WO2024123186A1

WO2024123186A1 - Floater ballast system

Info

Publication number: WO2024123186A1
Application number: PCT/NO2023/060112
Authority: WO
Inventors: Peter Christian LEITCH
Original assignee: Aker Solutions As
Priority date: 2022-12-06
Filing date: 2023-12-05
Publication date: 2024-06-13
Also published as: GB2625098A; GB202218284D0

Abstract

A floater (100) for carrying electrical distribution equipment, the floater (100) comprising a hull (101) having a plurality of ballast tanks (10a-d), each ballast tank (10a-d) having a ballast water pipe (11a-d) and a vent pipe (12a-d) fluidly connected thereto, wherein the ballast water pipes (11a-d) are interconnected such as to permit ballast water to be moved from each one of the plurality of ballast tanks to another one of the plurality of ballast tanks, and wherein the vent pipes (12a-d) are interconnected such as to permit gas to be moved from each one of the plurality of ballast tanks to another one of the plurality of ballast tanks, and wherein the ballast tanks (10a-d), ballast water pipes (11a-d) and vent pipes (12a-d) are fluidly interconnected and define a closed ballast volume.

Description

FLOATER BALLAST SYSTEM

The present disclosure relates to a ballast system for a floater, particularly a semisubmersible platform for electrical distribution equipment, and particularly to a system for managing ballast in such a floater.

BACKGROUND

Floaters, such as semisubmersible platforms or other types of vessels, are used for a variety of purposes in many industries, for example within exploration of petroleum resources offshore, for generation of renewable energy, for aquaculture or fish farming, or for distribution of electricity. With the increasing development of offshore renewable energy, one particularly relevant application is the use of floaters for carrying electrical distribution equipment, for example for offshore wind farms. In such applications, subsea I sea floor cables may be routed to and from the floater, for example such that a voltage step-up can be done before electric energy is further distributed, e.g. to a shore-based grid via one or more export cable(s).

Floaters often have demanding design requirements in order to be able to operate safely and reliably in harsh offshore environments. It is generally desirable that floaters have long design life and low maintenance requirements, as their construction, design and installation can be very expensive and because accessibility for inspections, maintenance and repairs may be restricted. Taking a floater out of operation for inspection, maintenance or repairs (in situ or particularly if moving the floater to a yard e.g. for dry-docking) may involve considerable costs.

In many cases, such floaters may need to be equipped with a ballast system which allows altering of the floater’s ballast distribution. Such ballasting or de-ballasting may be necessary if the payload or displacement of the floater changes, if it is desirable to modify the trim of the platform, and/or if the weight distribution on the floater changes. In some applications, active control of ballast distribution can be used to counteract effects of environmental impacts.

There is a continuous need for further improved technology for offshore floaters. The present disclosure has the objective to provide such improvements, or at least to provide useful alternatives to existing technology. SUMMARY

In an embodiment, there is provided a floater for carrying electrical distribution equipment, the floater comprising a hull having a plurality of ballast tanks, each ballast tank having a ballast water pipe and a vent pipe fluidly connected thereto, wherein the ballast water pipes are interconnected such as to permit ballast water to be moved from each one of the plurality of ballast tanks to another one of the plurality of ballast tanks, and wherein the vent pipes are interconnected such as to permit gas to be moved from each one of the plurality of ballast tanks to another one of the plurality of ballast tanks, and wherein the ballast tanks, ballast water pipes and vent pipes are fluidly interconnected and define a closed ballast volume.

Each vent pipe may be fluidly connected to a common vent equalisation pipe.

At least a part of the common vent equalisation pipe may extend horizontally above the hull.

Each ballast water pipe may be fluidly connected to a common ballast distribution Pipe.

At least a part of the common ballast distribution pipe may extend horizontally above the hull.

The floater may further comprise a plurality of pumps, each pump arranged in the hull and fluidly connected to a respective ballast tank. In this case, pump may be arranged in a respective ballast tank.

At least one or each ballast water pipe may comprise a ballast pipe valve operable to isolate the respective ballast tank from the other ballast pipe(s).

At least one or each ballast water pipe may comprise a ballast pipe valve operable to isolate the respective ballast tank from the common ballast distribution pipe.

The ballast pipe valve(s) may be located at an upper part of the hull, for example, at an upper half of the hull or at an upper 20% section of the hull. Alternatively, the ballast pipe valves may be located above a design waterline of the hull or above the hull. At least one or each vent pipe may comprise a vent pipe valve operable to isolate the respective ballast tank from the other vent pipe(s).

At least one or each vent pipe may comprise a vent pipe valve operable to isolate the respective ballast tank from the common vent equalisation pipe.

The vent pipe valve(s) may be located at an upper part of the hull, for example at an upper half of the hull, or at an upper 20% section of the hull. Alternatively, the vent pipe valves may be are located above a design waterline of the hull or above the hull.

The common vent equalisation pipe and/or the common ballast distribution pipe may be located at an upper part of the hull, for example at an upper half of the hull, or at an upper 20% section of the hull. Alternatively, the common vent equalisation pipe and/or the common ballast distribution pipe may be located above a design waterline of the hull or above the hull.

The hull may be a semi-submersible hull and comprise a plurality of vertical or substantially vertical columns.

Each ballast water pipe may be arranged vertically inside a column.

Each vent pipe may be arranged vertically inside a column.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other characteristics will become clear from the following description of illustrative, non-restrictive examples, with reference to the attached drawings, in which:

Figs 1 and 2 illustrate perspective views of a floater.

Fig. 3 shows a schematic view of a cross-section of a floater hull.

Fig. 4 illustrates schematically a ballast tank with a ballast water and vent gas distribution arrangement. DETAILED DESCRIPTION

Figs 1 and 2 illustrate a floater 100 having a hull 101. In this example, the hull 101 is a semi-submersible hull having four columns 102a-d and a pontoon structure 103 arranged below a design waterline 104 for the hull 101. The hull 101 may, alternatively, have fewer or more than four columns, such as three columns. The pontoon structure 103 may be a single pontoon structure, or may be made up of individual pontoon structure sections arranged between all or some of the columns 102a-d. Optionally some or all of the columns 102a-d may be interconnected by another type of structure than a pontoon, such as beams or trusses. The floater 100 is configured to carry a deck (not shown) on the columns 102a-d, with the deck having electrical distribution equipment arranged thereon, such as switchgear, shunt reactors, transformers, and other equipment which can for example be connected to an offshore wind farm to receive and redistribute electric power therefrom.

The hull 101 comprises a plurality of ballast tanks arranged therein. The ballast tanks can be arranged in the columns 102a-d, in the pontoon structure 103, or in both the columns 102a-d and in the pontoon structure 103. The hull 101 may, for example, have a number of permanent ballast tanks which are filled (typically with water) upon construction, and then closed and sealed. The hull 101 may also have fixed ballast arranged therein. Such permanent and fixed ballast may account for the majority of ballast used in the hull 101.

In addition, the hull 101 may have ballast tanks in which the level of ballast water can be varied during operation. For example, the hull 101 as illustrated in Figs 1 and 2 may have four such variable ballast tanks arranged in the hull 101, e.g. one ballast tank below or in each column 102a-d, or one ballast tank in the pontoon structure 103 between each pair of columns 102a-d. Such variable ballast tanks may be used to modify the ballast distribution of the hull 101 during operation.

Fig. 3 illustrates an example in which the hull 101 has two ballast tanks 10a, b arranged below two columns. Each of the ballast tanks 10a, b has a ballast water pipe 11a,b and a vent (i.e., ventilation) pipe 12a, b fluidly connected thereto. By means of the ballast water pipe 11a,b, ballast water can be added into or removed from the tank 10a, b. The vent pipes 12a, b allow gas (e.g. air or an inert gas such as nitrogen forming the tank atmosphere) to be removed from or added into the ballast tank 10a, b, in accordance with the removal or addition of ballast water from or into the tank 10a, b.

The ballast water pipes 11a, b are interconnected such as to permit ballast water to be moved from one of the ballast tanks 10a, b to the other tank 10a, b. As the two tanks 10a, b are arranged at different locations in the hull 101 , a redistribution of ballast water between the tanks can be used to influence the ballast distribution, for example to manipulate the trim of the floater 100.

Although only two tanks 10a, b are illustrated in Fig. 3, the skilled reader will understand that the floater 100 may be designed with three, four or more such tanks and associated pipe systems.

The vent pipes 12a, b are interconnected such as to permit gas to be moved from one of the ballast tanks 10a, b to the other tank 10a, b as ballast water is moved in the opposite direction.

The ballast tanks 10a, b, ballast water pipes 11a, b and vent pipes 12a, b are fluidly interconnected and define a closed interior volume for ballast. This closed interior volume, formed by the interior volumes of the ballast tanks 10a, b, ballast water pipes 11a, b and vent pipes 12a, b, has no fluid connection or opening to the ambient during operation of the floater 100. The ballast water and gas (e.g. air or an inert gas such as nitrogen) can be provided into the tanks 10a, b during construction of the hull 101 , and thereafter the interior volume can be closed and sealed from the ambient.

In this manner, the fluid contained in the interior volume (i.e. ballast water and gas) remains unchanged during operation. Particularly, no new water or air is provided into the interior volume, i.e. into the tanks 10a, b or associated pipes. This prevents corrosion of the interior of the tanks 10a, b and associated pipes, in that no fresh oxygen is permitted to enter the volume.

In a floater 100 as illustrated in Figs 1 and 2, four ballast tanks may be provided, and each of the ballast water pipes may be interconnected via a common ballast distribution pipe 14. This is illustrated in Fig. 4. Similarly, each vent pipe 12a-d can be fluidly connected to a common vent equalization pipe 13. Pipes 13 and 14 may, for example, be arranged as ring pipes extending around the hull 101.

Advantageously, the pipes 13 and 14 are arranged above the hull 101, for example on or integrated in a deck structure of the floater 100 which is supported on the top of the columns 102a-d (the deck is not illustrated in Figs 1 and 2). In this manner, ballast water can be selectively redistributed between desired tanks according to operational requirements.

Alternatively, in a floater 100 as illustrated in Figs 1 and 2, pairs of ballast tanks 10a- d may be interconnected, e.g. a ballast tank located below column 102a may be interconnected with a diagonally opposite ballast tank located below column 102c, and similarly for ballast tanks located below columns 102b and 102d.

Illustrated in Fig. 3, pumps 15a, b may be provided to pump ballast water between the tanks 10a-d. The pumps 15a, b may be arranged in the hull 101 and fluidly connected to a respective tank 10a-d. Advantageously the pumps 15a, b are arranged in a respective ballast tank 10a-d. Optionally, the pumps 15a, b can be fluidly connected to the respective tank 10a-d via piping.

One or more of the ballast water pipes 11 a-d may comprise a ballast pipe valve 16a, b (see Fig. 3) operable to isolate the respective ballast tank 10a-d from the other ballast pipe(s) 11a-d and/or from the common ballast distribution pipe 14.

Alternatively, or additionally, one or more of the vent pipes 12a-d may comprise a vent pipe valve 17a, b (see Fig. 3) operable to isolate the respective ballast tank 10a- d from the other vent pipe(s) 12a-d and/or from the common vent equalization pipe 13.

The ballast pipe valve(s) 16a,b and/or the vent pipe valve(s) 17a,b is/are advantageously located at an upper part of the hull 101, such as at an upper half of the hull 101 , at an uppermost 20% of the height of the hull 101 , and/or above a design waterline 104 (see Fig. 2) of the hull 101. The ballast pipe valve(s) 16a, b and/or the vent pipe valve(s) 17a,b may alternatively be arranged above the hull 101, for example on a deck or integrated in a deck structure of the floater 100.

Similarly, the common vent equalization pipe 13 and/or the common ballast distribution pipe 14 can advantageously be located at an upper part of the hull 101 , such as at an upper half of the hull 101, at an uppermost 20% of the height of the hull 101 , and/or above a design waterline 104 of the hull 101. The common vent equalization pipe 13 and/or the common ballast distribution pipe 14 may alternatively be arranged above the hull 101, for example on a deck or integrated in a deck structure of the floater 100.

Such arrangement of the valves 16a,b, 17a,b and/or pipes 13,14 can provide easier accessibility, for example for operation of the valves or for inspections or maintenance.

In some examples, the hull 101 is a semi-submersible hull and comprises a plurality of vertical or substantially vertical columns 102a-d. The hull 101 may, for example, be a four-column hull as illustrated in Figs 1 or 2. Each ballast water pipe 11a-d and each vent pipe 12a-d are advantageously arranged vertically inside a column 102a- d. The valves 16a, b, 17a, b may in such an arrangement be placed at or adjacent the top of each column 102a-d.

The floater 100 may be fitted with appropriate sensor equipment, for example tank gauges I level sensors in the tanks 10a-d in order to read the current ballast water levels; flow meters, discharge pressure gauges or power consumption sensors on pumps 15a,b to monitor ballast water flow rates; oxygen sensors in the interior volume in order to ensure that a low-oxygen atmosphere is maintained in the interior volume, etc. By providing such sensor equipment, better knowledge of the condition of the hull 101 can be obtained, and inspection requirements may be relaxed. For example, if having documented, consistently low oxygen levels over time in the interior volume, one may have sufficient confidence that no significant corrosion has occurred such as to optimize, obviate, or possibly delay the need for physical inspection.

According to examples described here, redistribution of ballast water, for example for floater trim adjustments, is possible with a lower risk that such operations provides fresh oxygen into interior volumes of the tanks or associated piping, which can lead to corrosion. By means of examples described here, a longer floater lifetime and reduced inspection requirements can thus be obtained. This may allow the floater 100 to operate for longer periods without inspection or with relaxed inspection requirements.

Although the disclosed examples and embodiments relate to a floater for carrying electrical distribution equipment, the teaching of the present disclosure and any embodiment described or claimed herein are not limited to such application and may equally well be employed for a floater for any purpose. The invention is not limited by the embodiments described above; reference should be had to the appended claims.

Claims

1. A floater (100) for carrying electrical distribution equipment, the floater (100) comprising a hull (101) having a plurality of ballast tanks (10a-d), each ballast tank (10a-d) having a ballast water pipe (11a-d) and a vent pipe (12a- d) fluidly connected thereto, wherein the ballast water pipes (11a-d) are interconnected such as to permit ballast water to be moved from each one of the plurality of ballast tanks to another one of the plurality of ballast tanks, and wherein the vent pipes (12a-d) are interconnected such as to permit gas to be moved from each one of the plurality of ballast tanks to another one of the plurality of ballast tanks, and wherein the ballast tanks (10a-d), ballast water pipes (11a-d) and vent pipes (12a-d) are fluidly interconnected and define a closed ballast volume.

2. The floater (100) of any preceding claim, wherein each vent pipe (12a-d) is fluidly connected to a common vent equalisation pipe (13).

3. The floater (100) of claim 2, wherein at least a part of the common vent equalisation pipe (13) extends horizontally above the hull (101).

4. The floater (100) of any preceding claim, wherein each ballast water pipe (11a-d) is fluidly connected to a common ballast distribution pipe (14).

5. The floater (100) of claim 4, wherein at least a part of the common ballast distribution pipe (14) extends horizontally above the hull (101).

6. The floater (100) of any preceding claim, comprising: a plurality of pumps (15a, b), each pump (15a, b) arranged in the hull (101) and fluidly connected to a respective ballast tank (10a-d).

7. The floater (100) of any preceding claim, wherein at least one or each ballast water pipe (11a-d) comprises a ballast pipe valve (16a,b) operable to isolate the respective ballast tank (10a-d) from the other ballast pipe(s) (11a-d).

8. The floater (100) of claim 4 or any one of claims 5 - 7 where dependent on claim 4, wherein at least one or each ballast water pipe (11a-d) comprises a ballast pipe valve (16a, b) operable to isolate the respective ballast tank (10a- d) from the common ballast distribution pipe (14).

9. The floater (100) of claim 7 or 8, wherein the ballast pipe valve(s) (16a, b) is/are located at an upper part of the hull (101), or wherein the ballast pipe valves (16a,b) are located above a design waterline (104) of the hull (101) or above the hull (101).

10. The floater (100) of any preceding claim, wherein at least one or each vent pipe (12a-d) comprises a vent pipe valve (17a, b) operable to isolate the respective ballast tank (10a-d) from the other vent pipe(s) (12a-d).

11. The floater (100) of claim 2 or any one of claims 3 - 10 where dependent on claim 2, wherein at least one or each vent pipe (12a-d) comprises a vent pipe valve (17a, b) operable to isolate the respective ballast tank (10a-d) from the common vent equalisation pipe (13).

12. The floater (100) of claim 10 or claim 11 where dependent on claim 10, wherein the vent pipe valve(s) (17a, b) is/are located at an upper part of the hull (101), or wherein the vent pipe valves (17a, b) are located above a design waterline (104) of the hull (101) or above the hull (101).

13. The floater (100) of claim 4 or any one of claims 5 - 12 where dependent on claim 4, wherein the common vent equalisation pipe (13) and/or the common ballast distribution pipe (14) is/are located at an upper part of the hull (101), or wherein the common vent equalisation pipe (13) and/or the common ballast distribution pipe (14) is/are located above a design waterline (104) of the hull (101) or above the hull (101).

14. The floater (100) of any preceding claim, wherein the hull (101) is a semisubmersible hull and comprises a plurality of vertical or substantially vertical columns (102a-d). The floater (100) of any preceding claim, wherein each ballast water pipe (11a-d) is arranged vertically inside a column (102a-d). The floater (100) of any preceding claim, wherein each vent pipe (12a-d) is arranged vertically inside a column (102a-d).