Title: Improvements relating to laying of pipe-in-pipe

FIELD OF THE INVENTION

The present invention relates to a fixation device configured ^' to fixate a position of an inner pipe of a double-walled pipe with respect to an outer pipe of said double-walled pipe.

BACKGROUND

In the offshore industry there is a need for underwater pipelines. These underwater pipelines may be provided by joining pipe sections together in a substantially vertical position to form a pipeline which is lowered from a vessel to an underwater bottom, for instance the bottom of the sea. In such pipe laying method, which is commonly referred to as a J-lay method, a plurality of pipe sections welded to one another, together forming a part of the pipeline, hang down from a vessel in a substantially vertical direction, where 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.

In a specific embodiment of the J-lay method, at least one end of the pipe sections may be provided with a collar for easier handling of the pipe sections. Upon completion of a weld, the end of the pipeline is gripped by the collar with a clamping device 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 pipeline. For some applications it is desirable to provide double walled pipelines, i.e. so-called pipe in pipe pipelines. Such double walled pipeline comprises at least an outer pipe and an inner pipe being arranged concentrically in said outer pipe. The inner pipe may in the axial direction be supported by bulkheads connecting the inner pipe to the outer pipe at regular intervals, or any other suitable connection means between the inner pipe and the outer pipe. The presence of the outer pipe may for instance prevent the inner pipe from buckling laterally. Also the space between the outer pipe and the inner pipe may serve as an insulation layer.

When laying a double-walled pipeline using a J-lay tower, the existing pipeline is held at the upper end of the outer pipe. As a result, due to motions of the pipe laying vessel on the sea surface,

an oscillating motion is induced into the outer pipe. The double- walled pipe may respond as a mass-spring system, wherein the oscillating motion is transferred from the outer pipe via the connection between the outer pipe and the inner pipe, for instance a bulkhead, to the inner pipe. As a consequence, there may be a relative motion between the upper end of the outer pipe and the upper end of the inner pipe.

When a new inner pipe section is to be welded to the inner pipe of the existing pipeline, the relative motion between the outer pipe of the existing pipeline held by a clamping device and the upper end of the inner pipe may lead to difficulties in positioning the lower end of the new inner pipe section with respect to the upper end of the inner pipe of the existing pipeline, since the line-up device for the new inner pipe section is not capable of following the movements of the existing inner pipe.

Moreover, even when these movements could be followed the welding of the new inner pipe section to the inner pipe of the existing pipeline would imply difficulties since also the welding equipment should be able to follow accurately the movements of the inner pipe and inner pipe section to make welding possible.

On the other hand it is not possible to simply clamp the inner pipe to fixate the inner pipe, since the inner pipe could be fixated at a position or at a motion speed of said inner pipe which would induce huge forces in the fixation device or in the inner pipe. These forces may be large enough to damage the inner pipe and/or the fixation device.

It has been proposed to stabilize the relative motion between the inner pipe and the outer pipe by filling the space between the inner pipe and the outer pipe with a friction material. However, the provision of such material takes a considerable amount of time and the insulation properties of the double walled pipe may decrease due to the presence of the material between the inner and outer pipe. In alternative embodiments it has been proposed to provide non- expandable wedges between the inner pipe and outer pipe for fixation of the inner pipe, but this method has also led to unsatisfactory results .

SUMMARY OF THE INVENTION

It is desirable to provide a fixation device for fixation of an inner pipe of a double-walled pipe with respect to a pipe laying structure and/or an outer pipe of said double-walled pipe, which fixation device allows relatively easy a quick fixation of said inner pipe in a certain position or position range in order to make proper welding of a new inner pipe section on the inner pipe of an existing pipeline, in particular in a J-lay tower, possible.

The fixation device can be applied for motions as well as for vibrations . The fixation device can be used in J-lay, S-lay, G-lay, vertical lay and in other suitable situations where an inner pipeline moves relative to an outer pipeline.

Preferably, the fixation device is to be operable by no more than two operators. In an embodiment the present invention provides a pipeline fixating device comprising an expansion organ which is at least partially insertable between an outer pipeline and an inner pipeline extending at least partially within the outer pipeline, the device comprising actuating means for expanding the expansion organ in a substantially radial direction with respect to the inner and outer pipeline for fixing the inner pipeline relative to the outer pipeline in at least an axial direction of the inner and outer pipeline. By placing the expansion organ between the inner and outer pipeline and by expanding it, the movements of the inner pipeline relative to the outer pipeline can relatively quickly be stopped.

In an embodiment, the actuating means are configured for alternating the expansion organ from a non-expanded state to an expanded state and vice versa. This allows an insertion of the expansion organ in the non-expanded state, followed by the expansion to the expanded state. When the fixation is no longer necessary, the expansion organ may be returned to the non-expanded state and removed .

Preferably, the expansion organ comprises an inner contact surface for engagement with the inner pipeline and an outer contact surface for engagement with the outer pipeline, wherein the expansion organ is configured to exert a force on both the outer pipeline and the inner pipeline in at least a radial direction via the inner and outer contact surfaces for fixating the inner pipeline relative to the outer pipeline in the axial direction via friction forces between

the respective contact surfaces and the respective inner and outer pipeline.

Friction forces are an effective way of securing the inner pipeline relative to the outer pipeline. In an embodiment at least one first support part is provided which is not expandable and which is configured to be at least partially inserted between the inner and the outer pipeline at a location which is spaced about the circumference of the inner pipeline from the location of the expansion organ. The first support part is a spacer member which bears the pressure of the expansion organ and redirects it to the outer pipeline .

In an embodiment the expansion organ comprises a first wedge part and a second wedge part which are movable relative to one another for radially expanding the expansion organ. Wedges are simple devices and are known to be able to exert high forces on their surroundings, resulting in high friction forces between the pipelines and the wedge parts for the fixation.

In an embodiment the actuating means is configured to be positioned at least partially outside of the outer pipeline, the device comprising a transmission means for transferring a force of the actuating means to the expansion organ, wherein the transmission means spans a distance between the position of the actuating means and the position of the expansion organ. This configuration allows a slender build of the expansion organ, making it possible to fit the expansion organ into relatively narrow areas between the inner and outer pipeline.

In an embodiment, the pipeline fixating device comprises an end face engagement surface which is configured to engage with at least a part of the end face of the outer pipeline, such that when the expansion organ is in a non-expanded state the pipeline fixating device rests on the end face of the outer pipeline. This feature allows an easy and accurate positioning of the fixating device.

The present invention also relates to a method for fixating an inner pipeline relative to an outer pipeline in at least an axial direction of the inner and outer pipeline with a pipeline fixating device, the method comprising:

- providing a free end of an outer pipeline and providing an inner pipeline extending at least partially within the outer pipeline;

- inserting at least one expansion organ of the pipeline fixating device at least partially in an area between the inner pipeline and the outer pipeline;

- expanding the expansion organ via actuating means in a substantially radial direction with respect to the inner and outer pipeline, such that the expansion organ exerts a force on both the outer pipeline and the inner pipeline, thereby substantially fixating the inner pipeline relative to the outer pipeline in the axial direction. The claims and advantages will be more readily appreciated as the same becomes better understood by reference to the following detailed description and considered in connection with the accompanying drawings in which like reference symbols designate like parts, or parts with the same or similar function.

BRIEF DESCRIPTION OF THE FIGURES

Figure 1 shows a cross-sectional view taken from the side of a part of an end of a pipe-in-pipe assembly with a fixation device according to the invention; Figure 2 shows a top view of a pipe-in pipe assembly with the fixation device according to the invention;

Figure 3 shows a cross-sectional view from the side of a part of an end of a pipe-in-pipe assembly with a fixation device according to the invention; Figure 4 shows a cross-sectional view taken from the side of an expansion organ according to the invention as well as from the side of a support block of the invention;

Figure 5A shows a cross-sectional view taken from the side of an expansion organ in an expanded state; Figure 5B shows a view of a hydraulic pump known in the field of the art;

Figure 6 shows a cross-sectional view taken from the side of an expansion organ according to the invention; and

Figure 7 shows another embodiment of the expansion organ according to the invention.

DETAILED DESCRIPTION OF THE FIGURES

Figures 1, 2 and 3 show a partial cross-section of the inner pipeline 10 and the outer pipeline 12. Insulation material 38 is cut back over a distance to allow the pipe fixation device to be placed

in the annulus 48 between the inner and outer pipe. The pipe fixation device 14 comprises an expansion organ 16 in the form of a wedge. The wedge has two parts 18a, 18b.

The wedge is operable via push/pull rod 20, which is connected via a transmission device 22 in the form of a tri-plate lever to a hydraulic actuator 24. A frame 52 is provided for supporting the various parts. The lever is pivotable about an axis 26.

The push/pull rod is connected to wedge part 18b via pivot axis 50. The fixation device comprises a contact surface 28 which can engage the end face 30 of the outer pipeline 12. Contact surface 28 is preferably shaped to suit the pipe end preparation of outer pipe 12.

Two actuators 24a, 24b are provided. Two support blocks 32a, 32 b are provided in order to support the inner pipeline in two radial directions 34, 36 relative to the outer pipeline 12 and to allow the axial fixation of the inner pipeline via friction forces once the expansion organ is in its expanded state. The support blocks 32a, 32b may have handles 46 which allow easy placing and/or removal by an operator of the support blocks. Figure 3 shows that the contact surfaces 42 of the wedge and the support blocks 32a, 32b are provided with brake shoe material in order to increase the friction with the inner and outer pipeline 10, 12.

A soft landing pad 44 is provided in order to allow easy positioning of the fixation device, and to avoid damaging the outer pipeline end face 30 during installation and/or removal of the fixation device. Figures 4, 5 and 6 show consecutive steps of the device in operation.

In Figure 4, the support blocks 32a, 32b are placed in the annular area 48 between the inner and outer pipeline. Also, the expansion organ or power wedge 16 is placed in the annulus. Figure 5A shows the actuation of the expansion organ with the actuator which forces the wedge parts 18a, 18b against the pipeline walls. This is the expanded state. It is shown that the moving parts stay within the radial boundaries of the wedge, such that the moving parts do not contact the walls of the pipes.

Figure 5B shows a hydraulic pump known in the field of the art. A manual or driven pump may be used.

Figure 6 shows the expansion organ in the non-expanded state which allows a removal of the expansion organ. After welding of the inner pipe, the power wedge is disengaged and subsequently removed. Next, the support blocks are removed.

Figure 7 shows another embodiment of the invention, wherein three wedge parts 18a, 18b, and 18c are provided. In Figure 7, the actuator and the transmission device are not shown. The first and second wedge part 18a, 18b are arranged movably in a radial direction relative to one another, and the third wedge part 18c is arranged to move in an axial direction relative to-fe the first and second wedge part. The second wedge part 18b is fixed to the frame 52, while the first wedge part 18a which is to contact the outer pipeline (not shown) is connected to the frame 52 via a double pivot axis 54, 56 and a chain organ or link plate 58.

In use, the double pivot axis 54, 56 allows the first wedge part 18a to move radially away from the second wedge part 18b in the direction of arrow 60 when the third wedge part 18c moves upward in the direction of arrow 62, and vice versa. The third wedge part 18c has a substantially triangular form, for forcing the first and second wedge part away from one another.

The push/pull rod is left away in Fig. 7 for clarity purposes, but is to be connected to wedge part 18b via a pivot axis 50. In a suitable form, the embodiment of Figure 7 has an advantage in that the first and second wedge parts 18a, 18b can move radially without substantially moving axially. Substantially no sliding of the wedge parts 18, 18b along the pipe surface is therefore necessary. It is conceivable that the three part wedge organ is oriented in a different direction to perform substantially the same function. It will be obvious to a person skilled in the art that numerous other changes in the details and the arrangement of the parts may be varied over considerable range without departing from the spirit of the invention and the scope of the claims.