ÖNORM EN 791

The general term Drill Rig Covers several differing types of machines for use in the construction industry, water well drilling industry, mining and quarrying, for use above ground as well as underground and for tunnel construction. The differing tasks determine the choice of drilling method and type of machine. For this reason there are many possible ways to separate drill rigs into different groups. e.g. in accordance with: the task; the drilling method used; the cutting removal method; - the type of construction work. The methods used for drilling can be basically differentiated in percussive and rotary drilling principles. Percussive drilling is a method by which the hole is produced by crushing the ground or rock at the bottom of the drill-hole by stricking it with the drilling tool and removing the cuttings out of the borehole . Rotary drilling is a method in which the drilling tool at the bottom of the borehole is rotated and at the same time, a feed force is applied by a foad system or drill collar. The ground or rock at the bottom of the borehole is crushed or cut by pressure, shear or tensile stress produced by the different drilling tools. The cuttings are periodically or continously removed out of the bore hole. Rotary percussive drilling is performed by a piston striking directly on the bit (down the hole hammer drills) or by percussive energy transmitted via a drill string to the bit. The piston is powered by either hydraulic fluid or compressed air. At the same time the drill bit is rotated either continuously or intermittently.