| 摘要 |
The tool comprises: - a jetting system arranged to impinge the object to be excavated with a jetted stream of a drilling fluid mixed with abrasive particles, the jetting system being provided with at least a mixing chamber (2) with a drilling fluid inlet (3), a second inlet (4) for abrasive particles, and an outlet nozzle for releasing the drilling fluid mixed with the abrasive particles; - a recirculation system arranged to recirculate at least some of the abrasive particles, from a return stream of the fluid mixe d with the abrasive particles downstream of the impingement surface of the jet with the object back to the jetting system, whereby the abrasive particles comprise a magnetic material, which recirculation system comprises a separat or magnet (7) for separating the abrasive particles from said return stream and for transporting the particles to the second inlet; - a piece of magnetic material (14) that is provided in or in the vicinity of the mixing chamber ( 2) such as to draw a part of the magnetic field generated by the separator magn et into the mixing chamber (2). |
