MULTI-LAYER PIPE AND METHOD OF ITS MAKING Russian patent published in 2007 - IPC F16L9/12 

FIELD: rigid pipes.

SUBSTANCE: multi-layer pipe comprises lining layer, sealing layer, and longitudinal layer of reinforcement and transverse layer of reinforcement arranged in series in the bulk of the wall. The reinforcement layers are made of continuous fibers submerged into a polymeric binder. The lining layer, sealing layer, and longitudinal layer of reinforcement are made of a pipe-blank. The outer side of the pipe-blank has roughness whose mean height is no less than 2.5 μm, and angle of inclination of the fibers in the longitudinal reinforcement layer to the longitudinal axis of the pipe ranges from -1.5° to +1.5°. The volumetric concentration of fibers in the longitudinal layer of reinforcement ranges from 30% to 85%. The sealing layer and lining layer are made of individual strips arranged along the axis of the pipe. The longitudinal edges of the strips of each layer are interconnected by means of adhesion and/or welding so that to provide a lap joint and two closed circuits. The number of overlaps in each circuit is no less than one, and the value of the overlap is no less than 3 mm. The transverse layer of the pipe is placed on the outer side of the pipe-blank. The volumetric concentration of fibers in the layer ranges from 30% to 85%. The adhesion layer is interposed between the rough outer surface of the pipe-blank and transverse layer of reinforce. The angle of inclination of the fibers in the transverse reinforce layer ranges from ±89.9° to ±45°. The ratio of the thickness of the longitudinal reinforcement layer to that of the transverse layer ranges from 1:5 to 5:1. The thickness of the sealing layer is at least 10 μm. The thickness of the lining layer is at least 25 μm. The method comprises producing lining and sealing layers and forming the layers of longitudinal and transverse reinforcement.

EFFECT: enhanced strength and durability of pipe.

2 cl, 12 dwg