Coal Age

OCT 2015

Coal Age Magazine - For more than 100 years, Coal Age has been the magazine that readers can trust for guidance and insight on this important industry.

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Page 20 of 51

The project was made more complicat- ed than a typical raise by its size. The rebar- reinforced foundation for the drill was a massive 32-ft-deep concrete box built by Cowin & Co. at the surface that required the removal of 2,500 cubic yards of material pri- or to building the platform. The drill strad- dled an open box's 1-ft-thick concrete liner, which was drilled out when the raise bore's head reached the surface. Drill operator James Bass said there is more power behind the 123RH C compared to other units he has used in the past. "I can feel more power and better control. And when I make a correction, there's almost an anticipation of my actions. I can feel the changes in the formation as it happens and change the drilling parameters smoothly and as necessary." The formation's high angle fractures with varying changes throughout the for- mation made it difficult to ream. "Because the head is so wide, I could be pulling though hard and soft formations at the same time," Bass said. "Pulling slowly through it, though, I can feel the torque change. The rpm and force show constantly on the control panel, and I hear and feel what needs to be adjusted more than I see it." Average drilling parameters put 2.5 rpm of head rotation at the pipe. The aver- age thrust was from 350,000 to 700,000 lb, with torque at or below 350 klbf. The sys- tem operates off two hydraulic systems, with RCS-based monitoring, for high machine availability. An external loop cooling system main- tains optimum drive and thrust system temperature. The drill runs on a 480-volt drive pack and a 700-hp hydraulic motor turning the drill string. Drilling operator Eric Todich agreed with Bass's assessment of the controls, and said, "The reaction with the 123RH C raise drill is quicker, yet it takes time to adjust after the command. This is almost a safety factor." He said the control allows for adjustments in the formation as need- ed, so there isn't damage to the drill or drill string. The machine's anti-jamming feature also prevents damage. When rotation pressure moves into the red range on the r a i s e b o r i n g c o n t i n u e d Rick Sidwell, general manager of Raisebor, a division of Cowin & Co. Inc. October 2015 19

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