Apparatus and method for welding pipes together

• US 20010015349A1
• Filed: 05/04/2001
• Published: 08/23/2001
• Est. Priority Date: 12/24/1998
• Status: Active Grant

• Current Assignee: Saipem SPA (Saipem)
• Original Assignee: Saipem SPA (Saipem)
• Inventors: Belloni, Antonio, Bonasorte, Renato
• Granted Patent: US 6,429,405 B2
• Time in Patent Office: Days
• US Class Current: 219/124.34
• CPC Class Codes: B23K 2101/06 Tubes
• CPC Class Codes: B23K 9/0286 with an electrode moving around the fixed tube during the welding operation
• CPC Class Codes: B23K 9/1276 Using non-contact, electric or magnetic means, e.g. inductive means

Abstract

Apparatus (10) and method of forming a deep sea pipeline or a cross country pipeline by welding pipes together to form the pipeline. Two pipes (2, 4) are arranged so that their ends (26, 27) define a circumferentially extending narrow angled (less than 10 degrees) groove (28). At least two arc welding torches (1) are arranged directly adjacent to each other on a single carriage that moves around the pipes, to form a twin arc welding system. The arcs of the torches (1) form a weld (3) in the groove. The carriage is moved around the pipe, the torches thus moving around the pipe with the same speed. Each torch (1) is independently oscillated so that the position of its arc oscillates between the walls of the groove. The arcs are guided automatically by an electronic guidance system, wherein electrical characteristics (such as arc current or voltage) of the welding of each torch (1) with regard to each pipe (2, 4), respectively, are ascertained and a comparison made between the electrical characteristics relating to one of the pipes with the corresponding electrical characteristics relating to the other of the pipes. The position of an arc of a torch (1) may thus be aligned with the center line of the groove (28).

Claims

1. A method of forming a deep sea pipeline or a cross country pipeline including a step of welding two pipes together, said step of welding two pipes together comprising the steps of:

arranging two pipes end to end, the pipes being so shaped that a circumferentially extending groove is defined between the ends of the pipes, the angle of separation of the walls defining the groove being less than 10 degrees,

effecting relative movement of a plurality of arc welding torches arranged on a single carriage around the pipes and operating the torches so that their arcs form a weld in the groove,

each torch being moved around the pipe with substantially the same component of velocity along the length of the groove,

each torch being independently moved so that the respective positions of the arcs within the groove oscillate between the walls of the groove in a direction having a component parallel to the axis of the pipe, and

automatically guiding the arc produced by each of the torches by ascertaining, in respect of an arc, electrical characteristics of the welding with regard to each pipe, respectively, and comparing the electrical characteristics relating to one of the pipes with the corresponding electrical characteristics relating to the other of the pipes.

3. The method according to

claim 1

, wherein each arc is independently automatically electronically guided.

4. The method according to

claim 1

, including the step of ascertaining the difference between a value representing an electrical characteristic relating to one pipe and a value representing the same electrical characteristic relating to the other pipe and then performing a correcting movement moving the position of the arc in dependence on the value of the difference.

5. The method according to

claim 4

, wherein a correcting movement is effected when the value of the difference falls outside an preset acceptable range of values.

6. The method according to

claim 5

, further comprising monitoring the values of the differences over time and if the values of the differences is indicative of the arc being substantially continuously to one side of the desired path effecting a correcting movement of the arc.

7. The method according to

claim 1

, wherein the electrical characteristics that are ascertained include one or more of the arc voltage, the current, and the arc impedance.

8. The method according to

claim 1

, wherein two of the torches effecting welding of the pipe, weld at different rates.

9. The method according to

claim 1

, wherein the separation between the respective arcs is less than a fifth of the circumference of the pipes.

10. The method according to

claim 1

, wherein the torches are arranged so that each torch is directly adjacent to another torch.

12. The method according to

claim 1

, wherein each torch is a continuous wire arc welding torch and the supply of the wire is mounted remotely from the carriage.

14. The method according to

claim 1

, wherein the angle of separation of the walls defining the groove is 6 degrees or less.

15. The method according to

claim 1

, wherein the walls defining the groove are substantially parallel.

18. The method according to

claim 1

, wherein the movement of each torch in said direction having a component parallel to the axis of the pipe is driven by a respective independent prime mover.

19. The method according to

claim 1

, wherein a single prime mover effects motion of the torches along the length of the groove.

20. The method according to

claim 1

, wherein each torch is cooled during operation.

21. The method according to

claim 20

, wherein the torches are water cooled.

22. The method according to

claim 1

, wherein the pipes are of a size and have a wall thickness suitable for forming a deep sea pipeline or a cross country pipeline, and the pipes are joined by butt welding effected by an automatically guiding welding apparatus, the method comprising the steps of

arranging coaxially two pipes to be joined next to each other, the end walls of the pipes facing each other defining a circumferentially extending bevelled groove having a left wall and a right wall,

providing a welding apparatus including

a guide mounted around the circumference of the pipe,

at least one automatic tracking trolley mounted on the guide for movement therealong and around the pipe under the control of a control unit, the or each trolley comprising locking and sliding devices engageable with the guide, and pulling units for pulling the or each trolley along the guide,

two continuous-wire oscillating welding torches mounted on the or each trolley, and

a wire feeding means for feeding wire to each oscillating welding torch,

moving the welding torches around the guide and operating the torches to effect welding of the left wall and right wall of the groove to weld the pipes together,

in respect of each torch, ascertaining, at each of a multiplicity of instants over time, electrical parameter values relating to the voltage, current intensity and voltaic arc impedance of both the left wall and the right wall of the groove during the continuous movement of the oscillating torches,

in respect of each torch, calculating the difference between the electrical parameter values for the right wall and for the left wall,

in respect of each torch, comparing the values of the differences calculated, at each instant, with preset values held in a processing means to determine, at each instant, the shifting of those values,

piloting the variation in the movements of each oscillating welding torch by activating, each time the shifting in relation to the respective torch exceeds a preset limit, a drive means for orienting the torch so that the welding run is deposited in the center of the throat of the groove and then substantially superimposing the welding run on the notional central line of the groove, and

providing a protective atmosphere of active carbon dioxide gas, whereby pipes with walls that are relatively thick and so beveled that the angle between the left and right walls of the groove defined between the ends of the pipes is relatively low may be quickly welded together in an economical manner.

25. The welding apparatus according to

claim 23

, wherein the apparatus is so configured that it is suitable for use in a method of forming a deep sea pipeline or a cross country pipeline according to

claim 1

.

27. A carriage having a plurality of welding torches mounted thereon for use in the method of

claim 1

.

2. A method of welding two pipes together, the method comprising the steps of:

arranging two pipes end to end, the pipes being so shaped that a circumferentially extending groove is defined between the ends of the pipes,

effecting relative movement of a plurality of arc welding torches at substantially the same speed around the pipes and operating the torches so that their arcs form a weld in the groove,

automatically guiding the arcs produced by the torches by ascertaining electrical characteristics of the welding with regard to each pipe, respectively, and comparing the electrical characteristics relating to one of the pipes with the corresponding electrical characteristics relating to the other of the pipes.

11. The method according to

claim 2

, wherein a plurality of welding torches are mounted on a single carriage.

13. The method according to

claim 2

, wherein the angle of separation of the walls defining the groove is less than 10 degrees.

16. The method according to

claim 2

, wherein each torch is movable independently in a direction having a component parallel to the axis of the pipe.

17. The method according to

claim 2

, wherein the torches are moved so that the respective positions of the arcs within the groove oscillate between the walls in a direction having a component parallel to the axis of the pipe.

24. The welding apparatus according to

claim 23

, wherein the apparatus is so configured that it is suitable for use in a method of welding two pipes together according to

claim 2

.

23. A welding apparatus for welding pipes together to form a pipeline comprising

a carriage carrying a plurality of arc welding torches,

a control unit for facilitating automatic guidance of the arcs produced by the torches, wherein the apparatus is so configured that it may be used to weld together two pipes laid end to end defining therebetween a groove, by arranging the apparatus so that

the carriage is mounted for movement around the circumference of the pipes,

the control unit receives signals representing electrical characteristics of the welding with regard to each pipe, respectively, whereby

the control unit facilitates automatic guidance of the arc of each torch along the groove by comparing the signals relating to one of the pipes with the corresponding signals relating to the other of the pipes.

26. The welding apparatus according to

claim 23

, wherein each torch is provided with a respective control unit.

28. A method of forming a deep sea pipeline or a cross country pipeline including a step of welding two pipes together, said step of welding two pipes together comprising the steps of

arranging two pipes end to end, the pipes being so shaped that a circumferentially extending groove is defined between the ends of said pipes, the angle of separation of the walls defining said groove being less than 10 degrees,

effecting relative movement of a plurality of arc welding torches at substantially the same speed around said pipes and operating said torches so that their arcs form a weld in said groove, at least two of said torches being so arranged that each torch is directly adjacent to another torch,

automatically guiding the arcs produced by said torches by ascertaining electrical characteristics of the welding with regard to each pipe, respectively, and comparing the electrical characteristics relating to one of the pipes with the corresponding electrical characteristics relating to the other of the pipes.

29. A method of forming a deep sea pipeline or a cross country pipeline including a step of welding two pipes together, said step of welding two pipes together comprising the steps of

arranging two pipes end to end, the pipes being so shaped that a circumferentially extending narrow groove is defined between the ends of said pipes, the angle of separation of the walls defining said groove being less than 6 degrees,

providing a carriage and a plurality of GMAW (Gas Metal Arc Welding) torches arranged directly adjacent to one another on said carriage,

effecting relative movement of said carriage around said pipes and operating said torches, using a MAG (Metal Active Gas) welding process, so that their arcs form a weld in said groove, and

automatically guiding the arcs produced by said torches by ascertaining electrical characteristics of the welding with regard to each pipe, respectively, and comparing the electrical characteristics relating to one of said pipes with the corresponding electrical characteristics relating to the other of said pipes.

30. A method of forming a deep sea pipeline or a cross country pipeline including a step of welding two pipes together, said step of welding two pipes together comprising the steps of

arranging two pipes end to end, the pipes being so shaped that a circumferentially extending groove is defined between the ends of said pipes, the walls defining the sides of said groove being substantially parallel,

effecting relative movement of a plurality of arc welding torches arranged directly adjacent to one another on a single carriage around said pipes and operating said torches so that their arcs form a weld in said groove, each torch being moved around said pipes with substantially the same component of velocity along the length of said groove,

causing the respective positions of the arcs within said groove to oscillate between the walls of the groove in a direction having a component parallel to the axis of said pipes, and

automatically guiding the arcs produced by said torches by ascertaining electrical characteristics of the welding with regard to each pipe, respectively, and comparing the electrical characteristics relating to one of said pipes with the corresponding electrical characteristics relating to the other of said pipes.

31. A method of forming a deep sea pipeline or a cross country pipeline including a step of welding two pipes together, said step of welding two pipes together comprising the steps of

arranging two pipes end to end, the pipes being so shaped that a circumferentially extending groove is defined between the ends of said pipes, the angle of separation of the walls defining the groove being less than 10 degrees,

effecting relative movement of a plurality of arc welding torches arranged directly adjacent to one another on a single carriage around said pipes and operating said torches so that their arcs form a weld in said groove, each torch being moved around said pipes with substantially the same component of velocity along the length of said groove,

causing the respective positions of the arcs within said groove to oscillate between the walls of said groove in a direction having a component parallel to the axis of said pipe, and

automatically guiding the arcs produced by said torches by ascertaining, in respect of each arc, the difference between a value representing an electrical characteristic relating to one pipe and a value representing the same electrical characteristic relating to the other pipe and then performing a correcting movement moving the position of the arc in dependence on the difference between said values, said values being determined as a result of measuring characteristics of the arc as it oscillates in the groove towards and away from the respective pipes.

32. A method of J-laying a deep sea pipeline including a welding step of welding a pipe section to the pipeline, said welding step comprising the steps of

holding a free end of a pipeline, providing a pipe section and arranging said pipe section coaxially and against said free end of said pipeline, said free end of said pipeline and said end of said pipe section being so shaped that a circumferentially extending groove is defined between them, the angle of separation of the walls defining said groove being less than 10 degrees,

effecting relative movement of a plurality of arc welding torches arranged directly adjacent to one another on a single carriage around said groove and operating said torches so that their arcs form a weld in said groove, each torch being moved along said groove with substantially the same component of velocity along the length of said groove,

causing the respective positions of the arcs within said groove to oscillate between the walls of said groove in a direction having a component parallel to the axis of the pipe section, and

automatically guiding the arcs produced by said torches by ascertaining electrical characteristics of the welding with regard to said pipe section and to said end of said pipeline, respectively, and comparing the electrical characteristics relating to one of said pipe section and said end of the pipeline with the corresponding electrical characteristics relating to the other of said pipe section and said end of the pipeline.

33. A method of forming a deep sea pipeline or a cross country pipeline including a step of welding two pipes together, said step of welding two pipes together comprising the steps of

a) arranging two pipes end to end, the pipes being so shaped that a circumferentially extending groove is defined between the ends of said pipes, said groove having two circumferentially extending walls, each wall extending from a throat of said groove, the angle of separation of said walls of said groove being less than 10 degrees,

b) providing a welding apparatus including

a guide mounted around said groove,

at least one carriage mounted on said guide for movement therealong and around said pipes under the control of a control unit having a processor, the or each carriage comprising locking and sliding devices engageable with said guide,

at least two continuous-wire oscillating welding torches mounted directly adjacent to one another on the or each carriage, and

a wire feeder associated with each oscillating welding torch,

c) effecting relative movement of the or each carriage around said pipes and operating said torches so that their arcs form a weld in said groove, each torch being moved around said pipes with substantially the same component of velocity along the length of said groove, the arc of each torch oscillating between said walls of said groove in a direction having a component parallel to the axis of the pipes, each torch being fed with wire from the respective wire feeder associated with the torch and

d) automatically guiding the arc produced by each torch by performing the following steps, in respect of each torch, ascertaining at each of a multiplicity of instants over time, electrical parameter values relating to the voltage, current intensity and voltaic arc impedance in respect of both walls of said groove during the continuous oscillating movement of said oscillating torches,

calculating the difference between the electrical parameter values for one wall of said groove and for the opposite wall of said groove,

comparing the values of the differences calculated, at each instant, with preset values held in said processor of said control unit to determine, at each instant, the shifting of those values,

controlling the movement of each oscillating welding torch by moving, each time the shifting in relation to the respective torch exceeds a preset limit, the centre of oscillation of the torch so that the arc of said torch is directed to the centre of said throat of said groove.

34. A method of J-laying a deep sea pipeline including a step of welding two pipes together, said step of welding two pipes together comprising the steps of

a) arranging two pipes end to end, the pipes being so shaped that a circumferentially extending groove is defined between the ends of said pipes, said groove having two circumferentially extending walls, each wall extending from a throat of said groove, the angle of separation of said walls of said groove being less than 6 degrees,

b) providing a welding apparatus including

a guide mounted around said groove on the outside of said pipes,

at least one carriage mounted on said guide for movement therealong and around said pipes under the control of a control unit having a processor, the or each carriage comprising locking and sliding devices engageable with said guide,

at least two continuous-wire oscillating GMAW (Gas Metal Arc Welding) torches mounted directly adjacent to one another on the or each carriage, and

a wire feeder associated with each oscillating welding torch,

c) effecting relative movement of the or each carriage around said pipes and operating said torches, using a MAG (Metal Active Gas) welding process, so that their arcs form a weld in said groove, each torch being moved around said pipes with substantially the same component of velocity along the length of said groove, the arc of each torch oscillating between said walls of said groove in a direction having a component parallel to the axis of the pipes, each torch being fed with wire from the respective wire feeder associated with the torch and

d) automatically guiding the arc produced by each torch by performing the following steps, in respect of each torch,

ascertaining at each of a multiplicity of instants over time, electrical parameter values relating to the voltage, current intensity or voltaic arc impedance in respect of both walls of said groove during the continuous oscillating movement of said oscillating torches,

calculating the difference between the electrical parameter values for one wall of said groove and for the opposite wall of said groove,

comparing the values of the differences calculated, at each instant, with preset values held in said processor of said control unit to determine, at each instant, the shifting of those values,

controlling the movement of each oscillating welding torch by moving, each time the shifting in relation to the respective torch exceeds a preset limit, the centre of oscillation of the torch so that the arc of said torch is directed to the centre of said throat of said groove.

35. Welding apparatus for welding pipes together to form a pipeline, the apparatus comprising

a carriage carrying a plurality of continuous wire arc welding torches arranged adjacent to one another, a supply of wire for each torch being mounted remotely from said carriage, each torch being provided with a water cooling system for cooling the torch during operation,

a control unit for facilitating automatic guidance of the arcs produced by said torches, wherein

the apparatus is so configured that it may be used to weld together two pipes laid end to end defining therebetween a groove, said apparatus being able to be so arranged that

said carriage is mounted for movement around the circumference of the pipes,

said control unit receives signals representing electrical characteristics of the welding with regard to each pipe, respectively, and

said control unit is able to facilitate automatic guidance of the arc of each torch along said groove by comparing the signals relating to one of the pipes with the corresponding signals relating to the other of the pipes.

36. Welding apparatus for welding two pipes together in a method of J-laying a deep sea pipeline, said two pipes being arranged end to end, the pipes being so shaped that a circumferentially extending groove is defined between the ends of said pipes, said groove having two circumferentially extending walls, each wall extending from a throat of said groove, the angle of separation of said walls of said groove being less than 6 degrees, the apparatus comprising

a guide mountable around the outside of the pipes to be welded,

at least one carriage mountable on said guide for movement therealong, the or each carriage comprising locking and sliding devices engageable with said guide,

at least two continuous-wire oscillating GMAW (Gas Metal Arc Welding) MAG (Metal Active Gas) welding torches mounted directly adjacent to one another on the or each carriage, each torch being so arranged that, when said guide is secured in position relative to a groove between the pipes to be welded and said at least one carriage is mounted on said guide, the arc of each torch oscillates between the walls of said groove in a direction having a component parallel to the axis of said pipes,

a plurality of wire feeders for feeding the welding torches with welding wire, each oscillating welding torch being associated with a respective wire feeder, and

a control unit having a processor, wherein said control unit is arranged

a) to receive signals relating to the voltage, current intensity or voltaic arc impedance in respect of both walls of said groove during the welding,

b) to calculate, in use, the difference between the signals received in respect of one wall of said groove and the opposite wall of said groove,

c) to perform a comparison of the difference calculated with a preset value held in said processor of said control unit, and

d) to control, in use, the movement of each oscillating welding torch by moving each respective torch in response to said comparison to move the torch so that the arc of said torch at the centre of oscillation of said torch is directed to the centre of said throat of said groove, whereby, in use, the arc produced by each torch is able to be automatically guided along said groove by said control unit.