WELDED JOINT OF PIPES WITH INTERNAL COATS AND METHOD OF CONNECTING PIPES WITH INTERNAL COATS Russian patent published in 1999 - IPC

FIELD: welding technology; method of welding pipes with internal coats, for example, with layer of enamel; oil, gas chemical and other industries. SUBSTANCE: welded joint includes two pipes whose ends are connected by means of weld seam including root weld welded in built-up layer of corrosion-resistant alloy at end sections of pipes and filling weld made in pipe. Inner surfaces of pipe ends at area of surfacing is made in form of bell mouth and ends of built-up layer have circular bore changing to termination of pipe edges. Method of connecting the pipes with internal coats consists in application of layer of corrosion-resistant alloy inside end sections of pipes followed by machining of built-up layer and preparation of edges for welding application of coat, for example, enamel, assembly for welding and welding of pipes. Prior to welding corrosion-resistant alloy, inner surface of pipe end is machined for bell mouth and in preparing the edges for welding, circular bore is made which changes to end of built-up layer; welding of end sections is performed in two stages: first root weld is filled with electrode whose composition is similar to that of built-up layer and then filling seam is filled. EFFECT: improved quality of joint of not only enameled tubes but also tubes having other anti-corrosive coats, for example, polyethylene, epoxy paints and other polymers. 3 cl, 2 dwg