FIELD

The invention relates to a pipe laying vessel comprising a pipe laying system for laying a pipe, the system being provided with a sawing apparatus for sawing the pipe, the apparatus comprising:

a sawing device; and,

a carriage for supporting the sawing device.

BACKGROUND

During installation of a pipeline on the bottom of the sea different pipe sections are welded together to form a pipeline which is lowered into the sea with a pipe laying system on a pipe laying vessel. The welding process is monitored, and after welding the weld is inspected with a non-destructive examination method to assure that the weld does not contain unacceptable defects. If a weld is rejected it needs to be cut, the edges of the pipe need to be prepared for welding and the pipe section may be welded to the pipeline again.

The cutting process may be time consuming because the wall of the pipe may be thick and the welding material may be difficult to remove.

Cutting methods currently used generally involve an apparatus that uses chisels to cut away pipe or weld material. This is a slow process that can take up to several hours. As the cutting operation takes place on the critical path of an expensive pipelay vessel, there is a need for improvement.

SUMMARY

It is therefore an objective of the invention to provide a pipe laying vessel comprising a pipe laying system provided with an improved pipe cutting apparatus. Accordingly there is provided a pipe laying vessel comprising a pipe laying system for laying a pipe, the system being provided with a sawing apparatus for sawing the pipe, the apparatus comprises:

a sawing device; and,

a carriage for supporting the sawing device; wherein the apparatus comprises:

a mover constructed and arranged for moving the carriage substantially around the pipe; and, the sawing device comprises a saw constructed and arranged for creating a saw slot in the pipe while being moved substantially around the pipe.

An advantage of a saw is that a smaller, less wide, cut can be made. As less material needs to be removed, a more efficient process can be achieved. It further allows for more cuts, when compared to a chisel, to be made on the same pipe section if required.

A further advantage includes that the cut can be completed in less time.

A further advantage includes the fact that during the rotation of the saw around the pipe, the saw cuts through a more or less constant length of pipe material at all times, which makes it easier to control the cutting operation.

According to a further embodiment the carriage may be moveable by the mover in a first rotational direction around the pipe. The blade of the saw may have a sawing direction at the saw slot in the same direction as the first rotational direction.

By having the direction of the blade of the saw at the saw slot being the same as the direction the carriage with the sawing device is being moved around the pipe the saw chips produced with sawing through the pipe are moved out of the pipe. It is advantageous to reduce the amount of saw chips in the pipe to a minimum as it may damage the inner wall of the pipeline or valves and contaminate the pipe.

According to a further embodiment the saw is a bandsaw.

The bandsaw is preferred as this offers the best possibilities to control the sawing operation as well as prevent saw chips to enter the pipeline.

The bandsaw has a good capacity to saw through the pipe and by moving the bandsaw substantially around the pipe during the sawing process the saw can be kept relatively small since it doesn't have to saw through the whole diameter of the pipe at once but only through the thickness of the pipe wall.

According to a further embodiment the mover is constructed and arranged for moving the carriage in a direction substantially perpendicular to a surface of the pipe at the saw slot.

Moving the carriage with the sawing device in a direction substantially perpendicular to the pipe surface makes it possible to move the blade at the beginning of the saw procedure slowly into the pipe. Moving the carriage with the sawing device may be done while the carriage is moving around the pipe.

According to a further embodiment the mover comprises: a guide for providing guiding around the pipe; a cart constructed to move over the guide while supporting the carriage; and, a motor for driving the cart over the guide around the pipe.

The cart and the guide around the pipe assure a good guidance of the saw along the pipe surface and assure that the blade of the saw will end the rotational movement around the pipe at substantially the same location on the pipe surface as where it started.

According to a further embodiment the guide comprises a clamp constructed and arranged for clamping the guide against the pipe.

By clamping the guide against the pipe a stiff connection between the pipe and the guide is assured. The saw is thereby provided a good reference position to the pipe whereby it may be assured that the blade of the saw will end the rotational movement around the pipe at substantially the same location on the pipe surface as where the saw started.

According to a further embodiment the guide comprises at least two guide elements mountable against each other to form the guide around the pipe.

In this way the guide can be mounted around a pipe while the pipe may be suspended from the top.

According to a further embodiment the guide is constructed to extend in a first plane substantially perpendicular to the pipe outer surface.

In this way the guide provides good guiding for a carriage being moved around the

Pipe- According to an embodiment the mover comprises at least two carts.

By having at least two carts moving over the guide extra stability may be provided to the saw.

According to an embodiment the cart is provided with a slide for allowing a movement of the carriage in a direction perpendicular to a surface of the pipe at the saw slot.

Moving the carriage with the sawing device in a direction perpendicular to the pipe surface makes it possible to move the blade at the beginning of the saw procedure slowly into the pipe. Advantageously, at least two carts with at least two of these slides are provided such that the sawing device is stable during movement. According to a further embodiment the carriage comprises a base frame and the baseframe is slidably connected to the slide of the cart and the apparatus comprises a motor for driving the baseframe in the direction perpendicular to a surface of the pipe at the saw slot over the slide.

Sliding the baseframe of the sawing device over the slides of the cart in a direction perpendicular to the pipe surface makes it possible to slide the blade at the beginning of the saw procedure in a controlled and stable manner into the pipe.

According to an embodiment the bandsaw comprises: a first and second wheel positioned to rotate in a second plane; a continuous blade running over the first and second wheel; and, a driving motor provided to the first wheel constructed and arranged to pull the blade through the saw slot.

By pulling the blade through the saw slot the blade is tensioned by the saw slot thereby creating a straight sawing direction. By pushing the blade through the saw slot the blade may wobble in all directions thereby creating non straight sawing. Therefore pulling the blade through the saw slot is advantageously.

According to an embodiment the first and second wheel are constructed and arranged with its second plane under an angle a little larger than 90 degrees with respect to the first plane.

The continuous blade is running over the first and second wheel with its inner side in contact with the wheels, the sawing action is accomplished by the thin side of the blade and to avoid contact between the wheels and the pipe the plane in which the first and second wheel are rotating can be a little larger than 90 degrees with respect to the first plane which extends substantially perpendicular to the pipe.

According to an embodiment the bandsaw comprises a blade angle adjustment instrument comprising two sliders constructed on two opposite sides of the blade to adjust the orientation of the blade to an orientation parallel to the first plane.

For good sawing the blade needs to move through the pipe parallel to the first plane perpendicular to the pipe. Since the wheels are running in the second plane under an angle a little larger than 90 degrees with respect to the first plane the blade is not parallel to the first plane. The blade angle adjustment instrument may adjust the angle under which the blade is engaging with the saw slot to make it perpendicular to the pipe.

According to an embodiment the first wheel is driven via a worm gear and a worm by the motor. The worm gear and the worm assure a very low gear ratio such that only one gear box is necessary. The latter being advantageously because it assures a very stiff torque between the motor and the first wheel. According to an embodiment the bandsaw is provided with a tensioner for providing a tension to the blade.

By providing a tension to the blade the blade is not slipping over the wheels and the orientation of the blade in the saw slot is well determined. According to a further embodiment the bandsaw comprises a guide wheel for guiding the blade.

The guide wheel may be provided with brushes to clean the blade from saw chips.

According to a further embodiment the apparatus comprises an oil dispenser for providing cutting oil to the blade.

The cutting oil helps to guide the blade smoothly through the saw slot while sawing through the pipe.

According to a further embodiment there is provided a sawing apparatus for cutting a pipe, the apparatus comprises:

a sawing device; and,

a carriage for supporting the sawing device; wherein the apparatus comprises:

a mover constructed and arranged for moving the carriage substantially around the pipe; and, the sawing device comprises a saw constructed and arranged for creating a saw slot in the pipe while being moved substantially around the pipe.

According to a further embodiment the sawing device is a bandsaw.

According to a further embodiment there is provided a pipeline cutting method, the method comprises:

supporting a sawing device with a carriage;

moving the carriage substantially around the pipe with a mover; and,

creating a saw slot in the pipe with a saw provided to the sawing device while the sawing device is being moved substantially around the pipe.

According to a further embodiment during the movement around the pipe, the sawing device cuts through a substantially constant thickness of pipe material. According to a further embodiment the pipe is cut in a single movement around the pipe.

According to a further embodiment the saw blade protrudes the pipe over a depth of substantially the wall thickness.

According to yet a further embodiment there is provided a method for installing a pipeline, the method comprises:

welding a pipe to a pipeline;

inspecting the weld; and

cutting the pipe.

BRIEF DESCRIPTION OF TH E DRAWI NGS

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying schematic drawings in which corresponding reference symbols indicate corresponding parts, and in which:

Figure 1 depicts a sawing apparatus for sawing a pipe according to an embodiment; Figure 2 depicts a bottom view on the sawing apparatus of figure 1 without pipe;

Figure 3 depicts a first top view on the sawing apparatus of figure 1 without pipe; Figure 4 depicts a second top view on the sawing apparatus of figure 1 with a pipe; and,

Figure 5 depicts schematically a cross-sectional top view of a sawing motion through the pipe.

DETAILED DESCRIPTION OF THE DRAWINGS In the offshore industry there is a need for underwater pipelines. These underwater pipelines may be provided by joining pipe sections together to form a pipeline which is lowered from a pipe laying vessel to an underwater sea bed with a pipe laying system. In such a pipe laying system a plurality of pipe sections are welded to one another to form the pipeline, which is suspended from the pipe laying vessel when an upper end of the most recently joined pipe section is to be welded to a lower end of a new pipe section being lined up above said upper end. Upon completion of a weld, the end of the pipe is gripped with a clamp and lowered to just below the welding position to prepare for a new pipe section to be arranged above the upper end of the lowered pipe. Both pipe ends have pipe end preparations, so called bevels that are made to create the weld gutter when the pipe ends are placed on each other.

The welding of two pipe sections requires precise positioning of the welding equipment, in particular the welding heads with respect to the weld gutter. Also, the position of the two pipe ends to be joined relative to each other is subjected to strict requirements before welding may start. Since pipe sections from a pipe manufacturer may not be perfectly shaped, it is impossible to get a line up where the two pipe ends line up perfectly with each other all around the circumference of the pipe. If during welding or examination of the weld it becomes clear that the weld is not acceptable a sawing device may be used to cut the pipeline. Subsequently the bevels may be prepared again and the welding step may be repeated to assure a pipeline with only acceptable welds.

The pipe laying system for laying a pipe may therefore be provided with a sawing apparatus for sawing the pipe. Figure 1 depicts a sawing apparatus for sawing a pipe according to an embodiment. The sawing apparatus 1 comprises a sawing device 3 and a carriage 5 for supporting the sawing device 3. The apparatus 1 comprises a mover 7 constructed and arranged for moving the carriage 5 substantially around the pipe 9. The pipe 9 may be provided with one or more layers of coating 1 1 which is generally applied at the location where the welding takes place and the sawing apparatus 1 is sawing after completion and approval of the weld.

The sawing device 3 may comprise a bandsaw 13 constructed and arranged for creating a saw slot in the pipe 9 while being moved substantially around the pipe 9. The bandsaw 13 has a good capacity to saw through the pipe 9, even if the device has to make a saw slot in material that is difficult to cut, for instance harder steels or Inconel®.

By moving the bandsaw substantially around the pipe during the sawing process the bandsaw can be kept relatively small since it doesn't have to saw through the whole diameter of the pipe 9 in once but only through the thickness of the pipe wall. Also the sawing slot may have the same size throughout the movement around the pipe 9, which is advantageously because the bandsaw than 13 continuously removes the same amount of pipe material. The bandsaw may than be running the most regularly which makes it easier to control the apparatus.

The carriage 5 may be moveable by the mover 7 in a first rotational direction 15 around the pipe 9. The blade 17 of the bandsaw may have a sawing movement at the saw slot in the same direction as the first rotational direction 15. The direction of the blade at the top 19 of the apparatus is opposite to the direction of the blade 17 at the saw slot. By having the direction of the blade 17 of the bandsaw at the saw slot in the same direction as the first rotational direction 15 the saw chips produced with sawing through the pipe is moved out of the pipe. It is advantageously to have as little saw chips as possible in the pipe 9 because it is difficult to get it out.

The mover 7 may be constructed and arranged for moving the carriage 5 in a direction perpendicular to a surface of the pipe 9 at the saw slot. Moving the carriage 5 with the sawing device 3 in a direction perpendicular to the pipe surface makes it possible to move the blade 17 at the beginning of the saw procedure slowly into the pipe 9 while the carriage 5 and the sawing device 3 are moved around the pipe 9.

The mover 7 may comprise a guide 21 for providing guiding around the pipe 9. At least two carts 23 may be constructed to move over the guide 21 while supporting the carriage 5. A rotation motor 24 may be used to drive the carts 23 over the guide 21 around the pipe 9. The carts 23 and the guide 21 around the pipe 9 assure a good guidance of the bandsaw along the pipe surface and assure that the blade 17 of the bandsaw will end the rotational movement around the pipe at substantially the same location on the pipe surface as where it started.

The guide 21 may comprise at least two guide elements 25 and 26 mountable against each other to form the guide 21 around the pipe 11. In this way the guide can be mounted on a pipe 9 while the pipe is suspended from the top. The guide is constructed to extend in a first plane substantially perpendicular to the pipe outer surface. In this way the guide provides good guiding for a carriage 5 being moved around the pipe 11.

The carts 23 may be provided with a slide 27 for allowing a movement of the carriage

5 in a direction perpendicular to a surface of the pipe 9 at the saw slot. Moving the carriage 5 with the sawing device 3 in a direction perpendicular to the pipe surface makes it possible to move the blade 17 at the beginning of the saw procedure slowly into the pipe 9 while the carriage 5 and the sawing device 3 are moved (or net yet moved) around the pipe 9. At least two carts 23 with at least two of these slides 27 are provided such that the sawing device 3 is stable during movement.

A sliding motor 29 may be provided to provide the sliding movement. The carriage 5 may comprise a base frame 31 and the baseframe is slidably connected to the slide 27 of the cart 23 and the sliding motor 29 may drive the base frame 31 in the direction

perpendicular to a surface of the pipe 9 at the saw slot over the slide. Sliding the baseframe 31 of the sawing device 3 over the slides 27 of the carts 23 in a direction perpendicular to the pipe surface makes it possible to slide the blade 17 at the beginning of the saw procedure slowly and stable into the pipe surface.

Alternatively the carriage may be rotatable around a vertical hinge so that the sawing device may be movable in a direction perpendicular to the surface of the pipe. Alternatively, the mover may comprise a robotic arm constructed and arranged to move the sawing device around the pipe while pressing the bandsaw against the pipe to saw through the wall of the pipe. The bandsaw 13 comprises a first wheel 33 and second wheel 35 positioned to rotate in a second plane and a blade 17 e.g. a continuous blade running over the first and second wheel. A driving motor 37 may be provided to drive the first wheel 33 to pull the blade 17 through the saw slot.

By pulling the blade 17 through the saw slot the blade is tensioned by the saw slot thereby creating a straight sawing direction. By pushing the blade 17 through the saw slot the blade may wobble in all directions thereby creating non straight sawing. Therefore pulling the blade through the saw slot is advantageously. The first wheel 33 may be driven via a worm gear and a worm by the driving motor 37. The worm gear and the worm assure a very low gear ratio such that only one gear box is necessary. The latter being

advantageously because it assures a very stiff torque between the motor 37 and the first wheel 33.

The bandsaw 3 may be provided with a tensioner 38 for providing a tension to the blade 17 via the second wheel 35. By providing a tension to the blade 17 the blade may not be slipping over the wheels and the orientation of the blade in the saw slot is well determined.

The second plane (in which the first and second wheel 33, 35 are rotating) may be constructed and arranged under an angle 39 a little larger than 90 degrees with respect to the first plane (perpendicular to the pipe surface). The blade 17 is running over the first and second wheel 33, 35 with its inner side in contact with the wheels, the sawing action is accomplished by the thin side of the blade and to avoid contact between the wheels and the pipe 9 the plane in which the first and second wheel are rotating can be a little larger than 90 degrees with respect to the first plane which extends substantially perpendicular to the pipe.

The bandsaw 3 may comprise a guide wheel 41 for guiding the blade 17 and which may be provided with brushes to clean the blade of the saw.

Figure 2 depicts a bottom view on the sawing apparatus 1. Two guide elements 25 and 26 are mountable against each other to form the guide around the pipe (not shown). The guide 21 comprises a clamp constructed and arranged for clamping the guide against the pipe. By clamping the guide against the pipe a stiff connection between the pipe and the guide is assured. The bandsaw is thereby provided a good reference position to the pipe whereby it is assured that the blade of the bandsaw will end the rotational movement around the pipe at substantially the same position on the pipe surface as where the bandsaw started.

An additional clamp 43 may be provided to provide extra support for the guide. The additional clamp 43 may be provided with a clamping mechanism 45 to clamp the additional clamp against the pipe.

Two carts 23 constructed to move over the guide while supporting the carriage 5 are also visable. The rotation motor 24 may be used to drive the carts 23 over the guide elements 25, 26 around the pipe. Figure 3 depicts a top view on the sawing apparatus 1. The first wheel 33 and second wheel 35 are rotating to move the blade 17 e.g. a continuous blade running over the first and second wheel. A driving motor 37 may be provided to drive the first wheel 33 to pull the blade 17 through the saw slot in a sawing direction 47. By pulling the blade 17 through the saw slot the blade is tensioned by the saw slot thereby creating a straight sawing direction.

The bandsaw 3 comprises two blade angle adjustment instruments 49 comprising two sliders constructed on two opposite sides of the blade 17 to adjust the orientation of the blade to an orientation parallel to the first plane. For good sawing the blade 17 needs to move through the pipe parallel to the first plane perpendicular to the pipe. Since the wheels 33, 35 are running in the second plane under an angle a little larger than 90 degrees with respect to the first plane the blade is not parallel to the first plane. The blade angle adjustment instruments 49 may adjust the angle under which the blade is engaging with the pipe at the saw slot.

The bandsaw 3 may be provided with a tensioner 38 for providing a tension to the blade 17 via the second wheel 35. The bandsaw 3 comprises an oil dispenser for providing cutting oil to the blade.

Figure 4 depicts a top view on the sawing apparatus 1. The first wheel 33 and second wheel 35 are rotating to move the blade 17 e.g. a continuous blade running over the first and second wheel. The driving motor 37 may be provided to drive the first wheel 33 to pull the blade 17 through the saw slot 51 in a sawing direction 47.

The bandsaw 3 may be moveable by the mover in a first rotational direction 15 around the pipe 9. The blade 17 of the bandsaw may have a sawing direction at the saw slot 51 in the same direction a the first rotational direction 15. By having the direction of the blade 17 of the bandsaw 3 at the saw slot 51 in the same direction as the first rotational direction 15 the saw chips produced with sawing through the pipe is moved out of the pipe 9. It is advantageously to have as less saw chips as possible in the pipe 9 because it is difficult to get it out.

Figure 5 depicts schematically a top view with a cross-section of the pipe 9 at the saw slot 51. It gives a top view of the blade 17 of the bandsaw at the saw slot 51 and its sawing motion through the pipe.

The bandsaw starts sawing with the blade 17 moving in the sawing direction 47 at the saw slot 51. The bandsaw slides in a direction 53 into the pipe 9 over the slides 27 (see figure 1) so that the saw slot 51 reaches the inside of the pipe 9 (situation a). During sawing the saw chips may be thrown out by the blade outside the pipe 9 in a direction 55.

The bandsaw may be moved by the mover 7 (in figure 1) in a first rotational direction 15 around the pipe 9 to situation b and c while continuous sawing. This process may be continued until the bandsaw has been moved around the complete circumference of pipe 9. It is to be understood that the disclosed embodiments are merely exemplary of the invention, which can be embodied in various forms. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present invention in virtually any appropriately detailed structure.

Furthermore, the terms and phrases used herein are not intended to be limiting, but rather, to provide an understandable description of the invention.

The terms "a" or "an", as used herein, are defined as one or more than one. The term another or subsequent, as used herein, is defined as at least a second or more. The terms including and/or having, as used herein, are defined as comprising (i.e., not excluding other elements or steps). Any reference signs in the claims should not be construed as limiting the scope of the claims or the invention. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. The scope of the invention is only limited by the following claims.