The invention relates to a device for an installation vessel with a deck to deploy a hydrocarbon transfer pipe composed of several pipe segments, the device comprising a trolley hoist lifting means, installed in a tower to lift a pipe segment from an horizontal position into a vertical position, an assembly platform, where a segment is connected to a previously launched transfer pipe string, the assembly platform being provided with a clamping device that is supported on the installation vessel and adapted to support the weight of the previously launched pipe string during assembling.

The present invention also relates to an offshore flexible hose installation method going from a vertical position to a horizontal position when deployed in the sea.

Background of the invention

Installation methods and devices for laying pipes from a vertical position to a horizontal position are already known, and described in various publications. In the international patent application WO2006085739 there is provided a method for installing an offshore pipeline where the weight of an accessory and a launched pipeline connected to the accessory is transferred from a clamping device to a controlled load hoisting device while the accessory and launched pipeline remain in a firing line. After disengaging the clamping device from the pipeline, the clamping device is moved out of the firing line. The accessory and launched pipeline are lowered along the firing line by the controlled load hoisting device. In US6361250, there is provided a system and method to lay sub-sea pipelines at great depth. There is provided a tower which is particularly suitable for laying rigid pipes at depths up to 3000 m, with maximum loading of 600 tons. Rigid pipes are laid without plastic deformation, flexible pipes can also be handled. The carriages used are individually motorized, and operate on e.g. a rack and pinion, permitting the pipes to be moved and held in position. Conveniently, welding takes place at deck level.

Demountable tower sections allow one tower to be used on another ship when necessary. Further, in patent application US2007/0189857, there is disclosed a pipe laying tower with an upper clamping element vertically displaceable along a frame, and a lower clamping element supported on a vessel support structure. As the lower clamping element is not part of the J-lay frame, but is supported on the vessel support structure, the weight of the tower itself is reduced. This allows easy mounting of the lightweight frame portions and reduces modifications and structural reinforcements. Integration of the lower clamping block on the vessel support structure provides a low vertical center of gravity, reducing the motion-induced support loads on the vessel and providing for increased stability.

Such systems, however, require very good metocean conditions; the handling is time consuming and hence they provideexpensive solutions. According to the present invention, there is provided a device and an offshore installation method to install a flexible hose offshore, which offer a large operation window as the operation can keep on going under high sea states such as for instance a sea state of 3 meters significant wave height.

The system according to the invention presents solutions that also increase the safety during installation, ease the access to personnel, and facilitate the key operations during installation.

Summary of the Invention

The system, according to the present invention, enables the assembly and deployment of interconnected hose segments by using an offshore installation vessel. The

interconnected hose segments form a flexible hose which can be used for offshore hydrocarbon (crude oil, liquefied gas, etc.) transfer between two offshore units. The system can accommodate several hose sizes and can accommodate specifically flexible hose segments with truncated hose ends.

The offshore flexible hose installation method is transfers hose segements from a vertical position at the upper deck of the installation vessel to a horizontal floating position when deployed in the sea to form an hose string. The deployment of the hose is carried out using the J-lay installation method going from a vertical to a horizontal position, the hose string floating at the sea surface.

It is therefore an object of the present invention to provide a device for an installation vessel with a deck to deploy a hydrocarbon transfer pipe which is a flexible hose string composed of several flexible hose segments that are assembled one to the other on an assembly platform. According to the invention the flexible hose string is guided from a vertical position into an inclined or a horizontal position via a hose string guide element which is placed under the assembly platform. A particularity of the hose string guide element is that it takes the out of plane bending loads of the tension in the hose string due to wave, wind and current and that it limits the bending radius of the hose string when going from a vertical position to a horizontal position.

A further aspect of the present invention provides a trolley hosting means which include a first and a second hosting means, so that an upended hose segment can be positioned and assembled with the first hoisting means, while reloading a new hose segment to be assembled with a second hosting means.

The present invention also provides an offshore flexible hose installation method comprising the steps of:

- providing an installation vessel with a tower, equipped with hoist lifting means with at least one trolley, a hose string clamping mechanism and a hose string guide means, - positioning and up-ending a hose segment so that it is in a vertical position,

- lowering the up-ended hose segment end and connecting it to the hose string that is clamped in the clamping mechanism,

- open the clamp and lower the connected hose segment through the clamps into the hose string guide mechanism, while guiding at the same moment the part of the hose string end that is near the installation vessel from a vertical position into an inclined or horizontal position via the hose string guide mechanism.

In accordance with a further aspect of the present invention, an offshore flexible hose installation method comprises the steps of:

- providing an installation vessel with a tower, equipped with hoist lifting means with at least twe trolleys, a hose string clamping mechanism and a hose string guide means, - positioning and up-ending a hose segment with one trolley so that it is in a vertical position,

- horizontally displacing the trolley from its predetermined position to another predetermined position and the other trolley from its predetermined position to another predetermined position,

- getting the hose segment in line with the clamped hose segment connected to a hose string,

- assembling the hose segment to the clamped hose segment and,

- simultaneously positioning and up-ending a new hose segment .

Further, the device enables displacing the dual trolley hoist lifting means from one position to another so that the installation of a subsequent hose segment can start as soon as the previous hose segment is up ended and installed in line with the clamped hose string.

Another advantage of a device according to the present invention is that the whole device is a removable device that can be mounted on different installation vessels.

Brief description of the drawings:

The invention will be further described below in connection with exemplary embodiments with reference to the accompanying drawings, wherein:

FIG. 1 shows a side view of a general embodiment of the device for laying a flexible line composed of several hose segments from an installation vessel according to the present invention,

FIGs.2 to 4 show the different main steps of the offshore flexible hose installation method, the hose passing from a vertical position to a horizontal position when deployed in the sea according to the present invention.

FIGs. 5a and 5b show detailed views of the clamping and holding means of the assembling platform of the present invention, and

FIG. 6 shows a detailed view of the hose string guide element in the last step of the installation method according to the present invention FIG. 1 shows a side view of a general embodiment of the device laying a flexible line 2 composed of several hose segments 3 from an installation vessel 4 according to the present invention.

On the deck 5 of the installation vessel 4 there is a tower 6 provided with a dual trolley hoist lifting means 10 that enables to up-end the hose segments 3. The hoist lifting means 10 lifts the hose segment 3 to the bolting location and aligns the hose segments 3 along all axes with the clamped hose 3c in the assembly platform 8. Close alignment with the clamped hose 3c is very important due to the tight tolerances of the bolt holes between the two hose segments 3 and 3c. Before the hose segment 3 is up-ended by the hoist lining means 10, a lining hub 9 is provided at the hose segment extremity and is connected to the lining means 10. The hub 9 and hose segment 3 are preinstalled in a gutter 14. While the hose segment 3 is up loaded by the hoisting means 10, it is contained and guided by the guiding system or gutter 14. Once the top extremity of segment 3 reaches a certain height, it is then contained in a locking hatch 18 to avoid the hose segment from swaying. Thereby, the top extremity of the hose segment and the lower hose end are both restricted from moving in all directions in every steps of the installation. Hence, the guiding means 14, 18 prevents the hose segment 3 from moving or dangling in unwanted directions due to vessel motions and is further useful to position the bottom of the up-ended hose segment 3 exactly in line with the clamped hose segment 3c at the assembly platform 8.

The combined operation of the tower 6, the dual trolley hoist lifting means 10 and the guiding means 14, 18 constrains the hose top- and bottom ends along all axes during upending and bolting, which renders the operation much safer.

FIGs.2 to 4 show the different main steps of the offshore flexible hose installation method going from a vertical position to a horizontal floating position when deployed in the sea.

The dual trolley hoist lifting means 10 are provided with two trolleys 11, 1 Γ which are displaceable in a horizontal direction, each from one predetermined position 11 a, 1 1 a' to another predetermined position 1 lb, 1 lb' in order to save time during the operation. In fact, displacing the dual trolley hoist lifting means from a position to another, enables the installation to benefit from the reloading function. Hence, the installation method for a new hose segment 3' can start as soon as the previous hose segment 3 is up ended and installed in line with the clamped hose segment 3c. The displaceable dual trolley hoist lifting means shortens the assembly time per hose segment and can make a large difference in the total operation time.

In FIG.3, the deck crane (not shown) has preinstalled a hose segment 3" in a gutter 14. This hose segment will be up ended by the trolley 11, once the trolley 11 will be displaced from location 11 a to location l ib. While the trolley 11 will be displaced, so will the trolley 1 1 ' from location 1 la' to location 1 lb' bringing the already up loaded hose segment 3' into position above the clamping device 13 in alignment with the clamped hose segment 3c (not shown) for assembly. In FIGs.2 to 4 it appears clearly that the dual trolley hoist lifting means 10 is composed of two trolleys 11 and 1 1 ' each connected to a hose segment 3, 3' via a lifting hub 9, 9'. Buoyancy modules 20 are preinstalled on the hose segments.

As shown in FIGs. 5a and 5b, there is a clamping system 13 fitted in or on the assembly platform 8. The clamping systemis required to hold the assembled hose string, or line 2 so that it is safe to bolt a new hose segment 3 to the hose string assembly 2.

During normal operating conditions, the hose string 2 first rests on the top of the clamping system 13 and then provides a certain pressure in order to overcome the up-lift of the hose string 2 due to relative motion between the installation vessel 4 and the hose string. In an emergency case i.e. where the hose string has been punctured, broken or cracked during the assembly operation, the clamp is to hold the fully assembled hose string, about 2 km long, fully flooded with seawater. The clamp can also open wide enough to allow buoyancy modules 20 to pass through the clamp. The buoyancy modules are pre-installed on the hose segments 3 before bolting to the hose string 2. The clamping and holding means of the assembly platform are composed of four plates 22 that can open or close by rotation. The plates 22 are equipped with translating clamps 24 that squeeze the hose segment under the action of hydraulic cylinders 21 as shown in FIG. 5b. The clamps 24 can be changed out to accommodate different hose sizes.

The assembly platform 8 also allows about 5-6 men to walk around the bolting area of the two hose segments 3 and 3 c, the platform 8 providing easy access during operation and/or maintenance.

When being clamped, a hose segment must not be bent. This is ensured by the hose string guide element 15 shown in FIG.6. The hose string guide element 15 takes up all out of plane loads, by creating only a vertical pulling force on the clamping system 13. The hose string guide element 15 is creating a gradually curved transition of the hose string 2 from the vertical to a horizontal position. It also restricts the hose 2 from bending further than its minimum allowable bending radius. Because the sheave is rotating around a shaft 16, there will be no shaving between the hose 2 and hose string guide element 15. The system is also fitted with D- fenders 17 bolted all around the circumference of the hose string guide element 15. The function of the D-fenders is to protect the buoyancy modules from being crushed by the forces induced by the current pushing on the already assembled hose string 2. The D- fenders 17 can absorb excessive loads on the buoyancy module while inside the sheave.

The hose string guide element 15 is positioned at an angle regarding the vessel's hull.

The angle chosen is the most favorable angle in relation to the wave and current directions. The hose string guide element 15 can have multiple fixed deployment angles (passive) or could be provided with bearings allowing the hose string guide element to rotate during operation (active). The hose string guide element will be supported on the deck 5 and on the hull of the installation vessel 4.

The combination of up-ending and constraining the both ends of the hose segments allows the operation to continue until high sea states, such as for instance a sea state of 3 meters significant wave height. This results in a large operation window and smaller chances of downtime. Although particular embodiments of the invention have been described and illustrated herein, it is recognized that modifications and variations may readily occur to those skilled in the art, and consequently, it is intended that the claims be interpreted to cover such modifications and equivalents.