The present invention relates to a spiral tube capable of improving resistance performance against a collapse load generated by the difference between an internal pressure and an external pressure, while having a reduced thickness, the spiral tube comprising: a tube body in which a strip is connected in a spiral shape and welded at the front end thereof; and a stiffener provided on the inner surface of the tube body.

Tube forming methods can be used for efficient transition in the production of tubes having varying thickness. Material used to form consecutive tubes may have the same thickness along a separation plane separating a first discrete section from a second discrete section of the material, and the first discrete section and the second discrete section may each have varying thickness in a feed direction of the material. With such a thickness profile, the first discrete section of the material may be formed into a first cylinder having varying thickness and separated from the second discrete portion as the second discrete section is formed into a second cylinder having varying thickness. In particular, the transition between the first cylinder and the second cylinder may be achieved without scrap and/or interruption, resulting in cost-savings and improvements in production throughput associated with forming tubes having varying thickness.

A tubular structure is disclosed. The tubular structure has an elongate pre-fabricated tube having a longitudinal axis, a machine direction and a first width, and a first sheet metal having a leading edge, a machine direction and a second width. The leading edge of the first sheet metal is bonded to an outer surface of the elongate pre-fabricated tube and is continuously and convolutely wound about the longitudinal axis forming a plurality of at least three convolutions coaxially disposed about the outer surface of the pre-fabricated tube. The first sheet metal has a tail portion. The tail portion of the first sheet metal is disposed upon and bonded to an immediately subjacent convolution of the first sheet metal along the width.

A double-wall spiral welded pipe includes a first steel belt layer and a second steel belt layer which have equal widths, are arranged in parallel and align with each other; at least two supporting steel bars perpendicular to the first steel belt layer and the second steel belt layer are arranged between the first steel belt layer and the second steel belt layer; the supporting steel bars are arranged on end parts of two sides of the first steel belt layer and the second steel belt layer and extend together with the first steel belt layer and the second steel belt layer; and the first steel belt layer, the second steel belt layer and the supporting steel bars on the end parts of the two sides are mutually welded to form a double-layer composite steel belt with a rectangular section in an extending direction.

According to the present invention, there is provided a pipe forming apparatus for forming a pipe at an installation site. The apparatus includes a former upon which material is wound, and a mold for receiving the former bearing the wound material. An applicator is provided for applying curable liquid within the mold. Advantageously, the pipe is formed at site to provide for efficient formation of a pipeline. A transported ISO container providing the material and curable liquid to the site can produce 800 metres of pipeline section, compared with 60 metres in the prior art, representing a significant increase in efficiency.

According to the present invention, there is provided a pipe forming apparatus for forming a pipe at an installation site. The apparatus includes a former upon which material is wound, and a mold for receiving the former bearing the wound material. An applicator is provided for applying curable liquid within the mold. Advantageously, the pipe is formed at site to provide for efficient formation of a pipeline. A transported ISO container providing the material and curable liquid to the site can produce 800 metres of pipeline section, compared with 60 metres in the prior art, representing a significant increase in efficiency.

The seamless pipe in which a thin-walled portion in a pipe circumferential direction is formed in a pipe axial direction, in which a line segment formed by connecting one end and the other end of the thin-walled portion along a pipe surface with a shortest distance in a formation direction of the thin-walled portion is inclined at an angle α of 5.0° or more with respect to the pipe axial direction. It is preferable that one end and the other end of the thin-walled portion are set from a region in a pipe selected with a shorter length between a length of 1.0 m in the pipe axial direction and 90% of a length in the pipe axial direction where the thin-walled portion turns once in the pipe circumferential direction.

A thermoplastic product includes a fabric-based reinforcing sheet and a polymerized thermoplastic material. The fabric-based reinforcing sheet is wound about a mandrel to form a plurality of layers having a cross-sectional shape that corresponds to the mandrel. The fabric-based reinforcing sheet includes a plurality of fiber bundles, which may have a bidirectional orientation or configuration. A polymerized thermoplastic material is disposed within each layer of the fabric-based reinforcing sheet. The polymerized thermoplastic material bonds each layer of the fabric-based reinforcing sheet to an adjacent layer.

A composite pipe including an inner liner layer, a reinforcement layer, a structural layer, and an outer protection layer. The inner liner layer, the reinforcement layer, the structural layer, and the outer protection layer are arranged in that order from the inside out along the radial direction of the pipe. The reinforcement layer includes wound bamboo strips; the structural layer includes a wound planed board; and the reinforcement layer and the structural layer are sandwiched between the inner liner layer and the outer protection layer.

A composite pipe including an inner liner layer, a reinforcement layer, a structural layer, and an outer protection layer. The inner liner layer, the reinforcement layer, the structural layer, and the outer protection layer are arranged in that order from the inside out along the radial direction of the pipe. The reinforcement layer includes wound bamboo strips; the structural layer includes a wound planed board; and the reinforcement layer and the structural layer are sandwiched between the inner liner layer and the outer protection layer.