metres per pattern. The current burden pattern is 6 metres by 7 metres. The tooling Rahman prefers is the Atlas Copco 77/8-inch tricone bit with aggressive conical buttons. Thirty-foot lengths of Atlas Copco 6�¼ inch OD pipe complete the drill string.

The company blasts daily at midday. Because the rock is unconsolidated and includes clays and gravels, energy disbursement in the blast is critical. Drill Foreman Rio Hartono explained the blasting method as being a 50kg and 50kg deck loading. The 8-metre hole is charged with 100kg of liquid emulsion, 50 on top and 50 on the bottom, shot in two stages.

Although the two levels are shot simultaneously - the bottom and top of the hole are separate non-electric charges - the double charge ensures good fragmentation throughout the bench.

Rudi Hartono has been a drill operator for six years and has operated four different drills rigs, including blasthole and crawler-type drills. He likes the ease and simplicity of the DM45 over all the drills he’s operated from various manufacturers.

He points out three things he says make the DM45 easier to operate than the other drills he’s run over the years:

  • First are the controls. He says the controls are hands-on simple and make it difficult to make mistakes.
  • Secondly are the connections - the act of adding and removing drill pipe. Connections are fast and simple with the DM45. “The action is quick and easy. There is no wasted effort.”
  • Finally, the safety shutout is a favourite feature for Rudi Hartono. Other blasthole drills will not lock out tramming when the pipe isn’t all the way back at its start position. He has seen occasions in which drillers will not get the drill pipe out of the hole before tramming, resulting in damage and downtime.

At Adaro mine the mining continues and with the Atlas Copco drill at the lead, it continues to be one of the world’s top coal producing sites.

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