This disclosure relates generally to corrugated pipe, and more particularly to corrugated pipe with an outer wrap. In one embodiment, a pipe includes an axially extended bore defined by a corrugated outer wall having axially adjacent, outwardly-extending corrugation crests, separated by corrugation valleys. The pipe also includes an outer wrap applied to the outer wall. The outer wrap may include fibers and plastic. The outer wrap may span the corrugation crests producing a smooth outer surface.

This disclosure relates generally to corrugated pipe, and more particularly to corrugated pipe with an outer wrap. In one embodiment, a pipe includes an axially extended bore defined by a corrugated outer wall having axially adjacent, outwardly-extending corrugation crests, separated by corrugation valleys. The pipe also includes an outer wrap applied to the outer wall. The outer wrap may include fibers and plastic. The outer wrap may span the corrugation crests producing a smooth outer surface.

A composite pipe structure including a pair of structural polymer layers disposed on opposed sides of a central metal layer. In a preferred embodiment, the thickness of the composite structure is comprised of approximately 40%-60% of the metal layer, with the remaining balance comprised of the pair of polymer layers.

A composite pipe structure including a pair of structural polymer layers disposed on opposed sides of a central metal layer. In a preferred embodiment, the thickness of the composite structure is comprised of approximately 40%-60% of the metal layer, with the remaining balance comprised of the pair of polymer layers.

A method of fabricating a conduit comprises steps of attaching a first first-tubular-outboard-ply-end of a first tubular outboard ply to a first inner collar portion of a first collar with a second weld and attaching a second first-tubular-outboard-ply end of the first tubular outboard ply to a second inner collar portion of a second collar with a fourth weld. The method also comprises steps of inserting a second tubular outboard ply into the first tubular outboard ply and inserting a tubular inboard ply into the second tubular outboard ply, so that the second tubular outboard ply is interposed between the tubular inboard ply and the first tubular outboard ply. The method further comprises steps of threadably interconnecting the first inner collar portion and a first outer collar portion of the first collar and threadably interconnecting the second inner collar portion and a second outer collar portion of the second collar.

A method of forming a corrugated fluoropolymer tube is disclosed. The method comprises the step of providing a tube comprising extruded fluoropolymer without corrugations or convolutions disposed on a mandrel. The mandrel has a first cylindrical portion and a flaring portion that extends to a second cylindrical portion, the second portion having an outer diameter which is larger than an outer diameter of the first portion. The method also includes the step of moving the tube on a longitudinal axis along the mandrel thereby forcing an outer surface of the tube into flights disposed at a pitch angle on a plurality of thread rollers which are rotating, the plurality of thread rollers adjacent to and circumferentially distributed around the flaring portion and/or second cylindrical portion of the mandrel, wherein external force is exerted on the outer surface of the tube to form corrugations having adjacent peaks and roots.

A method of forming a corrugated fluoropolymer tube is disclosed. The method comprises the step of providing a tube comprising extruded fluoropolymer without corrugations or convolutions disposed on a mandrel. The mandrel has a first cylindrical portion and a flaring portion that extends to a second cylindrical portion, the second portion having an outer diameter which is larger than an outer diameter of the first portion. The method also includes the step of moving the tube on a longitudinal axis along the mandrel thereby forcing an outer surface of the tube into flights disposed at a pitch angle on a plurality of thread rollers which are rotating, the plurality of thread rollers adjacent to and circumferentially distributed around the flaring portion and/or second cylindrical portion of the mandrel, wherein external force is exerted on the outer surface of the tube to form corrugations having adjacent peaks and roots.

A corner connecting structure for a box-like pipeline or container of corrugated steel plates comprises a pipeline formed by assembling corrugated steel wall plates. The planes of every two adjacent corrugated steel wall plates intersect along a straight line, and the corrugation directions of the corrugated steel wall plates are perpendicular to the line of intersection. At least one corrugated steel wall plate is composed of a first corrugated steel plate and a second corrugated steel plate, of which the corrugation directions are perpendicular to the line of intersection. An end surface of the first corrugated steel plate perpendicular to the corrugation direction and coplanar with the line of intersection intersects and is fixed to the second corrugated steel plate, and is then attached and connected to the adjacent corrugated steel wall plate through the second corrugated steel plate.

A corner connecting structure for a box-like pipeline or container of corrugated steel plates comprises a pipeline formed by assembling corrugated steel wall plates. The planes of every two adjacent corrugated steel wall plates intersect along a straight line, and the corrugation directions of the corrugated steel wall plates are perpendicular to the line of intersection. At least one corrugated steel wall plate is composed of a first corrugated steel plate and a second corrugated steel plate, of which the corrugation directions are perpendicular to the line of intersection. An end surface of the first corrugated steel plate perpendicular to the corrugation direction and coplanar with the line of intersection intersects and is fixed to the second corrugated steel plate, and is then attached and connected to the adjacent corrugated steel wall plate through the second corrugated steel plate.

A gas heat pump system including an outdoor unit having a compressor, an outdoor heat exchanger, and an expansion device; an indoor unit having an indoor heat exchanger; a refrigerant pipe to connect the outdoor unit and the indoor unit; an engine to combust mixed fuel in which fuel and air are mixed; a coolant tank to store a coolant; a radiator to emit, to an outside, heat which is transferred from the engine to the coolant; and a coolant pipe to connect the coolant tank and the radiator to allow the coolant to circulate therethrough, whereby the gas heat pump system has a cooling capability between 71 kW and 85 kW, the refrigerant is a mixed refrigerant having at least 50% R32, and the refrigerant pipe is a ductile stainless steel pipe having a delta ferrite matrix structure of 1% or less based on grain area.