METHOD FOR APPLYING THERMOPLASTIC COATINGS TO THE INTERNAL SURFACE OF METALLIC PIPES AND APPARATUS FOR CARRYING OUT SAID METHOD

摘要

The inventions relate to machine building technology, in particular to applying coatings made of thermoplastic materials to the internal surfaces of metallic pipes. The apparatus for applying a coating consists of an extruder with a universal head mounted thereon, the universal head consisting of a thermoplast supply channel, a distributing head and a nozzle which forms the coating surface. The thermoplast supply channel comprises a shaft with an axial opening, along which the heated thermoplast is supplied, and has tubular electric heaters placed into grooves bored out along the shaft generatrix. The distributing head has an opening passing into four channels along which the heated thermoplast is supplied. The nozzle is connected to the distributing head in the form of a metallic cylinder, into the cavity of which cooling liquid is supplied. The method for applying the coating comprises operations to clean and degrease the internal surface of the pipe, and, prior to the beginning of supplying the thermoplast, the supply channel is heated with the aid of the tubular electric heaters, and cooling liquid for cooling the nozzle walls is supplied under pressure into the nozzle cavity. When supplied, the thermoplast, having transferred into a viscous-flow state, passes under pressure along the supply channel into the distributing head and then along the channels. The invention ensures a reduction in the material consumption and labour intensity for applying thermoplastic coatings, an increase in the coating manufacturing accuracy and in the strength of the connection of the coating to the metallic surface.