WATERJET USE IN DECONTAMINATING SURFACES

摘要

Decontamination of surfaces with complex geometry requires that all the surfaces arerncontacted and cleaned. Not only must each point be reached, but the cleaning mechanism mustrnhave sufficient energy to dislodge and remove the contaminating material.rnThe most common method for removing dirt and a number of chemicals is through thernuse of fan shaped waterjet nozzles operated in much the same way as those found in arnconventional car wash. However the structures of many of these jets forming nozzles is poor,rnand they rapidly erode under use. As a result the jets which are produced rapidly disintegraterninto a mist of fine droplets which rapidly decelerate and become ineffective. Common stand-offrndistances for such nozzles are in the range from 15 to 30 cm, for example and yet many nozzlesrnwhich have been tested do not produce an effective jet stream beyond around 10 cm. Typicalrnresults from a comparative test program are included, along with a simple method for evaluatingrnnozzle performance.rnRapidly rotating round jet streams, inclined outwards so that they cover a conic pathrnprovide a more coherent structure, which carries a greater level of energy down onto the targetrnsurface over a much greater stand-off distance. However there is a trend to use higher andrnhigher pressures, with concomitantly smaller jet diameters, in order to conserve power and waterrnuse. This can result in a decrease in the range of the cleaning tool, which may not be evident tornthe untrained operator, given the structure of the jet stream and plume. Relatively effectivernoperating ranges are discussed and the benefits of different regimes in different circumstancesrnare reviewed.