WO2016096286A1

WO2016096286A1 - Overflow arrangement for a ballast system of a floating unit

Info

Publication number: WO2016096286A1
Application number: PCT/EP2015/076821
Authority: WO
Inventors: Lars-Olof Liberg
Original assignee: Gva Consultants Ab
Priority date: 2014-12-19
Filing date: 2015-11-17
Publication date: 2016-06-23
Also published as: NO20141571A1

Abstract

An inlet conduit assembly 4 for a ballast system of a floating unit 2 and a method for feeding ballast fluid to a ballast tank 8 are disclosed. The inlet conduit assembly 4 has an extension in at least a vertical direction V, and is adapted to provide a fluid communication between a source of ballast fluid 6 and a ballast tank 8 of the ballast system. The inlet conduit assembly 4 comprises a first overflow arrangement 10 adapted to discharge ballast fluid from the inlet conduit assembly at a first level 16 in the vertical direction V. The inlet conduit assembly 4 comprises an inlet conduit assembly top portion 16 that is located at a second level 18 arranged at a distance above the first level 12 in the vertical direction V. The inlet conduit assembly 4 further comprises a ballast fluid level increasing arrangement 20 adapted to actively increase the level of the ballast fluid in the inlet conduit assembly to the second level 18.

Description

OVERFLOW ARRANGEMENT FOR A BALLAST SYSTEM OF A FLOATING

UNIT

TECHNICAL FIELD

Inlet conduit assemblies for ballast systems and methods for feeding ballast fluid to a 5 ballast tank of a ballast system in a floating vessel are disclosed.

BACKGROUND

On a floating vessel, sea water, i.e. water ambient of the floating vessel, is used in many o applications, such as ballasting, fire-fighting and as a cooling fluid. The floating vessel must have a suitably arranged system for supply of sea water. Requirements on such sea water systems may be: high dependability, low risk of leakage, high priority consumers of sea water such as a firefighting system must be prioritized over lower priority consumers, low susceptibility to damage and easy maintenance.

5

A floating vessel, such as a ship or a semi-submersible vessel, is often provided with one or more ballast systems in order to control the draught and/or the inclination of the floating vessel. Generally, a ballast system comprises a ballast tank, and in practice, often a plurality of ballast tanks. A ballast tank is adapted to be filled with sea water and when it is0 to be emptied, the sea water often is directed back to the ambient environment.

GB 2169864 discloses a ballast arrangement including a sea-chest to which a pump is connected for pumping sea water through a conduit to a level above an uppermost ballast tank. From this level the sea water is distributed through a conduit to different ballast5 tanks. When a ballast tank is emptied the sea water is directed from the ballast tank back to the pump, which now is used for pumping the sea water overboard.

WO2010085203 A1 discloses a sea water system comprising a ballast system as well as connections for further uses of sea water on board a floating vessel. Sea water may be0 pumped through a conduit to an intermediate tank positioned at a level above an

uppermost ballast tank. In some embodiments, the sea water may flow from the intermediate tank to the ballast tank via self-flow, due to gravity. From the intermediate tank the sea water may be distributed to one or more ballast tanks as well as to other consumers, such as firefighting installations.

5 Although these systems have many advantages, one drawback may be related to the fact that the one or more ballast tanks are connected via valves to the conduit and/or the intermediate tank where sea water may be stored. If such a valve is accidentally left open or if a valve is defect, an open fluid passage exists between the inlet conduit or intermediate tank and the ballast tank. In such a case, in some circumstances sea water may unintentionally flow from the inlet conduit or the intermediate tank to the ballast tank. This may lead to suboptimal ballasting of a vessel comprising the ballast system. In exceptional cases, this may lead to potentially dangerous situations if left unattended.

SUMMARY

An object of the present disclosure is to provide an inlet conduit assembly for a ballast system and a method for feeding ballast fluid to a ballast tank of a ballast system, where the inlet conduit assembly and the method are adapted to avoid an unintentional flow, or at least minimize the risk of an unintentional flow, of ballast fluid.

The above object is obtained by an inlet conduit assembly according to claim 1 .

The inlet conduit assembly described herein may form part of a sea water system such as disclosed in e.g. WO2010085203 A1 . Especially, the inlet conduit assembly according to any of the embodiments described below may, at least partly, replace the inlet conduit assemblies disclosed therein.

An inlet conduit assembly for a ballast system of a floating unit is disclosed. The inlet conduit assembly has an extension in at least a vertical direction. The inlet conduit assembly is adapted to provide a fluid communication between a source of ballast fluid and a ballast tank of the ballast system. The inlet conduit assembly comprises a first overflow arrangement adapted to discharge ballast fluid from the inlet conduit assembly at a first level in the vertical direction. The inlet conduit assembly further comprises an inlet conduit assembly top portion that is located at a second level arranged at a distance above the first level in the vertical direction. The inlet conduit assembly further comprises a ballast fluid level increasing arrangement adapted to actively increase the level of the ballast fluid in the inlet conduit assembly to the second level. Since the ballast fluid level increasing arrangement is adapted to actively increase the fluid level, the risk that the second level is unintentionally reached in case of an interruption, such as a power failure or the like, is minimized. Due to the relative positions of the first and second levels, the ballast fluid cannot reach the second level without an 5 active intervention by the ballast fluid level increasing arrangement. The inlet conduit assembly is preferably arranged and configured such that the ballast fluid level may only reach the second level by an addition or increase of the potential energy of the ballast fluid level by the ballast fluid level increasing arrangement. The ballast fluid level increasing arrangement is thus configured to provide an increase in potential energy to o the ballast fluid. The ballast fluid level increasing arrangement preferably comprises one or more active components adapted for increasing the ballast fluid level. These components may be adapted to transform some form of energy, for example electrical energy, into increased potential energy of the ballast fluid. This may be realised for example by the ballast fluid level increasing arrangement comprising one or more 5 shovels, vanes or other arrangement for lifting a volume of water to the second level, or by one or more pumps for actively pumping water from an inlet of the pump located at a level vertically below the second level to the second level. Thereby, the risk of an unintentional filling of the ballast tanks can be reduced. 0 Throughout the description, reference is often made to a ballast fluid level increasing portion. This is to be understood as a portion of the inlet conduit assembly comprising at least the inlet conduit top portion and the ballast fluid level increasing arrangement.

The inlet conduit assembly preferably is adapted such that the connection to the ballast5 tank should be arranged downstream the second level. The ballast tank is preferably arranged at a vertically lower level than the second level. Thereby, if the ballast fluid level has reached the second level, ballast fluid may flow by self-flow, i.e., under the influence of gravity, toward the ballast tank. Since the ballast fluid level increasing arrangement actively increases the level of the ballast fluid in the inlet conduit assembly from a vertical0 level equal to, or lower than, the first level to the second level, ballast fluid may only flow to the ballast tank when the ballast fluid level increasing arrangement is active. When feeding of the ballast fluid tank is not required, the ballast fluid level increasing

arrangement is preferably inactive. Thereby, the control of flow of ballast fluid toward the ballast tank may be improved. The ballast fluid level increasing arrangement only needs5 to be activated during ballasting operations. The source of ballast fluid may be sea water ambient of the floating unit.

Preferably, when the ballast fluid level has been increased to the second level, the ballast 5 fluid may flow toward the ballast tank due to the influence of gravity. That is, the ballast fluid is not pumped into the ballast tank, but the ballast tank is filled by self-flow of the ballast fluid from the second level to the ballast tank. Due to filling by self-flow, the risk of the ballast tank being exposed to overpressure is minimized. Also, the need for a de- aerator may be avoided, since the fluid flow does not draw air with it to the ballast tank, in o particular if the water level is raised to a third level which is above the second level.

Further, due to the need to actively lift the ballast fluid level to the second level in order for self-flow to occur, the presence of self-flow of ballast fluid is controlled, and the flow rate of the self-flowing ballast fluid is limited. Thereby, the safety and stability of the vessel comprising the ballast system may be improved.

5

The pressure in the ballast tank may therefore be limited by the location of the second level or the third level, should the inlet conduit assembly be adapted to raise the fluid level up to a third level above the second level. 0 The overflow arrangement is adapted to lead away ballast fluid from a portion of the inlet conduit assembly, which, in turn, is adapted to be connected, directly or indirectly, to the ballast tank. The overflow arrangement is arranged to dispose of ballast fluid at the first vertical level. The maximum pressure within the inlet conduit assembly, especially upstream of the ballast fluid level increasing arrangement, is limited by the vertical5 position of the first level. The fluid column in the inlet conduit assembly can generally not be higher than the first level. Thereby, the pressure within the inlet conduit assembly, especially on the ballast fluid level increasing arrangement, is limited by the vertical position of the first level. Preferably, the overflow outlet is arranged to discharge, indirectly or directly, into the environment ambient of a vessel in which the inlet conduit assembly0 and the ballast system are arranged. The maximum vertical level of the overflow

arrangement, which corresponds to the first level, need not necessarily coincide with the overflow outlet, since the overflow outlet may be located below, and thus downstream, the maximum vertical level of the overflow arrangement. The inlet conduit assembly may comprise a main fluid level increasing arrangement, preferably a first pump assembly comprising at least one pump, adapted to actively increase the level of the ballast fluid in the inlet conduit assembly to the first level.

The main fluid level increasing arrangement, e.g. the first pump assembly, may be 5 arranged in the inlet conduit assembly for pumping ballast fluid through at least a first conduit portion towards the ballast tank. The first pump assembly may comprise a first pump, which may be adapted to pump ballast fluid into the inlet conduit assembly. The first pump assembly may comprise one or more further pumps. o The main fluid level increasing arrangement is preferably separate from the ballast fluid level increasing arrangement. Preferably, the main fluid level increasing arrangement is configured such that it, when active, may increase the ballast fluid level to the first level, but not to the second level. 5 The ballast fluid level increasing arrangement may comprise a second pump assembly comprising at least one pump. The second pump assembly is preferably electrically powered, and may thereby be configured to transform electrical energy into potential energy of the ballast fluid. The second pump assembly may be separate from the main fluid level increasing arrangement, e.g. the first pump assembly. The pump, or pumps, of0 the second pump assembly is preferably dimensioned to increase the ballast fluid level to a level vertically above the second level. Thereby, an air flow into the ballast system may be avoided.

The second pump assembly may comprise a vertical propeller pump. A propeller pump5 offers a relatively light weight and uncomplicated pump, which is easily decoupled and removed if necessary during maintenance. This may be the at least one pump of the second pump assembly. However, the second pump assembly may comprise more than one pump, for example, several vertical propeller pumps. 0 The inlet conduit assembly may comprise an at least partially closed sub tank that in turn comprises a sub tank inlet and a sub tank outlet. The sub tank outlet is located above the sub tank inlet in the vertical direction, and the second pump assembly is adapted to pump ballast fluid from the sub tank inlet to the sub tank outlet. Further, the sub tank may comprise a vent opening. The inlet conduit top portion may correspond to a vertical level5 in the sub tank at least as high as the maximum vertical position of the sub tank outlet. The sub tank outlet may be adapted to be connected, directly or indirectly, to an inlet of the ballast tank. Since the sub tank outlet is higher than the sub tank inlet, ballast fluid will flow through the sub tank outlet when the second pump assembly is running. If the ballast fluid level reaches the second level, ballast fluid may flow through the sub tank outlet and toward the ballast tank due to self-flow. If the second pump assembly is turned off, there is no flow of ballast fluid from the sub tank inlet to the sub tank outlet. Thereby, there will be no uncontrolled flow of ballast fluid caused by self-flow under the influence of gravity if the ballast fluid level increasing means is not active.

As mentioned above, the second pump assembly may be dimensioned to raise the ballast fluid level to a level vertically at or above the second level. The sub tank is therefore preferably provided with a second overflow arrangement, from which excess ballast fluid may escape. The second overflow arrangement may be arranged to discharge ballast fluid from the sub tank at the second level, or, preferably at a third level, located vertically above the second level. The maximum fluid pressure within a ballast tank connected to the sub tank may therefore be limited by the second or third vertical level.

The second overflow arrangement may be arranged to discharge, directly or indirectly, into the ambient environment of a vessel in which the inlet conduit assembly is arranged. Alternatively, the sub tank overflow arrangement may be arranged to discharge into an upstream portion of the inlet conduit assembly.

The inlet conduit assembly may comprise an inlet conduit bend portion that is located downstream of the second pump assembly, as seen in a direction of flow from the source of ballast fluid towards the ballast tank. The inlet conduit bend portion may comprise a bend, a portion of which is located at the second level. The inlet conduit top portion may thereby correspond to the portion of the bend located at the second level. The inlet conduit bend portion may further comprise a venting arrangement connected to the bend portion.

The inlet conduit bend portion may thereby be formed as an inverted water seal, preventing ballast fluid return flow toward the second pump assembly in the case of a halted second pump assembly. The second pump assembly may be positioned upstream of the bend portion. The inlet conduit bend portion may form an alternative to the sub tank described above. The inlet conduit bend portion may form at least a portion of a pipe arrangement, having a function analogue to that of the sub tank. The pipe arrangement may be arranged such 5 that it comprises a smaller volume of ballast fluid as compared to the volume generally comprised in a sub tank. The inlet conduit assembly may comprise more than one inlet conduit bend portion.

When the bend of the inlet conduit bend portion is located at the second level, ballast fluid o may only pass the inlet conduit bend portion as long as the second pump assembly is running. If the ballast fluid level is lifted to the second level, ballast fluid may flow from the second level toward a ballast tank due to self-flow. If the second pump assembly is turned off, there is no flow of ballast fluid passed the inlet conduit bend portion. Thereby, there is no uncontrolled flow of ballast fluid caused by self-flow under the influence of gravity. The 5 maximum pressure in the ballast tank may be limited by the second level.

The inlet conduit bend portion may be connected to or provided with a second overflow arrangement. The second overflow arrangement may be arranged to discharge ballast fluid from the inlet conduit bend portion or from a common point with which both the inlet0 conduit bend portion and the second overflow arrangement are in fluid communication. The inlet conduit bend portion and the second overflow arrangement may be connected to a common manifold. The second overflow arrangement may be arranged to discharge fluid therefrom at a third level. For an inlet conduit assembly with an inlet conduit bend portion as has been discussed above, the third level may preferably be positioned5 vertically between the first level and the second level. Thereby, a back flow of ballast fluid through the inlet conduit bend portion may be avoided. The second overflow arrangement may be arranged to discharge excess ballast fluid directly or indirectly into the ambient of a vessel in which the inlet conduit assembly is arranged. Alternatively, the second overflow arrangement may be arranged to discharge into a portion of the inlet conduit0 assembly upstream the second pump assembly. The maximum ballast fluid pressure in a ballast tank connected downstream of the inlet conduit bend portion may thereby be limited by the position of the third level.

The inlet conduit assembly may comprise an intermediate tank. The intermediate tank5 may be adapted to hold ballast fluid, such as sea water, for further distribution. The intermediate tank may form a container, in which ballast fluid may be held. The intermediate tank may thus act as a buffer of sea water for different consumers of sea water connected to the intermediate tank. As such, if any one, or several, of the above consumers of sea water require an increased flow rate, this increase may be provided by 5 increasing the flow rate through the first pump assembly. Such an increase of the flow rate through the first pump assembly may for instance be obtained by starting an additional pump in the first pump assembly and/or increasing the capacity of at least one of the operating pumps in the first pump assembly. Generally, it will take some time to provide a flow rate through the first pump assembly which meets - i.e. is equal to or o greater than - the sum of the desired flow rates of the consumers of sea water. However, due to the presence of the intermediate tank, the desired (increased) flow rates for the consumers of water may be obtained almost instantly even though the supply of sea water to the intermediate tank is somewhat delayed. 5 The ballast fluid may be held for a longer or shorter period of time depending on present need of ballast fluid, such as sea water, of the different consumers. It is envisaged that the intermediate tank may have a volume of 10 -100 cubic meters, preferably 20-70 cubic meters. From the intermediate tank, the sea water may be forwarded to reach an intended destination, such as different consumers e.g. the ballast tank, other ballast tanks, a fire-0 fighting system, a heat exchanger or a general sea water supply conduit assembly.

The intermediate tank may be located vertically below the first level, or with its vertically highest position at the first level. The intermediate tank may also be referred to as a high well tank, at least when used in vessels such as semi-submersible platforms.

5

The ballast fluid level increasing arrangement may be arranged downstream the intermediate tank.

A sub tank or an inlet conduit bend portion may be arranged downstream the intermediate0 tank, in direct or indirect connection with the intermediate tank.

A sub tank, as described above, may be arranged at least partly within the intermediate tank, for example at least partly in a top portion of the intermediate tank, or directly above the intermediate tank, in the vertical direction. The second pump arrangement may5 thereby be arranged to pump ballast fluid from the intermediate tank into the sub tank, toward the sub tank outlet. Thereby, a pump comprised in the second pump arrangement may be positioned with its inlet in the sub tank inlet, and its outlet at or vertically above the second level, which may be located at a vertical position higher than or equal to the sub tank outlet. The sub tank may be provided with a second overflow arrangement, as 5 described above. The second overflow arrangement may be arranged to discharge into the intermediate tank. Thereby, a ballast fluid supply may be at least partly secured, without any actual control equipment.

Alternatively, the second pump assembly may be arranged at least partly within or directly o above the intermediate tank, such that the inlet of the pump is located within or in the vicinity of an upper portion of the intermediate tank, and the outlet of the pump may be located at the inlet of an inlet conduit bend portion such as the inlet conduit bend portion as described above. The second pump assembly may be arranged to pump ballast fluid from the intermediate tank into the inlet conduit bend portion.

5

If the inlet conduit assembly comprises an inlet conduit bend portion, this may be arranged at least partly within the intermediate tank, for example in connection to the top portion of the intermediate tank, or it may be arranged directly vertically above the intermediate tank. Such inlet conduit bend portion may be one as described above. The0 inlet conduit bend portion may comprise a second overflow arrangement, similar to the one described above. The second overflow arrangement may be arranged to discharge into the intermediate tank. Thereby, a ballast fluid supply may be at least partly secured, without any actual control equipment. 5 The inlet conduit assembly top portion may be located between the ballast fluid level increasing arrangement and the ballast tank, as seen in a direction of flow from the source of ballast fluid towards the ballast tank.

The inlet conduit assembly may comprise a valve that is located between the ballast fluid0 level increasing arrangement and a connection to a ballast tank, as seen in a direction of flow from the source of ballast fluid towards the ballast tank.

The inlet conduit assembly may comprise a second overflow arrangement located downstream of the ballast fluid level increasing arrangement, as seen in a direction of flow5 from the source of ballast fluid towards the ballast tank. The second overflow arrangement is adapted to discharge ballast fluid from the inlet conduit assembly at a third level located at a distance above the second level.

The second overflow arrangement may be adapted to discharge ballast fluid from the inlet conduit assembly to the environment ambient of the inlet conduit assembly. Optionally, 5 the second overflow arrangement may be adapted to discharge ballast fluid from the inlet conduit assembly to a portion of the inlet conduit assembly that is located upstream of the ballast fluid level increasing arrangement.

A ballast system may be provided, comprising a ballast tank and an inlet conduit o assembly as described above.

A floating unit, preferably a semi-submersible unit, may comprise an inlet conduit assembly and/or a ballast system as described above. The semi-submersible unit may be a semi-submersible vessel, such as e.g. an oil drilling unit. A semi-submersible vessel 5 may have at least one float on which at least one column is arranged. The at least one column may carry a deck box. At least one ballast tank is normally arranged in the float and/or column. The ballast tank may be connected to an inlet conduit assembly as described above. 0 A second aspect of the present disclosure relates to a method for feeding ballast fluid to a ballast tank of a ballast system of a floating unit. The ballast system comprises an inlet conduit assembly having an extension in at least a vertical direction. The inlet conduit assembly is adapted to provide a fluid communication between a source of ballast fluid and the ballast tank. The inlet conduit assembly comprises a first overflow arrangement5 adapted to discharge ballast fluid from the inlet conduit assembly at a first level in the vertical direction. The inlet conduit assembly comprises an inlet conduit assembly top portion that is located at a second level arranged at a distance above the first level in the vertical direction. The inlet conduit assembly further comprises a ballast fluid level increasing arrangement adapted to actively increase the level of the ballast fluid in the0 inlet conduit assembly to the second level. The method comprises:

feeding the inlet conduit assembly with ballast fluid such that the ballast fluid reaches the first level;

activating the ballast fluid level increasing arrangement such that the ballast fluid level in the inlet conduit assembly reaches the second level, and

5 - feeding the ballast fluid to the ballast tank. The method may further comprise:

interrupting the feeding of the ballast fluid to the ballast tank by deactivating the ballast fluid level increasing arrangement.

5

The inlet conduit assembly may be an inlet conduit assembly as described above.

Since the ballast fluid level increasing arrangement actively increases the level of the ballast fluid the first level to the second level, ballast fluid may only flow to the ballast tank o when the ballast fluid level increasing arrangement is activated. When feeding of the ballast fluid tank is not required, the ballast fluid level increasing arrangement is preferably inactive. Thereby, the control of flow of ballast fluid toward the ballast tank is improved. The ballast fluid level increasing arrangement only needs to be activated during ballasting operations.

5

Further features of, and advantages with, the present disclosure will become apparent when studying the appended claims and the following description. Those skilled in the art realize that different features of the present disclosure may be combined to create embodiments other than those described in the following, without departing from the0 scope of the present disclosure, as defined by the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The various aspects of the inlet conduit assembly, including its particular features and5 advantages, will be readily understood from the following detailed description and the accompanying drawings, in which:

Fig. 1 schematically illustrates a sea water system comprising an inlet conduit assembly; Fig. 2 schematically illustrates a sea water system comprising an inlet conduit assembly0 comprising a sub tank;

Fig. 3 schematically illustrates an inlet conduit assembly comprising a sub tank and an intermediate tank;

Fig. 4 illustrates an inlet conduit assembly comprising a sub tank and an intermediate tank; Fig. 5 illustrates an inlet conduit assembly comprising an inlet conduit bend portion and an intermediate tank;

Fig. 6 schematically illustrates a section through a floating vessel comprising a sea water system comprising an inlet conduit assembly.

5

DETAILED DESCRIPTION

The inlet conduit assembly now will be described more fully with reference to the accompanying drawings, in which example embodiments are shown. However, this inlet o conduit assembly should not be construed as limited to the embodiments set forth herein.

Disclosed features of example embodiments may be combined as readily understood by one of ordinary skill in the art to which this invention belongs. Like numbers refer to like elements throughout. 5 Fig. 1 schematically illustrates a sea water system aboard a floating vessel 2, such as a ship or any other floating unit. By way of example, the sea water system may be used in a semi-submersible vessel (not shown), i.e. a vessel having a deck and a float and one or more supporting columns connecting the deck and the float to one another. It should be noted that a floating vessel may be provided with a plurality of independent or

0 communicating sea water systems. A semi-submersible vessel may be provided with one sea water system per supporting column. An example of a sea water system arranged in such a column is illustrated in Fig. 6. A semi-submersible vessel may have several floating conditions with differing draughts. Two exemplary positions may be a transporting position and an operating position. In the transporting position the draught is low and the5 still water surface of the semi-submersible vessel may be in the range of the float. In the operating position the draught is deeper and the still water surface 14 of the semi- submersible vessel may be somewhere along the column.

The sea water system illustrated in Fig. 1 comprises, among other features, an inlet0 conduit assembly 4.

Fig. 1 illustrates the inlet conduit assembly 4 in a ballast system of a floating unit 2. The inlet conduit assembly 4 has an extension in at least a vertical direction V. The inlet conduit assembly 4 is adapted to provide a fluid communication between a source 6 of5 ballast fluid and a ballast tank 8. In the example embodiment illustrated in Fig. 1 , the source of ballast fluid is sea water 6 ambient of the floating vessel 2. The inlet conduit assembly 4 comprises a first overflow arrangement 10 adapted to discharge ballast fluid from the inlet conduit assembly 4 at a first level 12 in the vertical direction. The overflow arrangement 10 may lead to outside the floating vessel 2, where overflowing sea water is discharged. The overflow arrangement 10 may end above the still water surface 14 of the water surrounding the floating vessel 2. Preferably, the overflow arrangement 10 is adapted to provide a permanent fluid communication between the inlet conduit assembly 4 and the environment ambient of the sea water system. In other words, the overflow arrangement 10 preferably does not comprise any valves or similar closing arrangements.

The inlet conduit assembly 4 further comprises an inlet conduit assembly top portion 16 located at a second level 18 arranged at a distance above the first level 12 in the vertical direction V. The distance between the first level 12 and the second level 18 is preferably such that, even if a vessel comprising a ballast system in which the inlet conduit assembly 4 is arranged is damaged or for other reason deviates from its intended inclination, ballast fluid will be prevented from reaching the second level 18 without active intervention of the ballast fluid level increasing arrangement 20. Preferably, the distance is at least 1 meter, more preferably at least 2 meters. The inlet conduit assembly 4 further comprises a ballast fluid level increasing arrangement 20 adapted to actively increase the level of the ballast fluid in the inlet conduit assembly 4 to the second level 18.

The inlet conduit assembly 4 may comprise a main fluid level increasing arrangement 22, which in Fig. 1 is exemplified as a first pump assembly 22 comprising at least one pump, adapted to actively increase the level of the ballast fluid in said inlet conduit assembly to the first level 12. The main fluid level increasing arrangement 22 may comprise further components, such as valves and one or more further pumps (not shown in Fig. 1 ).

Preferably, the inlet conduit assembly 4 does not comprise any valves between the most upstream pump of the main fluid level increasing arrangement 22 and the outlet 1 1 of the overflow arrangement 10.

The ballast fluid level increasing arrangement 20 preferably comprises a second pump assembly 24 comprising at least one pump. This pump may be a vertical propeller pump. The second pump assembly is preferably separate from the main fluid level increasing arrangement 22, e.g. the first pump assembly 20, and is arranged to pump ballast fluid from a vertical level corresponding to or lower than the first vertical level 12, such that the level of ballast fluid reaches the second level 18. From the second level 18, the ballast fluid may flow to the ballast tank 8 due to the influence of gravity. Although the portion of the conduit following downstream of the second pump assembly 24 is illustrated schematically in Fig. 1 as portions of straight lines, as will be described in more detail 5 below with reference to Fig. 5A to 5C, this portion may have the form of a bend portion, where the top of the bend portion is located at the second level 18. Thereby, the bend portion may represent the inlet conduit top portion 16. Alternatively, as is illustrated in Fig. 5A to 5C, a plurality of pumps comprised in a second pump assembly 24 and a plurality of bend portions may be provided. The second pump assembly 24 and at least a portion of o the inlet conduit assembly downstream the ballast fluid level increasing arrangement 20, comprising at least the inlet conduit top portion 16 of the inlet conduit assembly 4, may be referred to as a level increasing portion 21 .

The sea water system as illustrated in Fig. 1 further comprises an outlet pump

5 arrangement 26, adapted to pump sea water from the ballast tank 8 through an outlet conduit assembly 28 arranged after the outlet pump assembly 26 seen in the direction of sea water flow. The sea water may thereby be pumped back to the environment surrounding the floating vessel 2. The outlet pump assembly 26 comprises at least one pump, and may also comprise further components, such as valves and one or more0 further pumps (not shown in Fig. 1 ). The inlet conduit assembly 4 and the outlet conduit assembly 28 are preferably separate from each other. However, it is also envisaged that in a sea water system comprising an inlet conduit assembly of the present disclosure, the inlet conduit assembly 4 may be in fluid communication with the outlet conduit assembly 28.

5

Fig. 2 illustrates an embodiment where the inlet conduit assembly 4 comprises an at least partially closed sub tank 30. The sub tank 30 comprises a sub tank inlet 32 and a sub tank outlet 34. It may also comprise vent arrangements (not illustrated). As indicated in Fig. 2, the sub tank outlet 34 is located above the sub tank inlet 32 in the vertical direction V, and0 the second pump assembly 24 may be adapted to pump ballast fluid from the sub tank inlet 32 to the sub tank outlet 34. The sub tank outlet 34 may be located at the second level 18. The second pump assembly 24 is arranged to increase the ballast fluid level to the second level 18. The sub tank outlet 34 may be arranged to dispose ballast fluid from the sub tank 30 at the second level 18. The sub tank outlet 34 may be connected to the5 ballast tank 8 via a second conduit 36. A valve 38 may be arranged in the second conduit 36. A second overflow arrangement 40 may be provided, for discharging excess ballast fluid from the sub tank 30. In the embodiment illustrated in Fig. 2, the second overflow arrangement 40 discharges into ambient sea water 6. The second overflow arrangement 40 may be arranged to discharge excess ballast fluid at the third vertical level 19. The 5 third vertical level 19 may be arranged at a distance above the second level 18 in the vertical direction V. The relative dimensions of the components of the inlet conduit assembly 4 may be such that the maximum fluid level possible in the sub tank 30 is limited to the third level 19. Thereby, even with the second pump assembly 24 running, the ballast fluid level in the sub tank 30 will never exceed the third level 19. Thus, the

1 o maximum pressure in the ballast tank 8 may be limited by the position of the third level 19 with respect to the vertical position of the ballast tank 8. Further, the sub tank 30 preferably comprises a venting arrangement (not illustrated). The venting arrangement provides atmospheric pressure over a liquid surface in the sub tank 30. In this example, the second pump assembly 24 and the sub tank 30 together with its inlet 32, outlet 34 and

1 5 second overflow arrangement 40 may be referred to as the level increasing portion 21 .

As illustrated in Fig. 3, the inlet conduit assembly 4 may comprise an intermediate tank 42. A non-shown main fluid level increasing arrangement 22, for instance a first pump assembly 22, is adapted to pump ballast fluid, e.g. sea water to the intermediate tank 42.

20 Excess ballast fluid may flow through an overflow arrangement 10 connected to the

intermediate tank 42, directly or indirectly back to the ambient environment. The overflow arrangement 10 is arranged to dispose ballast fluid at the first level 12. The intermediate tank 42 may function as a collector of sea water, which may be distributed to different consumers on board the floating vessel. One example is the ballast system described

25 herein. However, on board floating vessels there are often a number of other consumers, such as firefighting installations, heat exchangers for heating or cooling purposes, etc. A further conduit assembly 44 comprising a third pump assembly 46 may be arranged to supply a fire-fighting system with sea water. The further conduit assembly 44 may connect to the intermediate tank 42 at a level below other consumers of sea water to ensure that

30 sea water supply to the fire-fighting system is prioritized over the other consumers. An additional conduit assembly 48 is arranged to provide sea water to one or more additional consumers. Further, the intermediate tank 42 preferably comprises one or more venting arrangements, such as vent pipes, at strategic locations, in order to secure an

atmospheric pressure over the surface of the ballast fluid present in the intermediate tank

35 42. According to the embodiment illustrated in Fig. 3, a sub tank 30, which may be similar to the one described above with reference to Fig. 2, is arranged vertically above a bottom portion of the intermediate tank 42. For example, the sub tank 30 may be arranged in a 5 top portion of the intermediate tank 42. Alternatively, it may be arranged directly on top of the intermediate tank 42. In the embodiment illustrated in Fig. 3, the second overflow arrangement 40 discharges into the intermediate tank 42. However, alternatively, it may discharge, directly or indirectly, into ambient sea water 6. Similar to what has been described with reference to Fig. 2, the maximum fluid level possible in the sub tank 30

1 o may be limited to the third level 19 by the second overflow arrangement 40. Thereby, even with the second pump assembly 24 running, ballast fluid level in the sub tank 30 may be limited to the third level 19. Thereby, the maximum pressure in the ballast tank may be limited by the third level 19. The level increasing portion 21 may here be referred to as comprising the second pump assembly 24 and the sub tank 30 together with its inlet

1 5 32, outlet 34 and second overflow arrangement 40.

Fig. 4 illustrates an embodiment which has many features in common with the one illustrated in Fig. 3. The sub tank 30 is positioned directly on top of the intermediate tank 42. The second pump assembly 24 here comprises a propeller pump arranged with the

20 propeller 50 and the guide vanes 52 positioned in the sub tank inlet 32 facing the

intermediate tank 42. The relative dimensions of the different features of the system are preferably such that the propeller pump is arranged to lift ballast fluid from the

intermediate tank 42 to the sub tank 30 such that the ballast fluid level reaches the second level 18. As illustrated in Fig. 4, especially in the insert section A-A, the sub tank

25 outlet 34 may be arranged as a funnel 54 within the sub tank 30. The opening of the

funnel 54 may be arranged at or below the second level 18. When the fluid level in the sub tank reaches the vertical level of the funnel 54, the ballast fluid flows into the second conduit 36, to which one or more ballast tanks 8 are connected via valves. Purely by way of example, and as is indicated in Fig. 4, a lid 55 may be arranged over the opening of the

30 funnel in order to reduce the amount of air entering the funnel 54.

When active, the second pump assembly 24 is preferably operated such that the ballast fluid level reaches the third level 19 and is allowed to flow back to the intermediate tank 42 via the second overflow arrangement 40. The second overflow arrangement 40 may 35 have similar functions and features as described above. Thereby a ballast fluid level regulation is achieved. As illustrated in Fig. 4, the outlet 33 of the propeller pump may be positioned vertically higher than the third level 19, which in the illustrated example corresponds to the maximum vertical level of the second overflow arrangement 40.

Thereby, a return flow through the propeller pump may be avoided. This is especially 5 advantageous if the second pump assembly comprises more than one vertical propeller pumps arranged in parallel in the sub tank 30. If the outlet 33 of each pump is arranged vertically above the third level 19, the risk of back flow through an inactive pump is minimized. The level increasing portion 21 may here be referred to as comprising the second pump assembly 24 and the sub tank 30 together with its inlet 32, outlet 34 and o second overflow arrangement 40.

Thus, the vertical order is preferably as follows, from the highest vertical level: the pump outlet or outlets 33 of the second pump arrangement is positioned highest, followed by the maximum vertical position of the second overflow arrangement 40, which is in turn 5 followed by the maximum vertical position of the sub tank outlet 34. The sub tank outlet may be arranged to discharge ballast fluid from the sub tank at, or above, the second level 18.

As can be seen in Fig. 4, the intermediate tank 42 may be divided into different

0 compartments, the purpose of which will not be discussed further here. If the ballast fluid level in the intermediate tank 42 reaches the first level 12, excess fluid will be discharged via the overflow arrangement 10.

Fig. 5A to 5C illustrate an embodiment wherein the inlet conduit assembly 4 comprises a5 pipe arrangement, comprising an inlet conduit bend portions 56 located downstream the second pump assembly 24, as seen in a direction of flow from the source 6 (not illustrated in Fig. 5) of ballast fluid towards the one or more ballast tanks 8 (not illustrated). The pipe arrangement may have a similar purpose as the sub tank arrangements illustrated in Fig. 3 and 4, and may form an alternative to such arrangement. In the embodiment illustrated0 in Fig. 5A to 5C, the second pump arrangement 24 comprises a propeller pump arranged with its propeller 50 and guide vanes 52 in a top portion of an intermediate tank 42, in an analogous way as the embodiment illustrated in Fig. 4. The inlet conduit bend portion 56 comprises a bend 58 a portion of which is located at the second level 18. This bend portion may thereby represent the inlet conduit top portion 16. The second pump

5 arrangement 24 is thereby arranged to pump ballast fluid from the intermediate tank 42 to the bend 58 located at the second level 18. When the ballast fluid level has reached this second level 18, it may flow toward the ballast tank by self-flow, i.e., under the influence of gravity. The second part 60 of the bend portion 56 may be connected to a manifold 62, located at the first vertical level 12. From the manifold 62, ballast fluid may flow toward the 5 ballast tank via a valve 38 and second conduit 36. As can be seen in Fig. 5A, the inlet conduit assembly 4 may comprise a plurality of bend portions 56, each of which is connected to the intermediate tank 42 via a respective propeller pump, which may all form part of the second pump assembly 24 of the ballast fluid level increasing arrangement 20. The manifold 62 may be common to all inlet conduit bend portions 56. The manifold 62 1 o may be connected to one or more second conduit parts 36 and valves 38, leading to one or more ballast tanks.

To the manifold 62 may also be connected a second overflow arrangement 64, leading ballast fluid from the manifold 62 back to the intermediate tank 42. This second overflow

1 5 arrangement 64 may comprise a bend portion 66. The bend 66 of this bend portion may be located at a third level 19, located vertically between the first level 12 and the second level 18. Thereby, a back flow through one or more of the pumps of the second pump assembly 24 is prevented, since the fluid level downstream the bend portion 58 will thereby not exceed the third level 19. Fig. 5B and 5C also illustrate venting arrangements

20 70, 72 positioned on the bend portions 58, 66 of the inlet conduit bend portion 56 and the second overflow arrangement 64, respectively. The level increasing portion 21 may here be referred to as comprising the second pump assembly 24, the inlet conduit bend portions 58, the manifold 62 and the second overflow arrangement 64. The maximum pressure in the ballast tank 8 may be limited by the position of the third level 19.

25

All the embodiments illustrated in Fig. 1 to 5 have in common that the ballast fluid level can only be increased to the second level 18 by active intervention of the ballast fluid level increasing arrangement 20. The fluid level may thereby only be raised to the second level 18 by the ballast fluid level increasing arrangement 20 increasing the potential energy of 30 the ballast fluid, by lifting the ballast fluid level to, at least, the second level 18. Especially, ballast fluid may only reach the second level 18 if one or more pumps comprised in the second pump assembly 24 are running, and thereby pump ballast fluid to the second level. Thereby, unintentional filling of ballast tanks may be avoided. Fig. 6 illustrates a section through a floating unit 2 according to example embodiments. Especially, the floating unit 2 may be a semi-submersible platform, of which a column 74 connected to a pontoon 75, especially a ring pontoon, is illustrated in Fig. 6. The floating unit 2 comprises a sea water system. An inlet conduit assembly 4 may comprise two 5 caissons 76, 78 extending vertically from a bottom portion of a hull 80 of the floating unit, an intermediate tank 42 and a second conduit portion 36 leading to a ballast tank 8.

At their lower ends the caissons 76, 78 may be in open communication with ambient sea water and at their upper ends the caissons are connected to the intermediate tank 42. A o curved pipe 82, 84 connects each caisson 76, 78 with the intermediate tank 42 at the upper side of the tank 42. One first pump 22a, 22b is arranged at a lower end of each caisson 76, 78. The first pumps 22a, 22b may be submersible centrifugal pumps, which may be hydraulically driven by hydraulic power supplied through hydraulic conduits 86, 88 from a hydraulic power unit 90. Optionally, the pumps may be electrically driven.

5

There may be placed a top lid 92, 94 on each caisson 76, 78. Each top lid 92, 94 may have a through connection for conduits 86, 88, e.g. hydraulic or electric conduits, leading to the first pumps 22a, 22b. At the upper end of each caisson 76, 78, between each caisson 76, 78 and a respective curved pipe 82, 84, a valve 96, 98, for instance a butterfly0 valve, may be arranged. Optionally, the butterfly valves may be replaced by spectacle flanges.

Preferably, and as is indicated in Fig. 6, each one of the curved pipes 82, 84 is connected to its corresponding caisson 76, 78 at a level above the first level 12 in order to prevent5 backflow to the caissons 76, 78.

At an upper side of the intermediate tank 42 an overflow arrangement 10 in the form of an overflow pipe 100 is connected. The overflow pipe 100 extends upwards from the intermediate tank 42. The overflow pipe is arranged to discharge ballast water at the first0 level 12. The maximum pressure in the inlet conduit system, especially at least upstream a ballast fluid level increasing arrangement 20, is thereby limited by the position of the first level 12.

The first pumps 22a, 22b inside the caissons 76, 78 are adapted to pump sea water up5 through the caissons 76, 78 to the intermediate tank 42. By means of the valves 96, 98 the connection between a corresponding caisson 76, 78 and the intermediate tank 42 can be closed. By closing the valve 96 of caisson 76 its top lid 92 can be opened, e.g. for removing the first pump 22a from the caisson 76, without having to stop the first pump 22b in the other caisson 78 from pumping sea water to the intermediate tank 42.

5

On top of the intermediate tank 42 a ballast fluid level increasing arrangement 21 comprising ballast fluid level increasing means 20 is arranged. The ballast fluid level increasing arrangement 21 may be according to any of the embodiments described with reference to Fig. 1 to 5 above. Especially, it may comprise a sub tank arrangement 1 o comprising a sub tank 30 and a second pump 24, as illustrated in Fig. 3 and 4, or a pipe arrangement comprising an inlet conduit bend portion 56 and a second pump 24, as illustrated in Fig. 5A to 5C. Thereby, ballast water may only reached the ballast tank 8 if the water level is actively increased to the second level 18 by the ballast fluid level increasing means 20.

1 5

From the intermediate tank 42, via the ballast fluid level increasing means 20 and through the second conduit portion 36 of the inlet conduit assembly, the sea water may reach the ballast tank 8. When sea water is to be removed from the ballast tank 8, an outlet pump 26 and an outlet conduit assembly 28 may be utilized. The outlet pump 26 may be 20 arranged to pump the water from the ballast tank 8 back to the environment surrounding the floating vessel, or to a part of the inlet conduit assembly 4.

It should also be noted that the water, after having been actively pumped or otherwise actively lifted to the second level 18, may be transferred from the level increasing portion

25 21 to the ballast tank 8 by means of gravity which requires that the ballast tank 8 is

located vertically below the second level 18. However, a marine structure may also comprise one or more ballast tanks (not shown) being located on the same level as - or even above - the second level 18. In order to fill such ballast tanks, the water system preferably comprises an additional ballast water assembly (not shown) with a ballast

30 pump assembly (not shown). The additional ballast water assembly may then preferably comprise a separate overflow arrangement (not shown).

From the intermediate tank 42, sea water may also be fed to further consumers of sea water. A further conduit assembly 44 with a third pump assembly 46 may be arranged to 35 provide sea water to a fire-fighting system (not illustrated). A heat exchanger pump 102 may be arranged to pump sea water through a heat exchanger 104 for heat exchange with a further fluid 106. From the heat exchanger 104 the sea water may flow back to the surrounding environment of the floating vessel through an outlet pipe 108. The outlet pipe 108 of the heat exchanger 104, the outlet conduit assembly 28 from the ballast tank 8 and the overflow pipe 100 of the intermediate tank 42 could all separately discharge sea water to the ambient environment but in this case they all lead to an overboard arrangement 1 10, from which the sea water is brought back to the ambient environment.

Due to the vertical order of outlets from the intermediate tank 42, the fire-fighting system always has sea water available as long as there is sea water in the intermediate tank 42. Sea water to the heat exchanger 104 is second in priority and sea water to the ballast tank 8 has the lowest priority. To this end, it should be noted that if the fluid level in the intermediate tank only reaches the vertical position of the intake to the heat exchanger pump 102, the ballast fluid level increasing means 20 does not necessarily have any ballast fluid to pump.

Since the intermediate tank 42 and the overflow pipe 100 are intimately connected with the caissons 76, 78, even though forming inner spaces, they can be considered to form part of the outer skin of the floating vessel. This means that sea water passing through the caissons 76, 78 into the intermediate tank 42 and from there straight on through the overflow pipe 100 would be considered to never have been taken aboard the floating vessel.

A first pump 22a, 22b arranged at a lower end of a caisson 76, 78 may be part of a first pump assembly 22 which is an non-limiting example of a main fluid level increasing arrangement 22. The outlet pump 26 may be part of an outlet pump assembly. The outlet pump assembly may comprise connections to a bilge water system 1 12 adapted for removing bilge water from the floating vessel. The outlet pump 26 may in this case also be used for pumping bilge water.

Fig. 6 shows that many parts of the sea water system may be arranged in a pump room 1 14 of the floating vessel, such parts for instance being: the intermediate tank 42, the upper ends of the caissons 76, 78 with associated elements, the pumps 46, 102, the heat exchanger 104 and the hydraulic power unit 90.

The valves 96, 98 and corresponding valves in any additional caissons may be the only valves in the inlet conduit assembly before the intermediate tank 42, i.e. a respective caisson extends uninterruptedly from the bottom of a hull of a floating vessel to above a still water surface 14 of the floating vessel. The only moving part below the still water surface 14 being a respective first pump submersed inside the caisson. Thus, no leakage prone joints are present in a caisson beneath the still water surface of the vessel.

Fig. 6 thus shows that the inlet conduit assembly top portion is located between the ballast fluid level increasing arrangement 20 and the ballast tank 8, as seen in a direction of flow from the source of ballast fluid 6 towards the ballast tank. Especially, a top portion of the inlet conduit assembly 4 is located at the second vertical level 18.

Further, common to the embodiments illustrated, the inlet conduit assembly 4 may comprise a valve 38 located between the ballast fluid level increasing arrangement 20 and the ballast tank 8, as seen in a direction of flow from the source of ballast fluid towards the ballast tank. The source of ballast fluid may ultimately be represented by the ambient sea water. However, the ballast fluid may, for various purposes, be stored in e.g. intermediate tank 42 positioned prior to the fluid level increasing means 20, as seen in a direction of flow from the source of ballast fluid toward the ballast tank.

One of the purposes of the inlet conduit assemblies 4 according to the examples described above is to feed ballast fluid to one or more ballast fluid tanks of a ballast system of a floating unit. Upon feeding ballast fluid to one or more ballast fluid tanks, the inlet conduit assembly is fed with ballast fluid such that the ballast fluid reaches the first level. This may be achieved by using a main fluid level increasing arrangement 22, e.g. a first pump assembly 22 as illustrated e.g. in any of Fig. 1 , 2 and 6. When the inlet conduit system comprises an intermediate tank 42, as illustrated in any of Fig. 3 to 6, ballast fluid is pumped to the intermediate tank 42, such that it reaches the first level 12.

The ballast fluid level increasing arrangement 20 may be activated such that the ballast fluid level in the inlet conduit assembly 4 is increased to the second level 18. Thereby, the ballast fluid level increasing arrangement may actively increase the level of the ballast fluid level in the inlet conduit assembly 4 from the first level to the second level. The ballast fluid level increasing arrangement 20 only needs to be activated during ballasting operations. The ballast fluid level increasing arrangement 20 may comprise a second pump assembly 24, which in turn may comprise one or more pumps which are dedicated 5 to this, i.e. whose purpose is to lift the ballast fluid from the first level 16 to the second level 18.

Subsequently, the ballast fluid is fed to the one or more ballast tanks 8. Preferably, at least in some embodiments, after having reached the second level 18, or the third level 19 o when a second overflow arrangement is present, the ballast fluid is fed by gravity to the ballast tank 8. Thereby, an overpressure in the ballast tank can be avoided, and also there is no need for a de-areator. Filling of the ballast tank due to self-flow of the ballast fluid from the second level 18 to the ballast tank can only take place when the second pump assembly 24 is operating.

5

The filling of the ballast tank can be interrupted by interrupting the feeding of the ballast fluid to the ballast tank by deactivating the ballast fluid level increasing arrangement 20. For example, the pumps of the second pump assembly 24 may be switched off. 0 Example embodiments may be combined as understood by a person skilled in the art.

Even though the disclosure has been described with reference to example embodiments, many different alterations, modifications and the like will become apparent for those skilled in the art. Part of the inlet conduit assemblies may comprise several parallel flow paths, such as several caissons leading to an intermediate tank or a manifold or several5 conduits leading to one or more ballast tanks.

Moreover, an overflow arrangement may be connected to each ballast tank and via the ballast tank be in fluid communication with the inlet conduit assembly. When outlets to ambient environment are described to be above a still water surface it is also envisaged0 that the physical outlet may be below a still water surface but the conduit leading to the physical outlet extends to a level above a still water surface.

Therefore, it is to be understood that the foregoing is illustrative of various example embodiments and is not to be limited to the specific embodiments disclosed and that5 modifications to the disclosed embodiments, combinations of features of disclosed embodiments as well as other embodiments are intended to be included within the scope of the appended claims.

Claims

1 . An inlet conduit assembly (4) for a ballast system of a floating unit (2), said inlet conduit assembly (4) having an extension in at least a vertical direction (V), said inlet conduit assembly being adapted to provide a fluid communication between a source of ballast fluid (6) and a ballast tank (8) of said ballast system, said inlet conduit assembly comprising a first overflow arrangement (10) adapted to discharge ballast fluid from said inlet conduit assembly at a first level (12) in said vertical direction,

ch aracterized i n th at

said inlet conduit assembly comprises an inlet conduit assembly top portion (16) that is located at a second level (18) arranged at a distance above said first level (12) in said vertical direction (V), said inlet conduit assembly further comprising a ballast fluid level increasing arrangement (20, 24) adapted to actively increase the level of the ballast fluid in said inlet conduit assembly to said second level (18).

2. The inlet conduit assembly (4) according to claim 1 , wherein said inlet conduit assembly comprises a main fluid level increasing arrangement (22), preferably a first pump assembly (22) comprising at least one pump, adapted to actively increase the level of the ballast fluid in said inlet conduit assembly to said first level (12).

3. The inlet conduit assembly (4) according to claim 2, wherein said ballast fluid level increasing arrangement (20, 24) is separate from said main fluid level increasing arrangement (22).

4. The inlet conduit assembly (4) according to claim 2 or 3, wherein said ballast fluid level increasing arrangement (20) comprises a second pump assembly (24) comprising at least one pump, said second pump assembly being separate from said main fluid level increasing arrangement (22).

5. The inlet conduit assembly (4) according to claim 4, wherein said second pump assembly (24) comprises a vertical propeller pump.

6. The inlet conduit assembly (4) according to any one of claims 4 or 5, wherein said inlet conduit assembly comprises an at least partially closed sub tank (30) that in turn comprises a sub tank inlet (32) and a sub tank outlet (34), said sub tank outlet being located above said sub tank inlet (32) in said vertical direction, said second pump assembly (24) being adapted to pump ballast fluid from said sub tank inlet (32) to said sub tank outlet (34).

7. The inlet conduit assembly (4) according to any one of claims 4 to 6, wherein said inlet conduit assembly comprises a inlet conduit bend portion (56) that is located downstream of said second pump assembly, as seen in a direction of flow from said source of ballast fluid towards said ballast tank, said inlet conduit bend portion comprising a bend a portion (58) of which is located at said second level (18).

8. The inlet conduit assembly (4) according to claim 7, wherein said inlet conduit bend portion (56) comprises a venting arrangement connected to said bend portion (58)

9. The inlet conduit assembly (4) according to any one of the preceding claims, wherein said inlet conduit assembly comprises an intermediate tank (42).

10. The inlet conduit assembly (4) according to any one of the preceding claims, wherein said source of ballast fluid (6) is sea water ambient of said floating unit (2).

1 1 . The inlet conduit assembly (4) according to any one of the preceding claims, wherein said inlet conduit assembly top portion (16) is located between said ballast fluid level increasing arrangement (20) and said ballast tank (8), as seen in a direction of flow from said source of ballast fluid towards said ballast tank.

12. The inlet conduit assembly (4) according to any one of the preceding claims, wherein said inlet conduit assembly comprises a valve (38) that is located between said ballast fluid level increasing arrangement (20, 24) and said ballast tank (8), as seen in a direction of flow from said source of ballast fluid towards said ballast tank.

13. The inlet conduit assembly (4) according to any one of the preceding claims, wherein said inlet conduit assembly (4) comprises a second overflow arrangement (40, 64) located downstream of said ballast fluid level increasing arrangement (20, 24), as seen in a direction of flow from said source of ballast fluid towards said ballast tank (8), said second overflow arrangement (40, 64) being adapted to discharge ballast fluid from said inlet conduit assembly at a third level (19) located at a distance above said second level (16).

14. The inlet conduit assembly (4) according to claim 13, wherein said second

overflow arrangement (40, 64) is adapted to discharge ballast fluid from said inlet conduit assembly to the environment ambient of said inlet conduit assembly (4).

15. The inlet conduit assembly (4) according to claim 13, wherein said second

overflow arrangement (40, 64) is adapted to discharge ballast fluid from said inlet conduit assembly to a portion of said inlet conduit assembly (4) that is located upstream of said ballast fluid level increasing arrangement (20, 24).

16. A ballast system comprising a ballast tank (8) and an inlet conduit assembly (4) according to any one of the preceding claims.

17. A floating unit (2), preferably a semi-submersible unit, comprising an inlet conduit assembly (4) according to any one of claims 1 to 15 and/or a ballast system according to claim 16.

18. A method for feeding ballast fluid to a ballast tank (8) of a ballast system of a floating unit (2), said ballast system comprising an inlet conduit assembly (4) having an extension in at least a vertical direction (V), said inlet conduit assembly being adapted to provide a fluid communication between a source of ballast fluid (6) and said ballast tank (8), said inlet conduit assembly (4) comprising a first overflow arrangement (10) adapted to discharge ballast fluid from said inlet conduit assembly at a first level (12) in said vertical direction, said inlet conduit assembly (4) comprising an inlet conduit assembly top portion (16) that is located at a second level (18) arranged at a distance above said first level (12) in said vertical direction (V), said inlet conduit assembly further comprising a ballast fluid level increasing arrangement (20) adapted to actively increase the level of the ballast fluid in said inlet conduit assembly to said second level (18), said method comprising: - feeding said inlet conduit assembly with ballast fluid such that said ballast fluid reaches said first level (12);

- activating said ballast fluid level increasing arrangement (20, 24) such that the ballast fluid level in said inlet conduit assembly reaches said second level (18),

5 and

- feeding said ballast fluid to said ballast tank (8).

19. The method according to claim 18, said method further comprising:

- interrupting said feeding of said ballast fluid to said ballast tank by deactivating o said ballast fluid level increasing arrangement (20, 24).