Parameter tolerance evaluation when laser cutting in decommissioning applications

Abstract

In conventional laser cutting it is well known that in order to maintain high quality edges, low heat affected zones and high cutting speeds, high tolerances have to be maintained on many of the parameters used. In particular, nozzle stand-off distances have to be small and kept constant, if good cut quality is to be maintained in plate and tube cutting. Recently, a potential application of laser cutting has arisen in a sector where the resulting cut quality is not important; that of decommissioning. In nuclear environments all over the world, there are extensive amounts of contaminated pipework and vessels of different types, which simply need to be size reduced, so that their constituent parts can be placed in containers for long term storage. This paper addresses the capability of a 5kW fibre delivered laser beam to cut plate material, in stainless and CMn steels, up to 25mm thickness, if the requirement for good cut quality is removed. It will be shown that even when cutting 25mm thickness material, separation speeds of up to 0.15m/min can be maintained, with nozzle to workpiece stand-off distances up to 75mm. This very wide tolerance to nozzle tip position is important for potential decommissioning applications which must be performed remotely. Such tolerances provide relaxed positional accuracy on any selected deployment method of the cutting head.In conventional laser cutting it is well known that in order to maintain high quality edges, low heat affected zones and high cutting speeds, high tolerances have to be maintained on many of the parameters used. In particular, nozzle stand-off distances have to be small and kept constant, if good cut quality is to be maintained in plate and tube cutting. Recently, a potential application of laser cutting has arisen in a sector where the resulting cut quality is not important; that of decommissioning. In nuclear environments all over the world, there are extensive amounts of contaminated pipework and vessels of different types, which simply need to be size reduced, so that their constituent parts can be placed in containers for long term storage. This paper addresses the capability of a 5kW fibre delivered laser beam to cut plate material, in stainless and CMn steels, up to 25mm thickness, if the requirement for good cut quality is removed. It will be shown that even when cutting 25mm thickness material, s...