Abstract: Apparatus for generating an abrasive fluid jet comprises a feeding device (2) for continuously passing abrasive particles at a constant rate to a mixing hopper (4) in which the abrasive particles are mixed with a carrier liquid to produce a slurry of consistent concentration. A pump (10) pumps the slurry from the mixing hopper (4) to a jetting head (12) into which a high speed fluid jet is introduced in a direction substantially axially, whereby the abrasive particles are entrained in the fluid jet and ejected from the head (12) at high speed to impinge upon an object to be abrasively treated.

Abstract: A carrier fluid with entrained particulate solid material (14), for abrasive purposes, is fed through an inlet (12) in a housing (3) so as to follow a spiral path, thereby preventing the particulate solid material (14) from settling under the influence of gravity. The housing (3) defines a transfer space (5) which is bounded, in part, by a first end (18) and a second end (20) of the housing (3). The fluid with the entrained particulate solid material (14) is deflected inwardly by the inner surfaces (15 and 16) of the first and second ends (18 and 20) of the housing (3) into a liquid jet (11) issuing from a jetting nozzle (9) in the first end (18) of the housing (3). The particulate solid material (14) is thereby entrained in the outer layer of the jet (11) issuing from an outlet aperture (8) in the second end (20) of the housing ( 3), thus enabling the jet (11) to be used for cutting or cleaning purposes.