GB2295345A

GB2295345A - Cooling method and apparatus for welding

Info

Publication number: GB2295345A
Application number: GB9523192A
Authority: GB
Inventors: Martin Collar
Original assignee: Stolt Comex Seaway Ltd
Current assignee: Stolt Comex Seaway Ltd
Priority date: 1994-11-15
Filing date: 1995-11-13
Publication date: 1996-05-29
Anticipated expiration: 2015-11-13
Also published as: NO954597L; NL1001662A1; NL1001662C2; GB9523192D0; GB2295345B; NO954597D0; GB9423011D0

Abstract

Apparatus and a method of dissipating heat from a first member (1) during welding includes a pair of cooling elements (10). Each cooling element (10) has a heat transfer element (20) which is deformable to contact a surface (12) of the first member (1) adjacent to a weld zone (8) to dissipate heat. The cooling elements (10) may be expandable under the pressure of cooling fluid passed through the cooling elements (10). The cooling elements (10) may also be mounted on a support device (11). <IMAGE>

Description

"Method and Apparatus for Welding" The present invention relates to cooling a member at a welding zone to control welding conditions.

Weld characteristics and quality are affected by a large number of factors, including temperature of the welding zone. Overheating at a welding zone can result in defects and/or weaknesses being created in a weld and/or in a member being welded. This can be a significant problem, for example, where a length of tube is to be welded onto a pipeline which is in service. In these circumstances, it is often desirable to pre-heat the welding zone, for example by using induction heating coils and a large disparity in heat loss exists between the main pipeline, heavily cooled by internal product flow, and the relatively uncooled side branch. This may result in undesirably high temperatures in the side branch during the welding process and/or during the pre-heating process and may be further exacerbated when the welding process is conducted underwater.

Cooling systems have been proposed for controlling the temperature of a side branch by means of an externally fitted cooling jacket. A number of proposals are described in UK Patent Application No 8900657.1 and the disclosures of this document are hereby incorporated by reference. However, these prior art systems have been shown to have a number of short comings. In particular, the cooling performance of systems in which a cooling fluid is circulated within a coiled pipe or a jacket has proved inadequate under certain circumstances. Where a cooling fluid flows directly over the surface of a side pipe it is difficult to ensure the integrity of a necessary mechanical seal which has to operate in a hostile environment in close proximity to the welding zone.

In accordance with a first aspect of the present invention, apparatus for dissipating heat from a first member during welding comprises a cooling element which comprises a heat transfer element, the heat transfer element being deformable to contact a surface of the first member adjacent to a weld zone to dissipate heat from the first member.

In accordance with a second aspect of the present invention, a method of dissipating heat from a first member during welding comprises providing a cooling element which comprises a deformable heat transfer element, and deforming the heat transfer element so that the heat transfer element contacts a surface of the first member adjacent to a weld zone to dissipate heat from the first member.

The heat transfer element is preferably ductile as well as deformable. In use, the heat transfer element, when deformed to contact the surface of the first member, preferably conforms to any asperities and/or surface roughness of the surface of the first member. The heat transfer element may be held against the surface of the first member by an applied force and/or pressure; this force or pressure may induce the heat transfer element to conform intimately to the surface of the first member.

The heat transfer element preferably has a low thermal resistance to facilitate conduction of heat therethrough. The heat transfer element is preferably constructed of a material having a high thermal conductivity; the material may be ductile and may be in the form of a thin sheet. The heat transfer element may be metallic; it may be made of copper which may be of high purity and may be fully annealed.

The heat transfer element may comprise a wall section of the cooling element.

The cooling element is preferably expandable between a first position in which the heat transfer element is spaced from the surface of the first member and a second position in which the heat transfer element contacts the surface of the first member.

The cooling element may be hollow and define a passageway or cooling chamber adapted to contain a cooling fluid. The cooling fluid is preferably in direct contact with the heat transfer element. The cooling fluid may circulate through the cooling chamber; circulation of the cooling fluid is preferably arranged as part of a cooling circuit which may be a closed circuit cooling circuit. The cooling fluid may be, for example, water or water based.

Expansion of the cooling element may be induced by pressurising the cooling fluid within the cooling chamber. Resilient means may be associated with the cooling chamber to encourage it to contract from the second position to or substantially to the first position when a pressure applied to the cooling fluid is released.

The apparatus may also include a support device to support the cooling element in use. The cooling element may be mounted or attached at or on the support device. The support device may provide a substantially rigid support against which the cooling chamber may expand. The cooling element may be in the form of an expandable sac or expandable bellows which is adapted, in use, to expand against the support device.

The support device may comprise a material which is substantially magnetically permeable; this may avoid the support device being heated by pre-heating induction coils when these are used to pre-heat the welding zone. The support device may be made of a suitable grade of stainless steel.

Typically, the heat transfer element contacts the surface of a first side of the first member and a welding tool at a second side of the first member is used to weld the first member.

The first member may be in the form of a hollow tube or pipe. In this case, the first side of the first member may be the interior of the tube or pipe and the second side may be the exterior.

An embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Fig. 1 is a side view, partially in cross section, of apparatus in accordance with the invention positioned at a welding zone; and Fig. 2 is a plan view of the apparatus.

The apparatus 3 shown in Fig. 1 is intended for use in a welding process in which a first member 1 is welded to a second member 2. In this example, the second member 2 is a steel pipeline containing a fluid (not shown) and the first member 1 is a steel side branch pipe to be welded onto the pipeline. The welding process may be carried out underwater.

Outer induction heating coils 5 and inner induction heating coils 6 are used to pre-heat a welding zone 8, prior to commencement of the welding process.

The apparatus 3 comprises a pair of expandable cooling elements 10 supported at a support member in the form of a reaction sleeve 11. The reaction sleeve 11 is provided by a substantially rigid tube that, in use, is inserted into the side branch pipe 1 to position the cooling elements 10 adjacent to a surface of a first side, in this case an interior side 12, of the side branch pipe 1. The reaction sleeve 11 is made of a suitable grade of stainless steel. It is substantially magnetically permeable in relation to the frequency at which the induction coils 5, 6 are used to pre-heat the welding zone. In this way, the induction coils 5, 6 do not induce significant eddy currents in the reaction sleeve 11 which would otherwise tend to increase its temperature.

The reaction sleeve 11 provides a shield and a support which reduces the likelihood of physical damage to the cooling elements 10. Each cooling element 10 is spaced from an end 14 of the reaction sleeve 11 to provide a degree of protection. Furthermore, handling and positioning of the cooling elements 10, especially underwater, is facilitated by their attachment to the reaction sleeve 11.

Each cooling element 10 is provided with a cooling fluid inlet 15 and a cooling fluid outlet 16. In use, a cooling fluid is passed through a passageway or cooling chamber 17 defined by the cooling element 10 from the inlet 15 to the outlet 16. In use, the cooling fluid passes over and is in direct contact with a heat transfer element 20.

The heat transfer element 20, which forms one surface of the cooling element 10 in this embodiment, is constructed from a thin sheet of fully annealed high purity copper. In this embodiment, the heat transfer element 20 is an integral part of the cooling element 10.

In use, the reaction sleeve 11 and the cooling elements 10 are positioned inside the side branch tube 1 as shown in Fig. 1. The cooling chambers 17 of the cooling elements 10 are then subjected to a first hydrostatic pressure by means of pressurising the cooling fluid. This causes the cooling elements 10 to expand such that the heat transfer elements 20 are brought into close contact with the surface of the interior side of the side branch tube 1. Each heat transfer element is forced into intimate contact with and conforms accurately to any roughness and/or asperities of the surface to provide an intimate thermal contact. The thinness and ductility of the heat transfer element 20 facilitate its conforming to the surface of the side branch tube 1 whilst its high thermal conductivity facilitates heat transferred therethrough.The reaction sleeve 11 provides a reaction force which acts against the expanded cooling elements 10.

Once the cooling elements have been positioned, the welding process is commenced. In this case, a welding tool (not shown) is passed around a second side 13, ie the exterior side, of the first member 1. Positioning of the cooling element 10 away from the second side 13 facilitates manipulation and use of the welding tool and reduces the risk of the cooling element 10 being damaged due to physical contact.

At least some of the heat generated by the welding process is dissipated from the side branch pipe 1 through the heat transfer element 20 to the cooling fluid contained within the cooling element 10. The cooling fluid flows in a closed loop cooling circuit (not shown) absorbing heat as it passes over the heat transfer element 20 and dissipating that heat at another part of the cooling circuit. During flow of the cooling fluid through the cooling chamber 17 of the cooling element 10, sufficient pressure is maintained to keep the heat transfer element 20 in intimate thermal contact with the surface of the side branch pipe 1.The pressure of the cooling fluid whilst it is flowing through the cooling element 10 may be lower than the first pressure to which the cooling element 10 is initially subjected to establish an intimate contact between the heat transfer element 20 and the surface of the side branch pipe 1.

The temperature of the side branch pipe 1 during the welding process may be accurately controlled by adjusting the rate of flow of the cooling fluid through the cooling element and/or by adjusting the input temperature of the cooling fluid.

Once the welding process has been completed, the pressure of the cooling fluid in the cooling elements 10 is reduced to allow the cooling elements 10 to contract from their expanded states. The cooling sleeve 11 and the cooling elements 10 are then withdrawn from the side branch pipe 1.

The described embodiment of the invention is particularly suited for use in association with an induction heating system for use in welding a side branch onto a live submarine pipeline.

Claims

1. Apparatus for dissipating heat from a first member during welding, the apparatus comprising a cooling element which comprises a heat transfer element, the heat transfer element being deformable to contact a surface of the first member adjacent to a weld zone to dissipate heat from the first member.

2. Apparatus according to claim 1, wherein the heat transfer element comprises a wall section of the cooling element.

3. Apparatus according to claim 1 or claim 2, wherein the cooling element further comprises an internal void adapted to contain cooling fluid.

4. Apparatus according to claim 3, wherein the cooling element further comprises a fluid inlet and a fluid outlet which communicate with the internal void.

5. Apparatus according to claim 3 or claim 4, wherein the heat transfer element is contacted by the cooling fluid.

6. Apparatus according to any of claims 3 to 5, and further comprising a pressurising device to pressurise the cooling fluid in the cooling element.

7. Apparatus according to any of the preceding claims, wherein the cooling element is expandable, and expansion of the cooling element deforms the heat transfer element.

8. Apparatus according to claim 7 when dependent on claim 6, wherein the pressurisation of the cooling fluid in the cooling element expands the cooling element.

9. Apparatus according to any of the preceding claims, wherein two cooling elements are provided each cooling element being semi-circular in shape.

10. Apparatus according to any of the preceding claims, and further comprising a support device to support the cooling element, in use.

11. Apparatus according to claim 9, wherein the cooling element is mounted on the support device.

12. Apparatus according to claim 10 or claim 11, wherein the support device is tubular and the cooling element or elements extend around the internal or external surface of the support device.

13. A method of dissipating heat from a first member during welding, the method comprising providing a cooling element which comprises a deformable heat transfer element, and deforming the heat transfer element so that the heat transfer element contacts a surface of the first member adjacent to a weld zone to dissipate heat from the first member.

14. A method according to claim 13, further comprising the step of expanding the cooling element to deform the heat transfer element.

15. A method according to claim 13 or claim 14, and further comprising passing cooling fluid through the cooling element to cool the heat transfer element.

16. A method according to claim 15 when dependent on claim 14, wherein pressurisation of the cooling fluid expands the cooling element.

17. A method according to any of claims 13 to 16, and further comprising locating the cooling element adjacent a support device to support the cooling element.

18. A method according to claim 17, wherein the cooling element is located between the first member and the support device.

19. Apparatus for dissipating heat from a first member during welding substantially as hereinbefore described, with reference to the accompanying drawings.

20. A method of dissipating heat from a first member during welding substantially as hereinbefore described, with reference to the accompanying drawings.