When drilling in hard rock there is no question that pneumatic Down-the Hole (DTH) hammers will outperform convention rotary drilling tools. DTH hammers have been the standard in quarry and construction when drilling 4”-24” dia holes. The question is how to deploy this technology for larger diameter shafts. This is where Center Rock’s line of LP Drills excels allowing you to drill up to 144” in solid rock with unmatched penetration rates. LP Drills can be built to any shaft diameter and for larger diameter shafts you can utilize a pilot shaft with a full face LP Drill and then a hole opener to expand the shaft to its final diameter.
However, what if your site access doesn’t allow for multiple compressors that are needed to run the larger LP Drills or the project calls for numerous different shaft diameters? This was the challenge presented to the team at Drillers’ Choice, Inc. (DCI) by a customer that needed to drill large diameter shafts in solid rock for transmission towers. The tower locations were primarily in mountainous terrain with steep access roads. Mobilizing the compressors and support equipment required for larger diameter LP Drills was not a feasible option.
DCI’s solution was to utilize one of their existing 24” LP Drills and build a template to be placed in the bottom of the shaft to keep the drill on location. The template allowed the customer to “Swiss cheese” the rock removing upwards of 95% of the rock. Then following up with conventional rotary tools to remove the remaining rock. What makes the 24” LP ideal is the performance that it can achieve with just a single 1,600 CFM @ 150PSI supplying air.
Based on the success of this first project we have now supplied templates for numerous other projects with sizes ranging from 60” – 144”.