Generation of abrasive liquid jets

Abstract

A method of generating an abrasive liquid jet comprising a high pressure liquid jet and abrasive particles for performing working operations such as cutting and cleaning. The method involves the delivery of the abrasive particles to the high pressure liquid in a dense phase slurry. The dense phase slurry is in the form of a paste which can be delivered along a supply line. Typically, the dense phase slurry comprises a mixture of an abrasive material, water and a thickening agent. The liquid jet and the abrasive slurry are brought together in a nozzle assembly ( 10 ). The nozzle assembly ( 10 ) has a body ( 11 ) defining a chamber ( 17 ). The liquid is introduced under pressure into the chamber ( 17 ) as a liquid jet through a delivery nozzle ( 13 ). The dense phase abrasive slurry containing the abrasive particles is introduced into the chamber ( 17 ) through supply openings ( 23 ). An outlet ( 19 ) is provided from the chamber ( 17 ) through which of the liquid and abrasive slurry can issue as an abrasive liquid jet.

The claims defining the invention are as follows:  
     
         1 . A method of generating an abrasive liquid jet comprising a high pressure liquid jet and abrasive particles, characterised in that the abrasive particles are delivered for interaction with the high pressure liquid in a dense phase slurry.  
     
     
         2 . A method according to  claim 1  wherein the dense phase slurry is in the form of a paste which can be delivered along a supply line.  
     
     
         3 . A method according to  claim 1  or  2  wherein the dense phase slurry comprises a mixture of an abrasive material, water and a thickening agent.  
     
     
         4 . A method according to  claim 1 ,  2  or  3  wherein the dense phase slurry interacts with the high pressure liquid jet in an interaction chamber.  
     
     
         5 . A method according to  claim 4  wherein the interaction chamber is defined within a nozzle assembly.  
     
     
         6 . A method according to  claim 4  or  5  wherein the dense phase abrasive slurry is drawn into the interaction chamber by the Venturi effect induced by the water jet.  
     
     
         7 . A method according to  claim 6  wherein the abrasive slurry is delivered to the interaction chamber at ambient pressure.  
     
     
         8 . A method according to  claim 6  or  7  wherein the liquid is delivered to the interaction chamber at a pressure from about 50,000 kPa up to 600,000 kPa.  
     
     
         9 . A method according to  claim 4  or  5  wherein the dense phase slurry is delivered into the interaction chamber under pressure.  
     
     
         10 . A method according to  claim 9  wherein the dense phase slurry is introduced into the interaction chamber at about the same pressure as the liquid jet.  
     
     
         11 . A method according to  claim 10  wherein the delivery pressure of the slurry and liquid jet is in the range of about 500 to 2500 bar.  
     
     
         12 . A method according to any one of the preceding claims wherein the dense phase abrasive slurry includes between about 10% to 95% abrasive material by mass.  
     
     
         13 . A method according to any one of the preceding claims wherein the liquid is water.  
     
     
         14 . A method according to any one of the preceding claims wherein the abrasive slurry includes between about 0.04% to 5% of thickening agent by mass.  
     
     
         15 . A method according to any one of the preceding claims wherein the thickening agent comprises a material capable of becoming highly hydrated in solution.  
     
     
         16 . A method according to  claim 15  wherein the thickening agent is selected from a group comprising attapulgite clay, sepiolite clay, sodium bentonite, sodium silicate, water glass, carboxy methyl cellulose, hydroxy ethyl cellulose, sodium carboxy methyl cellulose, polyethylene oxide, polyacrylamides, and the long carbohydrate chains such as gums, starches and cellulose chains.  
     
     
         17 . A method according to any one of the preceding claims wherein the abrasive material is selected from a group comprising silicon carbide, aluminium oxide, garnet, silica sand, metallic slag, glass beads and iron.  
     
     
         18 . A method according to any one of  claims 4  to  17  wherein the dense phase abrasive slurry is introduced into the interaction chamber to surround or otherwise be sidewardly of the liquid jet.  
     
     
         19 . A method according to any one of  claims 4  to  17  wherein the liquid jet is introduced into the interaction chamber to surround or otherwise be sidewardly of the abrasive slurry.  
     
     
         20 . A method of operating a high pressure liquid nozzle assembly having an interaction chamber, the method including supplying a dense phase abrasive slurry to the chamber, the abrasive slurry comprising a mixture of an abrasive material, water and a thickening agent.  
     
     
         21 . A nozzle assembly for generating a high pressure abrasive liquid jet by a method according to any one of  claims 1  to  19 .  
     
     
         22 . A nozzle assembly comprising a body defining an interaction chamber, liquid introduction means for introducing a liquid under pressure into the chamber as a liquid jet, slurry introduction means for introducing a dense phase abrasive slurry into the chamber, and an outlet from the chamber through which a mixture of the liquid and abrasive slurry can issue as an abrasive liquid jet.  
     
     
         23 . A nozzle assembly according to  claim 22  wherein the dense phase abrasive slurry is introduced into the chamber to surround or otherwise be sidewardly of the liquid jet.  
     
     
         24 . A nozzle assembly according to  claim 23  wherein the liquid introduction means is axially aligned with the outlet of the chamber.  
     
     
         25 . A nozzle assembly according to  claim 22  wherein the liquid jet slurry is introduced into the chamber to surround or otherwise be sidewardly of the dense phase abrasive slurry.  
     
     
         26 . A nozzle assembly according to  claim 25  wherein the abrasive slurry introduction means is axially aligned with the outlet of the chamber.  
     
     
         27 . A method of generating an abrasive liquid jet substantially as herein described.  
     
     
         28 . A nozzle assembly substantially as herein described with reference to the accompanying drawings.