NL1041879B1

NL1041879B1 - Anti-roll dump tank.

Info

Publication number: NL1041879B1
Application number: NL1041879A
Authority: NL
Inventors: Franciscus Maria Sas Ir
Original assignee: Franciscus Maria Sas Ir
Priority date: 2016-05-20
Filing date: 2016-05-20
Publication date: 2017-11-27

Abstract

Floating structure, for example a ship, vessel or the-like, including at least one anti-roll water reservoir (2) located substantially above a waterline (L) of the structure (1), wherein the water reservoir (2) includes at least one discharge means (3) for discharging water (W) therefrom. The invention provides a ship motion improving dump tank. The invention comprises of a tank located above the waterline of a vessel, that has a fast water release feasibility. The tank can be completely filled, or partly filled, to act as an anti roll tank and it can be a fixed part of the ship structure, or be separate tank, which is a part of the ships cargo.

Description

Title: Anti-roll dump tank.

The invention relates to a floating structure, for example a ship, vessel or the-like, including at least one anti-roll water reservoir. Particularly, the invention provides a ship motion improving dump tank. A vessel having an anti-roll water reservoir is know as such. The present invention provides an innovative floating structure, aiming at providing improved stability and safety, preferably at an economical manner.

According to an aspect of the invention there is provided a floating structure, for example a ship, vessel or the-like, including at least one antiroll water reservoir located substantially above a waterline of the structure, wherein the water reservoir includes at least one discharge means for discharging water therefrom.

In this way, the floating structure can have a good stability, particularly under normal sailing conditions. During abnormal conditions, e.g. in case of storm or damage to the ship, water present in the anti-roll water reservoir can be discharged by the discharge means to improve safety of the floating structure, e.g. to prevent capsizing.

In a preferred embodiment, the structure includes at least one top deck or upper deck, wherein the anti-roll water reservoir extends near that the upper deck. In that case it is preferred that the reservoir extends on or above a (top) deck of the structure. For example, the reservoir may be located on a coaming of an upper deck, e.g. a coaming of a rear deck of the structure, or on a roof or top wall of the structure, e.g. of user accommodation or the-like. Also, preferably, the reservoir is provided by one or more water containers (e.g. one or more watertight shipping containers) that is/are placed on the structure (e.g. onto a deck, roof or top wall of the structure). The containers can be removable or fixed

According to an embodiment, the invention can comprises of a water reservoir, e.g. a tank, located above the waterline of the structure, e.g. a vessel, that has a fast water release feasibility. For example, the configuration can be such that the reservoir can be substantially emptied within half of one ship motion period , preferably 2 to 10 seconds.

The term “waterline” is commonly known to the skilled person. Generally it is a horizontal line, usually being marked on an outer surface of a floating structure, indicating the level of a water surface intersecting the floating structure, under predetermined loading conditions and when the structure is stationary.

Also, in this application, the term “floating” means floating in water, or “floatable” in water, the water e.g. being example sea water, or fresh (river) water. Particularly, during operation (e.g. sailing), the structure floats.

According to an embodiment, the reservoir (or ‘tank’, as in the following) can be completely filled, or partly filled, to act as an anti roll tank and it can be a fixed part of the ship structure, or be separate tank, which is a part of the ships cargo.

The intension of the tank is to reduce the ship motions of the vessel. Ship roll motions of a vessel in waves are mainly determined by the roll period reference to the wave period. To have a good behaviour, a high centre of gravity (G) is required, resulting in a small meta- centric height (GM) and a large resonance period of the vessel (T resonance).

k =radius of gyration about the longitudinal axsis through the cente of gravity The Metacentre (M) is the virtual rotation point of the vessel. See figures 1 and 2. The height of the resulting centre of gravity, corrected with the free surface reduction (G’) is often limited by the damage stability requirements or other requirements that do not exist during normal operations.

By filling an, above the waterline positioned, tank, to a predetermined degree or with a correct level of water, the tank can work as an anti roll tank. Unlike normal cargo tanks, or ballast tanks the anti roll tanks have a water motion that is slower or alike the roll motion of the ship. The natural period of the water motion in the tank is than similar to the roll period of the vessel. The water of the tank will thus be of phase with the roll motion and reduce the motion (see figure 3)

Only in extreme conditions, e.g. when the ship has a constant heeling, the water in the tank will be reducing the stability (see figure 4).

Anti roll tanks of these types as such are common. They exist as flume tanks, and as U tanks. According to the present invention, both types of these tanks can be adjusted with the invention to become a dump tank. The anti roll tanks operate until maximum roll angles of approx. 6 to 12 degrees.

According to an aspect of the invention, we position the anti roll tank or dump at sufficient height above the waterline, so that in case of damage, or in case of to large roll angles, the side and/or bottom of the tank will partly open to discharge all water very fast from the tank.

With the dump tank a high located centre of gravity in normal operating conditions (with a dump tank filled) can be combined with a sufficient stability in damage or other critical conditions, (with the dump tank empty). Preferably, the dump tanks will have a beam of 80 % of the ships beam or more.

The discharge means can be configured in various ways, as well be appreciated by the skilled person.

According to an advantageous embodiment, the tank can be opened with a mechanical or other mechanism that opens at angles between 3 and 18 degrees, pending on the stability curve of the vessel.

The vessel can fulfil the design criteria for intact stability and as given by IMO (the International Maritime Organization) or other authority.

According to a preferred embodiment, the water can be discharged in such a short time, and the required openings in the dump tank will be so big that the dynamic stability will fulfil the severe wind and rolling criterion (weather criterion) requirements of the stability as specified by the IMO or other authorities.

Preferably, the structure is configured such that in damage condition, or at large roll angels, the tank will be substantially or completely discharged. Dumping of water will be possible e.g. on both sides of the vessel Port side and starboard.

The dependent claims provide extra advantageous embodiments of the invention. The invention will now be explained in more detail with reference to the drawings. Therein shows:

Figure 1 schematically a lateral cross-section of a first non-limiting embodiment of the present invention;

Figure 2 schematically a lateral cross-section of a second nonlimiting embodiment of the present invention;

Figure 3 a lateral cross-section as Fig. 1, of the ship during normal rolling;

Figure 4 a lateral cross-section as Fig. 1, of the ship at not operational extreme conditions;

Figure 5 a lateral cross-section as Fig. 1, of the ship at a large roll angle under extreme conditions, with the dumptank opened.

In this application, the same or corresponding features are denoted by the same or corresponding reference signs.

Figures 1-5 schematically depict embodiments of floating structures, for example a ship, vessel or the-like. In figure 1, the structure 1 includes an anti-roll water reservoir 2, of the flume tank type, being composed of a single water reservoir. In figure 2 the structure includes an anti-roll water reservoir 2’ of the U tank type, having two main reservoir sections 2’a, interconnected via a water duct 2’b allowing water to flow between the sections 2’a. As follows from the drawings, during operation, the anti-roll water reservoir 2 is at least partly filled with water during operation (e.g. during normal floating conditions of the respective structure 1).

Advantageously, the water reservoir 2 is located substantially above a waterline of the structure 1. In figures 1, 2, the water line is indicated by reference L; it is usually a line marked on an outer side of the structure 1, and may coincide with a surface level wl or surrounding water (as in the present examples), or be located above or below the surface level wl depending on the structure’s loading condition and under stationary (i.e. no roll et cetera.) conditions.

In a preferred embodiment, the water reservoir 2 includes at least one discharge means 3 for discharging water W therefrom.

For example, the structure 1 can include at least one upper deck, wherein the anti-roll water reservoir extends near that the upper deck. It is preferred that the reservoir 2 extends on or above an upper deck. For example, the reservoir may be located on a coaming of an upper deck, e.g. a coaming of a rear deck of the structure 1. Preferably, the reservoir is provided by one or more water containers that are placed on the structure 1 (e.g. onto a deck of the structure).

Also, for example, a bottom of the anti-roll water reservoir 2 can be located above the waterline L, for example at a height of at least 1 m above that waterline L. It is preferred that a bottom of the anti-roll water reservoir 2 is located at a height sufficient for entirely discharging that reservoir under influence of gravity in case of a relatively large predetermined roll angle Θ of the floating structure (see Fig. 4), e.g. a roll angle Θ angle of about 10 degrees or even a roll angle of about 15 degrees, or even a roll angle of about 20 degrees.

According to an embodiment, the discharge means can be configured to automatically discharge water therefrom, particularly depending on at least one parameter concerning the floating structure, for example a stability parameter. The floating structure may e.g. include a sensor, processor or other means for detecting or predicting a stability of the floating structure, and to control the discharge means (e.g. activate those means) in case it is found that the floating structure becomes or may become instable (e.g. in case of relatively large roll movements of the floating structure).

In an embodiment, the discharge means 3 include at least one water discharge opening, for example located in or near a side or bottom of the reservoir. In the example, two such openings 3 are depicted.

Particularly, each discharge opening is closed by a removable or displaceable closure 3a, for example a valve element or door, to prevent discharge of water under normal operating conditions of the floating structure. In the example, the closure 3a is swivably connected to a wall of the structure 1 (e.g. a side wall), wherein the closure can be held in a closed stated e.g. by controllable locking means (not shown), wherein the locking means can be brought to a release state to release the closure 3a so that it can open (e.g. under influence of water pressure from the water present in the reservoir 2). In a further embodiment, the releasing of the closure 3a (to initiate discharging of the reservoir 2) can be initialed or controlled by a control signal, e.g. a signal provided or generated by a control signal generator 5.

It should be noted that in the present example, the discharge means (reservoir discharge openings 3 and closures 3a) are located in an outer side of the structure 1, however, that is not required.

Preferably, each discharge 3 is being located above the waterline L of the vessel. For example, each discharge opening 3 can be located at a height of at least 1 m above the waterline L. For example, the discharge opening 3 can be located at a height sufficient for entirely discharging that reservoir under influence of gravity in case of a relatively large predetermined roll angle Θ of the floating structure (see Fig. 4), e.g. a roll angle Θ angle of about 10 degrees or even a roll angle of about 15 degrees, or even a roll angle of about 20 degrees.

Preferably, each discharge opening is relatively large, allowing a swift discharge of the water W. For example, a discharge opening 3 of each reservoir/tank 2 can have a cross-section of at least 1 m2 , for example a cross-section of at least 10 m2

Also, each water reservoir 2 may be provided with at least one discharge opening at a certain side (e.g. port side or starboard) of the structure 1, however, it is preferred that the water reservoir 2 includes a plurality of such discharge openings 3.

According to an advantageous embodiment, the discharge means 3 are configured to discharge water under influence of gravity, particularly without operation of driven water pumping means.

According to an advantageous embodiment, the discharge means 3 are configured to dump water via at least one side of the structure, and preferably at a starboard side as well as a port side of the structure.

According to an advantageous embodiment, the discharge means 3 are configured to discharge at least 50% of the reservoir’s internal volume within one roll motion period (i.e. in case the reservoir is filled for 25% with water, that water can be discharge within one roll motion period), particularly within 2 to 10 seconds

According to an advantageous embodiment the structure 1 includes a discharge means control signal generator 5 for controlling the discharge means, particularly for activating the discharge means in order to discharge water. For example, the control signal generator 5 can be configured to automatically generate a control signal in case of detection or estimation of a certain instability of the structure, and/or in case of a detection or estimation of a certain damage of the structure.

According to an advantageous embodiment he structure 1 includes a user interface (e.g. a knob, switch, keyboard, touch pad, voice control and/or the-like) for operating the control signal generator 5

According to an advantageous embodiment the at least one antiroll water reservoir 2 extends over at least 50%, preferably at least 80% of a beam of the structure (see the drawings, wherein the one anti-roll water reservoir 2 extends over substantially the entire beam).

In the present examples, the anti-roll water reservoir 2 is a fixed part of floating structure Alternatively, it is proposed that the anti-roll water reservoir 2 (and its respective water discharge means) is a separate reservoir, removably held by the floating structure, for example a water reservoir 2 placed on a cargo deck or in a cargo bay of the floating structure.

While specific embodiments have been described above, it will be appreciated that the invention may be practiced otherwise than as described. The descriptions above are intended to be illustrative, not limiting. Thus, it will be apparent to one skilled in the art that modifications may be made to the invention as described in the foregoing without departing from the scope of the claims set out below. Reference signs in the claims should not be construed as limitations of the claims. Also, it will be appreciated that various parts, units and/or features of embodiments described can be combined with various other parts, units and/or features of other embodiments described, in various ways.

For example, the invention can be applied to various types of structures. Non-limiting examples of a floating structure are: a vessel, a cargo ship, a bulk carrier, a container ship, a tanker, an offshore ship, a maritime platform, a sailing boat, a tugboat.

Claims

A floating structure, for example a ship, vessel or the like, provided with at least one anti-roll water reservoir (2) which is substantially above a water line (L) of the structure (1), the water reservoir (2) comprises at least one delivery means for discharging water therefrom.

A floating structure, according to claim 1, comprising an upper deck, wherein the anti-roll water reservoir extends just below the upper deck.

Floating structure according to claim 1 or 2, wherein a bottom of the anti-roll water reservoir (2) is above the water line (L), for example at a height of at least 1 m above that water line (L).

Floating structure according to one of the preceding claims, wherein the minimum stability criteria according to IMO or other authority are met in normal operational conditions and filled with the anti-roll dump tank, but not in extreme conditions, such as in extreme wind or wave conditions or in damaged condition. Filled with the anti roll dump tank.

A floating structure according to any one of the preceding claims, wherein the delivery means (3) are configured to automatically release water therefrom, in particular depending on at least one parameter concerning the floating structure, for example a stability parameter.

Floating structure according to any one of the preceding claims, wherein the dispensing means (3) comprise at least one water dispensing opening, for example in or near a side or bottom of the reservoir, the opening being in particular closed by a removable or movable closure (3a) ), wherein the opening is in particular above the waterline (L) of the structure.

Floating structure according to any one of the preceding claims, wherein the delivery means (3) are configured to release water under the influence of gravity, in particular without operation of driven water pumping means.

A floating structure according to any one of the preceding claims, wherein the delivery means (3) are configured to dump water through at least one side of the structure, and preferably both on a starboard side and a port side.

A floating structure according to any one of the preceding claims, wherein the delivery means (3) are configured to deliver at least 25% of the reservoir internal volume within 60 minutes, in particular within 10 minutes.

Floating structure according to one of the preceding claims, comprising a delivery means control signal generator (5) for controlling the delivery means, in particular for activating the delivery means for dispensing water.

A floating structure according to claim 9, wherein the control signal generator (5) is configured to automatically generate a control signal in the case of detection of a particular instability of the structure, and / or in the case of a detection or estimation of a certain damage to the structure.

A floating structure according to claim 9 or 10, comprising a user interface for operating the control signal generator.

A floating structure according to any one of the preceding claims, wherein the anti-roll reservoir (2) extends over at least 50%, preferably at least 80%, over the width of the structure.

A floating structure according to any one of the preceding claims, wherein the anti-roll reservoir (2) is a fixed part of the structure.

Floating structure according to any of claims 1-3, wherein the anti-roll reservoir (2) is a separate reservoir, which is kept releasable by the floating structure, for example a water reservoir (2) which is on a cargo deck or cargo hold of the floating structure is placed.

A floating structure according to any one of the preceding claims, wherein the structure is selected from at least one of: a vessel, a cargo ship, a bulk carrier, a container ship, a tanker, an offshore ship, a maritime platform, a sailboat.