NO20150337A1

NO20150337A1 - Subsea installation unit, a protective cover and method of installing protective covers

Info

Publication number: NO20150337A1
Application number: NO20150337A
Authority: NO
Inventors: Geir Huseby; Lars Espen Holm; Arnt-Frode Brevik; Bjørn Guldbrandsen
Original assignee: Compocean As
Priority date: 2015-03-17
Filing date: 2015-03-17
Publication date: 2016-09-19
Also published as: NO343052B1

Description

The present invention relates to a subsea installation unit for installation of a protective cover from a stack. The unit comprises a plurality of protective covers arranged in a stack, and a lifting sling for lifting the unit to a location below water level for deployment of the protective cover from the stack. The invention also presents a method for deployment of a protective cover from a subsea installation unit.

Subsea installations contain expensive equipment that operates under harsh environmental conditions and are subsequently subjected to large forces and wearing. Traditionally, some protection is applied to the installations in form of shield or cover to create a barrier against the external forces. A subsea protection cover is often arranged for protection of subsea installations. These covers are often made from glass fiber reinforced plastics, being strong, light in weight and easy to mass produce and handle.

A subsea installation can be large in scale and correspondingly large in extent. The job of making the covers, transportation to the location and deployment under the sea, can be extensive and not the least costly. A certain degree of mass production and standardization of the covers are desirable with consideration to the cost- and time saving aspect both in production and deployment.

As mentioned above a subsea protection cover can easily be mass produced and preferably molded in suitable size. A well known and appropriate method is to store and transport the covers in stacks. This method depends on the covers to have the same size and shape in order to be held firmly and securely together. The covers are often strapped together and stacked in a frame for the easy lifting and handling of the stack. Further, the stack is transported by ship to the desired location and lowered to the seabed in close proximity to the subsea installation to be protected or covered. Once positioned at the seabed, the stack is unstrapped and the covers are deployed in desired positions by taking the top cover from the stack, one by one, and thus work their way down the stack. Often the lifting sling has to be remounted for every protective cover to be deployed from the stack. This method facilitates the deployment of the covers in subsea operations, but the method has also many disadvantages being both time-consuming and depending on ancillary. Once the stack is positioned on the seabed, there will be need of assistance, i.e. ROV assistance, or other ancillary to deploy the covers from the stack.

Thus there is a need for a subsea installation system and method that can deploy subsea protection covers more effectively and cost saving.

Further, there is a need of a system that can minimalize the need for cleanup and containment of waste after installation, a system that has both economic and environmental benefits.

At least there is a need for a subsea installation system and a method that at least solves some of the problems mentioned in prior art.

SUMMARY OF THE INVENTION

It is an aim of the present invention to provide a subsea installation unit that is arranged such that it simplifies and streamlines the deployment of protective covers.

It is also an aim of the present invention to provide a flexible and easy handling installation unit during subsea operations.

Another aim of the invention is to manufacture the unit with minimal additional items/parts for easy storage, transport and mounting.

In addition, it is an aim of the invention to be able to prebuild installation units at a reasonable price and efficiently and as complete as possible at a traditional construction site, preferable readymade shelf goods from the manufacturer. Thereby, the costly finishing work or mounting work at sea will be minimized.

The invention discloses a subsea installation unit for installation of a protective cover from a stack. The unit comprises a plurality of protective covers arranged in a stack, and a lifting sling for lifting the unit to a location below seawater level. The lifting sling comprises a lifting head and the protective cover is arranged with a release device in order to release the protective cover from the lifting head and allow the deployment the protective cover from the lowermost position of the stack.

According to one embodiment of the present invention, the lifting sling is arranged trough each protective covers or adjacent to each protection cover in the stack. The lifting sling can be inserted to the stack by means of a recess or a channel through each protective cover, or threaded through a hole in the cover. At least one lifting line is arranged to lift the installation unit for deployment. According to a preferred embodiment of the invention, the installation unit is arranged with six lifting slings. Two lifting slings are arranged for deployment of the installation unit from a vessel. In this lifting position the installation unit can be hoisted down obliquely or in a tilted way. Additional four mounting lifting slings are passive during the lowering of the unit. Once at the seabed or at location, the two lifting slings are detached and the four mounting lifting sling is activated for lifting the unit in a horizontal position or in any desired angle for deployment of the protective covers.

According to one embodiment of the present invention, the lifting head is arranged to the end of the lifting sling for lifting of the stack. The end of the lifting sling is the end towards or connected to the protective covers arranged in the stack. The lifting head can both be preinstalled or it can be installed at site. The head can also be attached to the lifting sling after the lifting sling is passed trough the stack.

An installation unit according to an embodiment of the present invention is arranged with a plurality of protective covers stacked over each other. Preferably, the protective covers have the same shape and are molded in the same shape so that they can easily and sturdy rest on top of each other, creating a unit. The unit is easy to store, transport and handle. It is also important to note that the covers can have different shapes stacked one over each other creating an installation unit.

Each protective cover is arranged with the necessary parts to do installation from stack; hence, a minimum of additional items/parts shall be used during installation. The benefit is that it minimalizes the need for cleanup and containment of waste after installation. This has both economic and environmental benefits.

The protective covers can be made from fiber reinforced plastics, like glass fibers, Carbon, Kevlar, etc. Other materials can also be metal or concrete.

Each protective cover can be equipped such that the longitudinal and transversal (in the cover plane) loads are transferred between the covers within the stack. The load transferring mechanism can be an integrated design element. Like a geometrical lock, or a device that is fixed to the cover and that are able to transfer the load between the covers. To keep the covers squeezed together an arrangement of straps or locks can be arranged. The purpose of the straps or locks is to avoid the covers to be separated from the stack by falling or sliding out of position.

In an embodiment of the present invention a plurality of brackets are mounted at the side and in several columns on each protective cover in a stack. The brackets are mounted above each other in each column, and in a way that they are interlocking when the covers are stacked. There are holes in the protective covers so that the brackets can come into direct engagement with one another. The engagement ensures that the covers can not slip relative to each other in horizontal and transverse direction, and ensures force transmission between the covers. A lifting sling is arranged with a lifting head for lifting of the stack. In this embodiment the lifting head is a loop threaded through all brackets in a column. The brackets are equipped with a release device, like a locking bolt on each bracket. When the stack is lifted, all locking bolt must be mounted in position. The lowermost positioned protective cover is released by removing all locking bolts on the brackets mounted on the said cover. When the stack is lifted again by means of the lifting sling, the lifting loop will move to the next locking bolt position on the protective cover positioned above. It is within the scope of the invention that different numbers of columns containing the brackets can wary with respect to the shape of the covers and to the balancing of the stack during lifting.

According to another embodiment of the present invention the lifting sling is arranged through the stack. The plurality of protective covers that are stacked and constituting the unit has a through hole where the lifting sling is arranged. The lifting sling can be threaded through the hole in the cover, or there can be a channel or recess at the side of the cover for introducing the lifting sling. At the end of the lifting sling, towards the bottom of the stack a lifting head is arranged. The lifting head has a smaller shape than the through hole arranged on the protective covers, allowing the lifting head to pass through the hole. The lifting head can be preinstalled to the stack or the head can be fitted after the lifting sling is positioned.

In between each protective cover in the stack, a release device is arranged. In this embodiment the release device comprises a stopper plate with a recess or a slot covering the through hole on the cover. The stopper plate can be fastened with fastening strips or other fastening means between the covers. The purpose is that the stopper plate is jammed during lifting and handling operations, but it can also be removed in a simple way. The stopper plate main function is to prevent the lifting head to pass through. When the plate is removed, the bottom protection cover will be released from the stack since the lifting head at the lifting sling is smaller that the through hole at the protective cover, and thus the lifting head will be pulled through the hole. The lifting head will stop at the next stopper plate positioned above.

According to the invention, the unit comprising the protective covers arranged in a stack is prefabricated as a unit with arrangement according to the invention. The unit is easily transported to the location for lifting to the seabed. The lifting device can be any device known from prior art and used for offshore operations. The unit is lifted directly onto the predetermined location for the protective cover, and the cover is then released to be positioned. The unit is then moved to the next location for deployment of the next protective cover. The main benefit is that the unit at all time can be controlled from the surface and the protective covers are deployed one by one from the bottom of the stack. The purpose is to install a protective cover, reposition the stack and install the next protective cover without interruption. The real benefit of this method is that it saves time and money to install or deploy the protective covers from the bottom of the stack. Also it is advantageous to avoid the connection of lifting slings to every protective covers to be installed, and the invention enables to exploit the total weight of the stack while maneuvering under water. A certain submerged weight is required to avoid slack in the lifting slings during installation. For a stack, the ratio of submerged weight and area (drag) and added mass is greater than that of each cover separately. This means the subsea operation for deployment of the protective cover from a stack is easier to handle for the lifting slings, in that the invention mostly avoids slack in the lifting sling.

The invention also discloses a method of installing protective covers over a subsea structure, comprising the steps of: - arranging the protective covers in a stack such that the protective covers are stacked one over each other,

- position the stack in a first location over the subsea structure,

- releasing a first protective cover from a lowermost position of the stack such that a second protective cover replaces the first protective cover as the lowermost protective cover in the stack , and such that the first protective cover is deployed on the subsea structure at the first location, - repositioning the stack to a second location over the subsea structure leaving the first protective cover covering the subsea structure at the first location, and - releasing the second protective cover from the lowermost position of the stack such that the second protective cover is deployed on the subsea structure at the second location.

BRIEF DESCRIPTION OF THE FIGURES

The description above, as well as further objects, features and advantages of the present invention will be more fully appreciated by reference to the following detailed description of the preferred embodiment which should be read in conjunction with the accompanying drawings in which: Fig. lisa side elevation view of a stack with brackets mounted on the protective cover, according to the invention. Fig. 2 shows a side view of the stack from fig. 1 with the bottom locking bolt removed for deployment of the bottom cover.

Fig. 3 shows the same brackets from fig. 1 in position without the covers.

Fig. 4 shows the brackets, the locking bolts and the lifting loop surrounding the locking bolts. Fig. 5 is a side elevation view of another embodiment according to the invention where the lifting sling is arranged through a hole and with removable stopping plates.

DETAILED DESCRIPTION OF THE FIGURES

Figure 1 shows an installation unit 10 according to an embodiment of the present invention. The figure shows a plurality of protective covers 11 arranged in a stack 12. The covers 11 are arranged on top of each other resting on top of each other by gravity, but the protective covers can also be strapped together (not shown). As seen from the figure the protective covers 11 have the same shape so that they can easily and sturdy rest on top of each other, creating a subsea installation unit 10. The unit 10 comprises the protective cover stack 12, a lifting sling 14, a lifting head 15 and a release device 16. The unit 10 is easy to store, transport and handle.

Further from figure 1, a plurality of brackets 13 are mounted above each other in a column so that they are interlocking when the protective covers 11 are stacked. There are holes in the protective covers 11 so that the brackets come into direct engagement with one another. The engagement ensures that the covers can not slip relative to each other in horizontal and transverse direction, and ensures force transmission between the covers 11. A lifting sling 14 is arranged with a lifting head 15 at the end toward the stack 12. In this embodiment the lifting head 15 is a loop threaded through all brackets 13 in a column. The brackets 13 are equipped with a release device 16 in form of a locking bolt on each bracket 13. When the stack 12 is lifted, all locking bolt 16 must be mounted in position. The bottom protective cover 11 is released by removing all locking bolts 16 on brackets 13 mounted on the bottom cover 11. When the stack 12 is lifted by means of the lifting sling 14 the lifting loop head 15 will move to the next locking bolt 16 positions on the protective cover 11 positioned above.

As seen in figure 2, the lowermost or bottom protective cover 11 from the stack 12 is released upon removing of the corresponding locking bolt 16. According to the invention, this feature will always make sure that only the lowermost positioned cover 11 is to be released for deployment.

Figure 3 shows the same brackets 13 from figure 1 without the protective covers 11. As seen in the figure, the brackets 13 are mounted above each other in a column so that they are interlocking when the covers 11 are stacked. At each cover

11 position in the stack 12 a release device 16 in form of a locking bolt 16 is arranged. In the figure, the locking bolt 16 is designed with a pulling handle for the easy removal of the bolt. Figure 4 shows a lifting head 15 in form of a lifting loop 15. The lifting loop is threaded through all brackets 13 in a column as shown in the figure. When the stack 12 is lifted, all locking bolt 16 must be mounted in position. The lowermost positioned protective cover 11 is released by removing all locking bolts 16 on the brackets 13 mounted on the bottom cover 11. When the stack 12 is lifted by means of the lifting sling 14 the lifting head loop 15 will move to the next locking bolt 16 position on the protective cover 11 positioned above. As demonstrated in the figure, the lifting loop has the lifting point at the lowermost positioned locking bolt. Also demonstrated are that the lifting loop 15 will move to the next locking bolt 16 positioned above when the lowermost positioned locking bolt 16 is removed. Figure 5 shows another embodiment of the installation unit 10 according to the present invention. The protective covers 11 are arranged on top of each other in a stack 12. Each cover 11 has a through opening or hole 21 arranged at a predetermined and appropriate position for lifting purposes, creating a vertical through hole 21 for the stack 12. A vertical lifting sling 14 is arranged through the holes 21 at each protective cover 11 in the stack 12. The lifting sling 14 is arranged with a lifting head 15 at the end of the sling 14. The lifting head 15 can have different shape, but the size is smaller than the through holes 21 at the protective cover 11. The lifting head 15 in figure 5 has a shape of a square block; other shapes can be round, oval, conical, triangular or polygonal, etc. The main feature is that the lifting head 15 has a smaller shape than the through holes 21 arranged on the protective covers 11, allowing the lifting head 15 to pass through the holes 21. In between each protective cover in the stack, a release device 16 is arranged. In this embodiment the release device comprises a plate 16 with a recess or a slot covering the through hole 21 on the protective cover 11. The plate 16 can be fastened with fastening strips or other fastening means. The purpose is that the plate 16 is jammed during lifting and handling operations, but the stopping plate 16 can also be removed in a simple way. When the plate 16 is removed, the bottom protection cover 11 will be released from the stack since the lifting head 15 on the lifting sling 14 is smaller that the through hole 21 on the cover 11 and thus pulled through the hole 21. The lifting head will stop at the next stopper plate 16 arranged under the protective cover 11 positioned above.

Claims

1. A subsea installation unit (10) for installation of a protective cover (11) from a stack (12), wherein the unit (10) comprises a plurality of protective covers (11) arranged in a stack (12), and a lifting sling (14) for lifting the unit (10) to a location below water level,characterized in thatthe lifting sling (14) comprises a lifting head (15) and that the protective cover (11) is arranged with a release device (16) in order to release the protective cover (11) from the lifting head (15) and allow the deployment of the protective cover (11) from a lowermost position of the stack (12).

2. A unit (10) in accordance with claim 1, wherein the lifting sling (14) is arranged through or adjacent to each protection cover (11) in the stack (12).

3. A unit (10) in accordance with claim 1 or 2, wherein the lifting head (15) is arranged at the end of the lifting sling (14), towards the protective cover (11) , for lifting of the stack (12).

4. A unit (10) in accordance with any one of claims 1 to 3, wherein the lifting head (15) is an object (15), the object (15) being smaller and able to pass through an opening (21) in the protection cover (11) through which the lifting sling (14) is arranged.

5. A unit (10) in accordance with claim 4, wherein the release device (16) is a stopper plate (16) arranged between each protective cover (11) in the stack (12) , the stopper plate (16) preventing the lifting head (15) to pass through the opening (21).

6. A unit (10) in accordance with any one of claims 1 to 3, wherein the lifting head (15) is a lifting loop (15).

7. A unit (10) in accordance with claim 6, wherein the release device (16) is a locking bolt (16) arranged on a bracket (13) on the protective cover (11).

8. A unit (10) in accordance with claim 7, wherein the locking bolts (16) in the stack (12) is arranged in a column and through the eye of the lifting loop (15), and upon removing the lowermost positioned locking bolt (16), the lifting loop (15) will be released from the lowermost position and consequently move to the next locking bolt (16) position arranged above.

9. A protective cover (11) for arrangement in a stack (12),characterized inthat the cover (11) is arranged with a release device (15) for releasing the protective cover (11) from a lowermost position of the stack (12).

10. A cover (11) in accordance with claim 9, wherein the cover (11) comprises a through opening (21) for accommodating a lifting sling (14) and a lifting head (15), and that the release device (15) is a removable stopper plate (15) arranged between the covers (11) for preventing the lifting head (15) to pass through the opening (21).

11. A cover (11) in accordance with claim 9, wherein the cover (11) comprises a bracket (13) with a release device (15) in form of a removable locking bolt (15) for accommodating a lifting head (15) in form of a lifting loop (15).

12. A method of installing protective covers (11) over a subsea structure, comprising the steps of: - arranging the protective covers (11) in a stack (12) such that the protective covers (11) are stacked one over each other, - position the stack (12) in a first location over the subsea structure, - releasing a first protective cover (11) from a lowermost position of the stack (12) such that a second protective cover (11) replaces the first protective cover (11) as the lowermost protective cover (11) in the stack (12), and such that the first protective cover (11) is deployed on the subsea structure at the first location, - repositioning the stack (12) to a second location over the subsea structure leaving the first protective cover (11) covering the subsea structure at the first location, and - releasing the second protective cover (11) from the lowermost position of the stack (12) such that the second protective cover (11) is deployed on the subsea structure at the second location.