Characterization of Water Jets for Safe Removal of Explosive Fillings

This paper reports the characterisation of water jets to be used for washing out the filling of explosive ordnance. Water jets have advantages over conventional techniques in that they are non-polluting and can effectively disperse all compositions; pressed, cast, plastic and PBX. The water jets studied are produced by a gas gun consisting of a parallel barrel and a detachable tapered nozzle. Four nozzle designs were tested with exit-diameters ranging from 27 mm to 16 mm. A plastic piston regulates the volume of the water charge. For various combinations of water volume, breech pressure and nozzle diameter, high speed cine photography and flash radiography was used to characterise the water jets in terms of velocity and coherence. Water jets were achieved with jet-tip velocities between 100 and 600 m/s and breech pressures in the range of 30-100 MPa. The water jets have been fired at plastic explosive compositions and dispersed the explosive with little chance of initiating a reaction, even when heavily confined. The water jet is capable of penetrating moderate thicknesses of sheet metal so could be used where the explosive filling is directly accessible or thinly covered eg. fuse-well. Continuous water jets with similar characteristics could be used for demolition of unfused ordnance, eg. depot demolition, or following an EOD operation where the fuse(s) has been removed by some other technique. 1