WO2012020249A2

WO2012020249A2 - Pipe welding apparatus

Info

Publication number: WO2012020249A2
Application number: PCT/GB2011/051497
Authority: WO
Inventors: Lee David Screaton; Paul Robert Cairns
Original assignee: Subsea 7 Limited
Priority date: 2010-08-10
Filing date: 2011-08-08
Publication date: 2012-02-16
Also published as: GB201013427D0; GB2482693A; WO2012020249A3

Abstract

In pipe welding apparatus (1) for welding pipe sections together to form a pipeline,upper and lower pipe sections (2, 3) are abutted, end-to-end, and welded together by two or more welding heads (5) that travel around a circumferential guide (4) extending around one of the pipe sections (2). Welding supplies, such as electric power, cooling water and shielding gas are supplied from supply equipment (9, 10, 11) through a distribution manifold (18). The supply equipment (9, 10, 11) thus distributes welding supplies to each of the welding heads.

Description

PIPE WELDING APPARATUS

This invention relates to pipe welding apparatus for welding pipe sections together, end- to-end, to form a pipeline.

Examples of such pipe welding apparatus are known in the art, such as, in particular, for fabricating a pipeline laid on the seabed, to be used in transporting oil, gas or hydrocarbon fluids. One particular kind of such apparatus is disclosed in EP-B-1 148 966. This welding apparatus is arranged to weld pipe sections together when they are in a generally upright orientation (i.e. vertical or inclined-to-vertical) with the bottom of an upper pipe section abutting the top of a lower pipe section that defines the end of the pipeline. The welding apparatus includes a plurality of welding heads, and a welding head guide assembly for fixing around a pipe section. The guide assembly includes a guide track for guiding movement of each of the welding heads around the pipe section. The apparatus further comprises a rotary equipment holder mounted for rotation about a generally vertical axis and having a central opening through which pipe sections are able to pass as a pipeline is laid, the plurality of welding heads being angularly spaced about the rotary equipment holder. Each head of the plurality of welding heads is associated with a respective sector of the rotary equipment holder and the respective sector of the rotary equipment holder is able to revolve around the pipe section as the associated welding head revolves around the pipe section. The gas and power supply equipment for each welding head is mounted on the respective sector of the rotary equipment holder with which the welding head is associated.

Further examples of welding apparatus for welding vertically disposed pipe sections together end-to-end for pipelaying are disclosed in US 2007/0023479 and WO 00/38871 . Both these publications show arrangements which employ rotary equipment holders mounted for rotation about a generally vertical axis.

Since the welding apparatus includes a plurality of welding heads, there will be as many sets of gas supply equipment and as many sets of power supply equipment as there are welding heads, the number of welding heads being typically two, three or four. Multiplying each type of supply equipment, power and gas, in this way increases the amount of space taken up on the rotary equipment holder, leading to a more cluttered environment, making maintenance more difficult and compromising safety, or a larger equipment holder, in order to accommodate the different sets of supply equipment, while leaving adequate space for facilitating maintenance purposes. Still further, operation of the welding apparatus has to be stopped whenever any one of the sets of gas supply equipment runs out of gas. Thus, since there are typically two, three or four sets of gas supply equipment on the equipment holder (depending on the number of welding heads employed), the pipe welding operation has to be interrupted for replacement of one or more gas cylinders in each set of gas supply equipment, leading to undesired downtime, which it is to be avoided or minimised, if possible.

According to the invention, there is provided pipe welding apparatus for welding pipe sections together, end-to-end, to form a pipeline, comprising: a welding head guide for fixing around one of the pipe sections; a plurality of welding heads mounted on the welding head guide to be guided around said one pipe section for welding it and another pipe section together, end-to-end, in a vertical or inclined-to-the-vertical orientation along a common axis; an equipment carrier having an opening therein to enable the pipeline to pass through it as it is being laid; and supply equipment and a distribution manifold, wherein the supply equipment and the distribution manifold are supported by the carrier, wherein the supply equipment supplies at least one welding supply to the distribution manifold, and wherein the distribution manifold is connected to each of the plurality of welding heads to distribute the at least one welding supply between those welding heads.

Since the or each type of supply equipment supported in the equipment carrier is connected to distribute a welding supply between a plurality of welding heads, only one supply equipment of a given type is needed to meet the supply needs (such as any one or more of electrical power, shielding gas, cooling water and welding wire) of these welding heads. Accordingly, the equipment carrier becomes less cluttered than it would otherwise be, making use and maintenance of the supply equipment easier and safer.

Preferably, the at least one welding supply comprises a physical consumable item. Since the supply of a physical consumable item such as gas will then run out only after the welding heads have consumed all of the available material between them, the operation of the welding apparatus will have to be interrupted less often. In the case of gas, an interruption to enable the gas supply equipment to be re-charged or have gas canisters replaced, will be less frequent than would be the case if each welding head were to have its own separate gas supply equipment.

Where the welding supply is a physical consumable item, the welding supply may comprise cooling water provided by cooling water supply equipment or shielding gas provided by shielding gas supply equipment. The welding supply may also comprise welding wire provided by welding wire feeding equipment for feeding wire to a welding torch of each welding head. Alternatively, wire feeding equipment may be mounted on each welding head for feeding wire to a welding torch of each welding head, as the latter is guided around said one pipe section. This arrangement helps to reduce the distance over which welding wire has to be fed from storage, such as on a spool, to each welding head.

In one arrangement, the distribution manifold is connected to the welding heads by respective umbilicals, each umbilical being arranged for supplying the relevant welding supply or supplies to its respective welding head. The distribution manifold serves as a single location to which the supplies for the welding head are brought and from which they are distributed to the welding heads. Preferably, the equipment carrier is a rotary equipment carrier mounted for rotation about a vertical or inclined-to-the-vertical axis substantially in synchronism with the guidance of the welding heads around said one pipe section. The synchronisation referred to assists in simplifying the manner in which the supply equipment on the equipment carrier is connected to the said at least two welding heads, which is typically achieved using umbilicals. In particular, the length of the umbilicals can be kept relatively short, since each umbilical merely has to be long enough to accommodate the relatively small variations in relative separation between the connection point of each umbilical to its associated welding head on the welding head guide and the connection point of the umbilical on the equipment carrier.

In a preferred embodiment, the rotary equipment carrier is located above, and with a vertical separation from, the welding head guide and welding heads. Since operating personnel need to observe the welded joint as it is being formed and, if need be, adjust the operation of the welding apparatus to produce a welded joint of high quality, raising the rotary equipment carrier above the welding head guide and welding heads keeps the rotary equipment away from operating personnel, allowing them space in which to work.

Optionally, a stationary, substantially horizontal, work floor for operating personnel is located below, and with a vertical separation from, the welding head guide and welding heads, to provide a convenient working environment for operating personnel. Alternatively, the rotary carrier is located below, and with a vertical separation from, the welding head guide and welding heads, in which case the rotary carrier can serve as a base on which operating personnel can stand, as well as a carrier for the supply equipment.

The rotary equipment carrier may be mounted to rotate about the common axis of the end-to-end pipe sections. In this way, the diameter of the opening in the equipment carrier can be minimised to very slightly more than the outside diameter of the pipeline. Alternatively, the rotary equipment carrier can be mounted to rotate about a substantially vertical axis. Suitably, the rotary equipment carrier is rotatably mounted on the structure of the pipelaying vessel itself.

For a better understanding of the present invention, and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which:-

Figure 1 is a diagrammatic side view of principal parts of one form of pipe welding apparatus according to the invention, mounted on board a floating lay ship or the like;

Figure 2 is a cross-sectional view from above, taken along the line l l-l l in Figure 1 , showing various types of supply equipment on an overhead carousel of the welding apparatus; Figure 3 is an underneath sectional view on an enlarged scale, showing the arrangement of diametrically opposed welding heads on a welding head guide fitted around the upper one of two pipe sections being welded end-to-end;

Figures 4 to 6 are views corresponding, respectively, to those of Figures 1 to 3 of an alternative embodiment in which the welding heads include respective wire feeding arrangements, rather than the arrangement shown in the first embodiment in which wire is fed from a single wire feeder on the overhead carousel; and

Figure 7 is a view corresponding to that of Figure 1 , showing another embodiment in which the overhead carousel is arranged to rotate about a vertical axis, rather than an axis inclined to the vertical. Referring to Figures 1 to 3, there is shown a pipe welding apparatus 1 , for mounting on a pipe lay vessel 29 or the like, which serves to weld the lower end of an upper pipe section 2 to the upper end of a lower pipe section 3 being laid on the sea bed from the pipe lay vessel. The lower pipe section will be orientated at the lay angle, which will be substantially vertical (for J-lay) or inclined at an angle to the vertical. The lower pipe section 3 is made up of one or more pipe sections previously welded together by the pipe welding apparatus 1 in end-to-end abutted relationship.

As shown in Figure 1 , the lower end of the upper pipe section 2 and the upper end of the lower pipe section 3 are chamfered, so as to provide a circumferential V-groove at the abutment between the two pipe sections, in which weld material is progressively built up from the bottom of the groove until the groove is filled, in the manner to be described hereinbelow. After each upper section 2 has been welded to the lower pipe section 3, the resulting unitary pipe length is lowered, and a next upper pipe section 2 is aligned with, held in abutment with, and then welded to the upper end of the lower pipe section 3. The process is repeated until a pipeline of the required length has been formed and laid on the sea bed.

The welding apparatus 1 includes a welding head guide 4 which is releasably clamped to the upper pipe section 2, close to the abutment with the lower pipe section 3, and extends around the upper pipe section 2. Two welding heads 5 are mounted on the guide 4 in diametrically opposed positions and can be simultaneously driven along the guide 4 in the circumferential direction, so as to travel around the circumference of the upper pipe section 2, in an orbiting path centred on the common longitudinal axis of the pipe sections. For this purpose, the welding heads may be provided with respective synchronised drive units, or they may be connected by a common rotary structure which is rotated by a single drive unit. Both such drive arrangements are known in the art and can readily be implemented in a manner which is well known to skilled persons. Each welding head 5 carries a welding torch 6. The welding head guide 4 is clamped to the upper pipe section 2 in such a position along the length of the pipe section that each welding torch is aligned with the bottom of the V-groove, so that, in use of the apparatus, as the welding heads 5 are driven along the welding head guide 4 in the circumferential direction, the welding torches progressively deposit welding material in the groove and build it up as the groove becomes filled, thereby creating a strong welded joint between the two pipe sections 2,3. Mounted above the welding head guide 4 in spaced relationship thereto is a carousel 7 serving as a rotary equipment carrier. The carousel defines a centred opening 7a through which the pipeline being fabricated passes. As clearly shown in Fig. 2, the opening 7a is open to the exterior of the carousel at one side 7b, to allow each next upper pipe section 2 to be laterally displaced, from an initial position outside the carousel and in parallel relationship to the lower pipe section 3, to the centre of the carousel, in axial alignment with the lower pipe section.

The carousel is provided at equally-angularly spaced positions around its circumference with axles 8 which carry guide pinion wheels 27, which run on, and mesh with, a circular support track 28, so as to enable the carousel to rotate about the common pipe axis 31.

One or more drive motors (not shown) rotatably drive the pinion wheels, to cause the carousel 7 to rotate about its rotational axis, which is coincident with the aligned axes of the upper and lower pipe sections 2,3. The meshing between the pinion wheels and the support track ensures that there is no slippage when the carousel is rotated by the drive motor(s).

The carousel carries various forms of supply equipment for the welding heads 5. In particular, the carousel carries an electrical power supply and distribution unit 9, gas supply equipment 10, a water cooling unit 1 1 and a wire feeder 12. These four different kinds of supply equipment are supported by the carousel in respective regions, as may be appreciated from Figure 2. Electrical power is supplied from an external power supply (not shown) to a slip ring assembly 13, comprising a stationary slip ring 14 on the vessel 29 and a moving power take-off contact 15 on the carousel, the contact being connected by a power take-off line 16 to the power supply and distribution unit 9. This unit 9 has a first output for supplying power along power supply line 17 to a distribution manifold 18, and a second output connected by ancillary power supply line 30 to the water cooling unit 1 1 , where cooling water maintained at a pre-set temperature is circulated to/from distribution manifold 18 through a cooling water flow-return line 19 and back to the water cooling unit 1 1 . The power supply and distribution unit also supplies power to the drive motor(s) for the pinion wheels 27, the necessary power supply lines not being shown in Figures 1 to 3 for simplicity. Alternatively, the circular track 28 can be secured around the periphery of the carousel 7 and the pinion wheels 27, which mesh with the track 28, are rotated by drive motors that are mounted on the vessel 29, so as to rotate the carousel 7. The gas supply equipment 10 comprises a plurality of interconnected gas canisters 20, which serve to supply shielding gas for the welding torches 6 along a common gas supply line 21 to the distribution manifold 18. A control valve (also not illustrated) is incorporated in the gas supply line 21 , for selectively turning the gas supply on and off, as required. The wire feeder 12 delivers welding wire, stored on a spool, through a wire feed guide 22 to distribution manifold 18.

The distribution manifold 18 serves to distribute welding supplies to the welding heads 5. One such welding supply is electrical power for causing the welding torches to produce welding arcs. Other welding supplies are physical consumable items such as cooling water to prevent the welding torches from overheating, shielding gas to envelop the welding arc in an inert atmosphere and welding wire for consumption by the welding torches in the welding process. For this purpose, a single umbilical 23 connects a respective outlet of the distribution manifold 18 to a respective welding head 5. The umbilical incorporates multiple lines, being a power supply line, a cooling water supply line, a cooling water return line, a shielding gas supply line and a wire supply line.

A horizontal work floor 24 is provided for operating personnel 25, below the welding heads 5 and guide 4. An opening is formed in the work floor, to allow the pipeline to pass through.

The wire welding apparatus operates as follows.

Initially, the lower pipe section is held in position, extending down through the work floor 24 and the upper pipe section 2 is raised, by means well known in the art, in the lay tower

(not shown) of the pipe laying vessel 30, into an initial position, external to the carousel, in which it extends parallel to the lower pipe section 3 but is offset from the axis of the lower pipe section, so as to be external to the carousel 7, with its lower end at a higher level than the upper end of the lower pipe section. The upper pipe section is then horizontally displaced, so as to enter the opening in the carousel, from its open side 7b, pass over the welding head guide 4 and move into the central opening 7a, in alignment with the lower pipe section 3. The upper pipe is then lowered through the welding head guide 4 to bring its lower end into abutment with the upper end of the lower pipe, and held there.

Next, the welding head guide 4, together with the welding heads 5 located on it, is clamped around the upper pipe section 2. Then, power is supplied, via the slip ring assembly 13, power supply and distribution unit 9 and distribution manifold 18 to the welding heads, power is also supplied from the power supply and distribution unit 9 to the water cooling unit 1 1 , to cool water which is circulated to the welding heads, and an on-off valve (not shown) on the common gas supply line 21 is opened to allow shielding gas to be supplied from gas canisters 20 to the welding heads. At the same time, the welding heads are advanced on the welding head guide 4 around the pipeline joint to be welded, in synchronism with rotation of the carousel. Particularly if the welding heads are individually driven by separate drive units, there may not be perfect synchronisation in rotational speed between advancement of the welding heads and rotation of the carousel, but any small changes in relative angular position are accommodated by the flexible umbilicals 5. These umbilicals also accommodate small changes in relative spacing between portions of the carousel and the welding heads, for example caused by vibration.

As the welding heads progressively rotate around the V-groove at the joint to be welded following starting operation of the wire feeder 12, welding material deposited by the welding torch gradually builds up in the V-groove, starting at the bottom. The process is continued, until the groove has been filled with welding material to the level of the pipeline outer diameter, and is then stopped. In this way, a high quality welded joint can be formed between the upper and lower pipe sections.

It will be appreciated that, owing to the use of the two, diametrically-opposed, welding heads, the welded joint can be formed in roughly half the time, for any given rotational speed of the welding heads, as compared with the time that would be needed if only a single head were to be used. In modified arrangements, greater numbers of welding heads can be used. For example, three welding heads can be used, preferably positioned at 120° intervals about the pipeline axis. Another preferred arrangement would use four welding heads, positioned at 90° intervals about the pipeline axis. These arrangements further reduce the time required to finish welding the pipe joint. Since each item of supply equipment 9, 1 1 , 20 and 12 on the carousel is a common source of supply for both welding heads, each type of equipment being accommodated in a respective region of the carousel, it is not necessary to provide separate supply equipment of each type for each welding head, which would clutter the overhead carousel. Using common supply equipment for the welding heads saves space on the carousel, so that for any given carousel size, more free space is provided, to assist operation and maintenance, or a more compact carousel design can be provided with the same available free space, according to requirements.

Another advantage is that the gas canisters and wire feeder have to be re-charged or replaced, only when one or the other has run out so that neither of the welding heads can be used, whereas in the conventional arrangement disclosed in EP-A-1 148 966, operation of the welding apparatus has to be shut down to change gas canisters or fit a new spool of welding wire, whenever the gas or welding wire runs out for one welding head or the other, which would result in more frequent stoppages.

Orientating the rotational axis of the carousel so as to be coincident with the axis of the pipeline and the axis about which the welding heads can be orbited offers the benefit that the central hole in the carousel through which the pipeline passes can have a smaller diameter than that required for a pipeline whose orientation varies according to the lay orientation whereas the rotational axis of the rotary equipment holder is vertical, as in the case of the welding apparatus disclosed in EP-A-1 148 966.

Raising the carousel and its various supply equipment above the work floor 24 is advantageous, in that it results in a less congested, and therefore safer, workspace for operating personnel 25, while providing a horizontal floor on which to stand, which is easier for operating personnel to use.

In the embodiment according to Figs. 1 to 3, all four types of supply equipment are provided in respective regions of the carousel and each of them is connected to supply both of the welding heads. However, it is not essential that all supplies required for welding are supplied to each welding head in this way. Benefits are provided if even one of electric power, cooling water, shielding gas and welding wire are supplied in this way; it is sufficient. In some arrangements, it may be preferred if only at least one of these services is supplied in this way, but that other welding supplies are supplied from respective supply equipment, one for each welding head. An example of such an arrangement is disclosed with reference to Figs. 4 to 6. In Figs. 4 to 6, like reference numerals denote corresponding elements to those disclosed with reference to Figs. 1 to 3. Accordingly, such elements do not need to be further described herein; rather the description is confined to the disclosed differences. As can best be appreciated from Figs. 5 and 6, here the common wire feeder 12 of the first embodiment is replaced by respective wire feeders 12', respectively carried by the welding heads 5, and the gas supply equipment 10 is expanded into the space that is occupied by the wire feeder 12 in the Figs. 1 to 3 embodiment, thereby increasing the number of interconnected canisters 20 that can be accommodated and extending the total duration for which shielding gas can be supplied to the welding heads before the canisters need to be replaced/recharged. Furthermore, although only a single wire feeder 12 is used in the first embodiment, it needs to incorporate two separate wire spools, and the wire feeding paths, via distribution manifold 18, to the welding torches 5 are relatively long and convoluted, which can lead to potential wire feedings problems and jams. These are avoided by the short wire feeding paths between the wire spools 26 and the welding torches 6, as clearly shown in Fig. 6.

Other types of common supply equipment that are common to the welding heads (power supply units, gas canisters and cooling water systems) can be replaced by separate such units, respectively connected to supply the welding heads, providing at least one type of supply equipment commonly supplies the welding heads, thereby securing the advantages, for that type of supply equipment, to which reference has been made above.

With reference to Fig. 7, a third embodiment is shown in side elevation, corresponding to the side elevation views of Figs. 1 and 4, but in which the carousel is mounted for rotation about a vertical axis, irrespective of the orientation of the pipeline (vertical or inclined-to- the-vertical). Sectional views corresponding to those along the section lines l l-l l and I l l-I l l in Fig. 1 have not been included but would be substantially identical to those of Figs. 2 and 3, respectively.

As may be appreciated from Fig. 7, the umbilicals 23 will need to have adequate slack, considerably more than that required in the first two embodiments, in order to be able to accommodate changes in relative spacing between the distribution manifold 18 and the welding heads 5, as the carousel and welding heads rotate, in synchronism, about their respective, disparate, axes of rotation. It will be appreciated that, in the Fig. 7 embodiment, the central opening 7a in the carousel 7 will need to be slightly larger, in order to accommodate the different angles at which the pipeline can pass through the carousel, while the carousel rotational axis remains vertical (disregarding the motion of the lay vessel). On the other hand, operation and maintenance of the supply equipment on the carousel 7 are facilitated, in view of the horizontal orientation of the surface of the carousel on which the various types of supply equipment 9, 10, 1 1 , 12 are carried.

The embodiment according to Figure 7 can of course be modified, if required, so that separate wire feeders are provided, one for each welding head 5, in corresponding manner to that described with reference to Figures 4 to 6.

Although the carousel is located above the welding heads in the embodiments according to Figures 1 to 7, it could be located below the welding heads, where it would also serve as a work floor for operating personnel. However, the illustrated embodiments are preferred, since the work floor can be completely free of operating equipment and a stationary work floor is more acceptable to human operators.

In the above embodiments, the rotation of the carousel and the orbital rotation of the welding heads is synchronised. In a modified embodiment, the carousel can be a stationary structure, fixed relative to the pipe laying vessel. Then, the umbilicals connecting outlets of the distribution manifold with the welding heads need to be sufficiently long, such that they can wrap around an umbilical keep arrangement as the welding heads orbitally rotate about the pipe sections.

In the claims which follow, whilst any reference characters in parentheses denote counterparts for the recited elements and features, they have no restrictive effect on the protective scope, which is determined solely on the basis of the claim language.

Claims

1 . Pipe welding apparatus for welding pipe sections together, end-to-end, to form a pipeline, comprising: a welding head guide for fixing around one of the pipe sections; a plurality of welding heads mounted on the welding head guide to be guided around said one pipe section for welding it and another pipe section together, end-to-end, in a vertical or inclined-to-the-vertical orientation along a common axis; an equipment carrier having an opening therein to enable the pipeline to pass through it as it is being laid; and supply equipment and a distribution manifold, wherein the supply equipment and the distribution manifold are supported by the carrier, wherein the supply equipment supplies at least one welding supply to the distribution manifold, and wherein the distribution manifold is connected to each of the plurality of welding heads to distribute the at least one welding supply between those welding heads.

2. Pipe welding apparatus as claimed in claim 1 , wherein the at least one welding supply comprises a physical consumable item.

3. Pipe welding apparatus as claimed in claim 2, wherein the at least one welding supply comprises cooling water and the supply equipment comprises cooling water supply equipment.

4. Pipe welding apparatus as claimed in claim 2 or claim 3, wherein the at least one welding supply comprises shielding gas and the supply equipment comprises shielding gas supply equipment.

5. Pipe welding apparatus as claimed in any of claims 2 to 4, wherein the at least one welding supply comprises welding wire and the supply equipment comprises welding wire feeding equipment for feeding wire to a welding torch of each welding head.

6. Pipe welding apparatus as claimed in any of claims 1 to 4, wherein wire feeding equipment is mounted on each welding head for feeding wire to a welding torch of that welding head as it is guided around said one pipe section.

7. Pipe welding apparatus as claimed in any preceding claim, wherein the supply equipment comprises electrical power supply equipment.

8. Pipe welding apparatus as claimed in any preceding claim, wherein each of the welding heads is connected to the distribution manifold by a separate umbilical.

9. Pipe welding apparatus as claimed in any preceding claim wherein the equipment carrier is a rotary equipment carrier mounted for rotation about a vertical or inclined-to-the- vertical axis substantially in synchronism with the guidance of the welding heads around said one pipe section.

10. Pipe welding apparatus as claimed in claim 9, wherein the rotary equipment carrier is located above, and with a vertical separation from, the welding head guide and welding heads.

1 1 . Pipe welding apparatus as claimed in claim 10, wherein a stationary, substantially horizontal, work floor for operating personnel is located below, and with a vertical separation from, the welding head guide and welding heads.

12. Pipe welding apparatus as claimed in claim 9, wherein the rotary equipment carrier is located below, and with a vertical separation from, the welding head guide and welding heads.

13. Pipe welding apparatus as claimed in any of claims 9 to 12, wherein the rotary equipment carrier is mounted to rotate about a common axis of the end-to-end pipe sections.

14. Pipe welding apparatus as claimed in any of claims 9 to 12, wherein the rotary equipment carrier is mounted to rotate about a substantially vertical axis.