control system for a high pressure cutting arrangement is disclosed the cutting arrangement comprises a liquid stream and a slurry stream the slurry comprising abrasive particles suspended in a fluid the liquid stream and the slurry stream are both supplied under pressure of about 300 mpa to a cutting tool with at least a portion of the supplied pressure being converted to kinetic energy in the cutting tool to produce a combined liquid and abrasive stream at high velocity the cutting tool includes a combining chamber into which both the liquid and slurry streams are introduced the pressure in an entry region of the combining chamber being determined by the pressure of the liquid stream the control system acts to actuate or prevent flow of slurry in the slurry stream by activation or de activation of an energising means up stream of the chamber pressure in the slurry stream is substantially equal to the pressure in the entry region of the combining chamber whether or not slurry is flowing application_number US 67426308 A description fig4 shows a schematic arrangement of a high pressure cutting system 100 the cutting system 100 has a cutting tool 110 to which is attached two input lines a fluid or water flow stream 112 and a slurry flow stream 114 each of the water flow stream 112 and the slurry flow stream 114 are supplied to the cutting tool 110 under pressure pressure is applied to the water flow stream 112 by a first energising means being a constant pressure pump 116 in this embodiment the constant pressure pump 116 is an intensifier type pump the constant pressure pump 116 ensures that pressure in the water flow stream 112 is maintained at a constant desired pressure.