CN112673205B

CN112673205B - Fuel tank device for gas-fueled ship

Info

Publication number: CN112673205B
Application number: CN201880097344.5A
Authority: CN
Inventors: E·德尔索; A·斯科基
Original assignee: Wartsila Finland Oy
Current assignee: Wartsila Finland Oy
Priority date: 2018-09-11
Filing date: 2018-09-11
Publication date: 2022-12-27
Anticipated expiration: 2038-09-11
Also published as: WO2020052730A1; KR20210059711A; CN112673205A; KR102531802B1; EP3850266A1

Abstract

The invention relates to a fuel tank arrangement for storage of LNG fuel for a gas-fuelled marine vessel, the arrangement comprising an LNG fuel tank (12) and a tank connection space (26.2) arranged in communication with the LNG fuel tank (12), wherein the tank connection space (26.2) is formed by at least three separate compartments, namely one filling compartment (30.2) and at least two LNG fuel feeding compartments (70.3, 70.4).

Description

Fuel tank device for gas-fueled ship

Technical Field

The present invention relates to a fuel tank arrangement for such a gas-fueled marine vessel, which fuel tank arrangement uses Liquefied Natural Gas (LNG) as its sole fuel source. The present invention is primarily concerned with meeting the requirements of pure gas fuel for the construction of LNG fuel tanks. More particularly, the present invention relates to an LNG fuel tank arrangement comprising at least one shell, insulation and a tank connection space formed by a plurality of compartments arranged at the end or side of the LNG fuel tank.

Background

The use of LNG as a fuel for marine applications is increasing as it is an effective way to reduce emissions. Natural Gas (NG) is expected to be the fastest growing major energy source in the world in the next decades. The driving force behind this development is the known reduction in oil reserves, the increase in environmental awareness and the continued tightening of emission limits. All major emissions can be significantly reduced to truly create an environmentally sound solution. CO is difficult to achieve, particularly for conventional oil-based fuels ₂ Is reduced. NG is composed of methane (CH) ₄ ) And lesser concentrations of heavy hydrocarbons such as ethane and propane. Under normal ambient conditions NG is a gas, but it can be liquefied by cooling it to-162 ℃. In liquid form, the specific volume is significantly reduced, which allows the size of the storage tank to be reasonable relative to the energy content. The combustion process of NG is clean. High hydrogen-to-coal ratio (fossil fuel)Medium to highest) means that carbon dioxide emissions are lower compared to oil based fuels. When NG liquefies, all sulfur is removed, which means zero SO _X And (4) discharging. The clean burning characteristics of NG also significantly reduce NO compared to oil-based fuels _X And particle emissions. Especially in such cruise vessels, ferries and so-called passenger ships with passengers on board, the absence of smoke emissions and visible smoke in the exhaust gases of the ship's engines is a very important feature.

LNG is not only an environmentally friendly solution, but is also economically interesting in today's oil price situations. The most feasible way to store NG in a ship is in liquid form. In existing marine installations, LNG is stored in cylindrical, insulated single-or double-walled tanks made of stainless steel or some other suitable steel.

Non-pressurized prior art LNG tanks typically have only a single wall or shell covered with insulation such as polyurethane. Pressurized prior art LNG tanks have an inner wall or shell of stainless steel and an outer wall or shell spaced a distance from the inner shell. An isolation space is defined between the inner and outer shells. To empty an LNG tank, the LNG tank is provided with at least one stainless steel pipe which is connected at its first end to the LNG tank and at its second end to a tank connection space arranged at the side or end of the tank, either as an extension of the tank or as a separate chamber at a short distance from the tank. The tank connection space is typically a gas-tight enclosed space containing all tank connections, fittings, flanges and tank valves. The tank connection space is made of a low temperature resistant material, with a bottom well (bilge well) with a high level indicator and a low temperature sensor. The Tank Connection Space (TCS) is typically inaccessible and personnel must not enter the tank connection space unless checked for sufficient oxygen and no explosive atmosphere. For safety reasons, TCS is provided with permanent gas detection, fixed fire detection and mechanical forced ventilation, which can ventilate 30 times per hour.

As is well known, environmental awareness has driven shipyards toward the use of fuels that produce minimal carbon dioxide emissions. One way to achieve this goal is to build a vessel that runs only with NG, i.e. NG is the only available fuel for the engine/engines or other gas consumers. International safety regulations for ships using gas or other low flash point fuels, so-called IGF regulations, give many regulations for single fuel facilities. The purpose behind the regulations is to ensure that leakage or other problems associated with LNG tanks do not result in power losses, i.e. reduced maneuverability of the vessel.

There are two basic types of LNG tanks, considering their availability in ships using a single fuel. In the first type of tank, some leakage of the tank structure may occur and due to the risk of leakage, the IGF regulations dictate that the fuel storage must be divided into at least two tanks located in separate compartments, and that each tank must also be provided with the instrumentation and equipment required to transport the fuel from the tank to the engine. In other words, the first tank type requires full redundancy and isolation.

In the second type of tank, there is only a potential for leakage from the valve, and therefore if the tank has a tank connection space for each engine, the IGF regulations only require that a single fuel tank can be used to store fuel for multiple engines.

Therefore, it is natural that the second type of LNG tanks is an option for ships, in particular for ships with at least two engines. Constructing a single large LNG tank without leaks is more cost effective than constructing a large number of small tanks with multiple instruments and equipment for delivering fuel to each engine.

In the following, the second type of LNG tanks, and in particular the tank connection spaces arranged in connection therewith, will be discussed in more detail. As described above, IGF regulations dictate that a single LNG tank can be accepted if a single engine is provided with separate tank connection spaces to connect with the single LNG tank. However, the IGF rules dictate to make it completely open, how to divide the various meters and equipment between the individual tank connection spaces.

It is therefore an object of the present invention to design an LNG fuel tank arrangement for a gas-fuelled marine vessel such that the various instruments and equipment for handling LNG fuel are divided into more than one tank connection space in a practical manner.

Another object of the present invention is to design an LNG fuel tank arrangement for a gas-fuelled marine vessel such that the problem of feeding LNG fuel to one engine is isolated from the other engine/engines so that the other engine/engines can continue their trouble-free operation.

It is another object of the present invention to design such an LNG fuel tank arrangement such that an inert atmosphere is provided to its tank connection space whenever the TCS is shut down, i.e. it is not occupied by service and/or maintenance personnel.

Disclosure of Invention

At least one object of the present invention is substantially met by a fuel tank arrangement for storing LNG fuel in a gas-fuelled marine vessel, the arrangement comprising an LNG fuel tank, a tank connection space arranged in communication with the LNG fuel tank, the tank connection space being formed by at least three separate compartments, namely one filling compartment and at least two LNG fuel supply compartments.

Further features of the invention become apparent in the appended dependent claims.

The fuel tank device of the present invention has at least the following advantages:

only one LNG tank is needed to store fuel for one or more engines,

optimizing the division of instruments and equipment between the tank connection spaces,

the tank connection space is not continuously ventilated, whereby

Continuous noise associated with TCS ventilation is avoided,

the energy required for TCS ventilation is significantly reduced, and

reduce or virtually eliminate the risk of NG burning or explosion in the tank connection space, and

condensation and icing on cold equipment in the TCS due to humid ventilation air is avoided.

Drawings

In the following, the invention will be described in more detail with reference to the accompanying exemplary schematic drawings, in which:

fig. 1 schematically illustrates a side view of a marine vessel having an LNG fuel tank of the present invention on deck;

fig. 2a and 2b schematically illustrate two longitudinal and horizontal sectional variants of an LNG fuel tank according to a preferred embodiment of the present invention;

fig. 3 schematically illustratesbase:Sub>A partial cross-sectional side view of the tank connection space of the LNG fuel tank (i.e. its filling compartment) along linebase:Sub>A-base:Sub>A of fig. 2base:Sub>A;

fig. 4 schematically illustrates a partial cross-sectional side view of the tank connection space of the LNG fuel tank (i.e. a first variant of its LNG fuel supply compartment) along line B-B of fig. 2 a;

fig. 5 schematically illustrates a partial cross-sectional side view of the tank connection space of the LNG fuel tank (i.e. a second variant of its LNG fuel supply compartment) along line B-B of fig. 2 a;

fig. 6 schematically illustrates a further development of the refueling compartment of the LNG fuel tank of fig. 3; and

fig. 7 schematically illustrates a further development of the LNG fuel supply compartment of the LNG fuel tank of fig. 4.

Detailed Description

Fig. 1 illustrates schematically and in a very simplified manner a marine vessel 10 having an LNG fuel tank 12, which LNG fuel tank 12 is arranged on the deck of the marine vessel 10. Of course, the LNG fuel tank may also be located below deck. The figure also shows: an internal combustion engine 14 that receives fuel from the LNG fuel tank 12; and a drive 16 coupled to both the engine 14 and the propeller 18. The drive means may here comprise a mechanical gear or a generator (electric drive combination).

Fig. 2a schematically illustrates the basic configuration of an LNG fuel tank 12 according to a first modification of the preferred embodiment of the present invention. The fuel tank 12 is formed, for example, by an inner casing 20, an outer casing 22, and an insulator 24 between the inner and outer casings. At the end of the fuel tank 12 a so-called tank connection space or TCS 26.1 is arranged. Naturally, the tank connection space 26.1 may also be located at the side of the LNG fuel tank and not necessarily as an extension of the shell of the tank, but may also be at a distance from the shell of the tank, i.e. as a separate chamber at the side or end of the LNG fuel tank. However, in this case, a portion of the connection between the tank and the tank connection space should be provided with double pipes, which makes the connection less attractive. The tank connection space 26.1 is preferably, but not necessarily, provided with an insulating material 28. The tank connection space 26.1 is formed by one filling compartment 30.1 and two LNG fuel supply compartments 70.1 and 70.2.

Fig. 2b schematically illustrates the basic configuration of an LNG fuel tank 12 according to a second modification of the preferred embodiment of the present invention. As previously described, the fuel tank 12 is formed of an inner shell 20, an outer shell 22, and insulation 24 between the inner and outer shells. At the end of the fuel tank 12 a so-called tank connection space 26.2 is arranged. Naturally, the tank connection space may also be located at the side of the LNG fuel tank and not necessarily as an extension of the shell of the tank, but may also be at a distance from the shell of the tank, i.e. as a separate chamber at the side or end of the LNG fuel tank. The tank connection space 26.2 is preferably, but not necessarily, provided with an insulating material 28. The tank connection space 26.2 is formed by one filling compartment 30.2 and two LNG fuel supply compartments 70.3 and 70.4.

The only difference between fig. 2a and fig. 2b is the design of the tank connection spaces 26.1 and 26.2. The tank connection space 26.1 of fig. 2a has a filling compartment 30.1 of small size which is surrounded on one side by the LNG fuel tank and on three sides by the LNG fuel supply compartments 70.1 and 70.2. Thus, the filling compartment 30.1 is accessed from above or from below. The tank connection space 26.2 of fig. 2b has a larger sized filling compartment 30.2 which is surrounded on one side by the LNG fuel tank 12 and on both sides by the LNG fuel supply compartments 70.3 and 70.4 and the fourth side, i.e. the end of the filling compartment 30.2 opposite the LNG fuel tank 12, extends to the level of the end of the LNG fuel supply compartment, whereby the end wall of the filling compartment 30.2 also ensures free access to the filling compartment from the side of the filling compartment (however, through its wall).

Fig. 3 illustrates sectionbase:Sub>A-base:Sub>A of fig. 2base:Sub>A and discusses the equipment and equipment required to fill the LNG fuel tank 12 with LNG. According to the invention, such a device is provided in the filling compartment 30.1 of the tank connection space. The filling compartment 30.1 has an oil supply line 32 for receiving LNG from one of a land-based oil supply station, tanker truck, coastal tanker or tanker barge. The supply line 32 terminates in a supply valve 34 for delivering LNG to a bottom fill line 36 leading from the filling compartment 30.1 to the bottom of the LNG tank 12 or to a top fill line 38 leading to an LNG spray 40 in the upper part of the LNG tank 12. Preferably, the

LNG filling lines

36 and 38 pass directly from the filling compartment 30.1 through the walls or shells of the tank inside the LNG tank 12. However, it is also possible to arrange the corresponding lines to leave the filling compartment 30.1 first through the top wall of the filling compartment 30.1 and then enter the tank through the top wall of the tank, whereby the lines need to be provided with a double wall. The supply valve 34 can also be used to deliver LNG to both filling lines simultaneously. The filling compartment 30.1 also has a vapor return valve 42 having a vapor return line 44 for collecting vapor from the LNG tank 12 when filling the LNG tank 12. The vapour return line 44 carries vapour to the outside of the filling compartment 30.1 for recovery.

The filling compartment 30.1 also has an emergency relief valve 46 which opens a vent connection along a safety relief line 48 from the top or gas space of the LNG fuel tank 12 to a vent mast 50 in case the pressure in the tank 12 exceeds a predetermined value. Also provided in the filling compartment 30.1 is an instrument 52 for measuring the LNG level L in the LNG tank 12. In addition to the above described device for filling an LNG fuel tank 12 with LNG, the filling compartment 30.1 comprises a ventilation device comprising: an air or vent inlet line 54, the air or vent inlet line 54 having a first fire damper 56; and a ventilation outlet line 58, the ventilation outlet line 58 having a second fire damper 60 leading from the filling compartment 30.1 to the exhaust mast 50; and a blower 62, the blower 62 being positioned in the ventilation inlet line 54 or the ventilation outlet line 58 for ventilating the filling compartment 30.1. The first and

second fire valves

56, 60 are always open under normal operating conditions and automatically close only when a fire is detected in the filling compartment 30.1.

Furthermore, the filling compartment 30.1 also comprises a pressure relief valve 64 which connects the interior of the filling compartment 30.1 to the ventilation mast 48 via a pressure relief line 66. The pressure relief valve 64 is arranged to open when the pressure in the filling compartment 30.1 exceeds the maximum allowed filling compartment pressure p0, e.g. due to a temperature increase. The maximum permissible pressure p0 in the filling compartment 30.1 is generally between 0.1 bar and 0.5 bar (gauge) or between 1.1 bar and 1.5 bar absolute, preferably between 0.2 bar and 0.4 bar.

And finally, the filling compartment 30.1 has a drain 68 at the bottom of the filling compartment for collecting any liquid (glycol/water in the heat exchange circuit) that forms or leaks in the filling compartment 30.1.

Fig. 4 illustrates section B-B of fig. 2a and discusses the equipment and equipment needed for providing the engine with NG and according to the invention arranged in the LNG fuel supply compartment 70.1 of the tank connection space. The LNG fuel supply compartment has many of the same equipment as the filling compartment and these are now labelled with the same reference numerals but preceded by a "2". Accordingly, the ventilation device of the LNG fuel supply compartment comprises: an air or vent inlet line 254, the air or vent inlet line 254 having a first fire damper 256; and a vent outlet line 258, the vent outlet line 258 having a second fire damper 260 leading from the LNG fuel supply compartment 70.1 to the exhaust mast 250; and a blower 262, the blower 262 being positioned in the ventilation inlet line 54 or the ventilation outlet line 58 for ventilating the LNG fuel supply compartment 70.1. The first and

second fire valves

256, 260 are always open under normal operating conditions and automatically close only when a fire is detected in the LNG fuel supply compartment 70.1. In addition, the LNG fueling compartment also includes a pressure relief valve 264 that connects the interior of the LNG fueling compartment to the ventilation mast 250 via a pressure relief line 266. The pressure relief valve 264 is arranged to open when the pressure in the LNG-fuelling compartment 70.1 exceeds the maximum allowed LNG-fuelling compartment pressure p0, e.g. due to a temperature increase. The maximum allowable pressure p0 in the LNG fuel supply compartment is typically between 0.1 and 0.5 bar (gauge) or between 1.1 and 1.5 bar absolute, preferably between 0.2 and 0.4 bar. And finally, the TCS of the LNG-fueled compartment has a drain 268 at the bottom of the space for collecting any liquid (glycol/water in the heat exchange circuit) that forms or leaks in the LNG-fueled compartment.

The equipment, particularly located in the LNG fuel supply compartment (i.e. the equipment needed to provide NG fuel to the engine), includes an LNG outlet line 72 that takes liquid LNG from the bottom of the LNG tank 12. In this variation of the invention, LNG is carried to the main LNG vaporizer 76 via the LNG outlet valve 74. The LNG fuel is vaporized in vaporizer 76 and proceeds in a gaseous state to gas heater 78, from which heater 78 the heated gaseous NG is carried along fuel supply line 80 and to the engine via main gas valve 82. A line 84 leads from between the LNG outlet valve 74 and the main LNG vaporizer 76 and via a valve 86 to the top or gas space of the LNG tank 12 to bring the liquid LNG to the tank 12. Line 88 introduces vaporized LNG from between the main LNG vaporizer 76 and the gas heater 78 into the gas chamber of the LNG tank 12 via valve 90. Further, line 92 carries the heated NG from the fuel supply line 80 to line 84 via valve 94, which line 84 carries the heated NG into the gas chamber of the LNG tank 12. Furthermore, a boil off gas line, i.e. a BOG line 96, leads from the gas space of the LNG tank 12 and via a boil off gas valve 98 to a compressor chamber (not shown) outside the LNG fuel supply compartment 70.1. If desired, a boil-off gas heater, i.e., a BOG heater 100, may be coupled to the BOG line 96.

The LNG fueling compartment also includes a pressure accumulator 102 that carries LNG from the LNG outlet line 72 at the bottom of the LNG tank 12 via a pressure accumulator valve 104 to a pressure accumulator unit 106, i.e., a heat exchanger that vaporizes the LNG. The vaporized LNG is brought to the gas chamber of the LNG tank 12 via the pressure accumulation line 108 to increase the pressure therein. The recycle lines 84, 88 and 92 and the pressure build-up line 108 may be arranged to enter the LNG tank 12 from the LNG fuel supply compartment 70.1 via a single line.

Fig. 5 schematically illustrates a second variant of the LNG fuel supply compartment 70.1 of fig. 4. The only difference compared to the first variant discussed in fig. 4 is the way LNG is taken from the bottom of the tank 12. Here, in fig. 5, a cryogenic pump 110 is provided in the LNG outlet line 72 upstream of the LNG outlet valve 74. Now, the pump 110 replaces the pressure accumulation device in fig. 4.

Fig. 6 schematically illustrates a further development of the filling compartment 30.1 of fig. 3. According to fig. 6, there is provided a filling compartment 30.1 having means for arranging an inert atmosphere in the filling compartment 30.1 in addition to the equipment needed for filling the LNG fuel tank 12 with LNG as discussed in fig. 3. The venting inlet line 54 of the filling compartment 30.1 of the tank connection space is provided with a first shut-off valve 112 in addition to the first fire damper 56 and the venting outlet line 58 is provided with a second shut-off valve 114 in addition to the second fire damper 60, so that the filling compartment 30.1 can be closed off from the outside atmosphere to render it inert. The filling compartment 30.1 further comprises an inlet line 116 for introducing inert gas from an inert gas source 118 into the filling compartment 30.1 and a gas outlet line 120 for discharging gas from the filling compartment 30.1 to the ventilation mast 50. The inert gas inlet line 116 is provided with a first pressure regulating valve 122, preferably but not necessarily outside the filling compartment 30.1, to control the inert atmosphere in the filling compartment 30.1. The gas outlet line 120 is connected to the exhaust mast 50 via a second pressure regulating valve 124 therein. The gas outlet line 120 is provided with an oxygen analyzer 126 for monitoring the oxygen concentration of the gas discharged from the filling compartment 30.1. The oxygen analyzer 126 may also be positioned in connection with the filling compartment 30.1 upstream of the second pressure regulating valve 124 or the gas outlet line 120.

According to a first preferred operating variant of the invention, the first pressure regulating valve 122 is a pilot operated valve which receives its control signal from the pressure in the filling compartment 30.1, so that the first pressure regulating valve 122 opens when the pressure in the filling compartment 30.1 is below the upper limit pressure p1, i.e. the first pressure regulating valve 122 allows inert gas into the filling compartment 30.1 when the pressure in the filling compartment 30.1 is below p1. According to the same operating scheme, the second pressure regulating valve 124 is also a pilot operated valve, which receives its control signal from the pressure of the filling compartment 30.1. When the pressure in the filling compartment 30.1 is above the predetermined lower limit pressure p2, the second pressure regulating valve 124 opens, i.e. gas is discharged from the filling compartment 30.1 to the ventilation mast 50. Thus, p1> p2.

According to a second preferred operating scenario, the first pressure regulating valve 122 receives its control signal from the pressure of the filling compartment 30.1, such that when the upper limit pressure p1 is reached, the first pressure regulating valve 122 is regulated or instructed to close, in other words, when the pressure is lower than p1, the first pressure regulating valve 122 remains open. The second pressure regulating valve 124 receives its control signal from the pressure of the filling compartment 30.1, so that the second pressure regulating valve 124 is regulated or instructed to open at a pressure of px and to remain open until the pressure drops to p2, wherein px > p2. The pressures p1 and px may be equal or different, it being only important that p1 and px are greater than p2.

According to first alternative further features of the second preferred operating scheme, the opening of the second pressure regulating valve 124 at the pressure of px is used to indicate that the first pressure regulating valve 122 is closed, such that the first pressure regulating valve 122 remains closed until the second pressure regulating valve 124 is closed at the pressure of p2. Closing of the second pressure regulating valve 124 returns control of the first pressure regulating valve 122 to the filling compartment pressure, whereby the first pressure regulating valve 122 opens and the pressure in the filling compartment 30.1 increases until the second pressure regulating valve 124 receives its control signal from the filling compartment pressure at px, opening and taking over control of the first pressure regulating valve 122, closing it.

According to a second alternative further feature of the second preferred operating scheme, closing the first pressure regulating valve 122 at a pressure of p1 is used to indicate that the second pressure regulating valve 124 is open, taking over control of the first pressure regulating valve 122 and keeping it closed until the second pressure regulating valve 124 is closed at a pressure of p2. Thereafter, control of the first pressure regulating valve 122' is given the filling compartment pressure such that the first pressure regulating valve 122 opens to allow the pressure in the filling compartment 30.1 to increase and keeps the second pressure regulating valve 124 closed until the pressure of p1 is reached.

Since the maximum filling compartment pressure p0 is between 0.1 bar and 0.5 bar, the pressures p2, p1 or px used when placing the first and second pressure regulating valves in the operating state are rather low, but always apply for p2< p1 and p2< px.

Further, the oxygen concentration has an effect on the function of the first pressure regulating valve 122 and the second pressure regulating valve 124, as will be discussed later.

When using a new filling compartment 30.1 or inerting the filling compartment 30.1 after inspection, i.e. switching the filling compartment 30.1 from air atmosphere to inert atmosphere, the ventilation inlet line 54 and the ventilation outlet line 58 are closed by: the first and

second fire valves

56, 60 and the first and second

pressure regulating valves

122, 124 are activated, i.e. the

valves

122, 124 receive their control signals at least from the pilot pressure of the filling compartment. The inerting of the filling compartment 30.1 can be carried out in two substantially different ways, namely by continuous purging or by using a pressurization cycle.

A first way consists in keeping both the first pressure regulating valve 122 and the second pressure regulating valve 124 open, i.e. continuously purging the filling compartment 30.1, until the oxygen concentration of the gas in the filling compartment 30.1 (i.e. upstream of the gas outlet line 120) or the gas discharged from the filling compartment 30.1 downstream of the second pressure regulating valve 124 in the discharge line 120 is reduced below the maximum allowable oxygen concentration, as determined by the oxygen analyzer 126. Here, the first preferred operating variant is used such that the activation of the

pressure regulating valves

122 and 124 means that both

valves

122 and 124 remain open as long as the oxygen concentration in the filling compartment 30.1 (i.e. in the analyzer 126) is high, and that the first pressure regulating valve 122 or the second pressure regulating valve 124 is closed only after the maximum permissible oxygen concentration has been reached, i.e. after a control signal has been received from the oxygen analyzer 126. In the former case, the second pressure regulating valve 124 will also close as soon as the pressure in the filling compartment 30.1 drops below p2, whereas in the latter case the first pressure regulating valve 122 closes when the pressure in the filling compartment 30.1 reaches p1. Thus, the filling compartment pressure after inerting is p2 in the former case and p1 in the latter case. Naturally, the oxygen concentration may optionally be followed such that the first pressure regulating valve 122 or the second pressure regulating valve 124 is closed manually (instead of automatically controlled). Thus, both

valves

122 and 124 are deactivated, i.e. set to a standby mode from which they will be reactivated by increasing the oxygen concentration or decreasing the pressure in the filling compartment. Thus, the pressure control of the fuel compartment 30.1 is left to the pressure relief valve 64.

A second way involves using a pressurization cycle that requires setting the operation of the valve in a different way than the first operating scheme. Thus, according to the second preferred operating solution and its first alternative further features, when the filling compartment 30.1 is used or when the filling compartment 30.1 is inerted after service or repair, when the pressure in the filling compartment 30.1 is atmospheric pressure p1, the first pressure regulating valve 122 for introducing inert gas into the filling compartment 30.1 is opened and the second pressure regulating valve 124 remains closed until the pressure in the filling compartment 30.1 exceeds the predetermined pressure p1, causing the second pressure regulating valve 124 to open and, thereby, the first pressure regulating valve 122 to close, allowing the pressure to fall below the second predetermined value p2, which causes the second pressure regulating valve 124 to close and, thereby, the first pressure regulating valve 122 to open. Operation continues until the oxygen concentration of the gas in the filling compartment 30.1 (i.e. upstream of the gas outlet line 120) or the gas discharged from the filling compartment 30.1 downstream of the second pressure regulating valve 124 in the gas outlet line 120 is reduced below the maximum allowable oxygen concentration as determined by the oxygen analyzer 126, i.e. the following oxygen concentrations are reached: so that NG cannot be combusted regardless of the concentration of the fuel. When the desired oxygen concentration is reached, at least the first pressure regulating valve 122 or the second pressure regulating valve 124 is closed. Thereafter, the pressure in the filling compartment 30.1 is p2 or p1, respectively, and both

valves

122 and 124 may be deactivated, i.e. set to a standby mode, from which they will be reactivated by increasing the oxygen concentration or decreasing the pressure in the filling compartment 30.1. Thus, the pressure control of the fuel compartment 30.1 is left to the pressure relief valve 64.

Furthermore, according to the second preferred operating solution and its second alternative further features, when the filling compartment 30.1 is used or when the filling compartment 30.1 is inerted after service or repair, the first pressure regulating valve 122 for introducing inert gas into the filling compartment 30.1 is opened and the second pressure regulating valve 124 remains closed until the pressure in the filling compartment 30.1 exceeds the predetermined pressure p1, causing the first pressure regulating valve 122 to close and, as a result, the second pressure regulating valve 124 to open, when the pressure in the filling compartment 30.1 is atmospheric and therefore lower than p1. The first pressure regulating valve 122 remains closed allowing the filling compartment pressure to drop below the second predetermined value p2, which causes the second pressure regulating valve 124 to close and, thus, the first pressure regulating valve 122 to open. Operation continues until the oxygen concentration of the gas in the filling compartment 30.1 (i.e. upstream of the gas outlet line 120) or the gas discharged from the filling compartment 30.1 downstream of the second pressure regulating valve 124 in the gas outlet line 120 is reduced below the maximum allowable oxygen concentration as determined by the oxygen analyzer 126, i.e. the following oxygen concentrations are reached: so that NG cannot be combusted regardless of the concentration of the fuel. When the desired oxygen concentration is reached, at least the first pressure regulating valve 122 or the second pressure regulating valve 124 is closed. Thereafter, the pressure in the filling compartment is p2 or p1, respectively, and both

valves

Under normal operating conditions, i.e., when the vent inlet and outlet are closed and the inert atmosphere in the filling compartment is controlled by the first and second

pressure regulating valves

122 and 124, the operation of the first and

second fire valves

56 and 112 in the vent inlet line 54 and the second and

second fire valves

60 and 114 in the vent outlet line 58 should be periodically checked. To minimize waste of inert gas, a first shut-off valve 112 and a second shut-off valve 114 are provided on both the vent inlet line 54 and the vent outlet line 58. A check of the function of the fire damper and the shut-off valve is performed such that first the

fire damper

56 or 60 is closed and the shut-off

valve

112 or 114 is opened, and then the inlet line 54 or the outlet line 58 leading from the shut-off valve 112 or 114 (i.e. in the opposite direction to the filling compartment 30.1) is monitored to see if any leakage from the filling compartment 30.1 can be noticed. If not, the

fire damper

56 or 60 appears to be in good condition, after which the shut-off

valve

112 or 114 is closed and the

fire damper

56 or 60 is opened. Next, the inlet line 54 or the outlet line 58 leading from the shut-off valve 112 or 114 (i.e. in the opposite direction to the filling compartment 30.1) is again monitored to see if any leakage from the filling compartment 30.1 can be noticed. If not, the shut-off

valve

112 or 114 is also in good condition and can be shut off. Naturally, if any leaks are detected through any of the fire and shut-off

valves

56, 60, 112 or 114, or any other problems in its operation are found, the failed valve needs to be replaced or repaired.

When the filling compartment itself or any equipment therein needs to be serviced or repaired, the inert atmosphere in the filling compartment must be switched to an air atmosphere so that both the

pressure regulating valves

122 and 124 are deactivated, the fire and shut-off

valves

56, 60, 112 or 114 are opened and the blower 62 is activated, i.e. a standard vent is opened to flush out nitrogen and charge air into the filling compartment 30.1.

Fig. 7 schematically illustrates a further development of the LNG fuel supply compartment 70.1 of fig. 4. The illustrated further development is the same as discussed above in relation to the filling compartment. Now the same inerting equipment is brought or integrated into the LNG fuel supply compartment 70.1. Thus, according to fig. 7, there is provided an LNG fuel supply compartment 30.1 having means for arranging an inert atmosphere in the LNG fuel supply compartment 70.1 in addition to the equipment needed for filling the LNG fuel tank 12 with LNG as discussed in fig. 3. The vent inlet line 254 of the LNG fuel supply compartment 70.1 of the tank connection space is provided with a first shut-off valve 212 in addition to a first fire damper 256 and the vent outlet line 258 is provided with a second shut-off valve 214 in addition to a second fire damper 260 so that the LNG fuel supply compartment 70.1 can be shut off from the outside atmosphere to render it inert. The LNG-fueled compartment 70.1 further comprises an inlet line 216 for introducing inert gas from an inert gas source 218 into the LNG-fueled compartment 70.1 and a gas outlet line 220 for discharging gas from the LNG-fueled compartment 70.1 to the ventilation mast 250. The inert gas inlet line 216 is provided with a first pressure regulating valve 222, preferably but not necessarily outside the LNG fuel supply compartment 70.1, to control the inert atmosphere in the LNG fuel supply compartment. The gas outlet line 220 is connected to the exhaust mast 250 via a second pressure regulating valve 224 therein. The gas outlet line 220 is provided with an oxygen analyzer 226 for monitoring the oxygen concentration of the gas discharged from the LNG fuel supply compartment 70.1. The oxygen analyzer 226 may also be positioned in connection with the LNG-fueled compartment 70.1 upstream of the second pressure regulating valve 224 or the gas outlet line 220.

According to a first preferred operating scenario of the present invention, the first pressure regulating valve 222 is a pilot operated valve that receives its control signal from the pressure of the LNG fuel supply compartment 70.1 such that the first pressure regulating valve 222 opens when the pressure in the LNG fuel supply compartment 70.1 is below the upper limit pressure p1, i.e. the first pressure regulating valve 222 allows inert gas to enter the LNG fuel supply compartment 70.1 when the pressure in the LNG fuel supply compartment 70.1 is below p1. According to the same operating scheme, the second pressure regulating valve 224 is also a pilot operated valve, which receives its control signal from the pressure of the LNG fuel supply compartment 70.1. When the pressure in the LNG-fueled compartment 70.1 is above the predetermined lower limit pressure p2, the second pressure regulating valve 224 is opened, i.e., gas is discharged from the LNG-fueled compartment 70.1 to the ventilation mast 250. Thus, p1> p2.

According to a second preferred operating scenario, the first pressure regulating valve 222 receives its control signal from the pressure of the LNG fuel supply compartment 70.1, such that when the upper limit pressure p1 is reached, the first pressure regulating valve 222 is regulated or instructed to close, in other words, when the pressure is below p1, the first pressure regulating valve 222 remains open. The second pressure regulating valve 224 receives its control signal from the pressure of the LNG fuel supply compartment 70.1 such that the second pressure regulating valve 224 is regulated or instructed to open and remain open at a pressure of px, where px > p2, until the pressure drops to p2. The pressures p1 and px may be equal or different, it being only important that p1 and px are greater than p2.

According to a first alternative further feature of the second preferred operating scheme, the opening of the second pressure regulating valve 224 at the pressure of px is used to indicate that the first pressure regulating valve 222 is closed, such that the first pressure regulating valve 222 remains closed until the second pressure regulating valve 224 is closed at the pressure of p2. Closing of the second pressure regulating valve 224 returns control of the first pressure regulating valve 222 to the LNG fuel supply compartment pressure, whereby the first pressure regulating valve 222 opens and the pressure in the LNG fuel supply compartment 70.1 increases until the second pressure regulating valve 224 receives its control signal from the LNG fuel supply compartment pressure at px, opening and taking over control of the first pressure regulating valve 222, closing it.

According to a second alternative further feature of the second preferred operating scheme, the closing of the first pressure regulating valve 222 at a pressure of p1 is used to indicate that the second pressure regulating valve 224 is open, taking over control of the first pressure regulating valve 222 and keeping it closed until the second pressure regulating valve 224 is closed at a pressure of p2. Thereafter, control of the first pressure regulating valve 222' is given to the LNG fuel supply compartment pressure such that the first pressure regulating valve 222 opens to allow the pressure in the LNG fuel supply compartment 70.1 to increase and keeps the second pressure regulating valve 224 closed until the pressure of p1 is reached.

Since the maximum LNG fuel supply compartment pressure p0 is between 0.1 bar and 0.5 bar, the pressure p2, p1 or px used when placing the first and second pressure regulating valves in operation is rather low, but always applies for p2< p1 and p2< px.

Further, the oxygen concentration has an effect on the function of the first pressure regulating valve 222 and the second pressure regulating valve 224, as will be discussed later.

When using a new LNG fuel supply compartment 70.1 or inerting the LNG fuel supply compartment 70.1 after inspection, i.e. switching the LNG fuel supply compartment 70.1 from air atmosphere to inert atmosphere, the vent inlet line 254 and vent outlet line 258 are closed by: the first and second shut-off

valves

256, 260 and the first and second

pressure regulating valves

222, 224 are activated, i.e. the

valves

222, 224 receive their control signals at least from the pilot pressure of the LNG fuel supply compartment. Inerting of the LNG fuel supply compartment 70.1 can be done in two substantially different ways, namely by continuous purging or by using a pressurized cycle.

The first way includes keeping both the first pressure regulating valve 222 and the second pressure regulating valve 224 open, i.e., continuously purging the LNG-fueled compartment 70.1 until the oxygen concentration of the gas in the LNG-fueled compartment 70.1 (i.e., upstream of the gas outlet line 220) or the oxygen concentration of the gas discharged from the LNG-fueled compartment 70.1 downstream of the second pressure regulating valve 224 in the discharge line 220 is reduced below the maximum allowable oxygen concentration as determined by the oxygen analyzer 226. Here, the first preferred operating scheme is used such that the activation of the

pressure regulating valves

222 and 224 means that both

valves

222 and 224 remain open as long as the oxygen concentration in the LNG fuel supply compartment 70.1 (i.e. in the analyzer 226) is high, and that only after the maximum allowable oxygen concentration has been reached, either the first pressure regulating valve 222 or the second pressure regulating valve 224 is closed, i.e. after a control signal has been received from the oxygen analyzer 226. In the former case, the second pressure regulating valve 224 will also close as soon as the pressure in the LNG fuel supply compartment 70.1 drops below p2, whereas in the latter case the first pressure regulating valve 222 closes when the pressure in the LNG fuel supply compartment 70.1 reaches p1. Thus, in the former case, the inerted LNG fuel supply compartment pressure is p2, and in the latter case p1. Naturally, the oxygen concentration may optionally be followed such that the first pressure regulating valve 222 or the second pressure regulating valve 224 is closed manually (instead of automatically controlled). Thus, both

valves

222 and 224 are deactivated, i.e. set to a standby mode from which they will be reactivated by increasing the oxygen concentration or decreasing the pressure in the LNG fuel supply compartment. Thus, the pressure control of the LNG fuel supply compartment 70.1 is left to the pressure relief valve 264.

A second way consists in using a pressurization cycle that requires setting the operation of the valve in a different way from the first operating scheme. Thus, according to the second preferred operating scenario and its first alternative further features, when the LNG-fueled compartment 70.1 is used or is inerted after service or repair, when the pressure in the LNG-fueled compartment 70.1 is at atmospheric pressure p1, the first pressure regulating valve 222 for introducing inert gas into the LNG-fueled compartment 70.1 is opened and the second pressure regulating valve 224 remains closed until the pressure in the LNG-fueled compartment 70.1 exceeds the predetermined pressure p1, causing the second pressure regulating valve 224 to open, and thereby the first pressure regulating valve 222 to close, allowing the pressure to drop below the second predetermined value p2, which causes the second pressure regulating valve 224 to close, and thereby the first pressure regulating valve 222 to open. Operation continues until the oxygen concentration of the gas in the LNG-fueled compartment 70.1 (i.e., upstream of the gas outlet line 220) or the gas discharged from the LNG-fueled compartment 70.1 downstream of the second pressure regulating valve 224 in the gas outlet line 220 is reduced below the maximum allowable oxygen concentration as determined by the oxygen analyzer 226, i.e., the following oxygen concentrations are achieved: so that NG cannot be combusted regardless of the concentration of the fuel. When the desired oxygen concentration is reached, at least the first pressure regulating valve 222 or the second pressure regulating valve 224 is closed. Thereafter, the pressure in the LNG fuel supply compartment 70.1 is p2 or p1, respectively, and both

valves

222 and 224 may be deactivated, i.e. set to a standby mode, from which they will be reactivated by increasing the oxygen concentration or decreasing the pressure in the LNG fuel supply compartment 70.1. Thus, the pressure control of the LNG fuel supply compartment 70.1 is left to the pressure relief valve 264.

Furthermore, according to a second preferred operating scenario and second alternative further features thereof, when the LNG fuel supply compartment 70.1 is used or the LNG fuel supply compartment 70.1 is inerted after service or maintenance, the first pressure regulating valve 222 for introducing inert gas into the LNG fuel supply compartment 70.1 is open when the pressure in the LNG fuel supply compartment 70.1 is atmospheric pressure and thus below p1, and the second pressure regulating valve 124 remains closed until the pressure in the LNG fuel supply compartment 70.1 exceeds the predetermined pressure p1, resulting in the first pressure regulating valve 222 being closed, and thereby the second pressure regulating valve 2124 being open. The first pressure regulating valve 222 remains closed allowing the LNG fuel supply compartment pressure to drop below the second predetermined value p2 which causes the second pressure regulating valve 224 to close and, thus, the first pressure regulating valve 222 to open. Operation continues until the oxygen concentration of the gas in the LNG-fueled compartment 70.1 (i.e., upstream of the gas outlet line 220) or the gas discharged from the LNG-fueled compartment 70.1 downstream of the second pressure regulating valve 224 in the gas outlet line 220 is reduced below the maximum allowable oxygen concentration as determined by the oxygen analyzer 226, i.e., the following oxygen concentrations are achieved: so that NG cannot be combusted regardless of the concentration of the fuel. When the desired oxygen concentration is reached, at least the first pressure regulating valve 222 or the second pressure regulating valve 224 is closed. Thereafter the pressure in the LNG fuel supply compartment is p2 or p1, respectively, and both

valves

222 and 224 may be deactivated, i.e. set to a stand-by mode, from which they will be reactivated by increasing the oxygen concentration or decreasing the pressure in the LNG fuel supply compartment 70.1. Thus, pressure control of LNG fuel supply compartment 70.1 is left to pressure relief valve 64.

Under normal operating conditions, i.e., when the vent inlet and outlet are closed and the inert atmosphere in the LNG fuel supply compartment is controlled by the first and second

pressure regulating valves

222, 224, the operation of the first and

second fire valves

256, 212 in the vent inlet line 254 and the second and

second fire valves

260, 214 in the vent outlet line 258 should be periodically checked. To minimize waste of inert gas, both the vent inlet line 254 and the vent outlet line 258 are provided with the first shut-off valve 212 and the second shut-off valve 214. The checking of the function of the fire damper and the shut-off valve is performed such that first the

fire damper

256 or 260 is closed and the shut-off

valve

212 or 214 is opened, and then the inlet line 254 or the outlet line 258 leading from the shut-off valve 212 or 214 (i.e. in the opposite direction to the LNG fuel supply compartment 70.1) is monitored to see if any leakage from the LNG fuel supply compartment 70.1 can be noticed. If not, the

fire damper

256 or 260 appears to be in good condition, after which the shut-off

valve

212 or 214 is closed and the

fire damper

256 or 260 is opened. Next, the inlet line 254 or the outlet line 258 leading from the shut-off valve 212 or 214 (i.e. in the opposite direction to the LNG fuel supply compartment 70.1) is again monitored to see if any leakage from the LNG fuel supply compartment 70.1 can be noticed. If not, then shut-off

valves

212 or 214 are also in good condition and may be closed. Naturally, if any leaks are detected through any of the fire and shut-off

valves

256, 260, 212 or 214, or any other problems in their operation are discovered, the failed valve needs to be replaced or repaired.

When the LNG fuel supply compartment itself or any equipment therein needs to be overhauled or repaired, the inert atmosphere in the LNG fuel supply compartment has to be switched to an air atmosphere, whereby both

pressure regulating valves

222 and 224 are deactivated, the fire and shut off

valves

256, 260, 212 or 214 are opened and the blower 262 is activated, i.e. the normal ventilation is opened to flush out nitrogen and to charge the LNG fuel supply compartment 70.1 with air.

In view of the above, it should be noted that the inert gas used to inert the oil or fuel supply compartment is preferably nitrogen, although argon may also be used. The inert gas source 118/218 is a generator that separates the inert gas from air, and may also be a pressurized container with inert gas. In the case of a generator, it is preferred to store the inert gas in a buffer tank for later use. With respect to the preferred embodiments, operating schemes and variations thereof discussed above, it must be understood that they are merely exemplary embodiments, operating schemes and variations thereof and that other embodiments, operating schemes and variations thereof may be used without departing from the spirit of the invention. In a similar manner, the pressures p1, p2, px, or p0 do not necessarily represent the same pressure values in the various examples and in each example, but they may vary. Thus, as previously described, it is only important that in each exemplary embodiment, operating scheme or variation, p2< p1< p0 and p2< px < p0. Further, it should be noted that the first and second pressure regulating valves 122/222 and 124/224 may be positioned either inside or outside of the filling compartment or the LNG fuel supply compartment. Finally, it should also be understood that while fig. 3-7 discuss a tank, a refueling compartment, and an LNG fueling compartment having an inner shell and an outer shell, the present invention is also applicable to LNG tanks, refueling compartments, and LNG fueling compartments, and that the refueling compartment and LNG fueling compartment have only an inner shell with insulation.

It will be appreciated that the equipment required for filling the LNG fuel tank with LNG in the filling compartment and for providing NG for the engine in the LNG fuel supply compartment includes such lines, valves and other equipment not shown in fig. 3-7. One such device is a thermal valve and its associated piping for connecting any such portion of the various piping to the ventilation mast so that warming of the LNG or gaseous NG may increase the pressure. Moreover, all connections and lines (i.e., various water or water/glycol lines) associated with the heating or vaporization of LNG and the heating of NG have been eliminated.

It should also be understood that in the above exemplary embodiment/embodiments, the internal combustion engine (or engine in general) is used only as an example of various gas consumers. Such gas consumers include, for example, turbine gas burners in addition to engines.

While the invention has been described herein in connection with what is presently considered to be the most preferred embodiments of the invention, it is to be understood that the invention is not to be limited to the disclosed embodiments, but is intended to cover various combinations or modifications of its features and several other applications included within the scope of the invention as defined in the appended claims. It will be appreciated that the canister arrangement includes several features that are not shown in the figures for clarity. The details mentioned in connection with any of the above embodiments may be used in connection with any of the other embodiments, provided that such a combination is technically feasible.

Claims

1. A fuel tank arrangement for a gas-fuelled marine vessel for storing LNG fuel, the arrangement comprising an LNG fuel tank (12) and a tank connection space (26.1, 26.2) arranged in communication with the LNG fuel tank (12), characterized in that the tank connection space (26.1, 26.2) is formed by at least three separate compartments, one filling compartment (30.1: an LNG outlet line (72), the LNG outlet line (72) for taking LNG from the bottom of the LNG fuel tank (12); an LNG outlet valve (74); a main LNG vaporizer (76); and a fuel supply line (80), the fuel supply line (80) having a main gas valve (82) for delivering NG to the gas consumer.

2. The fuel tank arrangement as recited in claim 1, characterized in that the filling compartment (30.1, 30.2) contains equipment needed for filling the LNG fuel tank (12) with LNG.

3. The fuel tank arrangement as recited in claim 2, characterized in that the equipment required for filling the LNG fuel tank (12) with LNG and associated with the filling compartment (30.1: an oil supply line (32), the oil supply line (32) having an oil supply valve (34); a vapor return line (44); and an instrument (52), the instrument (52) for measuring the LNG level (L) in the LNG fuel tank (12).

4. The fuel tank arrangement as recited in claim 2, characterized in that the equipment in connection with the filling compartment (30.1: an exhaust mast (50); a safety pressure relief line (48), the safety pressure relief line (48) leading from the top or gas space of the LNG fuel tank (12) to the vent mast (50), the safety pressure relief line (48) having an emergency pressure relief valve (46).

5. The fuel tank arrangement as recited in claim 2, characterized in that the equipment in connection with the filling compartment (30.1, 30.2) further comprises a venting inlet line (54) with a first fire damper (56) therein and a venting outlet line (58) with a second fire damper (60) therein.

6. The fuel tank arrangement as recited in claim 2, characterized in that the arrangement in connection with the filling compartment (30.1, 30.2) further comprises a pressure relief line (66) with a pressure relief valve (64) therein.

7. The fuel tank arrangement as recited in claim 1, characterized in that the equipment needed for providing NG for gas consumers in the LNG fuel supply compartments (70.1, 70.2, 70.3, 70.4) comprises: a boil-off gas line (96), the boil-off gas line (96) having a boil-off gas valve (98) for taking boil-off gas from the top of the LNG fuel tank (12); and a heater (100), the heater (100) being for heating the boil-off gas.

8. The fuel tank arrangement as recited in claim 1, characterized in that the equipment needed for providing NG for gas consumers in the LNG fuel supply compartments (70.1, 70.2, 70.3, 70.4) comprises a pressure build-up line (108) branching off from the LNG outlet line (72), in which pressure build-up unit (106) is present, and which opens into the top of the LNG fuel tank (12).

9. The fuel tank arrangement as recited in claim 1, characterized in that the equipment required for providing NG for gas consumers in the LNG fuel supply compartments (70.1, 70.2, 70.3, 70.4) comprises a cryogenic pump (110) arranged upstream of the LNG outlet valve (74) in the LNG outlet line (72).

10. The fuel tank arrangement as recited in claim 1, characterized in that the equipment needed for providing NG for gas consumers in the LNG fuel supply compartments (70.1, 70.2, 70.3, 70.4) comprises: a vent inlet line (254) having a first fire damper (256) therein and a vent outlet line (258) having a second fire damper (260) therein; and a blower (262) connected with one of the vent inlet line (254) and the vent outlet line (258).

11. The fuel tank arrangement as recited in claim 1, characterized in that the equipment needed for providing NG for gas consumers in the LNG fuel supply compartments (70.1, 70.2, 70.3, 70.4) comprises a pressure relief line (266) with a pressure relief valve (264) therein.

12. A fuel tank arrangement according to claim 4, characterized in that the filling compartment (30.1.

13. The fuel tank arrangement as recited in claim 12, characterized in that a first pressure regulating valve (122) is arranged in flow communication with the inert gas inlet line (116).

14. The fuel tank arrangement as recited in claim 13, characterized in that the filling compartment (30.1, 30.2) is provided with a gas outlet line (120) arranged in flow communication with the exhaust mast (50).

15. A fuel tank arrangement according to claim 14, characterised in that a second pressure regulating valve (124) is arranged in flow communication with the gas outlet line (120) to maintain a desired pressure in the filling compartment (30.1.

16. The fuel tank arrangement as recited in claim 15, characterized in that an oxygen analyzer (126) is provided in connection with the filling compartment (30.1, 30.2) or downstream of the second pressure regulating valve (124) between the second pressure regulating valve (124) and the exhaust mast (50) in the gas outlet line (120).

17. The fuel tank arrangement as recited in any one of claims 12 to 16, characterized in that in the venting inlet line (54) there is a first fire damper (56) and a first shut-off valve (112), and in the venting outlet line (58) there is a second fire damper (60) and a second shut-off valve (114).

18. The fuel tank arrangement as recited in any one of claims 12-16, characterized in that a pressure relief valve (64) provides flow communication from the filling compartment (30.1, 30.2) to the mast (50), the pressure relief valve (64) being arranged to open when the pressure in the filling compartment (30.1, 30.2) exceeds a maximum allowable pressure p0.

19. The fuel tank arrangement as recited in claim 12, characterized in that the inert gas source (118) is one of an inert gas generator or a pressurized container.

20. The fuel tank device according to any one of claims 12 to 16, characterized in that the inert gas is one of nitrogen and argon.

21. The fuel tank arrangement as recited in any one of claims 13-16, characterized in that the first pressure regulating valve (122) is arranged to open when the pressure in the refilling compartment (30.1.

22. A fuel tank arrangement according to claim 15 or 16, characterized in that the second pressure regulating valve (124) is arranged to open when the pressure in the filling compartment (30.1.

23. The fuel tank arrangement according to claim 16, characterized in that the first pressure regulating valve (122) or the second pressure regulating valve (124) is arranged to close when the oxygen analyzer (126) indicates that the oxygen concentration is below a predetermined value.

24. The fuel tank arrangement as recited in claim 1, characterized in that the LNG fuel supply compartments (70.1, 70.2, 70.3, 70.4) are provided with an inert gas inlet line (216) for introducing inert gas from an inert gas source (218) into the LNG fuel supply compartments (70.1, 70.2, 70.3, 70.4).

25. The fuel tank arrangement of claim 24, characterized in that a first pressure regulating valve (222) is arranged in flow communication with the inert gas inlet line (216).

26. The fuel tank arrangement as recited in claim 25, characterized in that the LNG fuel supply compartment (70.1, 70.2, 70.3, 70.4) is provided with a gas outlet line (220) arranged in flow communication with an exhaust mast (250).

27. The fuel tank arrangement as recited in claim 26, characterized in that a second pressure regulating valve (224) is arranged in flow communication with the gas outlet line (220) to maintain a desired pressure in the LNG fuel supply compartment (70.1, 70.2, 70.3, 70.4).

28. The fuel tank arrangement as recited in claim 27, characterized in that between the second pressure regulating valve (224) and the exhaust mast (250) in the gas outlet line (220), an oxygen analyzer (226) is provided in connection with the LNG fuel supply compartments (70.1, 70.2, 70.3, 70.4) or downstream of the second pressure regulating valve (224).

29. The fuel tank arrangement as recited in any one of claims 24 to 28, characterized by a first fire damper (256) and a first shut-off valve (212) in the venting inlet line (254) and a second fire damper (260) and a second shut-off valve (214) in the venting outlet line (258).

30. The fuel tank arrangement as recited in any one of claims 24-28, characterized in that a pressure relief valve (264) provides flow communication from the LNG fuel supply compartment (70.1, 70.2, 70.3, 70.4) to the exhaust mast (250), the pressure relief valve (264) being arranged to open when the pressure in the LNG fuel supply compartment (70.1, 70.2, 70.3, 70.4) exceeds a maximum allowed pressure p0.

31. The fuel tank arrangement of claim 24, wherein the inert gas source (218) is one of an inert gas generator or a pressurized container.

32. The fuel tank device as recited in any one of claims 24 to 28, characterized in that the inert gas is one of nitrogen and argon.

33. The fuel tank arrangement as recited in any one of claims 25-28, characterized in that the first pressure regulating valve (222) is arranged to open when the pressure in the LNG fuel supply compartment (70.1, 70.2, 70.3, 70.4) drops below a predetermined pressure p1, and the first pressure regulating valve (222) is arranged to close when the pressure in the LNG fuel supply compartment (70.1, 70.2, 70.3, 70.4) exceeds the predetermined pressure p1.

34. A fuel tank arrangement according to claim 27 or 28, characterized in that the second pressure regulating valve (224) is arranged to open when the pressure in the LNG fuel supply compartment (70.1, 70.2, 70.3, 70.4) exceeds a predetermined pressure p2, and that the second pressure regulating valve (124) is arranged to close when the pressure in the LNG fuel supply compartment (70.1, 70.2, 70.3, 70.4) decreases below the predetermined pressure p2.

35. The fuel tank arrangement as recited in claim 28, characterized in that the first pressure regulating valve (222) or the second pressure regulating valve (224) is set closed when the oxygen analyzer (226) indicates that the oxygen concentration is below a predetermined value.