DEVICE FOR PRUDENT PENETRATION OF A CASING THROUGH SENSIBLE OVERBURDEN OR SENSIBLE STRUCTURES

The present invention relates to a method and a device for driving down casings (2) through sensible overburden or sensible structures, making use of a drilling device (1) activated by compressed air that at the lower part of the drilling device (1) is led through exhaust channels (14, 142) in such a way that the major part (B) of the compressed air flow is directed upwards to be led away between the casing (2) and the drill stem together with the cuttings and a minor part (D) of the compressed air being fed to the drill bit. The characterizing feature for the invention is that the compressed air in the exhaust channels (14, 142) is controlled in order to adapt the intensity of the compressed air flow to the material that is penetrated. The compressed air (D) fed to the drill bit is led away through jet action from the major part (B) of the compressed air.