Mining Publication: Technology News 480 - Controlled Start for Drill Motors on Roof Bolting Machines

Operators of roof bolting machines have one of the most dangerous jobs in underground mining. The main hazards include unsupported roof and movement of equipment and machine appendages in confided surroundings. Many bolter operators have been injured because their hands or gloves have been caught by rotating drill steels or bolt wrenches. A bolter operator must manually place the drill steel and wrench into the drill chunk and then hold onto it as the drill is guided to the hole placement or the wrench is raised to the bolt head. During these actions, the inadvertent actuation of the drill's rotation control can catch the operator's hand or glove, which can cause serious injury. NIOSH , Pittsburgh Research Laboratory, has developed a mechanical/hydraulic method to reduce this type of injury. Although an experienced bolter operator can sometimes 'feather' the hydraulic controls on modern bolting machines to achieve a relatively slow rotational speed, the control designs are not normally optimized for this. Inadvertent control actuation invariably results in full-on operation. The main reason for these types of incidents is that the sudden full-speed rotation of the drill catches the operator by surprise. The technique that we developed intentionally limits the rotational speed and torque of the hydraulic drill motor(s) for several seconds during startup. During this time, the operator has the chance to see that drill rotation has started and can stop the rotation or release his/her hand before injury occurs. The technology is suited for incorporation into new machine designs by the manufacturer or implementation by mines or rebuild shops on a retrofit basis.