NL2022098B1

NL2022098B1 - Vessel with venting arrangement

Info

Publication number: NL2022098B1
Application number: NL2022098A
Authority: NL
Inventors: Dingeman Stroo Jacobus; Arnold Manschot Dolf; Ferdinand Jacobus Van Leeuwen Edwin
Original assignee: Ulstein Design & Solutions B V
Priority date: 2018-11-29
Filing date: 2018-11-29
Publication date: 2020-06-26

Abstract

Vessel including a hull extending to a main deck, a ballast tank adjacent to a first side wall ofthe hull, at least partially below a waterline, a venting pipe for venting the ballast tank, extending from the ballast tank to an opening above the waterline and below the main deck, the venting pipe comprising a riser portion extending from the ballast tank to a position above the waterline and a transverse portion connecting the riser portion to the opening, wherein the transverse portion extends inboard from the first side wall at least a distance sufficient to remain at least partially above the waterline under maximum heeling ofthe vessel.

Description

P6073263NL %! Vessel with venting arrangement

BACKGROUND OF THE INVENTION

1. Field of the invention

[0001] The present invention relates to a vessel with a ballast tank and venting pipe. It is particularly relevant to offshore construction vessels having flush working decks. The invention also relates to a method of retrofitting a vessel with such a venting pipe.

2. Description of the related art

[0002] Offshore construction vessels or ships (e.g. those shown in JP6241669 or GB2174347, the contents of which are incorporated herein by reference in their entirety) typically have a main working deck with multiple large water ballast tanks or ballast tanks underneath. The ballast tanks are watertight compartments which are meant to regulate the draught, trim, heel and stability of the vessel by controlling the amount of water therein. Water can be pumped into the ballast tanks when a vessel has no or a limited amount of cargo, to lower its center of gravity. Water can be removed from the ballast tanks when the vessel is being loaded with cargo. To this end, the vessel is equipped with pumps and pipes for loading and unloading of water from the ballast tanks.

[0003] The ballast tanks can have different forms. They can extend centrally across the width of the vessel, in the double bottom of the vessel's hull. Alternatively, they may be provided at a side of the vessel, extending up part of the side wall from the hull’s bottom to the deck. Often, a plurality of ballast tanks are provided in a longitudinal direction along the length of the vessel. Typically, vessels comprise multiple different types of ballast tanks.

[0004] Ballast tanks need to be vented. While water is being pumped into or out of the ballast tank, air must be allowed to flow the other way to avoid excessive high or low pressures inside the ballast tanks. In order to vent all of these tanks, usually for each tank at least one vent head (or air ventilation pipe or overflow pipe) is provided on the main deck. This results in a large number, typically at least twenty, of vent heads on the main deck. The vent heads may be equipped with an automatic closing device, which closes in case of immersion to block entry of water to the tanks.

[0005] However, the presence of the vent heads on the main deck also involves a number of disadvantages. The vent heads occupy an area on the deck which cannot be used for regular operations or cargo. Furthermore, vent heads can be damaged as a result of the operations on the deck. Damage may happen in harbour, e.g. by collision with cargo, fork lifts or swinging crane loads during loading or unloading, but also offshore, during operations carried out on the deck. Damage of the vent heads may result in safety hazards, for example by blocking the escape/ingress of air from the tanks or by impairing the automatic closing device.

[0006] According to international regulations (in particular the International Load Line Convention (ILLC) of the International Maritime Organization (IMO)), a vent head height of 760 mm above the freeboard deck is required. The freeboard deck is defined as the uppermost watertight deck. The minimum required vent head height safeguards the watertight integrity of the vessel and limits the 40 capsizing risk, because it prevents water flowing over the deck from flowing into the ballast tank

(even with a damaged automatic closing device). At the same time, it allows the vessel to lean over to larger heel angles without the vent head being entirely under water. The regulations however limit the possibilities for resolving the disadvantages above, since the height of the vent above the deck makes it particularly vulnerable to damage and an obstruction to operations on deck.

[0007] In light of the above, it would be desirable to provide a vessel which at least partially overcomes some of the inconveniences of the prior art.

SUMMARY OF THE INVENTION

[0008] According to the invention there is provided a vessel, including a hull extending to a main deck, a ballast tank adjacent to a first side wall of the hull, at least partially below a waterline, a venting pipe for venting the ballast tank, extending from the ballast tank to an opening above the waterline and below the main deck, the venting pipe comprising a riser portion extending from the ballast tank to a position above the waterline and a transverse portion connecting the riser portion to the opening, wherein the transverse portion extends inboard from the first side wall.

[0009] It may be required that the transverse portion extends inboard from the first side wall at least a distance sufficient to remain at least partially above the waterline under maximum heeling of the vessel.

[0010] The vessel according to the invention has the advantage that no vent heads on the main deck are required, which enlarges the effective area of the deck and greatly reduces the risk of damage to the vent heads. Collision of equipment and/or cargo on the deck is no longer possible, which improves the safety of the vessel. Furthermore, the venting pipe can be completely within the confines of the vessel and is thus less exposed to weather conditions, and from the resulting corrosion, wear and other damage.

[0011] The ballast tank is provided entirely or partially below the waterline. In this context, reference to the waterline is intended to denote the waterline during usual operation of the vessel. The ballast tanks may extend to the bottom of the hull and/or to the main deck. If a ballast tank is damaged at the outside, e.g. in a ship collision, and water ingress happens, the vessel may heel towards the side of that ballast tank. In this event, the opening for venting that ballast tank remains above the waterline, because it extends sufficiently far inboard. It will thus prevent progressive flooding through the venting pipe or through other venting pipes on the same side of the vessel, which correspond to other ballast tanks. The distance by which the transverse portion extends inboard depends on the overall construction of the vessel, but is preferably at least 25% ofthe hull’'s width.

[0012] It will be understood that reference above to a ballast tank adjacent to a first side wall of the hull is not intended to denote that the vessel only has one.

[0013] Preferably, the ballast tanks for a given side of a vessel are provided entirely at that side of a vertical plane through a central line connecting the bow and stern ends of the vessel. In other words, the ballast tanks do not span the centreline of the vessel. For such vessels the present invention is particularly advantageous since they may have a larger capsizing risk than vessels with 40 all ballast tanks extending from one side wall to an opposite side wall.

[0014] The vessel may be an offshore construction vessel, or it may be any other vessel with a large flat deck. They may be vessels with deck sizes of at least 50 m x 20 m, preferably about 100 m x 35 m (length x width). In particular, the invention relates to vessels in which a flush working deck is preferred. Preferably, the main deck is flush or planar for substantially its entire area, i.e. except for practically necessary arrangements such as stair openings, fences etc. In particular, the vessel may be a vessel with a main deck without a gunwale.

[0015] The or each ballast tank may be vented using a single venting pipe, or using multiple venting pipes, preferably 1 or 2 per ballast tank

[0016] When the ballast tank is being filled, water may be pumped into the tank through a separate ballast pipe. The venting pipe serves to properly facilitate the overflow of water to outside the vessel. The venting pipe is designed to ensure that the water flows out of the vessel and does not end up inside the hull or on deck. The opening is provided above the waterline. The opening can be an outlet overboard or an opening in another pipe leading to an outlet overboard.

[0017] The riser portion of the venting pipe will generally be substantially vertical and preferably extends from the ballast tank to a position further above the waterline than the opening. The transverse portion is preferably substantially horizontal. By using the riser portion and the transverse portion the venting pipe minimally obstructs the interior space of the hull and remains above the waterline under maximum heeling. The transition between the riser portion and the transverse portion may be an elbow in the venting pipe or it may be a separate component or joint, welded or bolted to the riser portion and the transverse portion. Preferably, the transverse portion is provided close to the lower side of the main deck, preferably less than 1 m below the lower side of the main deck.

[0018] In a particularly advantageous embodiment, the opening is provided in a second side wall, which is opposite to the first side wall.

[0019] An arrangement with a venting pipe extending from the ballast tank at the first side of the vessel to the opening at the second, opposite side of the vessel (and vice versa) may be referred to as a cross-vent arrangement. Thus the port side ballast tanks will vent to starboard and vice- versa. This arrangement has the advantage that no pipes along the length of the vessel are required. It also has the advantage that even further heeling of the vessel is allowed without water ingress into the venting pipe.

[0020] In an embodiment, the opening leads to a main pipe arranged along the longitudinal direction of the hull, and wherein the main pipe has an outlet overboard. Overboard is to say that the outlets leads to outside the vessel such that water flowing through the main pipe to the outlet will end up outside the vessel.

[0021] The main pipe acts as a common overflow for the venting pipes. The outlet may be provided at a bow and/or stern end of the vessel. The vessel may include two main pipes along the longitudinal direction of the hull that both have outlets at the bow and/or at the stern of the vessel. Multiple venting pipes from multiple different ballast tanks adjacent to the same side wall of the vessel may be connected to the same main pipe. An advantage of the main pipe is that fewer outlets 40 in the vessel’s side wall are needed. The main pipe is preferably connected to outside the vesselwithout an automatic closing device which may block water and/or air from flowing between the main pipe and outside the vessel.

[0022] In an embodiment, the main pipe leads to a transverse pipe across the hull, and the transverse pipe includes outlets to outside the vessel in both side walls.

[0023] This has the advantage that water can flow out at both sides of the vessel. When two main pipes are present, both may be connected to the same transverse pipe. In this embodiment, the transverse pipe embodies the outlets from both main pipes to outside the vessel.

[0024] In an embodiment, the distance over which the transverse portion extends inboard from the first side wall is at least 25% of the hull's width, preferably at least 40% of the hulls width, more preferably at least 50% of the hull’'s width. The extent to which the transverse portion extends inboard from the first side wall depends on the overall construction of the vessel; in any case, it needs to be sufficiently far to stay above the waterline under maximum heeling of the vessel.

[0025] In an embodiment, the vessel further includes a second ballast tank adjacent to a second side wall of the hull, which is opposite to the first side wall, at least partially below a waterline, a second venting pipe for venting the second ballast tank, extending from the second ballast tank to a second opening above the waterline and below the main deck, the second venting pipe comprising a second riser portion extending from the second ballast tank to a position above the waterline and a second transverse portion connecting the second riser portion to the second opening, wherein the second transverse portion extends inboard from the second side wall at least a distance sufficient to remain at least partially above the waterline under maximum heeling of the vessel.

[0026] This embodiment has the advantage that the safety of the vessel is improved for heeling towards both sides. The first side wall may be provided at the port-side of the vessel and will thus also be referred to as port-side wall and the second side wall will also be referred to as starboard- side wall. The first ballast tank will thus also be referred to as port-side ballast tank and the second ballast tank will also be referred to as starboard-side ballast tank. A person skilled in the art will understand that the features and advantages are equivalent at the vessel's opposite side. The second venting pipe may be a mirrored version of the venting pipe with respect to a vertical plane through a line connecting the vessel's bow and stern, apart from a translation in the longitudinal direction of the vessel.

[0027] In an embodiment, the vessel comprises a freeboard deck below the main deck, wherein the freeboard deck is substantially planar and parallel to the main deck, and preferably wherein the opening is provided between the main deck and the freeboard deck. The space between the freeboard deck and the main deck may be either a full deck of conventional height or may be limited to the space required for utilities such as the vent pipes mentioned above and any required height between the freeboard deck and the openings. Preferably, the transverse portion of the venting pipe is provided between the main deck and the freeboard deck.

[0028] Virtual freeboard is according to international regulations defined as the line at a level of 760 mm below the lowest vent head, as long as it is not above the main deck. The virtual freeboard 40 defines the maximum draught of the vessel and thus also the maximum cargo load. In practice,

lowering the vent heads / openings means lowering the virtual freeboard thus reducing the maximum cargo. No actual deck at virtual freeboard is required, but it may be beneficial to have one as the freeboard deck improves the structural strength of the vessel.

[0029] In an embodiment, the venting pipe comprises an automatic closing device between the 5 ballast tank and the opening, configured to allow air or water flow out of the ballast tank and prevent water from flowing into the ballast tank.

[0030] The automatic closing device serves two purposes: that the venting pipe is open for venting air from the tank, while simultaneously avoiding water ingress into the tank. Failure of the automatic closing device may cause one of the two purposes to malfunction, i.e. the venting pipe being either always closed or always open. An always open venting pipe may result in significant water ingress at large heel angles, which is an already critical situation, possibly leading to capsizing. An always closed venting pipe may result in problems when filling the tank, e.g. excessive pressures or overfilling.

[0031] In an embodiment, the automatic closing device is provided between the riser portion and the transverse portion. This has the advantage that no water can flow into the riser portion, while water can freely flow into and out of the transverse portion. In this way the automatic closing device will only close when there is an actual risk of water flowing into the ballast tank, while normally no water can stay between the automatic closing device and the opening. Alternatively, the automatic closing device may be provided in the transverse portion, in particular at an end of the transverse portion, near the opening. This has the advantage that substantially no water can flow into the transverse portion too.

[0032] In an embodiment, the venting pipe comprises an end part, adjacent to the opening, which slants or extends downwards towards the opening. In the event of heavy seas with waves above the virtual freeboard, water ingress into the venting pipe is possible. The slanted end part mitigates the risk of water ingress, because most of the water entering the venting pipe will immediately flow back out.

[0033] In an embodiment, the vessel comprises a plurality of ballast tanks, preferably at least three adjacent to each side wall.

[0034] Having a plurality of ballast tanks improves the safety of the vessel since damage to a single ballast tank is less detrimental if it represents only a fraction of the total ballast tank volume. International regulations are in place which require industrial vessels to have a plurality of separate ballast tanks. However, a large number of tanks would normally result in a large number of venting heads on the main deck. When using the venting pipes according to the present invention, the large number of ballast tanks does not affect the effective working area on the main deck. Therefore, venting large numbers of ballast tanks is possible without sacrificing deck area.

[0035] Preferably, the vessel comprises a venting pipe as described herein for each ballast tank. Alternatively, such pipes are applied to a limited number of the ballast tanks, while for the other ballast tanks conventional vent heads are used. In an embodiment, all ballast tanks below the planar part of the main deck or working deck are equipped with a venting pipe according to the present 40 invention, while ballast tanks under the bridge and accommodations do not need to have them andmay be vented by conventional means. Preferably, at least 50% of the ballast tanks or at least 50% of the ballast tank volume is equipped with such venting pipes.

[0038] In an embodiment, the main deck is unobstructed by vent heads. The person skilled in the art will understand that the main deck will have practically necessary arrangements such as stair openings, fences, etc. but may otherwise be largely unobstructed.

[0037] In an embodiment, the venting pipes have a minimum internal diameter of 10 cm, preferably between 15 and 45 cm.

[0038] According to an aspect of the invention, and in accordance with the advantages and effects described hereinabove, there is also provided a method of ballasting and venting a vessel, the vessel comprising a hull extending to a main deck, and having at least a port-side ballast tank and a starboard-side ballast tank, wherein the method comprises venting the port-side ballast tank via a first venting pipe to an opening at a starboard side of the vessel, below the main deck, and venting the starboard-side ballast tank via a second venting pipe to an opening at a port side of the vessel, below the main deck.

[0039] According to an aspect of the invention, and in accordance with the advantages and effects described hereinabove, there is provided a method of retrofitting a vessel, in particular an offshore construction vessel, or any other vessel with a large flat deck, the method comprising: providing a vessel, comprising: a hull extending to a main deck; a ballast tank, adjacent to a first side wall of the hull and extending to below a waterline; a venting pipe for venting the ballast tank, extending from the ballast tank via a riser portion to an opening above the waterline; redirecting the venting pipe by connecting a transverse portion between the riser portion and the opening, wherein the transverse portion extends inboard from the first side wall at least a distance sufficient to remain at least partially above the waterline under maximum heeling of the vessel.

[0040] It will be understood that any retrofitting process will comprise other actions in which elements of the existing structure are removed or reconfigured. In an embodiment, the method includes retrofitting the vessel with other features as described in the context of the vessel hereinabove.

[0041] In an embodiment, the method further comprises constructing a freeboard deck below the main deck, wherein the transverse portion of the venting pipe is located above the freeboard deck.

Instead of constructing a freeboard deck below the main deck, the method may include assigning a virtual freeboard deck below the main deck.

[0042] According to an aspect of the invention, and in accordance with the advantages and effects described hereinabove, there is provided a method of retrofitting a vessel, in particular an offshore construction vessel, or any other vessel with a large flat deck, the method comprising: providing a vessel, comprising: a hull extending to a main deck; a ballast tank, adjacent to a first side wall of the hull and extending to below a waterline; a venting pipe for venting the ballast tank, extending from the ballast tank to an opening above the main deck; constructing a substantially flush additional deck above the main deck and above the opening. In this way, the additional deck will become the working deck and is not obstructed by vent heads because they are provided 40 between the additional deck and the main deck.

[0043] According to a particular aspect of the invention, there is provided a vessel including a hull extending to a main deck, a ballast tank adjacent to a first side wall of the hull, at least partially below a waterline, a venting pipe for venting the ballast tank, extending from the ballast tank to an opening above the waterline and below the main deck, the venting pipe comprising a riser portion extending from the ballast tank to a position above the waterline and a transverse portion connecting the riser portion to the opening, wherein the opening is provided in a second side wall, which is opposite to the first side wall.

[0044] According to an alternative aspect of the invention, there is provided a vessel including a hull extending to a main deck, a ballast tank adjacent to a first side wall of the hull, at least partially below a waterline, a venting pipe for venting the ballast tank, extending from the ballast tank to an opening above the waterline and below the main deck, the venting pipe comprising a riser portion extending from the ballast tank to a position above the waterline and a transverse portion connecting the riser portion to the opening, wherein the transverse portion extends inboard from the first side wall at least a distance sufficient to remain at least partially above the waterline under maximum heeling of the vessel, wherein the opening leads to a main pipe along the longitudinal direction of the hull, the main pipe having an outlet to outside the vessel, the outlet being above the waterline and below the main deck.

BRIEF DESCRIPTION OF THE DRAWINGS

[0045] The features and advantages of the invention will be further appreciated upon reference to the following schematic drawings of a number of exemplary embodiments, in which corresponding reference symbols indicate corresponding parts.

[0046] Figures 1A and 1B show a cross-sectional view of a vessel according to the prior art;

[0047] Figures 2A-2C show a cross-sectional view of a vessel according to the invention;

[0048] Figure 3 shows a side view of a vessel of Fig. 2;

[0049] Figure 4 shows a perspective view of a cross-section of the vessel according to an embodiment;

[0050] Figure 5A shows a perspective view of a cross-section of the vessel according to an alternative embodiment;

[0051] Figure 5B shows a schematic top view of the vessel of Fig. SA.

[0052] The figures are for illustrative purposes only, and do not serve as a restriction on the scope or the protection as laid down by the claims.

DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0053] Figures 1A and 1B schematically show a cross-sectional view of a vessel 101 according to the prior art. The vessel 101 comprises a hull 102 and a main deck 103. The hull 102 comprises a first, or port-side ballast tank 111, which is vented via a substantially vertical venting pipe 112 leading to a vent head 113 provided just above the main deck 103. In this particular case, the port- side ballast tank 111 extends from above to below the waterline WL. It will be understood that anumber of further similar or identical ballast tanks will be present along the port—side of the vessel, each having a similar vent head. Figure 1B shows the vessel 101 leaning towards the port side, with the main deck 103 partially flooded. The port side is fully below the water level WL. This may be due to damage of the port-side ballast tank 111, which is shown to be full of water. As can be seen, the vent head 113, which is connected to the port-side ballast tank 111 is also under water and the same will apply to all other vent heads on the port side of the vessel. This particular configuration involves the risk of progressive flooding: the other port-side ballast tanks may quickly gain weight due to ingress of water via their vent heads. Even if the vent head 113 includes an automatic closing device 117, this may still happen, especially when the automatic closing device 117 breaks down, e.g. due to high pressures or collision.

[0054] Figure 2A shows a cross-sectional view through a vessel 1 according to an embodiment of the invention. The vessel 1 comprises a hull 2 and a main deck 3. Adjacent to the first side wall, also referred to as port-side wall 10, the vessel 1 comprises a first or port-side ballast tank 11. Adjacent to the second side wall, also referred to as starboard-side wall 20, the vessel 1 comprises a second or starboard-side ballast tank 21. Both ballast tanks 11, 21 extend above and below the water level WL. Figure 2A further shows a venting pipe 12 for venting the port-side ballast tank 11. The venting pipe 12 includes a riser portion 15 and a transverse portion 16, emerging via an opening

14. The opening 14 is provided in the starboard-side wall 20 of the hull 2. The venting pipe 12 and the opening 14 have a typical internal diameter of 25 cm.

[0055] Both the transverse portion 16 of the venting pipe 12 and the opening 14 are provided in between the main deck 3 and a freeboard deck 4. The opening 14 is positioned at a first distance d1 above the freeboard deck 4. The first distance d1 is preferably larger than 760 mm. Preferably, the distance between the opening 14 and the level of the main deck 3 is about 1 m. An automatic closing device 17 is included in the venting pipe 16. In this particular embodiment, the automatic closing device 17 is provided in between the riser portion 15 and the transverse portion 16, but alternative placement in the path of the venting pipe 12 can be contemplated.

[0056] Figure 2B shows the vessel of Figure 2A leaning towards the port-side, meaning that the port-side wall 10 and the port-side ballast tank 11 are entirely below the water level WL. At the same time, the starboard-side wall 20 is lifted and extends further above the water level WL.

Consequently, the opening 14, which is connected via the venting pipe 12 to the port-side ballast tank 11, is provided well above the water level WL such that ingress of water into the venting pipe 12 is prevented.

[0057] Figure 2C shows the vessel of Figures 2A-2B leaning to the opposite, second side, meaning that the starboard-side wall 20 is entirely below the water level WL. Simultaneously, the port-side wall 10 as well as the port-side ballast tank 11 are lifted and extend further above the water level WL. Although the opening 14 is below the water level WL, water ingress into the venting pipe 12 is counteracted because the end of the venting pipe 12 near the port-side ballast tank 11 is higher than the opening 14. As such, the venting pipe 12 is generally slanted downwards (with respect to the water level WL) to the opening 14 such that water entering the venting pipe 12 will 40 tend to flow out again.

[0058] The arrangements and advantages related to Figures 2A-2C equivalently apply for the starboard-side ballast tank, upon interchanging the port side and starboard side and mirroring the related features.

[0059] Figure 3 shows a side view of the vessel 1 of Figure 2. The vessel 1 comprises a hull 2 in which five starboard-side ballast tanks 21, 21a, 21b, 21c, 21d are provided. The ballast tanks 21, 21a, 21b, 21c, 21d are placed adjacent to one another in a longitudinal direction along the length of the vessel 1. Simultaneously, the vessel 1 comprises five port-side ballast tanks (not shown), which are vented by means of venting pipes (not shown). The venting pipes of the port-side tanks communicate with openings 14, 14a, 14b, 14c, 14d in the starboard-side wall 20, just below the main deck 3, defining a virtual freeboard VF below the openings 14, 14a, 14b, 14c, 14d. No vent heads are needed on the main deck 3.

[00860] Figure 4 shows according to a further embodiment of the invention a cross-sectional perspective view of a vessel 201 with a hull 202 extending to a main deck 203. This embodiment differs from the previous one only in that it has a different ballast tank lay-out and that slanted end parts are provided. In the hull 202 there is provided a port-side ballast tank 211, adjacent to the port-side wall 210 and the bottom 204 of the hull 202, which is vented by a venting pipe 212 including a riser portion 215 and a transverse portion 216, and extending to an opening 214 in the starboard-side wall 220. An automatic closing device 217 is provided in between the riser portion 215 and transverse portion 216. The transverse portion 216 comprises an end part 218 which slants downward towards the opening 214. The end part 218 is slanted at an angle of about 30 degrees with respect to the main deck 203. The vessel 201 likewise comprises a starboard-side ballast tank 221, which is vented using a second venting pipe 222 including a slanted end part 228 and extending to an opening 224 in the port-side wall 210. Because of the slanted end parts 218, 228, water ingress into the venting pipes 212, 222 is counteracted.

[9081] Figure 5A shows, according to an alternative embodiment, a cross-sectional perspective view of a vessel 301 with a hull 302 including a port-side ballast tank 311 adjacent to a port-side wall 310. The ballast tank 311 can vent through a venting pipe 312 to an opening 314 which is in direct and unobstructed connection with outside air. The venting pipe 312 includes a riser portion 315 extending vertically from the port-side ballast tank 311 and a transverse portion 316 connecting the riser portion 315 to the opening 314. An automatic closing device 317 is provided in between the riser portion 315 and transverse portion 316. The opening 314 leads to and forms a connection with a main pipe 319 which extends longitudinally along the vessel 301. The main pipe 319 leads to a transverse pipe 331 which forms an open connection between the two side walls 310, 320 of the hull 302. The transverse pipe 331 forms outlets 330 from the main pipe 319 to outside the vessel

301. The main pipe 319 is provided sufficiently far removed from the port-side wall 310 such that it stays above water under maximum heeling of the vessel 301, so that no water can flow into the port-side ballast tank 311 via the main pipe 319. In the embodiment shown, the main pipe 319 is positioned at a distance of about 75% the width of the hull 302 from the port-side wall 310. The outlets 330 are provided below the main deck 303.

[0082] Similar to the ballast tank 311 adjacent to the port-side wall 310, there is provided a starboard-side ballast tank 321 adjacent to the second or starboard-side wall 320. This starboard- side ballast tank 321 can vent in an equivalent way, via a venting pipe 322 including a riser portion 325 and a transverse portion 326. An automatic closing device 327 is provided in between the riser portion 325 and transverse portion 328. The transverse portion 326 leads via an opening 324 to a main pipe 329 in the longitudinal direction of the vessel 302. The main pipe 329 lead to the same transverse pipe 331 as the main pipe 319 described earlier, thus forming an outlet 330 from the main pipe 329 to outside the vessel 301. The main pipe 329 is provided sufficiently far removed from the starboard-side side wall 320 such that it stays above water under maximum heeling of the vessel 301, so that no water can flow into the starboard-side ballast tank 320 via the main pipe 329. In the imaged embodiment, the main pipe 329 is positioned at a distance of about 75% the width of the hull 302 from the starboard-side side wall 320. Like in the previous embodiment, the transverse portions 316, 326 slant downwards towards the openings 314, 324, in order to avoid water flowing into the transverse portions 316, 326.

[0083] Figure 5B shows a schematic top view of the venting configuration of the vessel 301 of Figure 5. The venting pipes 312, 312a, 312b extending from ballast tanks (not shown) adjacent to the port-side wall 310 include transverse portions 316, 316a, 316b leading to openings 314, 314a, 314b in the main pipe 319. Similarly, venting pipes 322, 322a, 322b extending from ballast tanks (not shown) adjacent to the starboard-side wall 320 include transverse portions 326, 326a, 326b leading to openings 324, 324a, 324b in main pipe 329. Venting pipes 312, 312a, 312b, 322, 322a, 322b from multiple separate ballast tanks thus end up in the same main pipes 319, 329. Since there are typically only one or two outlets 330 per main pipe 319, 329, the number of openings or outlets in the hull 302 of the vessel 301 is (much) smaller than the number of ballast tanks.

[9084] The invention has been described by reference to certain embodiments discussed above.

It will be recognized that these embodiments are susceptible to various modifications and alternative forms well known to those of skill in the art.

[9065] Many modifications in addition to those described above may be made to the structures and techniques described herein without departing from the spirit and scope of the invention. Accordingly, although specific embodiments have been described, these are examples only and are not limiting upon the scope of the invention.

Claims

CONCLUSIONS

A vessel comprising a hull extending to a main deck, a ballast tank adjacent to a first sidewall of the hull. at least partially below a waterline, a vent pipe for venting the ballast tank, which extends from the ballast tank to an opening above the waterline and below the main deck, the vent pipe comprising an ascending portion extending from the ballast tank to a position above the waterline and a transverse part connecting the ascending part to the opening. the transverse portion extending inwardly from the first sidewall for at least a distance sufficient to remain at least partially above the waterline at maximum tilt of the vessel.

Vessel according to claim 1, wherein the opening is provided in a second side wall. which is opposite the first side wall.

The vessel of claim 1, wherein the opening leads to a main pipe arranged along the longitudinal direction of the hull. and wherein the main pipe has an outlet to the side.

A vessel according to claim 3, wherein the main pipe leads to a transverse pipe across the hull, and wherein the transverse pipe comprises outlets from the vessel in both side walls.

Vessel according to any of the preceding claims, wherein the distance over which the transverse section extends from the first side wall inwards is at least 25% of the width of the hull, preferably at least 40% of the width of the hull, more preferably at least 50% of the width of the hull.

Vessel according to any one of the preceding claims, wherein the vessel comprises a freeboard deck located below the main deck. the freeboard deck being substantially flat and parallel to the main deck, and preferably wherein the gap between the main deck and the freeboard deck is provided.

Vessel according to any one of the preceding claims, wherein the vent pipe comprises an automatic closing device between the ballast tank and the opening. designed to allow air or water to flow out of the ballast tank and to prevent water from entering the ballast tank.

Vessel according to any of the preceding claims, wherein the vent pipe comprises an end portion adjacent to the opening which slopes down or extends down towards the opening.

Vessel according to any of the preceding claims, wherein the vessel comprises a plurality of ballast tanks, preferably at least three adjacent to each side wall.

Vessel according to any of the preceding claims, wherein the main deck is free from venting heads.

Il. Vessel according to any of the preceding claims, wherein the ballast tank is fully provided on one side of a vertical plane through a central line connecting bow and stern of the vessel.

Vessel according to any of the preceding claims. wherein the vent pipe has a diameter of at least 10 cm, preferably between 15 and 45 cm.

A method of ballasting and venting a vessel, the vessel comprising a hull extending to a main deck and having at least one port ballast tank and one starboard ballast tank, the method comprising venting the ballast tank on the port side via a first vent pipe to an opening on the starboard side of the vessel, below the main deck, and venting the ballast tank on the bar stern side via a second vent pipe to an opening on the port side of the vessel. under the main deck.

The method of claim 13, wherein the vessel is a vessel according to any of claims 1-12.

15. Method of retrofitting a vessel, in particular an offshore work vessel. or any other large flat deck vessel, the method comprising: providing a vessel. comprising: a hull extending to a main deck; a ballast tank adjacent to a first side wall of the hull and extending below a waterline: a vent pipe for venting the ballast tank, which extends from the ballast tank through an ascending portion to an opening above the waterline; diverting the vent pipe by connecting a transverse section between the ascending section and the opening, the transverse section extending inward from the first side wall for at least a distance sufficient to remain at least partially above the waterline at maximum tilting of the vessel.

The method of claim 15, further comprising: - constructing a freeboard deck below the main deck, the transverse portion of the vent pipe being above the freeboard deck.