The proposed utility model relates to production tubing, and more particularly to tubing that is suitable for a whole range of operations related to the oil industry, geological prospecting and drilling. A bimetallic production tubing comprises a main outer pipe made of carbon steel and, immediately adjacent same, a thin-walled inner pipe made of stainless steel. The thin-walled inner pipe is fitted inside the outer tube by plastic deformation of the thin-walled inner pipe such as to lie in complete and direct contact with the inner surface of the main outer pipe. The technical result of the claimed utility model is that of simplifying the structure of a production tubing, while at the same time increasing the durability thereof.

The proposed utility model relates to production tubing, and more particularly to tubing that is suitable for a whole range of operations related to the oil industry, geological prospecting and drilling. A bimetallic production tubing comprises a main outer pipe made of carbon steel and, immediately adjacent same, a thin-walled inner pipe made of stainless steel. The thin-walled inner pipe is fitted inside the outer tube by plastic deformation of the thin-walled inner pipe such as to lie in complete and direct contact with the inner surface of the main outer pipe. The technical result of the claimed utility model is that of simplifying the structure of a production tubing, while at the same time increasing the durability thereof.

One aspect of the invention provides a composite tube including: an inner plastic tube; an aluminum layer circumferentially surrounding the inner plastic tube; and an outer plastic layer circumferentially surrounding the aluminum layer. The aluminum layer is an alloy selected from the group consisting of: AL 3004, AL 3005, AL 3105, AL 5052, AL 6061, and AL 8006. The aluminum layer has a thickness within a corresponding range disclosed for the alloy in Table 2. Another aspect of the invention provides: a composite tube including: an inner plastic tube; an aluminum layer circumferentially surrounding the inner plastic tube; and an outer plastic layer circumferentially surrounding the aluminum layer. The aluminum layer can be an alloy having 0.1% or greater magnesium by mass.

One aspect of the invention provides a composite tube including: an inner plastic tube; an aluminum layer circumferentially surrounding the inner plastic tube; and an outer plastic layer circumferentially surrounding the aluminum layer. The aluminum layer is an alloy selected from the group consisting of: AL 3004, AL 3005, AL 3105, AL 5052, AL 6061, and AL 8006. The aluminum layer has a thickness within a corresponding range disclosed for the alloy in Table 2. Another aspect of the invention provides: a composite tube including: an inner plastic tube; an aluminum layer circumferentially surrounding the inner plastic tube; and an outer plastic layer circumferentially surrounding the aluminum layer. The aluminum layer can be an alloy having 0.1% or greater magnesium by mass.

A method protects a field joint of a pipeline, where chamfered edges of thermally-insulating parent coatings on conjoined pipe lengths are in mutual opposition about a longitudinally-extending gap. The method includes manufacturing an hourglass-shaped inner layer around the pipe lengths, which layer may be moulded. The inner layer extends longitudinally along the gap between the chamfered edges and at least partially overlies the chamfered edges. A thermally-insulating solid insert is assembled from two or more parts to lie in the gap surrounding the inner layer, and pressure is applied radially inwardly from the insert to the inner layer. An outer layer of molten material is manufactured around the insert to form a watertight barrier and to form one or more melted interfaces with the inner layer. Corresponding field joint arrangements are also disclosed.

A method protects a field joint of a pipeline, where chamfered edges of thermally-insulating parent coatings on conjoined pipe lengths are in mutual opposition about a longitudinally-extending gap. The method includes manufacturing an hourglass-shaped inner layer around the pipe lengths, which layer may be moulded. The inner layer extends longitudinally along the gap between the chamfered edges and at least partially overlies the chamfered edges. A thermally-insulating solid insert is assembled from two or more parts to lie in the gap surrounding the inner layer, and pressure is applied radially inwardly from the insert to the inner layer. An outer layer of molten material is manufactured around the insert to form a watertight barrier and to form one or more melted interfaces with the inner layer. Corresponding field joint arrangements are also disclosed.

An insulating insert is positioned around a field joint of a pipeline to insulate the field joint. The insert comprises a longitudinal series of annular or part-annular filler segments of insulating material, curved about a longitudinal axis, that are each joined to one or more adjacent segments of the series by at least one link. The links may be webs, rods or articulated links. The links are flexible relative to the segments to facilitate bending of the insert along its length by enabling relative angular displacement between adjacent segments of the series.

An insulating insert is positioned around a field joint of a pipeline to insulate the field joint. The insert comprises a longitudinal series of annular or part-annular filler segments of insulating material, curved about a longitudinal axis, that are each joined to one or more adjacent segments of the series by at least one link. The links may be webs, rods or articulated links. The links are flexible relative to the segments to facilitate bending of the insert along its length by enabling relative angular displacement between adjacent segments of the series.

A subsea pipeline has a steel pipe surrounded by a thermally-insulating coating system having at least one thermal insulation layer. The thermal insulation layer has a thermally-insulating matrix in which elongate tensile elements of a thermoplastic polymer, such as monofilament yarns, are embedded. The pipe is preheated to promote bonding between the matrix and the elongate elements and between successive layers of the coating system.

The invention relates to a pipe having a thermoplastic casing surface and a glass-fibre-reinforced thermo-setting coating surrounding the thermoplastic casing surface. The thermo-setting coating is formed from multiple layers of glass-fibre matting or glass-fibre fabric, or a combination of the two, wherein the layers are applied to the thermoplastic casing surface in a wet-on-wet method using a vinylester, polyester or epoxy resin. According to the invention, an outer layer of the thermo-setting coating is formed from cross-wound glass-fibre fleece or glass-fibre fabric.