AU742763B2

AU742763B2 - Method and apparatus for subsea cable installation

Info

Publication number: AU742763B2
Application number: AU19103/97A
Authority: AU
Inventors: Brigt Lokke Friis; John Oivind Norholmen; Lars Aksel Solberg
Original assignee: Nexans SA
Current assignee: Nexans SA
Priority date: 1997-04-28
Filing date: 1997-04-28
Publication date: 2002-01-10
Anticipated expiration: 2017-04-28
Also published as: AU1910397A

Description

P/00/011 28/5/91 Regulation 3.2

AUSTRALIA

Patents Act 1990

ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT Invention Title: METHOD AND APPARATUS FOR SUBSEA CABLE INSTALLATION" The following statement is a full description of this invention, including the best method of performing it known to us:- X024 102 280497 This invention relates to a method and means for the installation of elongated articles and in particular to transferring a construction from a horizontal to a vertical position and vice versa. More specifically the invention relates to handling of heavy bodies, such as a housing which constitutes a termination of an elongated article. The elongated article may be a cable, an umbilical containing cables and/or pipes and similar articles which are to be lowered to or lifted from the sea bed.

When the housing interconnected with and terminating the elongated article is very heavy and rigid as compared to the article itself, the area of interconnection is usually protected with a bending restrictor or a bending strain restrictor. Utmost care must, however, be taken to prevent damage to the elongated article when the construction is to be lifted from a horizontal rest position to a vertical position and vice versa. Similar problems arise when a construction is to be lowered into the sea from a vertical position to a horizontal position on the sea bed and vice versa.

An object of the present invention is to provide a method and means for handling 15 constructions mentioned above without damaging the components of the construction, in particular the elongated article.

According to a first aspect of the invention, there is provided a method for transferring a construction comprising an elongated article provided with at least one termination housing, between a vertical position and a horizontal position and vice versa, 20 said method comprising the step of: attaching handling means to the termination so as to balance and handle the termination substantially at a combined centre of gravity and thereby prevent undue bending of the elongated article during the transfer.

oo*. According to a second aspect of the invention, there is provided an apparatus for transferring a construction, comprising an elongated article provided with at least one termination, between a vertical position and a horizontal position and vice versa, said apparatus including means for handling and balancing the termination housing substantially at a combined centre of gravity and thereby prevent undue bending of the elongated article during the transfer.

With the invention we have obtained a reliable method and means for handling termination housings of elongated articles. When rotating the construction about its combined center of gravity the bending moment outside the termination housing is reduced to a minimum so that bending strain relievers can be reduced correspondingly without causing damage to the elongated article.

In order that the invention may be readily carried into effect, embodiments thereof will now be described in relation to the accompanying drawings, in which: Figure 1 illustrates a termination housing and part of an elongated article, Figure 2 illustrates housing handling means, Figure 3 shows handling means attached to the housing, Figures 4 and 5 illustrate cross-sections through Figures 1, 2 and 3, Figures 6 to 11 illustrate several stages in lowering a first end of an elongated article, Figures 14 to 19 illustrate an alternative way of lowering the first end, and Figures 20 to 24 illustrate several stages in lowering a second end of an elongated article.

15Is In Figure 1 is illustrated a terminated end 1 of an elongated article 2 including a :°:termination housing 3. The transition from the elongated article to the housing is usually protected with a bending strain restrictor device 4. The weight of the termination housing may, however, be more than 5.000 kg and there is a risk of damaging the elongated article ooo when handling the housing. The end portion 5 of the termination housing is provided with .r 20 a groove 6 for handling purposes. The housing 3 is also provided with a slot 7 on both sides for defining the location of the housing. The elongated article 2 may be a cable, an ooo :umbilical containing cables and/or pipes and similar articles. The end portion is designed with a plug-in connector (not shown).

S

Figure 2 and Figures 3 to 5 illustrate the principles of means 10 for handling the terminated end 1. There are provided guiding means 11 for engaging the groove 6 and defining the axial position of the handling means 10 relatively to the housing 3. An example of guiding means 11 in shown in Figure 5B. There are also provided locking means 12, Figure 4B, which are arranged to be locked around the housing 3. When the locking means 12 are released, the guiding means 11 may move in or out of the groove 6.

When the locking means 12 are locked, tilted positions of the housing is fully controlled by the handling means 10. The locking means may also be designed to rotate the housing about its longitudinal axis.

The locking means 12 may be controllable locking arms as indicated, but in some cases releasable straps (not shown) would be sufficient. In Figures 2 and 3 are indicated one of two guide pins 13 which is arranged to be inserted into the slot 7 on both sides of the housing 3 thereby locking the rotation of the article 2 and housing 3 to the rotation of the handling means 10. The handling means 10 is also provided with pivot means 14 arranged slightly offset from a combined centre of gravity of the housing 3 and the means The means 10 is also provided with a handling eye Whereas Figure 1 shows a termination housing 3 of an elongated article 2 and Figure 2 shows one embodiment of handling means 10, Figure 3 illustrates how the means 10 can he arranged on the housing 3. Figures 4 and 5 schematically and respectively show cross-sections IV-IV and V-V taken through Figures 1, 2 and 3.

In Figures 6 to 23 are illustrated techniques and procedures for lowering an elongated article having a termination housing in each end, to a sea bed. In Figure 6 to 13 and 14 to 19 are illustrated techniques for lowering a first end 20 to the sea bed, whereas :Figures 20 to 24 illustrate remedies for lowering the second end Figure 6 illustrates a housing 20 which is hanging vertically in the sea by its elongated article 21 (Figure 7) from a floating surface vessel (not shown). Handling means 444*44 S° 22 which are locked to the housing 20 as explained above, are provided with a buffer or 20 sled like structure 23 on each side of the housing. Figure 7 to 10 illustrate how the :,,°°housing can be smoothly lowered to and deposited on the sea bed 24. The purpose of the structure 23 is to prevent the end portion 25 of the housing from penetrating into the sea bed 24 upon touchdown. The structure 23 is designed and balanced so that it remains in a 4 4 horizontal position during the lowering procedures.

When the structure 23 reaches the sea bed and the elongated article 2 is still paid off from the surface vessel, the housing 20 will start rotating about a combined centre of gravity pivot 26. The critical area is the interconnection between the article 21 and the housing 20 where the bending diameter should be determined by the bending strain restrictor. Actually the pivot 26 is placed slightly offset from the real centre of gravity in order to make sure that the housing 20 tilts in the desired direction, in this case to the left.

When the housing and elongated article reaches a position shown in Figure 9 means are arranged for collapsing one of the supporting legs 27 and 28 and deposit the housing Rhorizontally and safely on the sea bed by means of a hydraulic device 29. The final lowering step is illustrated in Figures 10 and 11, the latter showing the deposited housing seen from the end portion If required, in order to prevent undue bending of the interconnection between the housing and its elongated article, buoyancy devices (not shown) can be attached to the handling means 22. In the horizontal position (Figure 12) of the housing 20, the handling means 22 (Figure 13) will be released by an ROV and lifted to the surface vessel by attaching a wire to a handling eye 15. The first housing and termination has now been placed in a target area and position on the sea bed where it can easily be pulled into contact with a first subsea installation.

In Figures 14 to 19 are illustrated how an alternative buffer arrangement 30 can be used for depositing the first termination housing 20 on a sea bed. The buffer 30 is pivotably attached to the handling means 31 by two guide arms 32 and 33 on each side of the housing. The arrangement is designed so that the buffer remains in a horizontal position during the lowering of the article and housing. The elongated article and its S 15 termination housing will be rotated from the vertical to the horizontal orientation about a combined slightly offset centre of gravity 34. Figures 15 to 19 are assumed to be selfo °explanatory.

When the first end housing 20 and the elongated article 21 which can be several Kilometres long has been installed on the seabed, the second end has to be lowered to 20 the sea bed close to a second sea bed installation (not shown).

In Figures 20 to 22 are illustrated how the elongated article 21 with its second housing 40 can be lowered to the sea bed 41 by a wire 42 attached to a handle 43 on o handling means 44. The handle 43 is attached to the handling means 44 at a combined centre of gravity pivot 45 in order to prevent undue bending of the elongated article 21.

A critical area is the interconnection 46 between the housing 40 and the article 21, and as in the case of the lowering of the first housing 20 the optimum situation is that the overall bending diameter is as determined by the bending strain restrictor. The pivot 45 is slightly offset from the actual combined centre of gravity in order to define the direction of rotation, in this case to the right.

As in the case of installing and releasing the first housing 20, the second housing is also released by having an ROV manipulate various control handles on the handling means 44. The handling means 44 may be lifted to the surface by the handle 43, as illustrated in Figure 24. A wire 47 may be attached to the handling means 44 for maintaining it in a horizontal position.

If a housing (and elongated article) need to be released from the subsea installation and lifted to the surface for maintenance or of other reasons, the handling, means 44 may be used for lifting any of the housings 20 and 40. The handling means is simply lowered into position with the guiding means 11 fitted into the groove 6 Figures 2, 3 and 5 whereupon the Locking means 12 Figures 2,3 and 4 are activated by an ROV and the lifting process can start. The housing will be rotated about its centre of gravity and no damage will be done to the elongated article or to the termination housing. The arrows shows in Figures 20 and 21 indicate that the handle 43 can be used for both lowering and lifting the housing 40 (and When using the handling means 10 or 22 or 31 or 44 for catching and lifting a termination off the ground or from a sea bed, the guide pin(s) 13 need not be activated.

These guide pins are activated on the surface vessel before lowering the article with its 15 terminations to the sea bed.

The above detailed description of embodiments of this invention must be taken as i examples only and should not be considered as limitations on the scope of protection. If the termination housings for instance have other configurations this will require oooo otherwise designed handling means. The principle of handling the housings substantially at the combined centre of gravity is the main feature. When rotating the construction about its combined centre of gravity the bending moment outside the termination housing is reduced to a minimum so that bending strain relievers can be reduced correspondingly without causing damage to the elongated article.

C

Techniques for passing the housings and handing means out of (and into) a surface vessel into (from) the sea are not described.

Claims

1. A method for controlling the transition of an assembly including an elongated article and a termination housing between a substantially veirtical orientation and a substantially horizontal orientation and/or vice versa, the handling means including a handling point or points, the method including: locating the handling means on the termination housing, whereby the point or points are arranged at or proximate to the combined centre of gravity of the termination housing and the handling means, attaching handling means to the termination housing, whereby bending moments from the housing and handling means are substantially eliminated during the transition, so that undue bending of the elongated article is substantially reduced. se*

2. A method as claimed in claim 1, wherein the handling points form a pivot axis. 15 3. A method as claimed in claim 1 or claim 2, for transferring said elongated article between a surface vessel and a sea bed, said method comprising the steps of: *.Ve mounting handling means to a first termination housing by employing guiding means and locking means as well as guide pins to secure the housing in a oeooo Spredetermined lengthwise and rotational position relatively to the handling means, 20 attaching buffer means pivotably connected to the handling points, go• lowering the article from the vessel to the sea bed and depositing the termination housing in a first desired target area and position on the sea bed, releasing the handling means and buffer means from the housing and lifting them to the vessel, progressively installing the elongated article along a predetermined path on the sea bed, mounting if not done at a previous stage, handling means to a second termination housing attached to a second end of the elongated article, by employing guiding means, locking means and guide pins to secure the housing in a predetermined lengthwise and rotational position relatively to the handling means, said handling means also including handle means pivotably connected to the combined centre of gravity, lowering the article and housing from the vessel to the sea bed and depositing the termination housing in a second desired target area and position on the sea bed, and releasing the handling means from the housing and lifting the handling means to the vessel.

4. A method as claimed in claim 1 or claim 2, for lifting a termination housing from a sea bed to a surface vessel, said method including the steps of: lowering the handling means by handle means down to the housing, locking the handling means to the housing by activating locking means, and lifting the housing to the vessel.

5. A handling means which is releasably attachable to an assembly including an o "elongated assembly including an elongated article terminated by a termination housing, the 15 handling means including: register means for locating the transport member on the housing; clamping means to releasably grip the housing; handling points at or proximate to the combined centre of gravity of the of few**: the housing and transport member; °oo° 20 the handling points facilitating transition from a substantially vertical to a substantially horizontal orientation without unduly stressing the elongated article. S

6. Handling means as claimed in claim 5, wherein the handling points form a pivot axis.

7. An apparatus as claimed in claim 5 or claim 6, including guiding means and locking means for releasably attaching it to a termination housing.

8. An apparatus as claimed in claim 5 or claim 6, including guide pins for defining the rotational orientation of the housing during a horizontal deposition procedure.

9. An apparatus as claimed in claim 5 or claim 6, including buffer or sled means for preventing a lowered first termination from penetrating a horizontal surface.

10. An apparatus as claimed in claim 9, wherein the buffer means is attached to the handling means at a position slightly offset from the true combined centre of gravity in order to define a lowering procedure.

11. An apparatus as claimed in claim 9, wherein the buffer means is attached to the handling means at two positions which together constitute a slightly offset centre of gravity.

12. An apparatus as claimed in claim 5, including handle means pivotably attachable to the handling points for lowering/lifting a termination housing to/from a horizontal surface.

13. An apparatus as claimed in claim 12, wherein the handle means is attached to the handling means at a position slightly offset from the true combined centre of gravity in order to define a lowering procedure.

14. An apparatus as claimed in claim 5, including means for lowering/lifting the handling means separately, in a horizontal orientation. An apparatus as claimed in claim 5, arranged for lowering and lifting the construction to and from a sea bed from a surface vessel. 0@ S16. A handling means as claimed in claim 5 wherein the pivot means are slightly offset °in relation to the centre of gravity, so that the pivot axis is slightly above the centre of I 15 gravity when the assembly is in the horizontal position.

17. A transport mechanism for lowering an assembly including an elongated article terminated by a termination housing and a handling means as claimed in 5 or claim 16, the mechanism including a buffer member including a base and one or more S pivot arms connected between corresponding base pivot points and pivot means on the 20 transport member, the pivot arm or arms being dimensioned so that the base extends beyond 0 ooo° the end of the termination housing when the mechanism is suspended in a substantially vertical orientation, the pivot arms and pivot means being arranged so that the elongated element will deploy in a preferred direction when the base contacts a substantially horizontal surface.

18. A method substantially as herein described with reference to Figures 1 20, of the accompanying drawings.

19. An apparatus substantially as herein described with reference to Figures 1 20 of the accompanying drawings. DATED THIS THIRD DAY OF SEPTEMBER 2001 NEXANS by its Datent attorneys Freehills Carter Smith Beadle OS 00 00 S OS OS 0000 S 05 0 gOOSeS 0 SO.. 6@ 00 0 0@5005 0 0 050005 0 *OO* 0 5055 0550 00 S. 0505 0 0 0000 00 5 0 00 0 0000 0000 S 0