Fuel containment and supply system for a vessel and method for operating the same

Abstract

The present invention relates to a fuel containment and supply system for a vessel designed to use a first fuel and a second fuel, as well as to a method for operating the same. The system according to the invention comprises one or more tanks for the first fuel (1a, 1b) and one or more tanks for the second fuel (3a, 3b). Each tank for the second fuel (3a, 3b) is provided with a jacket (5a, 5b) defining, together with the outer surface of said tank for said second fuel, a cofferdam (7a, 7b), which is used as additional tank for the first fuel. In this way, the use of space can be optimized and the amount of first fuel on board the vessel can be increased without any additional space being required. In a preferred embodiment of the invention, the first fuel is diesel and the second fuel is methanol.

Description

[0001] “Fuel containment and supply system for a vessel and method for operating the same ”

[0002] DESCRIPTION

[0003] Technical Field

[0004] The present invention relates to a fuel containment and supply system for a vessel as well as to a method for operating said system; more particularly, the present invention relates to a fuel containment and supply system for the so-called 'bi-fuef vessels.

[0005] The present invention further relates to a 'bi-fuef vessel equipped with the aforementioned fuel containment and supply system as well as to a method for operating said vessel.

[0006] The present invention finds particular, though not exclusive, application within the field of pleasure crafts, specifically within the field of luxury pleasure crafts such as yachts. Background Art

[0007] Luxury pleasure crafts are known comprising a hull and a main deck on which a superstructure is provided capable of housing, for example, a passengers’ cabin and / or the helm station for the craft owner.

[0008] Inside the hull, the space is divided in one or more overlying decks, which accommodate further spaces for passengers’ use as well as the engine room, the compartments for the crew, and the rooms intended to house technical installations, onboard equipment and so on.

[0009] In particular, the engine room is located in the lowest deck inside the hull, delimited below by the floor-boards and the inner surface of the hull, and houses the engines and generators that provide the necessary power for both the propulsion of the vessel and the operation of the systems provided on board the vessel.

[0010] It is clear that, being luxury vessels, the space for passengers cannot be reduced and, on the contrary, it is necessary to provide large and comfortable rooms and spaces for a large number of recreational activities.

[0011] Consequently, the presence of bulky engine rooms is a major disadvantage in this type of vessels.

[0012] In addition to the footprint of the engines and generators themselves, consideration must also be given to the footprint of all the equipment connected to these engines and necessary for their operation, as well as the footprint of the fuel tanks and the equipment connected thereto.

[0013] On the other hand, the need to comply with stringent technical and safety requirements for machinery intended for propulsion and, more generally, for the proper operation of the vessel (together with the need to provide effective propulsion for the vessel itself) imposes considerable limits on the overall size of the engine room and associated equipment.

[0014] In recent times, the need to reduce pollutant emissions has been increasingly felt.

[0015] Internal combustion engines using diesel as fuel are a major source of pollution, and in particular of emissions of nitrogen oxides (NOx), sulphur oxides (SOx) and carbon dioxide (CO2).

[0016] It is estimated that the shipping and marine sector contributes about 3% of total greenhouse gas (GHG) emissions.

[0017] In this sector in particular, the need to reduce pollutant emissions is therefore felt, and regulations on pollutant emissions are becoming increasingly stringent.

[0018] For this reason, there is a strong drive to replace diesel for powering internal combustion engines with other fuels that can guarantee a reduced emission of pollutants.

[0019] Correspondingly, so-called 'bi-fuef engines have been developed for large ships, which are able to be powered indifferently with two different types of fuel. In particular, 'bi- fuef engines have been developed that are able to operate using only diesel fuel or a mix of a second fuel with a reduced amount of diesel fuel, so that the emission of pollutants in this second mode of operation is strongly limited.

[0020] As a second fuel, liquefied petroleum gas (LPG) and liquefied natural gas (LNG) are widely used.

[0021] However, these fuels have the disadvantage of being in gaseous form under ambient conditions, requiring, when brought in liquid form, tanks of a shape, construction and size incompatible with use in the marine sector (with particular reference to pleasure crafts, such as yachts).

[0022] For this reason, there is growing interest in the use of methanol as a second fuel in 'bi-fuef applications.

[0023] Methanol, indeed, has the advantage of being in liquid form under ambient conditions, whereby there is no need to provide systems to maintain tanks at high pressures and / or low temperatures.

[0024] With particular reference to the marine sector, the use of grey methanol (of fossil origin) makes it possible to reduce SOx and particulate emissions by more than 95% compared to traditional marine fuels, and CO2 emissions by around 15% compared to traditional marine fuels.

[0025] In addition, the possibility of obtaining methanol from biomass (so-called biomethanol) or by using CO2 captured from the atmosphere and hydrogen from renewable sources (so-called e-methanol or green methanol) favors the achievement of 'carbon neutrality' targets (balance between CO2 emissions in use and CO2 absorption from the air for methanol production).

[0026] In the light of all the above, vessels are being developed capable of using methanol as a fuel, particularly in combination with traditional fuels (diesel).

[0027] The possibility of still being able to use diesel - instead of using methanol as the sole fuel - is linked to the foreseeable difficulties in finding methanol, which is currently not yet available in all harbors.

[0028] However, the use of methanol, particularly on board vessels, is not without drawbacks.

[0029] In particular, methanol has a lower energy density than diesel fuel, which leads to the need for higher capacity methanol tanks (with the same cruising range); in the case of 'bi-fuef engines, there are also dedicated diesel tanks.

[0030] In addition, the use of methanol involves a number of safety issues, as methanol is a more flammable compound than diesel fuel and with potentially toxic vapors. In particular, methanol bums with an invisible flame, which can lead to a more difficult visual detection of fire in the event of leaks and flame ignition.

[0031] For these reasons, current regulations for the transport of methanol on ships require methanol tanks to be surrounded by a voluminous containment gap, at least for tank surfaces that are not also external surfaces of the hull.

[0032] Such gap (called 'cofferdam') enables the containment and segregation of any leaks from the methanol tank in the event of cracks or losses of tightness in the tank walls.

[0033] It also makes it possible to contain and segregate any methanol vapors generated during operation and escaping from the tank due to cracks or losses of tightness.

[0034] According to current shipbuilding regulations, the containment gap must also be large enough to allow inspection for the direct detection of the presence of possible methanol infiltration or methanol vapors. In particular, a minimum width of 80 cm is required for the said gap.

[0035] The need to provide a cofferdam around methanol tanks, in addition to the need to provide high-capacity tanks due to the lower energy density of methanol, results in a considerable overall footprint.

[0036] Documents CN115817707 and CN 115092331 describe examples of ships equipped with 'bi-fuef engines which use diesel and methanol as fuels and provide for the presence of a cofferdam.

[0037] As mentioned above, the large footprint due to the need to provide a cofferdam is an extremely disadvantageous drawback, especially in the case of luxury pleasure crafts, where the usable space for passengers’ cabins and recreational activities must be maximized.

[0038] In particular, the footprint related to the use of a 'bi-fuef containment and supply system using diesel and methanol is totally unacceptable on pleasure crafts under 60 meters in length that maintain their current cruising range characteristics.

[0039] With the known solutions and in light of current regulations, the installation of 'bi- fuef engines using methanol on recreational crafts in the 24-meter to 60-meter length category is de facto impossible, except by drastically reducing the cruising range or giving up large spaces for passengers’ use.

[0040] An object of the present invention is therefore to overcome the prior art drawbacks and limitations described above, by providing a fuel containment and supply system for a vessel, especially for a vessel having a 'bi-fuef engine using methanol that requires less space dedicated to fuel containment.

[0041] In particular, an object of the present invention is to provide a fuel containment and supply system for a vessel especially for a vessel having a 'bi-fuef engine using methanol that has a footprint compatible with the application to pleasure crafts, especially with applications to luxury pleasure crafts.

[0042] Another object of the present invention is to provide a fuel containment and supply for a vessel using methanol that meets high standards in terms of safety and incident prevention.

[0043] Finally, an object of the present invention is to provide a method for operating said fuel containment and supply system for a vessel.

[0044] These and other objects are achieved with the fuel containment and supply system for a vessel and the method for operating the same as claimed in the appended claims. Summary of Invention

[0045] The invention relates to a fuel supply system for a vessel using a first fuel and a second fuel.

[0046] In particular, the first fuel can be a conventional fuel, whereas the second fuel can be a 'carbon neutral' fuel that makes it possible to remarkably reduce engine emissions.

[0047] The fuel containment and supply system according to the invention comprises one or more tanks for the first fuel and one or more tanks for the second fuel.

[0048] Each tank for the second fuel is provided with a jacket located around at least one portion of the outer surface of said tank for the second fuel and defining with said outer surface a gap (cofferdam).

[0049] According to the invention, the gap (cofferdam) provided between the tank for the second fuel and the jacket thereof forms an additional tank for the first fuel and is used for this purpose.

[0050] By exploiting the cofferdam as additional tank for the first fuel, the use of space can be optimized.

[0051] Furthermore, the amount of first fuel on board the vessel - and consequently the cruising range of the vessel - can be increased without any additional space being required.

[0052] In a preferred embodiment of the invention, the first fuel is diesel (including the so- called marine diesel) and the second fuel is methanol.

[0053] According to an embodiment, sensors capable of detecting the presence of said second fuel inside said cofferdam are provided.

[0054] Thanks to the presence of said sensors, the cofferdam, while being used as an additional tank for the first fuel, effectively performs the functions of safety and prevention, as it is possible to timely detect and properly segregate leaks of the second fuel or vapors thereof from the tank for the second fuel.

[0055] In particular, where said second fuel is methanol, it is possible to timely detect leaks of methanol from the tank for the second fuel and prevent methanol dispersion in the bilge, thus avoiding the risk of fires.

[0056] In addition, it is possible to timely detect leaks of methanol vapors from the tank for the second fuel and prevent the spread of methanol vapors in the bilge, thus avoiding the risk of explosions or intoxication for personnel in the area.

[0057] Advantageously, where the first fuel is diesel and the second fuel is methanol, it is possible to exploit the fact that methanol and diesel are immiscible, and that methanol has a lower density than diesel.

[0058] Accordingly, methanol will tend to rise and occupy the upper portion of the cofferdam.

[0059] Correspondingly, the sensors capable of detecting the presence of the second fuel (methanol) or vapors thereof will be arranged at the upper portion of the cofferdam.

[0060] This configuration can also be adopted if other fuels are used, provided they are immiscible and have different densities.

[0061] In a preferred embodiment of the invention, the sensors capable of detecting the presence of said second fuel of vapors thereof inside said cofferdam are part of a safety system that may further comprise:

[0062] - one or more acoustic and / or light signaling devices that can be activated if said sensors detect the presence of said second fuel or vapors thereof inside said cofferdam;

[0063] - means for maintaining an inert atmosphere with the presence of an inerting gas (for example, nitrogen) in said tank for the second fuel, and possibly means for releasing inerting gas into said cofferdam if said sensors detect the presence of said second fuel or vapors thereof inside said cofferdam, in order to neutralize the risks of developing potentially dangerous methanol gas / vapor mixtures;

[0064] - means for blocking the flow of the first fuel from the cofferdam towards the engine if these sensors detect the presence of said second fuel or vapors thereof inside said cofferdam; and

[0065] - a control unit to control said one or more acoustic and / or light signaling devices and / or said means for releasing an inerting gas into the cofferdam and / or said means for blocking the flow of the first fuel towards the engine in response to data detected by these sensors.

[0066] In a preferred embodiment of the invention, the cofferdam is divided in a plurality of separate compartments, and sensors capable of detecting the presence of said second fuel or vapors thereof are provided in each separate compartment.

[0067] Thanks to this provision, in the event of leaks from the tank for the second fuel towards the cofferdam, the safety measures will only concern the compartment(s) that is / are affected by the infiltration of the second fuel, whereas the remaining compartments of the cofferdam can continue to operate normally.

[0068] Advantageously, where the first fuel is diesel and the second fuel is methanol, it is possible to arrange the inlet port of the diesel pickup tube at the lower portion of the cofferdam.

[0069] In this way, even in the event of methanol infiltration into the cofferdam, it will still be possible to use the (uncontaminated) diesel present in the lower portion of the cofferdam.

[0070] This configuration can also be adopted if other fuels are used, provided they are immiscible and have different densities.

[0071] In a preferred embodiment of the invention, a positive pressure gradient is maintained by means of an inerting gas between the inside of the tank for the second fuel and the cofferdam surrounding said tank.

[0072] In this way, in the event of cracks or losses of tightness in the tank for the second fuel, the second fuel will be allowed to flow into the cofferdam, but the first fuel contained in the cofferdam will be prevented from penetrating inside the tank for the second fuel.

[0073] From the above it is clear that, according to the invention, the method for operating the fuel containment and supply system for a vessel as described above comprises the following steps: a) providing one or more tanks for a first fuel; b) providing one or more tanks for a second fuel, wherein each tank for the second fuel is provided with a jacket located around at least one portion of the outer surface of said tank for the second fuel and defining with said outer surface a gap (cofferdam); c) using said cofferdam as an additional tank for the first fuel, by filling said cofferdam with said first fuel and withdrawing said first fuel from said cofferdam.

[0074] Brief Description of Drawings

[0075] Further features and advantages will become more evident from the following detailed description of some preferred embodiments of the invention that are given by way of non-limiting examples with reference to the annexed drawings, in which:

[0076] Fig. 1 is a schematic view in a longitudinal section of a vessel according to a first embodiment of the invention;

[0077] Fig. 2 is a schematic view in a transverse section taken along line II - II of the vessel of Figure 1;

[0078] Fig. 3 is a schematic view in a transverse section taken along line III - III of the vessel of Figure 1;

[0079] Fig. 4 shows in a more detailed manner the particular IV of Figure 3;

[0080] Fig. 5 schematically shows a methanol tank and a corresponding cofferdam of a vessel according to a second embodiment of the invention.

[0081] Description of Embodiments

[0082] Hereinafter, reference will be made particularly to a luxury pleasure craft, more specifically to a yacht.

[0083] The invention should in no way be construed as being limited to this type of vessels.

[0084] Also, in the preferred embodiments of the invention described here below, reference will be made to the case in which the first fuel is diesel and the second fuel is methanol.

[0085] In this case, too, however, the invention should not be construed as being limited to the use of these specific fuels.

[0086] Referring to Figure 1, a pleasure craft or vessel 100 generally comprises a hull 102 and a main deck 104, on which a superstructure 106 is provided that can house, for example, a passengers’ cabin and / or the helm station for the craft owner. Inside the hull 102, the space is divided in one or more overlying decks (in the example shown, two overlying decks 108, 110) and accommodates further spaces for passengers’ use as well as the engine room, the compartments for the crew, and the rooms intended to house technical installations, on-board equipment and so on.

[0087] More particularly, the engine room and the technical compartments are located in the lower deck 110 in the hull, said lower deck being delimited inferiorly by the floorboards, and houses the engines necessary for both the propulsion of the vessel and the operation of the systems provided on board the vessel.

[0088] The invention refers to the possibility of powering the engines of the vessel 100 with two different fuels.

[0089] Correspondingly, the fuel containment and supply system according to the invention comprises one or more tanks for the first fuel (diesel) and one or more tanks for the second fuel (methanol).

[0090] Referring to Figure 2, in a manner known per se, the fuel containment and supply system according to the invention comprises one or more diesel tanks la, lb, arranged under the floor-boards 112.

[0091] In addition, as shown in Figure 3, said fuel containment and supply system according to the invention comprises one or more methanol tanks 3a, 3b.

[0092] As mentioned above, current regulations on the transport of methanol on vessels require methanol tanks to be surrounded by a voluminous containment gap, at least for tank surfaces that are not also external surfaces of the vessel’s hull.

[0093] Therefore, the fuel containment and supply system according to the invention comprises, for each methanol tank 3a, 3b, a corresponding jacket 5a, 5b arranged around at least one portion of the outer surface of the respective methanol tank and defining with said outer surface a gap or cofferdam 7a, 7b.

[0094] With reference to the shown example, each methanol tank 3a, 3b comprises a first portion of outer surface which coincides with a portion of external surface of the hull 102, and a second portion of outer surface which is separated from the external surface of the hull 102.

[0095] In this case, each jacket 5a, 5b is located around said second portion of outer surface of the respective methanol tank 3a, 3b, and a gap or cofferdam is defined between the inner surface of the jacket 5a, 5b and the second portion of outer surface of the methanol tank 3a, 3b.

[0096] It is evident that if a methanol tank had no outer surfaces in common with the hull 102, the corresponding jacket would be located around the whole outer surface of said methanol tank and define therewith a corresponding cofferdam.

[0097] According to the invention, the gaps or 'cofferdams' 7a, 7b provided between the methanol tanks 3a, 3b and the respective jackets 5a, 5b are additional tanks for diesel fuel and therefore contain, at least for part of their volume, diesel fuel.

[0098] Thanks to the fact that the 'cofferdams' 7a, 7b are used as additional tanks for diesel fuel, a larger quantity of diesel can be loaded on the vessel 100, thereby increasing the cruising range thereof.

[0099] A methanol tank 3a and the corresponding cofferdam 7a are shown in greater detail in Figure 4.

[0100] It is evident that the ensuing description is also entirely applicable to the other methanol tank 3b and the corresponding cofferdam 7b or other methanol tanks present on board.

[0101] The methanol tank 3a is provided superiorly with a filling duct 9a through which methanol can be introduced into the tank.

[0102] The methanol tank 3a is also equipped with a methanol pickup tube Ila through which methanol can be withdrawn from the tank and sent to an engine of the vessel 100.

[0103] The inlet end of the methanol pickup tube Ila is preferably located near the bottom of the methanol tank 3 a and the methanol pickup tube Ila extends over the entire height of said tank until it protrudes therefrom, so as to be joined to connection ducts 12a for connection to the engine to be supplied.

[0104] Along the portion of the methanol pickup tube 1 la that protrudes from the methanol tank 3a, a sensor 13a can optionally be provided in order to detect the presence of diesel fuel, so that any diesel infiltration from the cofferdam 7a to the methanol tank 3a can be timely detected.

[0105] However, it should be noted that, in a preferred embodiment of the invention, the pressure inside the methanol tank 3a is maintained higher than the pressure inside the cofferdam 7a.

[0106] Thanks to the positive pressure gradient, in the event of cracks or losses of tightness in the methanol tank 3a, the methanol contained in said tank can flow into the cofferdam 7a, but the diesel contained in the cofferdam 7a cannot penetrate into the methanol tank 3a.

[0107] The cofferdam 7a is delimited on its outside by the jacket 5a and on its inside by the portion of outer surface of the methanol tank 3a that is separated from the external surface of the hull 102. In order to be used as an additional diesel tank, said cofferdam is equipped superiorly with a filling duct 15a through which diesel can be introduced into the cofferdam.

[0108] The cofferdam 7a is further provided with a diesel pickup tube 17a through which diesel can be withdrawn from the cofferdam and sent to an engine of the vessel 100.

[0109] The inlet end of the diesel pickup tube 17a is preferably located near the bottom of the cofferdam 7a and the diesel pickup tube 17a protrudes from the jacket 5a, so as to be joined to connection ducts 18a for the engine to be supplied.

[0110] As mentioned above, a pressure gradient is maintained between the methanol tank 3a and the cofferdam 7a, so that, in the event of cracks or losses of tightness of the methanol tank 3a, the methanol or vapors thereof contained in said tank can flow into the cofferdam 7a and remain confined therein after having been detected.

[0111] Consequently, according to the invention, the cofferdam 7a, while being used as an additional diesel tank, is still capable of effectively performing the required safety and prevention functions.

[0112] To this aim, inside the cofferdam 7a there are provided one or more sensors 19a capable of detecting the presence of methanol or vapors thereof.

[0113] In the shown example, it must be considered that methanol and diesel are immiscible, and methanol has a lower density than diesel. Therefore, in the event of leaks from the methanol tank 3a, the leaked methanol or vapors thereof will settle above the surface of the diesel and therefore towards the upper portion of the cofferdam 7a.

[0114] Correspondingly, the sensors 19a capable of detecting the presence of methanol or vapors thereof are preferably located at said upper portion of the cofferdam 7a, so as to be capable of timely detecting any leaks.

[0115] Said sensors are capable of detecting the presence of both methanol in liquid form and methanol vapors.

[0116] In this way, it is possible to effectively prevent leakage of liquid methanol into the bilge and the related risk of fires as well as leakage of methanol vapors into the bilge and the related risk of explosions or intoxication for the personnel.

[0117] Advantageously, the fuel containment and supply system according to the invention provides for means to maintain the presence of inerting gas 21a in the methanol tank 3 a and means for releasing an inerting gas 23a into the cofferdam 7a if said sensors 19a detect the presence of methanol or vapors thereof inside said cofferdam.

[0118] Nitrogen, for example, can be used as an inerting gas.

[0119] In order to introduce inerting gas into the methanol tank 3a it is possible to use the methanol filling duct 9a; similarly, in order to release inerting gas into the cofferdam 7a it is possible to use the diesel filling duct 15a.

[0120] Alternatively, separate ducts for the introduction of inerting gas can be provided.

[0121] The fuel containment and supply system according to the invention further provides for means for stopping withdrawal of the first fuel 25a from the cofferdam 7a if said sensors 19a detect the presence of methanol or vapors thereof inside said cofferdam.

[0122] Said means for stopping withdrawal of the first fuel 25a from the cofferdam 7a can consist, for example, of a valve arranged on the diesel pickup tube 17a.

[0123] However, it should be noted that, as mentioned above, methanol or vapors thereof that may have leaked from the methanol tank 3a would settle above the surface of the diesel contained in the cofferdam 7a and accordingly the diesel contained in the lower portion of the cofferdam would not be contaminated in any way.

[0124] Therefore, should the need arise, it would still be possible to deactivate the means for stopping withdrawal of the first fuel 25a from the cofferdam 7a and resume diesel withdrawal for supplying the engines of the vessel.

[0125] Preferably, the fuel containment and supply system according to the invention further provides for one or more acoustic and / or light signaling devices that can be activated if said sensors 19a detect the presence of methanol or vapors thereof inside the cofferdam 7a.

[0126] In addition, the fuel containment and supply according to the invention may comprise a control unit to automatically control the means for maintaining the presence of an inerting gas 21a in the methanol tank 3a, the means for releasing an inerting gas 23a into the cofferdam 7a, the means for stopping diesel withdrawal 25a from the cofferdam 7a and the acoustic and / or light signaling devices in response to data detected by these sensors 19a capable of detecting the presence of methanol.

[0127] Turning now to Figure 5, in an alternative embodiment of the invention it is possible to provide to divide each cofferdam in a plurality of separate compartments.

[0128] Only a methanol tank 3 a and a corresponding cofferdam 7a are shown in Figure 5.

[0129] It is evident that the following description is in any case also fully applicable to other methanol tanks on board as well as to the corresponding cofferdams.

[0130] In this second embodiment, the methanol tank 3a consists of a single space (as in the previous embodiment), whereas the cofferdam is divided in a plurality of separate compartments, for example by means of corresponding bulkheads 8a.

[0131] In the shown embodiment, two bulkheads 8a are provided that define three separate compartments 7a’, 7a”, 7a’”.

[0132] However, it is clear that it would also be possible to envisage a division into a different number of compartments.

[0133] In this embodiment, there are provided a single filling duct 9a for the methanol tank 3a and single means for maintaining the presence of the inerting gas 21a in said methanol tank 3a. Similarly, there is provided a single methanol pickup tube Ila through which methanol can be withdrawn from the tank and sent to an engine of the vessel through a connection duct 12a.

[0134] Instead, each cofferdam compartment 7a’, 7a”, 7a’” is provided with its own diesel filling duct 15a (said diesel filling ducts being possibly joined to one another upstream of the cofferdam).

[0135] In addition, each compartment of the cofferdam 7a’, 7a”, 7a’” is provided with its own means for releasing an inerting gas 23a into said compartment and / or its own means for stopping diesel withdrawal from said compartment and / or its own acoustic and / or light signaling devices in the event of the presence of methanol or methanol vapors within said compartment. It is evident, in this regard, that each cofferdam compartment 7a’, 7a”, 7a’” is provided with its own sensors capable of detecting the presence of methanol or vapors thereof.

[0136] Similarly, each cofferdam compartment 7a’, 7a”, 7a’” is provided with its own diesel pickup tube 17a through which diesel can be withdrawn from the respective compartment and sent to an engine of the vessel through a corresponding connection duct 18a (said connection ducts being possibly joined to one another downstream of the cofferdam).

[0137] Thanks to this provision, in the event of infiltrations from the methanol tank, the safety measures will only concern the compartment(s) of the cofferdam that is / are affected by the infiltrations of methanol or vapors thereof, whereas the remaining compartments of the cofferdam can continue to operate normally.

[0138] It will be evident from the above description that the invention achieves the above- mentioned objects, as it combines the need to reduce space requirements on pleasure crafts with the possibility of using advantageous fuels such as methanol while effectively complying with the safety regulations currently in force.

[0139] Moreover, it should be noted that the fuel containment and supply system according to the invention could be installed on a vessel even before 'bi-fuef motorizations are available, as all the thanks could temporarily be used to contain diesel fuel.

[0140] It would therefore be possible to manufacture vessels ready for being retrofitted with 'bi-fuef engines in advance of their availability and without penalizing tank capacity and cruising range before the retrofitting is carried out.

[0141] From the above it is evident that the method for operating the fuel containment and supply system for a vessel 100 as described above comprises the following steps: a) providing one or more tanks for a first fuel la, lb; b) providing one or more tanks for a second fuel 3a, 3b, wherein each tank for the second fuel 3a, 3b is provided with a jacket 5a, 5b located around at least one portion of the outer surface of said tank for the second fuel and defining therewith a gap or cofferdam 7a, 7b; c) using said cofferdam 7a, 7b as an additional tank for the first fuel.

[0142] From the above it is also evident that the method for operating a vessel 100 as described above and equipped with engines that can be supplied with two different fuels comprises the following steps: a) providing a fuel containment and supply system inside said vessel 100, said fuel containment and supply system using a first fuel and a second fuel and comprising one or more tanks for the first fuel la, lb and one or more tanks for the second fuel 3a, 3b, each tank for the second fuel 3a, 3b being provided with a jacket 5a, 5b located around at least one portion of the outer surface of said tank for the second fuel and defining therewith a gap or cofferdam 7a, 7b; b) filling said cofferdam 7a, 7b with said first fuel; c) filling said one or more tanks for the second fuel 3a, 3b with said second fuel; d) withdrawing said first fuel from said cofferdam 7a, 7b and sending said first fuel to the engines of said vessel 100 to supply said engines with said first fuel; e) withdrawing said second fuel from said one or more tanks for the second fuel 3a, 3b and sending said second fuel to the engines of said vessel 100 to supply said engines with said second fuel.

[0143] It will also be evident to the person skilled in the art that the detailed description provided above has been given as a non-limiting example and that numerous modifications and variants are possible without thereby departing from the scope of protection as defined by the appended claims.

Claims

CLAIMS1. Fuel containment and supply system for a vessel (100), comprising one or more tanks for a first fuel (la, lb) and one or more tanks for a second fuel (3a, 3b), wherein each tank for the second fuel (3a, 3b) is provided with a jacket (5a, 5b) located around at least one portion of the outer surface of said tank for the second fuel and defining therewith a gap or cofferdam (7a, 7b), characterized in that said cofferdam (7a, 7b) is an additional tank for the first fuel and contains said first fuel.

2. System according to claim 1, wherein said tank for said second fuel (3a) is at a pressure higher than that of said cofferdam (7a, 7b), preferably thanks to the presence of an inerting gas.

3. System according to claim 1 or 2, wherein said cofferdam (7a) is provided with a filling duct (15a) for introducing the first fuel into said cofferdam, and a pickup tube (17a) for withdrawing the first fuel from said cofferdam.

4. System according to claim 3, wherein the inlet end of said pickup tube (17a) is located near the bottom of said cofferdam (7a).

5. System according to any of the preceding claims, wherein said cofferdam (7a) is equipped with one or more sensors (19a) for detecting the presence of the second fuel or vapors thereof.

6. System according to claim 5, wherein the first fuel and the second fuel are immiscible, the second fuel has a density lower than the density of the first fuel and said one or more sensors (19a) for detecting the presence of the second fuel or vapors thereof are preferably located at an upper portion of said cofferdam (7a).

7. System according to claim 5 or 6, comprising means for maintaining the presence of an inerting gas (21a) in said tank for the second fuel (3a).

8. System according to claim 5 or 6 or 7, comprising means for releasing an inerting gas (23a) into said cofferdam (7a), said means being actuatable in response to data detected by said one or more sensors (19a) for detecting the presence of the second fuel or vapors thereof.

9. System according to claim 5 or 6, comprising means for stopping withdrawal of the first fuel (25a) from said cofferdam (7a).

10. Fuel containment and supply system according to claim 1 or 2, wherein said cofferdam (7a) is divided in a plurality of separate compartments (7a’, 7a”, 7a’”), and wherein each of said compartments is provided with a filling duct (15a) for introducing the first fuel into said compartment, and a pickup tube (17a) for withdrawing the first fuel fromsaid compartment.

11. Fuel containment and supply system according to claim 10, wherein each of said compartments (7a’, 7a”, 7a’”) is provided with one or more sensors for detecting the presence of the second fuel of vapors thereof.

12. Fuel containment and supply system according to claim 11, comprising means for releasing an inerting gas into each of said compartments (7a’, 7a”, 7a’”) of said cofferdam.

13. Fuel containment and supply system according to claim 11, comprising means for stopping withdrawal of the first fuel (25a) from each of said compartments (7a’, 7a”, 7a’”) of said cofferdam.

14. Fuel containment and supply system according to any of the preceding claims, wherein the first fuel is diesel, and the second fuel is methanol.

15. Method for operating a fuel containment and supply system for a vessel (100) comprising the following steps: a) providing one or more tanks for a first fuel (la, lb); b) providing one or more tanks for a second fuel (3 a, 3b), wherein each tank for the second fuel (3a, 3b) is provided with a jacket (5a, 5b) located around at least one portion of the outer surface of said tank for the second fuel and defining therewith a gap or cofferdam (7a, 7b); c) filling at least partially said cofferdam (7a, 7b) with the first fuel; d) withdrawing the first fuel from said cofferdam (7a, 7b), thus using said cofferdam as an additional tank for the first fuel.

16. Method according to claim 15, wherein said method further comprises the step of maintaining said one or more tanks for the second fuel (3a) at a pressure higher than the pressure inside said cofferdam (7a).

17. Method according to claim 15 or 16, further comprising the step of detecting the presence of the second fuel or vapors thereof in said cofferdam.

18. Method according to claim 17, further comprising the step of releasing an inerting gas (23a) into said cofferdam (7a) when the presence of the second fuel or vapors thereof is detected in said cofferdam (7a).

19. Method according to claim 17, further comprising the step of stopping withdrawal of the first fuel from said cofferdam (7a) when the presence of the second fuel or vapors thereof is detected in said cofferdam (7a).

20. Method according to any one of claims 15 to 19, wherein the first fuel is diesel and the second fuel is methanol.

21. Vessel, in particular pleasure craft, comprising a hull (102), a main deck (104), and one or more decks (108, 110) located within said hull, characterized in that it comprises a fuel containment and supply system according to any of claims 1 - 14.

22. Vessel according to claim 21, wherein each tank for the second fuel (3a, 3b) comprises a first portion of outer surface which coincides with a portion of external surface of said hull (102) and a second portion of outer surface which is separated from the external surface of said hull (102), and wherein each tank for the second fuel (3a, 3b) is provided with a jacket (5a, 5b) located around said second portion of outer surface of said tank for the second fuel and defining therewith said cofferdam (7a, 7b).

23. Method for operating a vessel according to claim 21 or 22, comprising the steps of: a) filling said cofferdam (7a, 7b) with said first fuel; b) filling said one or more tanks for the second fuel (3a, 3b) with said second fuel; c) withdrawing said first fuel from said cofferdam (7a, 7b) and sending said first fuel to the engines of said vessel (100) to supply said engines with said first fuel; d) withdrawing said second fuel from said one or more tanks for the second fuel (3a, 3b) and sending said second fuel to the engines of said vessel (100) to supply the engines with said second fuel.

24. Method for operating a vessel according to claim 23, further comprising the steps of detecting the presence of the second fuel or vapors thereof in said cofferdam (7a) and stopping withdrawal of said first fuel (25a) from said cofferdam (7a) when the presence of the second fuel or vapors thereof is detected in said cofferdam (7a).

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