Manufacture of pipes

Abstract

The present invention relates to a method of manufacturing a pipe, which method comprises cold-gas dynamic spraying of particles onto a suitable support member thereby producing a pipe, and separating the pipe from the support member.

Claims

1. A method of manufacturing a pipe, the method comprising: pre-heating a mandrel, the mandrel made of a single material having a coefficient of thermal expansion; cold-gas dynamic spraying of particles of at least one of titanium or titanium alloy directly onto the material of the pre-heated mandrel to produce the pipe; and allowing the pre-heated mandrel and the pipe to cool prior to removal of the pipe from the mandrel, wherein the coefficient of thermal expansion of the pre-heated mandrel material is greater than the coefficient of thermal expansion of the pipe, so that separation of the pipe from the pre-heated mandrel takes place by contraction of the pre-heated mandrel away from the pipe when the pre-heated mandrel and the pipe are allowed to cool.

2. The method according to claim 1, wherein the surface of the pre-heated mandrel is smooth and defect-free.

3. The method according to claim 1, wherein the composition of the pipe varies along the length and/or across the thickness of the pipe.

4. The method according to claim 3, wherein the pipe comprises two or more discrete lengths and/or layers of different materials.

5. The method according to claim 3, wherein the composition of the pipe varies gradually along the length and/or across the thickness of the pipe.

6. The method according to claim 1, wherein the pipe comprises a material to confer corrosion and/or wear resistance to a surface of the pipe.

7. The method according to claim 1, wherein the pre-heated mandrel comprises surface features that impart an increased surface area to a corresponding surface of the pipe.

8. The method according to claim 1, wherein an average size of the particles and the operating parameters of the cold-gas dynamic spraying are selected so the pipe is free of connected micro-voids.

9. The method according to claim 1, further comprising after removal of the pipe from the mandrel applying a load to an outer surface of the pipe with a roller to at least one of size or finish of the pipe.

10. The method according to claim 1, further comprising applying a load to an outer surface of the pipe with a roller to at least one of size or finish of the pipe.

11. The method according to claim 1, wherein the particles have a diameter of 5 to 45 microns.

12. The method according to claim 1, wherein the mandrel includes a cavity extending through it.

13. The method according to claim 1, wherein the pipe is adapted to transport fluid either above or below ground or sub-sea, the fluid comprising at least one of acidic or alkaline fluids, water, oil, gas or chemicals.

14. A method of manufacturing a pipe, the method comprising: pre-heating a mandrel formed entirely of a material having a first coefficient of thermal expansion, the material of the mandrel defining an outer surface of the mandrel; cold-gas dynamic spraying particles of a second material onto the outer surface of the pre-heated mandrel to produce a pipe such that an inner surface of the pipe forms on the outer surface of the pre-heated mandrel, the second material comprising titanium or a titanium alloy and having a second coefficient of thermal expansion; and allowing the pre-heated mandrel to contract away from the inner surface of the pipe as the pre-heated mandrel and the pipe cool prior to removal of the pipe from the mandrel such that a difference between the first coefficient of thermal expansion and the second coefficient of thermal expansion separates the mandrel from the pipe.

15. The method according to claim 14, wherein the outer surface of the pre-heated mandrel is smooth and defect-free.

16. The method according to claim 14, wherein the composition of the pipe varies along the length and/or across the thickness of the pipe.

17. The method according to claim 16, wherein the pipe comprises two or more discrete lengths and/or layers of different materials.

18. The method according to claim 14, wherein an average size of the particles and the operating parameters of the cold-gas dynamic spraying are selected so the pipe is free of connected micro-voids.

19. A method of manufacturing a pipe, the method comprising: pre-heating a mandrel, the mandrel having an inner surface or core and an outermost surface, the mandrel formed of a material having a first coefficient of thermal expansion at the inner surface or core and the outermost surface thereof; cold-gas dynamic spraying particles of a second material onto the mandrel to produce a pipe such that an inner surface of the pipe forms on the outermost surface of the mandrel, the second material comprising titanium or a titanium alloy and having a second coefficient of thermal expansion; and removing the pipe from the mandrel after the pipe and the mandrel have cooled such that a difference between the first coefficient of thermal expansion and the second coefficient of thermal expansion separates the mandrel from the pipe.

20. The method according to claim 19, wherein cold-gas dynamic spraying particles of the second material onto the mandrel includes the outermost surface of the mandrel having structural features extending therefrom such that an inner surface of the pipe formed on the outermost surface has an increased surface area.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a pictorial illustration of a rolling test rig and lathe; and

(2) FIG. 2 is a pictorial illustration of titanium heat exchanger pipes.

DETAILED DESCRIPTION

EXAMPLES

(3) The following non-limiting examples illustrate particular embodiments of the present invention.

Example 1

(4) The method of the present invention may be conducted on the specially designed in situ rolling test rig and lathe illustrated in the accompanying drawing (FIG. 1). In particular, titanium pipes up to 125 mm in diameter (internal) and up to 450 mm in length may be manufactured on the test rig (with no limitations on the diameter, wall thickness and/or length of the pipes produced).

(5) The (laboratory) facility of FIG. 1 is designed so that the rolling pressure, applied by the pressure roller head 1, may be maintained during cold spraying and the traverse speeds of both the pressure roller slide 2, driven by the slide drive motor 3, and the cold spraying nozzle (not shown) may be synchronized to move along the pipe as it is being formed. The cold spraying nozzle would typically be positioned directly opposite the mandrel. Multiple nozzles may be used in tandem for cold spraying mandrels of considerable length, wall thickness and/or diameter. The use of multiple nozzles may also speed up the manufacturing process. The mandrel 4 would be firmly fixed between the lathe drive head 5 and the lathe tailstock 6 so that it may be rotated at high speed for cold spraying deposition. Once the desired pipe length and wall thickness are achieved, the titanium coated mandrel may be detached from the test rig and the mandrel may be removed to reveal the cold sprayed titanium pipe.

(6) Alternatively, titanium and/or titanium alloy pipes may be manufactured on the test rig by cold spraying titanium and/or titanium alloy powder onto the mandrel and omitting the rolling (finishing) step.

(7) Typically, the cold spraying machine parameters are as follows:

(8) Equipment: CGT Kinetic 3000 or 4000

(9) Number of supersonic nozzles: one or more

(10) Mandrel material: Stainless steel

(11) Mandrel speed: up to 600 RPM

(12) Stand-off: 20-100 mm

(13) Spray material: CP Titanium and/or titanium alloy powder

(14) Particle diameter: 10-30 microns

(15) Gas pressure: 10-40 bar

(16) Gas: Helium, nitrogen, argon or air

(17) Carrier gas: Helium, nitrogen, argon or air or mixtures thereof

(18) Powder feed rate: 10-200 g/min

(19) Traverse rate: 10-100 mm/min

Example 2

(20) Titanium/mild steel duplex pipes have been manufactured for transporting corrosive liquids. A stainless steel mandrel (external diameter, 50 mm; length, 300 mm) was cold sprayed with a 5 mm thick layer of commercially pure titanium. An additional 5 mm thick mild steel layer was deposited on the titanium layer to produce a duplex pipe of 10 mm thickness. The stainless steel mandrel was removed by utilizing the difference between the thermal expansion coefficient of titanium and the stainless steel.

(21) Typically, the cold spraying machine parameters for producing the duplex pipe are as follows:

(22) Equipment: CGT Kinetic 4000

(23) MOC super sonic nozzle

(24) Mandrel material: Stainless steel

(25) Mandrel speed: up to 600 RPM

(26) Stand-off: 30 mm

(27) Spray material: Commercially pure Titanium and Mild Steel

(28) Particle diameter: 10-30 microns for Titanium and Mild Steel

(29) Gas pressure for titanium 38 bar and 35 bar for Mild Steel

(30) Gas: Nitrogen 99.999% pure for both powders

(31) Carrier gas: Nitrogen 99.999% pure for both powders

(32) Powder feed rate: 30 g/min for both powders

(33) Traverse rate: 20 mm/min for both powders

Example 3

(34) Seamless titanium and titanium alloy pipes with complex internal shapes have been manufactured using cold spraying. An aluminum alloy mandrel was machined on the external surface to produce a spline shaped mandrel that in turn increased the internal surface area of the cold sprayed titanium pipe. The spline contained ten gear shaped teeth around the circumference and each tooth measured 3 mm wide by 3 mm deep. Alternatively the spline shape is not limited to the example provided and the spline tooth depth and width can be varied according to the amount of heat transfer required. The aluminum spline was placed in a lathe machine for the purpose of rotating the mandrel at the required speed. Titanium or titanium alloy was cold sprayed on the surface of the mandrel to build-up the wall thickness of the heat exchanger pipe to 6 mm thick. After cold spraying, the mandrel was removed by dissolving in a sodium hydroxide solution to reveal the titanium heat exchanger pipe. The titanium heat exchanger pipes are shown in FIG. 2.

(35) Typically, the cold spraying machine parameters are as follows:

(36) Equipment: CGT Kinetic 4000

(37) MOC super sonic nozzle

(38) Mandrel material: Aluminum alloy

(39) Mandrel speed: up to 600 RPM

(40) Stand-off: 30 mm

(41) Spray material: Commercially pure Titanium

(42) Particle diameter: 10-30 microns

(43) Gas pressure: 38 bar

(44) Gas: Nitrogen 99.999% pure

(45) Carrier gas: Nitrogen 99.999% pure

(46) Powder feed rate: 30 g/min

(47) Traverse rate: 20 mm/min

(48) Throughout this specification and the claims which follow, unless the context requires otherwise, the word “comprise”, and variations such as “comprises” and “comprising”, will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

(49) The reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be taken as an acknowledgment or admission or any form of suggestion that that prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavor to which this specification relates.

(50) Although the present invention has been illustrated and described with respect to several preferred embodiments thereof, various changes, omissions and additions to the form and detail thereof, may be made therein, without departing from the spirit and scope of the invention.