A helically wound tubular structure is disclosed. The tubular structure has a first sheet metal helically wound about a longitudinal axis, a second sheet metal having voids disposed therein helically wound about the longitudinal axis and coaxially about the first sheet metal, and a third sheet metal helically wound about the longitudinal axis and coaxially about the first sheet metal and the second sheet metal.

A tubular structure is disclosed. The tubular structure has a first sheet metal having a machine direction. The first sheet metal is convolutely wound about a longitudinal axis and 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.

An elongate tubular structure is disclosed. The elongate tubular structure has a first and second tubular structure wherein a first end of the first tubular structure is matingly and fasteningly engaged to a first end of the second tubular structure. The first and second tubular structures each have a first sheet metal having a machine direction being convolutely wound about a first longitudinal axis. The first sheet metal has a tail portion that is disposed upon and bonded to an immediately subjacent convolution of the first sheet metal to form the respective first and second tubular structures.

The present invention provides a tubular article (10), such as may be used as an oil and gas pipeline, having a longitudinal axis X comprising inner and outer separate strips (12, 14) of spirally wound overlapping material each having a longitudinal axis L and first and second edges (16, 18, 16, 18), in which each strip (12, 14) comprises two or more longitudinally extending ridges (20, 22, 20, 22), each of which extends along said longitudinally extending axis L in parallel to each other and in which said ridges (20, 22, 20, 22) each comprise asymmetric ridges having a leading edge (24, 24) forming a contact portion (28, 28) and wherein said leading edges (24, 24) are each in contact with each other and further comprising a non-contact trailing edge portion (26, 26) which are spaced from each other by an amount G.

A helically wound tubular structure formed from helically wound sheet metals is disclosed. The tubular structure has a first sheet metal helically wound about a longitudinal axis. A second sheet metal having voids disposed therein is helically wound about the longitudinal axis and coaxially about the first sheet metal. A third sheet metal is helically wound about the longitudinal axis and coaxially about the first sheet metal and the second sheet metal.