| 摘要 |
A conduit (3) Can be cleaned by directing jets (10-14, 25) of abrasive mixture from a pressurized supply at its internal wall from a plurality of nozzles (7, 13, 16) which have no tangential component about the conduit axis. Nozzles preferably includes two types, one type (7) which is inclined in one direction to the axis and another type (13) which is inclined in the opposite direction to the axis. When the conduit (3) has an open end, the nozzles (7) directed away from that end are preferably closer to the end than those (13) directed towards it. The density of abrasive mixture supplied by the different types of nozzles is arranged to be different by swirling the mixture and supplying different types of nozzles from different radii in the swirl output chamber (6).
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