FI123947B

FI123947B - Ship

Info

Publication number: FI123947B
Application number: FI20125498A
Authority: FI
Inventors: Mika Hovilainen
Original assignee: Aker Arctic Technology Oy
Priority date: 2012-05-09
Filing date: 2012-05-09
Publication date: 2013-12-31
Also published as: NO20141485A1; KR101927571B1; KR20150017729A; WO2013167805A1; FI20125498A; NO348144B1

Abstract

The invention relates to a marine vessel having a hull structure (2) with a bottom surface (21). The marine vessel has an internal compartment (3), a so-called moon pool or keel cavity. The internal compartment (3) extends downwards to the bottom surface (21) of the hull structure (2) and is provided with a closure mechanism (4). In order to eliminate the risk of inflow of unwanted objects, such as ice formations (IF), into the internal vertical compartment (3), the closure mechanism (4) includes at least two pairs of turnable hatch elements (42, 43, 45, 46), which are arranged to form an extension (5) of the internal compartment (3) below the bottom surface (21) of the hull structure (2) of the marine vessel (1).

Description

Marine Vessel Technical field

The invention relates to a marine vessel comprising a hull structure, which ma-5 rine vessel is provided with an internal compartment having a first end and a second end with a rectangular cross-section, which internal compartment is arranged to extend downwards at least to the bottom of the hull structure of the marine vessel with said second end and which internal compartment is provided with a closure mechanism at said second end, according to the preamble of claim 1.

10 Background art

Marine vessels, intended and equipped for operations at sea, additional to pure transit, have been provided with downwards open internal compartments e.g. in the form of so-called moon pools or so-called keel cavities. Typical marine vessels in this case would include e.g. installation vessels, feeder vessels, support 15 vessels, construction vessels, survey vessels, research vessels, seismic vessels, diving support vessels, drill ships, oil tankers as well as other water craft. The internal compartments are intended for carrying out off-shore operations such as installation, excavation, drilling, laying and surveying pipe lines and cables, salvage, loading, and mooring, etc. on the sea bed or in submerged conditions, 20 which operations represent so-called moon pool operations or submerged loader ing operations. A moon pool, usually in the form of an internal vertical shaft, pro- g vides access to sites below the water level of a surrounding body of water from g the inside or from an open deck of the marine vessel (an example may be found g in WO 2012/032163 A1). A keel cavity normally provides a submerged connec- 25 tion e.g. for submerged turret loading (an example may be found in US 6,517,290

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qq B1). Normally the above mentioned operations are carried out in open seas.

σ> sj- £! Traditionally such internal compartments have been kept open at the downwards δ ^ extending lower end opening into a surrounding body of water, whereby the up per end of the compartment has been provided with a hatch or other correspond- 2 ing arrangement. Closure mechanisms at the lower end have also been used in order to facilitate navigation and movement of the marine vessel in open seas, when the compartment is not in use. Such closure mechanisms have included e.g. pontoons or turnable flaps. The known solutions mainly enhance the hydro-5 dynamic properties of the marine vessel, but do not e.g. provide adequate water tight properties nor protection in ice conditions. For operation in ice conditions and arctic environments the risk of ice formation or of invasion of ice in the internal compartment poses additional problems.

Summary of the invention 10 An object of the present invention is to avoid the above mentioned problems and to provide a marine vessel that ensures reliable and secure facilities for so-called moon pool operations or submerged loading operations independently of prevailing conditions. This object is attained by a marine vessel according to claim 1.

The basic idea of the invention is to provide a closure mechanism for the internal 15 compartment, i.e. a moon pool or a keel cavity, of the marine vessel that ensures sufficiently protected and ice free subsea operations from or through the internal compartment. This is realized by providing a closure mechanism that includes at least two pairs of turnable hatch elements including a first pair of hatch elements and a second pair of hatch elements, wherein the first pair of hatch elements and 20 the second pair of hatch elements are arranged to form an extension of the internal compartment below a bottom surface of the hull structure of the marine ves-sel in a downwards turned first open position of the hatch elements. The downed wards turned hatch elements provide a barrier against any inflow of ice or other g objects into the opening at the second end of the internal compartment. In addi- g 25 tion a sufficient closure of the bottom of the hull structure can be provided so that x the marine vessel can efficiently and safely operate in a conventional manner.

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§ Preferably, in the downwards turned first open position of the hatch elements, the oj hatch elements are arranged to support against each other in forming the exten- ° sion of the internal compartment. This provides for additional mutual support of 3 the hatch elements against movements of the marine vessel and in case of external ice loads.

Advantageously, at least one pair of the first pair of hatch elements and the second pair of hatch elements is arranged to be turned into a closed position in or-5 der to provide a closure at the second end of the internal compartment.

For improving the closure, it is advantageous that the first pair of hatch elements and the second pair of hatch elements are both arranged to be turned into a closed position in order to provide a chamber between the first pair of hatch elements and the second pair of hatch elements.

10 In view of improving the efficiency of the closure, it is preferable that at least one pair of the first pair of hatch elements and the second pair of hatch elements is arranged to be turned into a closed position in order to provide a watertight closure at the second end of the internal compartment.

For improving the watertight properties of the closure, it is advantageous that the 15 first pair of hatch elements and the second pair of hatch elements are arranged to be turned into a closed position in order to provide a chamber that is watertight between the first pair of hatch elements and the second pair of hatch elements. This also provides for a so-called double bottom configuration for the marine vessel as required for some types of marine vessels according to prevailing maritime 20 regulations.

^ Advantageously a first water discharge system is connected to the internal com- partment, whereby the internal compartment can be drained when the second g end of the internal compartment is closed. In this way loss of buoyancy and pay- § load capacity of the marine vessel can be avoided.

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tr 25 Advantageously, a second water discharge system is connected to the watertight oo σ> chamber between the first pair of hatch elements and the second pair of hatch

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™ elements. This provides for draining any residual water from the chamber and for δ ^ monitoring the watertight properties of the closure mechanism.

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In order to enhance the monitoring a leakage sensor can be provided in the chamber between the two pairs of hatch elements.

Advantageously, at least one pair of the first pair of hatch elements and the second pair of hatch elements is turnably fastened to the hull structure of the ma-5 rine vessel.

Preferably, at least one pair of the first pair of hatch elements and the second pair of hatch elements is arranged to be turned against a bottom surface of the hull structure of the marine vessel in a second open position of the hatch elements. This provides for a streamlined arrangement with respect to the surround-10 ing sea, particularly when transiting in open seas or operating in shallow waters.

Advantageously, the at least one pair of the first pair of hatch elements and the second pair of hatch elements is arranged to be turned against the bottom surface of the hull structure of the marine vessel and into a recess provided in the bottom surface of the hull structure of the marine vessel. This further enhances 15 the streamlined arrangement.

Preferably, at least one pair of the first pair of hatch elements and the second pair of hatch elements is turnably fastened within the internal vertical shaft. In this way any turning mechanism may be kept within the internal compartment.

Advantageously, at least one pair of the first pair of hatch elements and the se-20 cond pair of hatch elements is arranged to be turned against an inside wall of the ^ internal compartment in a second open position of the hatch elements. In this ^ manner the outside configuration of the hull structure can remain intact without g any protruding elements.

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The first pair of hatch elements is arranged below the second pair of hatch ele-25 ments.

00 05 lo The internal compartment may advantageously be a so-called moon pool in the o form of an internal vertical shaft having a rectangular cross-section and extending from a deck area of the marine vessel to the bottom surface of the hull structure of the marine vessel.

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Alternatively, the internal compartment may advantageously be in the form of a keel cavity extending from the inside of the hull structure to the bottom surface of the hull structure of the marine vessel.

Advantageous features of the present invention are defined in claims 2-17.

5 Brief description of drawings

In the following the invention will be described by way of example only with reference to the accompanying schematic drawings, in which

Figure 1 illustrates a marine vessel provided with an internal compartment,

Figure 2 illustrates a mutual support arrangement of the hatch elements of the 10 internal compartment,

Figures 3-5 illustrate a first embodiment of the present invention,

Figures 6-9 illustrate a second embodiment of the present invention,

Figure 10 illustrates a further advantage of the present invention, and Figure 11-13 illustrate a third embodiment of the present invention.

15 Description of the invention

Figure 1 illustrates a marine vessel 1, more particularly a ship in this embodiment of the present invention. The marine vessel 1 comprises a hull structure 2 with a bow 12, a stern 13, a deck area 11, a waterline WL, and a bottom with a bottom o ^ surface 21. The marine vessel 1 is provided with an internal compartment 3. The

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° 20 internal compartment 3 has a first end 31 and a second end 32 with a rectangular

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° cross section and four inside walls 33. The first end 31 extends and opens up-

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£ wards towards the deck area 11 of the marine vessel 1 and the second end 32 § opens downwards towards the bottom surface 21 of the hull structure 2. In this ou embodiment, the internal compartment 3 is a so-called moon pool, whereby the ° 25 internal compartment forms an internal vertical shaft with a rectangular configura tion within the hull structure of the marine vessel. The internal compartment 3 is 6 arranged to extend downwards at least to the bottom surface 21 of the hull structure 2 with said second end 32.

The internal compartment may also be in the form of a keel cavity which has a second end 32 with a rectangular configuration and which extends downwards at 5 least to the bottom surface 21 of the hull structure 2, whereby the first end 31 would extend only to a certain degree or level into the hull structure 2 of the marine vessel 1, and not all the way to the deck area 11. This is only schematically indicated in Figure 10 with a broken line KC. This would be the case e.g. in connection with a submerged turret loading arrangement.

10 The internal compartment 3 is provided with a closure mechanism, generally indicated by reference numeral 4, at said second end 32 of the internal compartment 3. The closure mechanism 4 (Figures 5, 8 and 12) includes at least two pairs of turnable hatch elements, a first pair 41 (Figures 3, 6 and 11) of hatch elements, including a first hatch element 42 and a second hatch element 43, and a 15 second pair 44 (Figures 3, 6 and 11) of hatch elements, including a third hatch element 45 and a fourth hatch element 46. The first pair 41 of hatch elements and the second pair 44 of hatch elements are shown in a downwards turned first open position, wherein they form an extension 5 of the internal compartment 3 below the waterline WL, more particularly below the bottom surface 21 of the hull 20 structure 2 of the marine vessel 1 (discussed more in detail below).

In order to stabilize and strengthen the extension 5 so that it can sufficiently with-stand the force of water and ice formations IF passing below the hull structure 2 o and against the extension 5, the hatch elements are arranged to support against g each other in forming the extension 5 of the internal compartment 3. Figure 2 ex- g 25 emplifies how the second hatch element 43 and the third hatch element 45 are x supported against each other. The second hatch element 43 is also provided with a support 47 against which the third hatch element 45 can rest in order to stabler lize its position. A similar support would be provided at the other end of the se- g cond hatch element in order to support the fourth hatch element. The first hatch

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30 element would in a corresponding manner be provided with respective supports for supporting the third hatch element and fourth hatch element. In order to se- 7 cure such a support, the hatch elements can be releasably fixed to each other by e.g. a latch arrangement.

Figures 3-5 illustrate a first embodiment of the present invention, in which the closure mechanism 4 including the first pair 41 of hatch elements and the second 5 pair of hatch elements 44 are arranged to form the extension 5 of the internal compartment 3 below the bottom surface 21 of the hull structure 2 of the marine vessel in a downwards turned first open position. At least one pair of the first pair 41 of hatch elements and the second pair 44 of hatch elements is arranged to be turned into a closed position in order to provide a closure of the second end 32 of 10 the internal vertical shaft 3. The first pair 41 of hatch elements is arranged below the second pair 44 of hatch elements, i.e. the first pair 41 hatch elements is arranged to face towards a body of water surrounding the marine vessel 1 and the second pair 44 hatch elements is arranged within the internal compartment 3.

Figure 3 shows the closure mechanism 4 with the hatch elements in the first 15 open position forming an extension 5 of the internal compartment 3. In this first open position the first pair 41 of hatch elements, including the first hatch element 42 and the second hatch element 43, and the second pair 44 of hatch elements, including the third hatch element 45 and the fourth hatch element 46, are turned downwards into the body of water surrounding the marine vessel 1. The hatch 20 elements are more or less in a vertical position aligned with the internal walls 33 (shown in Figure 10) of the internal vertical shaft 3.

In this manner the extension 5 formed by the downwards turned first pair 41 of

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δ hatch elements and the downwards turned second pair 44 of hatch elements CM r ιό provides a barrier to the inflow of e.g. ice formations IF or other objects into the g 25 internal compartment 3 of the hull structure 2 of the marine vessel 1. In order to x stabilize the extension 5, the hatch elements can be mutually supported as dis-

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cussed above in connection with Figure 2. Thus, so-called moon pool and other ? corresponding operations can be carried out in protected and secure surround ed δ in9s-

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Figure 4 shows a first phase of a closing of the closure mechanism 4. In this phase the third hatch element 45 and the fourth hatch element 46 of the second pair 44 of hatch elements has been turned inwards against the second end 32 of the internal compartment 3 in order to close the internal compartment 3. In prac-5 tice this means that the third hatch element 45 and the fourth hatch element 46 have been turned against each other into a generally horizontal position.

Figure 5 shows a second phase of the closing of the closure mechanism 4. In this phase also the first pair 41 of hatch elements, including the first hatch element 42 and the second hatch element 43, is in a closed position. The first hatch element 10 42 and the second hatch element 43 have been turned against each other into a generally horizontal position in order to close the second end 32 of the internal compartment 3. In this position the closed first pair 41 of hatch elements form part of the bottom surface 21 of the hull structure 2 of the marine vessel 1. The first pair 41 of hatch elements is thus arranged below the second pair 44 of hatch 15 elements.

In this embodiment the first pair 41 of hatch elements is turnably fastened, e.g. hinged or journalled, to the hull structure 2 and the second pair 44 hatch elements is turnably fastened (e.g. hinged or journalled) within the vertical shaft 3, e.g to an inside wall 33 (shown in Figure 10) of the internal compartment 3. Both 20 pairs of hatch elements could also be turnably fastened within the internal compartment. The manner and exact position of the fastening means falls within the competence of the skilled person in the art.

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o In order to be able to drain the internal compartment 3 when the closure mecha- ιό nism 4 is in a closed position, the internal compartment 3 is provided with a first g 25 water discharge system 71 as schematically indicated in Figure 10. Particularly, if x the internal compartment 3 is relatively large, this avoids loss of buoyance of the marine vessel. The first water discharge system 71 can also be used to drain any ? residual water remaining in the internal compartment 3 in order to avoid sloshing g during any movement of the marine vessel 1.

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Further, as schematically illustrated in Figure 10, in this first embodiment, the first pair 41 of hatch elements, including the first hatch element 42 and the second hatch element 43, and the second pair 44 of hatch elements, including the third hatch element 45 and the fourth hatch element 46, are arranged to be turned into 5 the above discussed closed positions in order to provide a chamber 6 between the first pair of hatch elements and the second pair of hatch elements.

Advantageously the closure formed by the first pair 41 of hatch elements and the second pair 44 of hatch elements is watertight, whereby the chamber 6 between the two pairs of hatch elements also is watertight. A second water discharge sys-10 tern 72 can be connected to the chamber 6 in order to drain any residual water from the chamber 6 after the hatch elements have been turned into their respective closed positions. This allows for monitoring the respective closures, i.e. the chamber 6, with regard to their watertight properties. For monitoring purposes a leakage sensor 8 is also arranged in the chamber 6 between the two pairs of 15 closed hatch elements. The manner in which the watertight properties are achieved fall within the competence of a person skilled in the art.

Drainage can be arranged e.g. by suction lines connected to the bilge, ballast or fire lines of the marine vessel.

The internal compartment 3 may be in the form of a keel cavity extending only to 20 a certain level KC into the hull structure, as discussed above (shown in Figure 10). In this case the applicability of the hatch element arrangement of this first embodiment is dependent on the internal configuration of the internal compart-δ ment.

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ΙΛ 9 Figures 6-9 illustrate a second embodiment of the present invention, which to a

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° 25 large extent corresponds to the first embodiment discussed above.

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jjq The first pair 41 of hatch elements and the second pair of hatch elements 44 are

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J arranged to form the extension 5 of the internal compartment 3 below the bottom

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5 surface 21 of the hull structure 2 of the marine vessel 1 in a downwards turned

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first open position. At least one pair of the first pair 41 of hatch elements and the 30 second pair 44 of hatch elements is arranged to be turned into a closed position 10 in order to provide a closure of the second end 32 of the internal compartment 3. The first pair 41 of hatch elements is arranged below the second pair 44 of hatch elements, i.e. the first pair 41 hatch elements is arranged to face towards a body of water surrounding the marine vessel 1 and the second pair 44 hatch elements 5 is arranged within the internal compartment 3.

Figure 6 shows the closure mechanism 4 with the hatch elements in a first open position forming an extension 5 of the internal compartment 3. In this first open position the first pair 41 of hatch elements, including the first hatch element 42 and the second hatch element 43, and the second pair 44 of hatch elements, in-10 eluding the third hatch element 45 and the fourth hatch element 46, are turned downwards into the body of water surrounding the marine vessel 1. The hatch elements are more or less in a vertical position aligned with the internal walls 33 (shown in Figure 10) of the internal compartment 3.

In this manner the extension 5 formed by the downwards turned first pair 41 of 15 hatch elements and second pair 44 of hatch elements provides a barrier to the inflow of e.g. ice formations IF or other objects into the internal compartment 3 of the hull structure 2 of the marine vessel 1. In order to stabilize the extension 5, the hatch elements can be mutually supported as discussed above in connection with Figure 2. Thus, so-called moon pool and other corresponding operations can 20 be carried out in protected and secure surroundings.

Figure 7 shows a first phase of a closing of the closure mechanism 4. In this phase the third hatch element 45 and the fourth hatch element 46 of the second

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o pair 44 of hatch elements has been turned inwards against the second end 32 of ιό the internal compartment 3 in order to close the internal compartment 3. In prac- σ> 25 tice this means that the third hatch element 45 and the fourth hatch element 46 o x have been turned against each other into a generally horizontal position.

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§ Figure 8 shows a second phase of the closing of the closure mechanism 4. In this sj- eu phase also the first pair 41 of hatch elements, including the first hatch element 42 ° and the second hatch element 43, is in a closed position. The first hatch element 30 42 and the second hatch element 43 have been turned against each other into a 11 generally horizontal position in order to close the second end 32 of the internal compartment 3. In this position the closed hatch elements form part of the bottom surface 21 of the hull structure 2. The first pair 41 of hatch elements is thus arranged below the second pair 44 of hatch elements.

5 In this embodiment the first pair 41 of hatch elements is turnably fastened, e.g. hinged or journalled, to the hull structure 2 and the second pair 44 hatch elements is turnably fastened (e.g. hinged or journalled) within the internal compartment 3, e.g to an inside wall 33 (shown in Figure 10) of the internal compartment 3. The manner and exact position of the fastening falls within the compe-10 tence of the skilled person in the art.

In order to be able to drain the internal compartment 3 when the closure mechanism 4 is in a closed position, the internal compartment 3 is provided with a first water discharge system 71 as schematically indicated in Figure 10. Particularly, if the internal compartment 3 is relatively large, this avoids loss of buoyance of the 15 marine vessel. The first water discharge system 71 can also be used to drain any residual water remaining in the internal compartment 3 in order to avoid sloshing during any movement of the marine vessel 1.

Further, as schematically illustrated in Figure 10, in this second embodiment, the first pair 41 of hatch elements, including the first hatch element 42 and the se-20 cond hatch element 43, and the second pair 44 of hatch elements, including the third hatch element 45 and the fourth hatch element 46, are arranged to be turned into the above discussed closed position in order to proved a chamber 6 o between the first pair of hatch elements and the second pair of hatch elements.

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9 Advantageously the closure formed by the first pair 41 of hatch elements and the

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° 25 second pair 44 of hatch elements is watertight, whereby the chamber 6 between

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£ the two pairs of hatch elements also is watertight. A second water discharge Sysco tern 72 can be connected to the chamber 6 in order to drain any residual water oj from the chamber 6 after the hatch elements have been turned into their respec- ^ tive closed positions. This allows for monitoring the respective closures, i.e. the 30 chamber 6, with regard to their watertight properties. For monitoring purposes a 12 leakage sensor 8 is also arranged in the chamber 6 between the two pairs of closed hatch elements. The manner in which the watertight properties are achieved fall within the competence of a person skilled in the art.

Drainage can be arranged e.g. by suction lines connected to the bilge, ballast or 5 fire lines of the marine vessel.

Further, in this second embodiment, the bottom surface 21 of the hull structure 2 of the marine vessel is provided with a first recess 22 and a second recess 23 to receive the first hatch element 42 and the second hatch element 43 respectively.

In Figure 9 it is shown how the first hatch element 42 and the second hatch ele-10 ment 43 are both turned into a second open position against the bottom surface 21 of the hull structure 2. More particularly the first hatch element 42 is turned into the first recess 22 and the second hatch element 43 is turned into the second recess 23 formed in the bottom surface 21 of the hull structure 2. This provides for a streamlined configuration of the bottom surface 21 of the hull structure 2 15 when the hatch elements are in their second open position. Figure 9 also shows how the fourth hatch element 46 of the second pair of hatch elements 44 is turned into a second open position against an inside wall 33 (shown in Figure 10) of the internal compartment 3. The third hatch element 45 of the second pair 44 of hatch elements is also turned against the opposite inside wall of the internal 20 compartment 3 (not shown in Figure 9). In this manner the internal compartment 3 can be kept open towards the surrounding body of water without having the hatch elements protruding into the surrounding body of water, δ ™ Thus, the second open position of the hatch elements allows for operation in

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9 open seas where there is no risk of sloshing or inflow of unwanted objects into

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° 25 the area of the internal compartment 3, i.e. a moon pool.

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<30 The internal compartment 3 may be in the form of a keel cavity extending only to

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J a certain level KC into the hull structure 2, as discussed above (shown in Figure

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o 10). In this case the applicability of the hatch element arrangement of this second

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embodiment is dependent on the internal configuration of the internal compart-30 ment.

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Figures 11-13 illustrate a third embodiment of the present invention, which to some extent corresponds to the second embodiment discussed above.

The first pair 41 of hatch elements and the second pair of hatch elements 44 are arranged to form the extension 5 of the internal compartment 3 below the bottom 5 surface 21 of the hull structure 2 of the marine vessel 1 in a downwards turned first open position. At least one pair of the first pair 41 of hatch elements and the second pair 44 of hatch elements is arranged to be turned into a closed position in order to provide a closure of the second end 32 of the internal compartment 3.

Figure 11 shows the closure mechanism 4 with the hatch elements in a first open 10 position forming an extension 5 of the internal compartment 3. In this first open position the first pair 41 of hatch elements, including the first hatch element 42 and the second hatch element 43, and the second pair 44 of hatch elements, including the third hatch element 45 and the fourth hatch element 46, are turned downwards into the body of water surrounding the marine vessel 1. The hatch 15 elements are more or less in a vertical position aligned with the internal walls 33 of the internal compartment 3.

In this manner the extension 5 formed by the downwards turned first pair 41 of hatch elements and second pair 44 of hatch elements provides a barrier to the inflow of e.g. ice formations IF or other objects into the internal compartment 3 of 20 the hull structure 2 of the marine vessel 1. In order to stabilize the extension 5, the hatch elements can be mutually supported as discussed above in connection with Figure 2. Thus, so-called moon pool or other corresponding operations can o be carried out in protected and secure surroundings.

in 9 Figure 12 shows a closing of the closure mechanism 4. The second pair 44 of σ> ° 25 hatch elements, including the third hatch element 45 and the fourth hatch ele-

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£ ment 46, is in a closed position. The third hatch element 45 and the fourth hatch § element 46 have been turned against each other into a generally horizontal posi- eu tion in order to provide a closure of the second end 32 of the internal compart- ° ment 3. In this position the closed hatch elements form part of the bottom surface 30 21 of the hull structure 2. The closure is preferably watertight. The manner in 14 which the watertight properties are achieved fall within the competence of a person skilled in the art.

In order to be able to drain the internal compartment 3 when the closure mechanism 4 is in a closed position, the internal compartment 3 is provided with a first 5 water discharge system 71 as schematically indicated in Figure 10. Particularly, if the internal compartment 3 is relatively large, this avoids loss of buoyance of the marine vessel. The first water discharge system 71 can also be used to drain any residual water remaining in the internal compartment 3 in order to avoid sloshing during any movement of the marine vessel 1.

10 Drainage can be arranged e.g. by suction lines connected to the bilge, ballast or fire lines of the marine vessel.

Further, in this third embodiment, the bottom surface 21 of the hull structure 2 of the marine vessel is provided with a first recess 22 and a second recess 23 to receive the first hatch element 42 and the second hatch element 43 respectively. 15 In addition, the bottom surface 21 of the hull structure 2 of the marine vessel is provided with a third recess 25 and a fourth recess 26 to receive the third hatch element 45 and the fourth hatch element 46 respectively.

In this embodiment the first pair 41 of hatch elements and the second pair 44 of hatch elements are turnably fastened, e.g. hinged or journalled, to the hull struc-20 ture 2 of the marine vessel 1. The manner and exact position of the fastening falls within the competence of the skilled person in the art.

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g In Figure 13 it is shown how the first pair 41 of hatch elements, including first g hatch element 42 and the second hatch element 43, and the second pair of hatch g elements 44, including the third hatch element 45 and the fourth hatch element 25 46, are both turned into a second open position against the bottom surface 21 of Q_ qq the hull structure 2. More particularly the first hatch element 42 is turned into the 05 $ first recess 22 and the second hatch element 43 is turned into the second recess

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5 23 formed in the bottom surface 21 of the hull structure 2. In a corresponding

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manner the third hatch element 45 is turned into the third recess 25 and the 15 fourth hatch element 46 is turned into the fourth recess 26 formed in the bottom surface 21 of the hull structure 2.

This provides for a streamlined configuration of the bottom surface 21 of the hull structure 2 when the hatch elements are in their second open positions. In this 5 manner the internal compartment 3 can be kept open towards the surrounding body of water without having the hatch elements protruding into the surrounding body of water. In this manner this embodiment provides an alternative solution to the second embodiment as discussed above in connection with Figure 9.

Thus, the second open position of the hatch elements allows for operation in 10 open seas where there is no risk of sloshing or inflow of unwanted objects into the area of the internal compartment 3, i.e. the moon pool, and no risk of the water freezing within the area of the internal compartment 3.

The internal compartment 3 may be in the form of a keel cavity extending only to a certain level KC into the hull structure, as discussed above (shown in Figure 15 10). The hatch element arrangement of this third embodiment would only require that the second end 32 of the internal compartment 3 would have a rectangular cross-section.

The following provides a short summary of the operation of the marine vessel in connection with the above discussed three embodiments of the present inven-20 tion.

^ The present invention provides a marine vessel 1, e.g. a ship, provided with an g internal compartment 3, a so-called moon pool or keel cavity. When the marine g vessel 1 sets out to the site where the moon pool or other corresponding subsea g operations are to be carried out, the closure mechanism including at least one of £ 25 the first pair 41 of hatch elements and the second pair 44 of elements is kept in a

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oq closed position.

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™ As described in connection with the first and second embodiments of the present δ ^ invention, particularly Figure 5 and Figure 8 above, the lower pair, i.e. the first pair 41 of hatch elements, is arranged to form a part of the bottom surface 21 of 16 the hull structure 2 of the marine vessel 1 in a streamlined manner. In connection with the third embodiment, the second pair 44 of hatch elements, including the third hatch element 45 and the fourth hatch element 46, is arranged to form a part of the bottom surface 21 of the marine vessel 1 (Figure 12).

5 By having the closures formed by both pairs of hatch elements constructed in a watertight manner, the closures fulfil the prevailing regulations regarding watertight double hulls. This is described more in detail in connection with Figure 10 relating to the first and second embodiments of the present invention.

When the marine vessel 1 arrives at the site for the subsea operations, the first 10 pair 41 and the second pair 44 of hatch elements can be turned into their first open position forming the extension 5 of the internal vertical shaft 3 so that a protective and resistant barrier against any possible inflow of unwanted objects is formed below the hull structure 2 of the marine vessel 1. The desired operations can thus be performed without hindrance, particularly in ice conditions.

15 The internal compartment 3 can advantageously be positioned in an angle with respect to the longitudinal axis of the marine vessel 1, whereby the marine vessel can more easily move forward in ice conditions with the internal compartment in an operative position. The forward corner, i.e. the corner facing in the direction of navigation of the marine vessel, of the rectangular second end of the internal 20 compartment would thus be facing the direction of inflowing ice, which assists in diverting the inflowing ice and which lessens the impact of the force of the inflow-ing ice formations IF against the extension 5. δ ^ Additionally, as described in connection with the second embodiment of the pre- m 9 sent invention, particularly Figure 9, by providing a second open position for the σ> ° 25 hatch elements, i.e. a position in which the first pair of hatch elements is turned

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£ against the bottom surface 21 of the hull structure 2 and in which the second pair § 44 of hatch elements is turned inwards against the inside wall 33 of the internal sj- vertical shaft 3, the present invention also provides a resistance free arrangers ment for operations in open seas, where there is no risk of inflow of unwanted 30 objects into the internal compartment.

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An alternative manner to achieve the same object is described in connection with third embodiment of the present invention, particularly Figure 12. In this alternative both pairs of hatch elements are turned into a second open position against the bottom surface 21 of the marine vessel 1.

5 After the subsea operations have been carried out, the closure mechanism 4 may again be turned into the closed position, whereby the two pairs of hatch elements provide a closure at the second end 32 of the internal compartment 3, preferably in a streamlined manner by having the first pair 41 of hatch elements, including the first hatch element 42 and the second hatch element 43, closed in alignment 10 with the bottom surface 21 of the hull structure 2 (first and second embodiments of the present invention). In the third embodiment of the present invention the closure is formed by the second pair 44 of hatch elements.

The description and the accompanying schematic drawings are only intended to clarify the basic idea of the invention, whereby the invention may vary in detail, 15 e.g. regarding the type of marine vessel, the type of internal compartment, the fastening of the hatch elements, the means for effecting the turning and positioning of the hatch elements, the means for stabilizing the extension, the means for achieving the necessary watertight properties of the hatch elements, etc., within the scope of the ensuing claims.

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Claims

A sea-going vessel comprising a hull structure (2), the sea-going vessel (1) being provided with an inner compartment (3) having a first end (31) and a second end (32) and a rectangular cross-section, the inner compartment (3) being arranged extending downwardly at least on the bottom surface (21) of the hull (2) of the sea-going vessel (1), said inner end (3) being provided with a closure mechanism (4) at said second end (32) characterized in that said closure mechanism (4) includes at least two pairs of swingable hatch elements including a first pair (41) of hatch elements and a second pair (44) of hatch elements 10, and wherein the first pair of hatch elements (41) and the second pair (44) of hatch elements are arranged to form an extension (5) of the inner compartment (3) below the bottom surface (21) of the hull (2) of the sea-going vessel (1) in the first open-down position of the hatch elements.

A seagoing vessel according to claim 1, characterized in that in the first open position of the hatch elements, the hinge elements are arranged to lean against each other to form an extension (5) of the inner compartment (3).

A seagoing vessel according to claim 1, characterized in that at least one pair of hatch elements (41) and second pair (44) of hatch elements are arranged to be pivotable to a closed position to form a closure at one end (32) of the inner compartment (3).

A seagoing vessel according to claim 3, characterized in that the first pair of hatch elements (41) and the second pair of hatch elements (44) are arranged to be pivotable to a closed position to provide a chamber (6) for a first pair of hatch elements. (41) and a second pair (44) of hatch elements. 00 CD

The sea-going vessel according to claim 3, characterized in that at least one pair of hatch elements CVJ 5 from the first pair (41) of hatch elements and second pair (44) of hatch elements is arranged to be pivotable in a closed position to form a watertight seal at one end of the inner compartment (3). (32).

A seagoing vessel according to claim 5, characterized in that the first pair of hatch elements (41) and the second pair of hatch elements (44) are arranged to be pivotable in a closed position to provide a watertight chamber (6) for the first pair of hatch elements and 5.

A sea-going vessel according to claim 1 or 5, characterized in that a first drainage system (71) is connected to the inner compartment (3).

A seagoing vessel according to claim 6, characterized in that a second dewatering system (72) is connected to the chamber (6) between the first pair of hatch elements (41) and the second pair of hatch elements (44).

A sea-going vessel according to claim 8, characterized in that a leakage sensor (8) is provided in the chamber (6) between the first pair of hatch elements (41) and the second pair of hatch elements (44).

A seagoing vessel according to claim 1, characterized in that at least one pair of hatch elements 15 and 41 are rotatably attached to the hull structure (2) of the sea vessel (1).

A seagoing vessel according to claim 10, characterized in that at least one pair of hatch elements from the first pair (41) and the second pair of hatch elements 20 (44) is arranged to be pivoted against the bottom surface (21) of the hull (1) ° position. i CD O

A seagoing vessel according to claim 11, characterized in that at least one of the first pair (41) of the hatch elements CVJ and the second pair of hatch elements tr 25 (44) is arranged to be pivoted into respective recesses (22, 23, 25). 26) formed on the bottom surface (21) of the hull (2) of the sea-going vessel (1). δ CM

A sea-going vessel according to claim 1 or 10, characterized in that at least one pair of hatch elements (41) and the second pair (44) of hatch elements are pivotally mounted inside the inner compartment (3).

A seagoing vessel according to claim 13, characterized in that at least one pair of hatch elements first pair (41) and second pair of hatch elements 5 (44) are arranged to be pivoted against the inner wall (33) of the inner vertical shaft (3) in the second open position.

A seagoing vessel according to claim 1, characterized in that the first pair of hatch elements (41) is arranged below the second pair of hatch elements (44) 10.

A seagoing vessel according to claim 1, characterized in that the inner compartment (3) is a moon pool opening in the form of an internal vertical shaft having a rectangular cross-section and extending from the deck area (11) of the seagoing vessel (1) to the bottom surface (21).

A seagoing vessel according to claim 1, characterized in that the inner compartment (3) is a keel cavity extending from the inside of the hull structure (2) to the bottom surface (21) of the hull structure (2) of the marine vessel (1). CO δ CvJ CD o i CO C \ J X IX Q. CO σ> m C \ J δ C \ J