THERMALLY INSULATED TUBING Russian patent published in 2013 - IPC F16L57/00 E21B17/00 

FIELD: oil and gas industry.

SUBSTANCE: method involves application of silicate enamel coating to internal surface of internal pipe, and multi-layer screen heat insulation made on its external surface. Sorbent is used as gas absorber between layers of heat insulation. Cutting of cone-buttress thread is made on ends of external pipe. Internal pipe is arranged inside external pipe on centralisers. Sealing of inter-tube space by means of welding in vacuum using tight welds on the side of pipe ends, as well as creation of vacuum of 10^-8 10^-10 mm Hg in inter-tube space is provided. Sealing ring is arranged at the joint between thermally insulated pipes at their clutch coupling. Before enamel coating is applied to internal surface of internal pipe, its ends are upset outwards. Then, it is subject to cleaning by burning and shot-blasting action. Both external and internal surfaces of external pipe are subject to shot-blasting action. Prior to vacuum treatment, the internal pipe is heated from inside up to 300°C with an electric heater of tubular air heater type (TAH) by its being arranged inside the pipe throughout its length, after preliminary plugging of inter-tube space by means of welding on the side of one of its ends. At that, the temperature of external pipe shall be constantly monitored. If its temperature exceeds 24°C, the thermally insulated pipe is rejected. After vacuum treatment of inter-tube space, heat-insulating bushings are installed with pre-load into the outward upset ends. As sealing ring there used is ring of self-sealing type from elastic material. At that, heating of internal pipe is performed by means of TAH by arranging the latter inside the pipe throughout its length. Polypropylene or heat-resistant rubber is used as material for thermally insulating bushing and sealing ring. Application of silicate enamel coating is performed at least in two layers and two stages; at that, application of the second layer is performed after the pipe is cooled down to the room temperature.

EFFECT: improvement of the method.

9 cl, 3 dwg