| CPC F16L 9/14 (2013.01) [B21B 1/224 (2013.01); B21B 1/28 (2013.01); B21B 23/00 (2013.01); B21B 27/021 (2013.01); B21B 31/00 (2013.01); B21B 39/34 (2013.01); F16L 9/16 (2013.01); B21B 2015/0092 (2013.01); B21B 2205/04 (2013.01)] | 14 Claims |

|
1. A tubular structure comprising:
a base having a first surface and a second surface opposite one another, the first surface defining an elongate cavity, and the base having a tubular shape defining a longitudinal axis extending along the elongate cavity; and
a wrap supported on the second surface of the base, the wrap including a plurality of layers, and each layer having a first longitudinal edge and a second longitudinal edge coupled to one another along a respective spiral seam associated with the given layer and extending about the longitudinal axis of the base, wherein the base and each one of the plurality of layers are metal, a first layer of the plurality of layers is joined to the base via a first weld penetrating into the base, and a collective thickness of the wrap and the base varies in a direction parallel to the longitudinal axis of the base.
|