PIPE COATING METHOD

摘要

1414059 Forming protective coatings by winding HIELEMA EMMONS PIPE COATING Ltd 19 July 1973 [31 July 1972] 34378/73 Heading B8G [Also in Division F2] A method of forming a protective coating consisting of a thermoplastic resin and a resin compatible adhesive on an object having an elongated circular surface, e.g. a steel pipe 10, includes the steps of rotating the pipe 10 about its longitudinal axis whilst simultaneously advancing the pipe 10 longitudinally, extruding a sheet 22 of the adhesive on to the surface 12 of the pipe 10, thus forming helical windings 24 of the -adhesive on the pipe 10 and extruding a sheet 34 of the resin on to the adhesive covered pipe in sufficiently close proximity of time to the first extruding step to assure bonding of the helical windings 36 of the resin to the adhesive. The rates of rotation and longitudinal advancement of the pipe 10 are chosen such that (a) the distance advanced by the pipe 10 per revolution is no greater than one-half the width of the narrowest sheet, thus ensuring that at least two plies of each sheet is wound on to the pipe and (b) the speed of the surface of the pipe 10 due to its rotation is at least equal to and not more than 5% faster than the speed at which the resin sheet 34 is extruded. The extruders 20 and 32 are also positioned such that the lengths of the sheets 22, 34 before they contact the pipe are less than their widths. The pipe 10 is cleaned at a cleaning station 14 before the coatings are applied, the pipe 10 being at the temperature of the ambient air when the adhesive layer is applied. After coating the pipe 10 passes a cooling station 40. As described, the adhesive consists of a synthetic rubber composition and forms a two-ply layer 26 (Fig. 3), on the pipe 10 and the resin may be polyethylene, polyvinyl chloride or acrylonitrile-butadiene-styrene copolymer and forms a three-ply layer 38.