EP3803190A1

EP3803190A1 - Method for controlling the filling levels of tanks

Info

Publication number: EP3803190A1
Application number: EP19736422.7A
Authority: EP
Inventors: ROMAIN Pasquier; Eric GERVAISE; Nicolas LEROUX; Bruno ROBILLART
Original assignee: Gaztransport et Technigaz SA
Current assignee: Gaztransport et Technigaz SA
Priority date: 2018-05-31
Filing date: 2019-05-28
Publication date: 2021-04-14
Anticipated expiration: 2039-05-28
Also published as: CN112204296B; JP7333344B2; SG11202011735UA; EP3803190B1; CN112204296A; FR3082015A1; JP2021526618A; US11828421B2; ES2910266T3; KR20210016424A; FR3082015B1; US20210207773A1; CA3100556A1; WO2019229368A1

Abstract

Method for controlling the filling levels of a plurality of tanks arranged in a vessel, said tanks being interconnected such as to allow liquid to be transferred therebetween, the method comprising: providing an initial state (7) of the tanks; determining a target state (8) defining respective final filling levels of said tanks; determining a liquid transfer scenario (9), the transfer scenario defining one or more flows of liquid to be transferred between the tanks during a transfer period in order to switch from the initial state to the target state of the tanks; calculating a probability of damage to the tanks (10) during the course of said transfer scenario, according to successive filling levels of the tanks during the transfer period; and if the probability of damage to the tanks satisfies an acceptance criterion, transferring (13) the liquid between the tanks in accordance with said transfer scenario.

Description

Method for managing tank filling levels

Technical area

The invention relates to the field of tanks arranged in a floating structure such as a ship such as sealed and thermally insulating tanks with membranes. In particular, the invention relates to the field of sealed and thermally insulating vessels for the storage and / or transport of liquefied gas at low temperature, such as tanks for the transport of liquefied petroleum gas (also called LPG) having by for example a temperature between -50 ° C and 0 ° C, or for the transport of Liquefied Natural Gas (LNG) at about -162 ° C at atmospheric pressure. These tanks may be intended for the transport of liquefied gas or to receive liquefied gas used as fuel for the propulsion of the floating structure.

In one embodiment, the liquefied gas is LNG, that is a high methane content mixture stored at a temperature of about -162 ° C at atmospheric pressure. Other liquefied gases can also be envisaged, in particular ethane, propane, butane or ethylene. Liquefied gases can also be stored under pressure, for example at a relative pressure of between 2 and 20 bars, and in particular at a relative pressure of around 2 bars. The tank may be made according to various techniques, in particular in the form of an integrated membrane tank or a self-supporting tank.

Technological background

During storage and / or transport, the liquid contained in a tank is subjected to different movements. In particular, the movements at sea of a ship, for example under the effect of climatic conditions such as the state of the sea or the wind, cause agitation of the liquid in the tank. The agitation of the liquid, generally referred to as "sloshing" or sloshing, causes stresses on the walls of the tank that can affect the integrity of the tank. However, the integrity of the tank is particularly important in the context of an LNG tank due to the flammable or explosive nature of the transported liquid and the risk of cold spot on the steel hull of the floating unit. In order to reduce the risk of tank deterioration due to liquid movements in the tanks, the LNG carriers usually operate with empty or full tanks. Indeed, in an empty tank, the residual liquid contained in the tank has a limited weight and generates only small stresses on the cell walls. In a full tank, the residual space not occupied by the liquid in the tank is limited, thereby limiting the freedom of movement of the liquid in the tank and therefore the force of the impacts on the tank walls. Thus, the LNG carriers must generally navigate with tanks filled to less than 10% of their capacity or on the contrary to more than 70% of their capacity in order to limit the risks of degradation of the walls of tanks related to the impacts of liquid moving in the vats.

Document JP H107190 discloses a method for managing the filling levels of a plurality of vessels of a cryogenic liquid carrier vessel. In this document, the transfer of liquid from one tank to another takes place when it is determined that, in a tank, the movement of the liquid it contains is approaching its resonance period, which risks having negative consequences in terms of damage to the tank ("sloshing").

summary

This filling state of the tanks represents an ideal ideal filling state that is not always possible to achieve. In particular, in the event of an emergency departure of a vessel while its cargo is being loaded or unloaded, the vessel may be required to go to sea with partially filled tanks. Indeed, the operations of loading and unloading the liquid contained in the tanks are long operations that it is necessary to stop prematurely in case of an emergency requiring an emergency departure. Such alerts can be linked to many reasons such as a natural disaster such as a tsunami, an earthquake or an alert linked to a deterioration of the port facilities.

An idea underlying certain embodiments of the invention is to limit the risks associated with the movements of liquid in an off-shore vessel comprising a plurality of partially filled tanks. An idea behind some modes embodiment of the invention is to transfer the liquid between tanks with levels of filling risk of degradation to obtain filling levels of said tanks with a lower risk of degradation. An idea underlying certain embodiments of the invention is to provide one or more transfer scenarios for moving from an initial filling state of the tanks to a target filling state of said tanks. An idea underlying certain embodiments of the invention is to transfer the liquid between the tanks according to a transfer scenario having a satisfactory level of security during the course of said transfer scenario. For this, an idea underlying certain embodiments of the invention is to calculate probabilities of damage to the tanks during the course of one or more transfer scenarios.

According to one embodiment, the invention provides a method for managing the filling levels of a plurality of tanks arranged in a vessel, said tanks being connected in such a way as to allow a transfer of liquid between said tanks, the process comprising

- provide an initial state defining initial filling levels of the tanks,

- determining at least one target state defining final filling levels of said tanks,

determining a liquid transfer scenario, the transfer scenario defining one or more streams of liquid to be transferred between the tanks during a transfer period to go from the initial state to the target state of the tanks,

calculating a probability of damage to the tanks as a function of successive filling levels of the tanks during the transfer period, the probability of damage to the tanks defining a probability that at least one tank will be damaged during the course of the transfer scenario ,

generating a series of instructions for transferring the liquid between the tanks in accordance with said transfer scenario if the probability of damage to the tanks meets an acceptance criterion.

The method according to the invention defines at least one liquid transfer scenario (liquefied gas), preferably a plurality of liquid transfer scenarios, between the tanks in such a way that an operator, or the crew, is able to choose the scenario he wants. In this case, the plurality of scenarios proposed to the operator are all intended to reduce the risk of damage to the tanks, however these scenarios may differ from each other in terms of the time required for their completion as well as final refills of each of the tanks.

Thanks to these characteristics, the risk of degradation of the tanks is evaluated for the transfer scenario by taking into account the successive filling levels of the tanks during transfers. Thus, thanks to these characteristics, the risk of damage to the tanks is calculated not only for the target state to be achieved but also during the transfer of liquid.

Thus, when a vessel carrying liquefied gas is docked, with at least a partial cargo of its tanks, the invention allows the crew or an operator to return as quickly as possible in a secure situation, for example when a storm requires the departure of the boat from its point of attachment or even if it is necessary to leave the boat quickly.

According to embodiments, such a management method may comprise one or more of the following characteristics.

According to one embodiment, the target state has a probability of damage to the tanks lower than the probability of damage to the tanks of the initial state.

Thanks to these characteristics, a vessel with partially filled tanks can be secured by transferring the liquid contained in said tanks together to achieve a more secure tank filling state.

According to one embodiment, the management method further comprises, if the probability of damage to the tanks meets the acceptance criterion, transfer the liquid between the tanks in accordance with said transfer scenario. According to one embodiment, the management method further comprises the step of providing a transfer capacity parameter defining a transfer capacity between the tanks, the transfer scenario being determined according to said transfer capacity parameter between the tanks. .

According to one embodiment, the transfer capacity parameter includes a pump number parameter for one, or each tank. According to one embodiment, the transfer capacity parameter comprises a pumping flow parameter of the tank pump or pumps. According to one embodiment, the transfer capacity parameter includes a volume parameter of the tanks. According to one embodiment, the transfer capacity parameter between the vessels comprises one or more diameter parameters of the connection pipes between the tanks.

According to one embodiment, the management method further comprises a step of providing at least one environmental parameter defining environmental data of the ship, the calculation of the probability of damage to the tanks being carried out as a function of said at least one environmental parameter.

According to one embodiment, the one or more environmental parameters comprise one or more of the following parameters: the height of the sea of the wind, the height of the swell, the period of the sea of the wind, the period of the swell, the direction of the wind sea, wave direction, wind force, wind direction, current strength, current direction, relative wind, wave, current, wind report to the ship.

Preferably, the environmental parameter or parameters comprises the height of the sea or the height of the swell, and more preferably the height of the sea and the height of the swell are the two environmental parameters considered at least by the method according to the invention.

According to one embodiment, the calculation of the probability of damage to the tanks is made as a function of at least one parameter chosen from the group of parameters comprising the movements of the vessel, the levels of the impacts of liquid on the walls of the tank, the statistical behavior of the impacts of the liquid movements, the resistance of the tanks as a function of the position in said tanks, the time spent in different filling levels, the rate of evaporation of gas induced by the transfer of liquid, the loading state of the ship structure.

Preferably, the probability of damage calculation considers at least the statistical behavior of the liquid movement impacts or the time spent in different filling levels, and even more preferably the statistical behavior of the liquid movement impacts and the time spent in different filling levels are the two parameters considered at least for the calculation of damage.

According to one embodiment, the filling level of a tank is determined by the height of liquid in said tank. According to another embodiment, the filling level of a tank is determined by a volume of liquid contained in said tank.

According to one embodiment, the management method further comprises the step of determining a parameter in real time and take into account said parameter to determine the transfer scenario.

According to one embodiment, the management method further comprises the step of determining a parameter in real time and take into account said parameter to determine the calculation of probability of damage to the tanks.

According to one embodiment, the ship comprises one or more sensors making it possible to provide a parameter of the real-time transfer scenario, in particular the initial filling levels, the capacities of the tanks, the flow rates of the pumps, etc.

According to one embodiment, the vessel comprises one or more sensors making it possible to provide a parameter for calculating the probability of damage to the tanks in real time, in particular the movements of the vessel, the environmental parameters, etc.

According to one embodiment, the vessel comprises a database comprising data corresponding to one or more parameters of the transfer scenario. According to one embodiment, the vessel comprises a database comprising data corresponding to one or more parameters parameter of the calculation of probability of damage to the tanks.

According to one embodiment, the acceptance criterion is a criterion of risk of damage to the tanks during the transfer scenario.

According to one embodiment, the calculation of the probability of damage to the tanks is carried out according to the formula:

in which tk_n represents the number of the tank n,

SC represents the conditions of navigation as a function of the filling level fl_n of the tank tk_n,

Prob _tk-n represents the density of probability of meeting a pressure PreS _surf on an internal surface of the tank tk_n greater than the resistance Res _surf of said inner surface of the tank tk_n according to the conditions of navigation SC (fl_n),

surf is the internal surface impacted by the liquid, and

t _ope is the duration of operation to go from the initial state to the target state.

According to one embodiment, the navigation conditions SC also depend on at least one of:

the angle of incidence between the sea state and the ship

the period of the sea state

the significant height of the sea state

the movements of the ship

the speed of advance of the ship.

It should be noted that a sea state can be decomposed in sea of wind and swell, even crossed swell. Thus a sea state can be defined with several components. According to one embodiment, the probability density

Pmb _tk-n ( _Surf PreSurf> _Surf Res, tk_n, SC (fl_n) is predefined.

According to one embodiment, the density or probability of damage to the tank are predefined from tests of liquid movement in the laboratory. According to one embodiment, the tank damage probability laws are predefined by means of data acquisition campaigns on ships at sea.

According to one embodiment, the method further comprises the step of continuously monitoring successive real states of the tanks during the transfer period and, in response to the detection of a divergence between the successive successive states of the tanks and successive successive states of tanks determined by the transfer scenario, reiterate the process defined above.

According to one embodiment, the method further comprises:

determining a plurality of different transfer scenarios, each transfer scenario defining one or more liquid streams to be transferred between the vessels during a respective transfer period to go from the initial state to the target state,

calculating for each transfer scenario a respective probability of damage to the tanks as a function of successive filling levels of the tanks during the corresponding transfer period, the probability of damage to the tanks defining a probability that at least one tank will be damaged during the progress of said transfer scenario,

selecting a scenario from the plurality of transfer scenarios, and generating the series of instructions for transferring the liquid between the vessels in accordance with the selected transfer scenario if the corresponding probability of damage to the tanks satisfies an acceptance criterion.

According to one embodiment, the method further comprises: determining a plurality of target states, each target state defining final filling levels of the tanks,

determining a plurality of different transfer scenarios, each transfer scenario defining one or more liquid streams to be transferred between the vessels during a respective transfer period to change from the initial state to a target state of the plurality of target states, calculating for each transfer scenario a respective probability of damaging the tanks as a function of successive filling levels of the tanks during the corresponding transfer period, the probability of damaging the tanks defining a probability that at least one tank is damaged during the course of said transfer scenario,

According to one embodiment, one or more scenarios can thus be determined for one, several or each target state.

According to one embodiment, the transfer scenario is selected according to the probability of damage to the tanks, for example to minimize this probability.

According to one embodiment, the scenario is selected according to the acceptance criterion.

The scenario can be selected according to various acceptance criteria. According to one embodiment, the scenario is selected according to the time spent exposed to the risk of damage to the tanks related to the movements of liquid in the tanks. According to another embodiment, the scenario is selected according to the duration of transfer of the scenarios. According to one embodiment, the scenario is selected according to a volume of gas available in the tanks to the end of the transfer scenario for supplying the ship's propulsion means, for example an engine consuming gas.

According to one embodiment, certain parameters such as, for example, the level of liquid movement in the tanks, the movements of the ship and / or the weather are determined in real time, for example by on-board sensors.

According to one embodiment, certain parameters such as, for example, the level of liquid movement in the tanks, the movements of the ship and / or the weather are determined by prediction.

According to one embodiment, the liquid is a liquefied gas, for example liquefied natural gas.

According to one embodiment, the invention also provides a computer-implemented tank filling level management system comprising means for:

provide an initial state defining initial fill levels of the tanks,

determining a target state defining final filling levels of said tanks,

determining a liquid transfer scenario, the transfer scenario defining one or more flows of liquid to be transferred between the tanks during a transfer period to go from the initial state to the target state of the tanks,

calculating a probability of damage to the tanks as a function of successive filling levels of the tanks during the transfer period, the probability of damage to the tanks defining a probability that at least one tank will be damaged at the heart of the progress of the transfer scenario,

generating a series of instructions for transferring the liquid between the tanks in accordance with said transfer scenario if the probability of damage to the tanks satisfies an acceptance criterion. According to one embodiment, the management system further comprises a data acquisition means, for example one or sensors or one or more data acquisition means by an operator. According to one embodiment, the management system further comprises a data display means. According to one embodiment, the means of the management system for performing the steps indicated above are or comprise at least one processor and at least one memory comprising an integrated software module.

Such a method or system for managing the tank filling levels can be installed in a floating structure, coastal or in deep water, in particular a LNG tanker, a floating storage and regasification unit (FSRU), a floating production unit and remote storage (FPSO), barge and others.

According to one embodiment, the invention also provides a vessel for transporting a cold liquid product comprising a double hull, a plurality of tanks and the aforementioned management system.

Brief description of the figures

The invention will be better understood, and other objects, details, characteristics and advantages thereof will appear more clearly in the course of the following description of several particular embodiments of the invention, given solely for illustrative and non-limiting purposes. with reference to the accompanying drawings.

• Figure 1 is a schematic representation in longitudinal section of a vessel having a plurality of tanks in an initial filling state;

FIG. 2 is a diagram illustrating the various steps of the method for managing the filling levels of the tanks making it possible to pass from the initial filling state of FIG. 1 to the target filling state of FIG. 3;

• Figure 3 is a schematic representation in longitudinal section of the vessel of Figure 1 in a target filling state of the tanks; FIG. 4 is a schematic representation of a system for managing vessel filling levels of the vessel of FIG.

1;

Fig. 5 is a plurality of graphs illustrating the liquid transfers over time to move from the initial fill state of Fig. 1 to the target fill state of Fig. 2;

FIG. 6 is a cutaway schematic representation of a vessel of a LNG tanker comprising a system for managing the tank filling levels and a loading / unloading terminal for this tank.

Detailed description of embodiments

The figures are described below in the context of a vessel 1 comprising a double shell forming a supporting structure in which are arranged a plurality of sealed and thermally insulating tanks. Such a carrier structure has for example a polyhedral geometry, for example of prismatic shape.

Such sealed and thermally insulating tanks are provided for example for the transport of liquefied gas. The liquefied gas is stored and transported in such tanks at a low temperature which requires thermally insulating tank walls to maintain the liquefied gas at this temperature. It is therefore particularly important to maintain the integrity of the cell walls on the one hand in order to maintain the tightness of the tank and to prevent leakage of liquefied gas out of the tanks and, on the other hand, to avoid damage to the insulating characteristics. of the tank to maintain the gas in its liquefied form.

Such sealed and thermally insulating tanks also include an insulating barrier anchored on the double hull of the ship and carrying at least one waterproof membrane. By way of example, such vessels may be produced using Mark III® type technologies, as described for example in FR2691520, of type N096® as described for example in FR2877638, or other such as described for example in WO14057221. . Figure 1 illustrates a vessel 1 having four tanks 2 sealed and thermally insulating. On such a vessel 1, the tanks 2 are connected together by a cargo handling system (not shown) which can include many components, for example pumps, valves and pipes so as to allow the transfer of liquid from the tank. one of the tanks 2 to another tank 2.

The four tanks 2 have in Figure 1 an initial filling state. In this initial state, the tanks are partially filled. A first tank 3 is filled to about 60% of its capacity. A second tank 4 is filled to about 35% of its capacity. A third tank 5 is filled to about 35% of its capacity. A fourth tank 6 is filled to about 40% of its capacity.

This partial filling of the tanks 3, 4, 5, 6 can generate significant risks of damage to said tanks 3, 4, 5, 6 when the ship 1 sails at sea. Indeed, when at sea, the ship 1 is subject to many movements related to navigation conditions. These movements of the vessel 1 have repercussions on the liquid contained in the tanks 3, 4, 5, 6 which, consequently, is subject to displacements in the tanks 3, 4, 5, 6. These movements of the liquid in the tanks 3 , 4, 5, 6 generate impacts on the cell walls 3, 4, 5, 6 which can degrade the cell walls 3, 4, 5, 6. However, it is important to maintain the integrity of the cell walls 3 , 4, 5, 6 to maintain the sealing and insulating characteristics of the vessels 3, 4, 5, 6.

To avoid damage to tanks 3, 4, 5, 6, the vessel comprises a filling level management system, an embodiment of which is illustrated in FIG. 4 and whose operating method is illustrated in FIG.

With reference to FIG. 2, the tank filling level management system, hereinafter the management system, firstly needs to know the initial filling state of the tanks 3, 4, 5, 6. this, the initial filling levels of the tanks 3, 4, 5, 6 are supplied to the management system in a first step 7. These initial filling levels can be manually supplied by an operator by means of an interface of acquisition of the management system or obtained automatically by any appropriate means, for example means of tank fill level sensors 3, 4, 5, 6 (see FIG. 4). These filling levels are for example defined as a percentage of liquid height in the tank 3, 4, 5, 6.

The management system determines in a second step 8 a target filling state of the tanks 3, 4, 5, 6. In this target filling state, the liquid transported by the vessel 1 is distributed between the tanks 3, 4, 5, 6 so as to limit the risks associated with the movements of the liquid in the tanks 3, 4, 5, 6. More particularly, the management system determines a target filling state in which all of the liquid transported by the vessel is distributed between the different tanks so as to limit the risks associated with the movements of liquid in the tanks. Typically, the management system determines a target filling state in which the liquid transported by the vessel is distributed between the tanks 3, 4, 5, 6 so that the tanks are filled to more than 70% or on the contrary to less than 10%.

FIG. 3 illustrates the vessel of FIG. 1 in such a targeted filling state of the tanks 3, 4, 5, 6 making it possible to limit the risks associated with the movements of liquid in said tanks 3, 4, 5, 6. 3, the first tank 3 is filled to 95%, the second tank 4 and the third tank 5 are filled to 5% and the fourth tank 6 is filled to 95%.

The space not occupied by the liquid contained in the tanks 3, 6 is reduced. This reduced residual space limits the movements of said liquid in said tanks 3, 6 and therefore the force of the impacts related to said movements of said liquid. Thus, the first tank 3 and the fourth tank 6 have a risk of degradation due to limited liquid movements.

Conversely, the second tank 4 and the third tank 5 have a risk of degradation due to limited liquid movements because the liquid contained in said second and third tanks 4, 6 is of insufficient weight to generate significant impacts on the walls of said tank 4, 5.

The management system then calculates (step 9) a plurality of transfer scenarios for changing from the initial filling state to the target filling state. These transfer scenarios are calculated from the initial fill levels in tanks 3, 4, 5, 6 and vessel characteristics 1. In particular, the characteristics of the ship 1 taken into account for the calculation of the transfer scenarios include at least one of the parameters among the number of pumps in the tanks 3, 4, 5, 6, the pumping capacities of the pumps, the volume of the tanks 3, 4, 5, 6, the diameters of the pipes connecting the tanks 3, 4, 5, 6 between them. The management system calculates from this data all the possibilities of tank-to-tank transfer, which gives a list of tank-to-tank transfer scenarios to reach the target filling levels from the initial filling levels.

Each transfer scenario defines a plurality of transfer phases between the tanks 3, 4, 5, 6. More particularly, each transfer phase defines, for each tank 3, 4, 5, 6 and as a function of the liquid transfer capacities. between the various tanks 3, 4, 5, 6, one or more liquid streams to be transferred between the tanks 3, 4, 5, 6. The management system defines for each transfer phase a phase start filling level, an end-of-phase fill level as well as a transfer time required to pass from the phase-in fill level to the end-of-phase fill level. These successive transfer phases make it possible to go from the initial filling state to the target filling state.

However, these transfer phases require transferring a large quantity of liquid between the tanks 3, 4, 5, 6. However, such a transfer may require a significant period during which the tanks 3, 4, 5, 6 may remain subject to significant risks related to fluid movements. Consequently, after calculating the different scenarios in step 9, the management system calculates (step 10) for each scenario the risks of degradation of the tanks 3, 4, 5, 6 during the course of said transfer scenario.

In other words, for each transfer scenario, the management system also calculates a probability of damage to the tanks 3, 4, 5, 6 during said transfer scenario.

This probability of damage to the tanks 3, 4, 5, 6 is calculated according to many parameters. Several quantities must be estimated by statistical or physical calculation, by real-time measurements, on board or in tests to calculate these probabilities of damage to tanks 3, 4, 5, 6.

The parameters that can be taken into account for the calculation of damage to tanks 3, 4, 5, 6 may include vessel movement parameters 1, environmental conditions of vessel 1, structural parameters of ship 1, or parameters related to the liquid contained in the tanks 3, 4, 5, 6.

The vessel's movement parameters are, for example, parameters of the ship's movements according to the ship's six degrees of freedom (caving, lurching, heave, rolling, pitching, yawing) which can be represented in the form of movement, speed, temporal or spectral acceleration. These vessel movement parameters may also include the ship's route in terms of heading, speed and GPS position.

The parameters of environmental conditions are mainly related to the weather. These parameters of environmental conditions include for example the height of the sea of the wind, the height of the swell, the period of the sea of the wind, the period of the swell, the direction of the sea of the wind, the direction of the swell, the wind force, the wind direction, the force of the current, the direction of the current, the relative direction of the wind, the swell, the current, the sea of the wind relative to the ship.

The structural parameters of the vessel 1 comprise for example the resistance of the walls of the tanks 3, 4, 5, 6 as a function of the position on the tank, the resistance of the insulation system of the tanks 3, 4, 5, 6 as a function of the position on the tank or the statistical behavior of the impacts of the movements of liquid.

The parameters related to the liquid contained in the tanks 3, 4, 5, 6 are, for example, the levels (force, pressure, amplitude, frequency, surface) of the liquid impacts on the walls of the tanks 3, 4, 5, 6 , the time spent in different filling levels of the tanks 3, 4, 5, 6, the liquid gas evaporation level induced by the transfer of liquid, the loading state of the ship structure 1.

Thus, the management system calculates for each scenario the total time of the operation to go from the initial filling state to the final filling state and the risk of damage to the cell walls 3, 4, 5, 6 during said surgery. This risk of damage to the insulation is calculated according to the following function:

in which tk_n represents the number of the tank n,

surf is the internal surface impacted by the liquid, and

The SC navigation conditions may also depend on at least one of:

the angle of incidence between the sea state and the ship

the period of the sea state

the significant height of the sea state

the movements of the ship

the speed of advance of the ship.

It should be noted that a sea state can be decomposed in sea of wind and swell, even crossed swell. Thus a sea state can be defined with several components.

The laws Prob _tk are statistical laws for example of type GEV, Weibull, Pareto, Gumbel. One, several or all of the parameters of these laws are for example defined from tests of liquid movement in laboratory or measurement campaigns on board the sea.

The management system thus provides a list of transfer scenarios (step 1 1) and various information related to said calculated transfer scenarios. In addition, the scenarios are preferably classified according to the acceptance criterion, for example from the most risky scenario to the least risky scenario in terms of damage to the tanks 3, 4, 5, 6.

A scenario is then selected (step 12) according to the acceptance criterion.

Preferably, each scenario is provided in the form of a set of control signals and / or instructions for implementing the different transfer phases of said transfer scenario. For example, the scenario may include a series of instructions provided in a human-readable format that can accurately guide an operator throughout the transfer period to execute the transfer scenario.

According to one embodiment, the scenario may be provided in the form of a series of instructions in a computer-readable format and / or a series of control signals for controlling the members of the handling system of the computer. cargo, for example operating the ship's pumps, switching the valves etc., to execute the transfer scenario.

The acceptance criterion can take many forms. This acceptance criterion can be predefined or chosen by the operator. For example, this acceptance criterion may be, whether predefined or chosen by the operator, the risk of damage to the tanks 3, 4, 5, 6, the available navigation autonomy after the transfers, the time total flow of the transfer scenario or other.

The selected transfer scenario meeting the acceptance criterion is then implemented (step 13) to go from the initial filling state to the target filling state.

As indicated above, the different quantities corresponding to the parameters necessary for the scenario calculations (step 9) and the probability of damage calculations (step 10) can be obtained or estimated by statistical or physical calculation, by real-time measurements, on board or in tests.

FIG. 4 illustrates an exemplary management system structure 14. This management system 14 comprises a central unit 15. This central unit 15 is configured to perform the various transfer scenario and payload scenario calculations. probabilities of damage to tanks 3, 4, 5, 6 (steps 9 and 10). This central unit 15 is connected to a plurality of on-board sensors 16 making it possible to obtain the various quantities indicated above. Thus, the sensors 16 comprise, for example and in a non-exhaustive manner, a flow sensor of the pumps 17, a level sensor of each tank 18, different sensors 19 (accelerometer, strain gauge, strain gauge, sound, light) allowing the central unit 15 via a dedicated algorithm to detect the impacts related to the movements of the liquid in the tanks 3, 4, 5, 6, etc.

The management system 14 further comprises a man-machine interface 20. This man-machine interface 20 comprises a display means 21. This display means 21 allows the operator to obtain the various information items. This information is for example information on the different transfer scenarios, the instructions for implementing said transfer scenarios, the quantities obtained by the sensors 16 such as the intensity of the liquid movements in the tanks, information on the impacts. related to these movements of the liquid, the movements of the ship, the state of loading of the ship or even meteorological information.

The human-machine interface 24 furthermore comprises an acquisition means 22 enabling the operator to manually supply quantities to the central unit 15, typically to supply the central unit 15 with data that can not be obtained by sensors because the vessel does not have the required sensor or the sensor is damaged. For example, in one embodiment, the acquisition means allows the operator to enter information on the number of pumps and the maximum height of the waves.

The management system 14 includes a database 23. This database 23 comprises for example certain quantities obtained in the laboratory or during measurement campaigns on board at sea.

The management system 14 also includes a communication interface 24 allowing the central unit 15 to communicate with remote devices for example to obtain meteorological data, position data of the ship or other. Figure 5 shows graphs illustrating the filling levels of the tanks 3, 4, 5, 6 over time. Thus, a first graph 25 illustrates the level of filling 26 of the first tank 3 over time. A second graph 27 illustrates the filling level 28 of the second tank 4 over time. A third graph 29 illustrates the level of filling 30 of the third tank 5 over time. A fourth graph 31 illustrates the filling level 32 of the fourth tank 6 over time.

During a first phase 33 of the selected transfer scenario, the valves of the vessel 1 are configured to connect the first tank 3 and the second tank 4 and to connect the third tank 5 and the fourth tank 6. In addition, the pumps of the tanks 3, 4, 5, 6 are configured to transfer the liquid contained in the second tank 4 to the first tank 3 and to transfer the liquid contained in the third tank 5 to the fourth tank 6.

The first graph 25 and the second graph 27 show that the first tank 3 receives liquid from the second tank 4 during this first phase 33 of the transfer scenario. Thus, the first graph 25 illustrates that the fill level 26 of the first tank 3 changes from an initial fill level of 60% to a target filling level of 95% during the first phase 33. Similarly, Second graph 27 illustrates that the second tank 4 is emptied so as to go from an initial fill level of 35% to a first phase end fill level of 20%.

During this first phase 33, the liquid contained in the third tank 5 is transferred to the fourth tank 6. Thus, the filling level 30 of the third tank 5 changes from an initial filling level of 35% to a filling level. end of the first phase of 20% and the filling level 32 of the fourth tank 6 goes from 40% to a filling level of end of first phase 60%.

During a second phase 34 of the transfer scenario, the valves of the vessel 1 are switched to connect the second tank 4 to the fourth tank 6. This switching of the valves requires many handling maneuvers and therefore requires a certain time. During these maneuvers of handling, the liquid contained in the third tank 5 continues to be transferred to the fourth tank 6, the third tank 5 having a second phase end filling level of 10% and the fourth tank 6 having a final filling level second phase of 70%.

Since the pipes connected to the fourth tank 6 and the pumps of the fourth tank 6 do not make it possible to absorb a flow of liquid coming simultaneously from the third tank 5 and from the second tank 4, only the second tank 4 connected to the fourth tank 6 is emptied to continue filling the fourth tank 6 in a third phase of the transfer scenario.

Indeed, at the beginning of the third phase 35, corresponding to the end of the handling maneuvers to connect the second tank 4 to the fourth tank 6, the second tank 4 is still filled with 20% while the third tank 5 is no longer present. than a fill level of 10%. It is therefore preferable to empty first of all the second tank 4, the filling level of which presents a higher risk than that of the third tank 5. Thus, during the third phase 35 of the transfer scenario, only the liquid contained in the second Vat 4 is transferred to the fourth vat 6. The second vat 4 thus has a third phase start fill level of 20% and an end of third phase fill level of about 5%.

When the second tank is substantially empty, the pipes and pumps of the vessel are switched to transfer the liquid contained in the third tank 5 to the fourth tank 6. Thus, in a fourth phase 36 of the transfer scenario, the liquid still transferred in the third tank 5 is transferred to the fourth tank 6 so that the final filling level of the third tank 5 is of the order of 5% and the target filling level of the fourth tank 6 is of the order of 95%.

The commutations of the valves and the activation of the pumps allowing the transfers between the tanks can be manual and / or automated. In the case of manual operations, the man-machine interface 20 provides the operator with a series of instructions for implementing the transfer scenario. The management system 14 takes into account in its calculations (steps 9 and 10) a duration corresponding to these operations. Preferably, the management system 14 checks in real time the progress of the selected scenario (step 37 figure 2). In case of discrepancy between the actual state of the fills levels 26, 28, 30, 32 provided for the selected scenario and the actual fill levels, real-time or anticipated warnings are sent to the user to warn him of these divergences (step 38, FIG. 2). Such warnings may also be sent to the operator if the weather conditions, the movements of liquid in the tanks, the movements of the ship or the like change in a different way so that they could cause differences in the evolution of the scenario. transfer.

If a discrepancy is found between the selected transfer scenario and the actual state over time of tanks 3, 4, 5, 6, for example because the actual pumping rate of some pumps was overestimated when calculating scenarios transfer (step 9), the management system 14 can restart the calculation method illustrated in Figure 2 in order to apply or propose to the operator new transfer scenarios. Preferably, this new calculation of the scenarios is carried out by taking into account the relevant data recorded which led to this divergence, for example the actual actual flow rate of the pumps. In addition, in one embodiment, this new calculation of the scenarios is performed by directly selecting the same target filling state as the target filling state determined during the first iteration of said calculation. In other words, the calculation illustrated in FIG. 2 is repeated directly from the scenario calculation step.

The technique described above for managing the filling levels of the tanks can be used in different types of tanks, for example for an LNG tank in a floating structure such as a LNG tank or other.

Referring to Figure 6, a cutaway view of a LNG tank 70 shows a sealed and insulated tank 71 of generally prismatic shape mounted in the double hull 72 of the ship. The wall of the tank 71 comprises a primary sealed barrier intended to be in contact with the LNG contained in the tank, a secondary sealed barrier arranged between the primary waterproof barrier and the double hull 72 of the ship, and two insulating barriers arranged respectively between the primary watertight barrier and the secondary watertight barrier and between the secondary watertight barrier and the double hull 72. In a manner known per se, loading / unloading lines 73 arranged on the upper deck of the ship can be connected, by means of appropriate connectors, to a marine or port terminal to transfer a cargo of LNG from or to the tank 71.

FIG. 6 represents an example of a marine terminal comprising a loading and unloading station 75, an underwater pipe 76 and an onshore installation 77. The loading and unloading station 75 is a fixed off-shore installation comprising an arm mobile 74 and a tower 78 which supports the movable arm 74. The movable arm 74 carries a bundle of insulated flexible pipes 79 that can connect to the loading / unloading pipes 73. The movable arm 74 can be adapted to all gauges of LNG carriers . A connection pipe (not shown) extends inside the tower 78. The loading and unloading station 75 enables the loading and unloading of the LNG tank 70 from or to the shore facility 77. liquefied gas storage tanks 80 and connecting lines 81 connected by the underwater line 76 to the loading or unloading station 75. The underwater line 76 allows the transfer of the liquefied gas between the loading or unloading station 75 and the onshore installation 77 over a large distance, for example 5 km, which makes it possible to keep the tanker vessel 70 at great distance from the coast during the loading and unloading operations.

In order to generate the pressure necessary for the transfer of the liquefied gas, pumps on board the ship 70 and / or pumps equipping the shore installation 77 and / or pumps equipping the loading and unloading station 75 are used.

Although the invention has been described in connection with several particular embodiments, it is obvious that it is not limited thereto and that it comprises all the technical equivalents of the means described and their combinations if they are within the scope of the invention.

Some of the elements, including the components of the management system, can be realized in different forms, unitarily or distributed, by means of hardware and / or software components. Usable hardware components are ASIC specific integrated circuits, FPGA programmable logic networks or microprocessors. Software components can be written in different programming languages, for example C, C ++, Java or VHDL. This list is not exhaustive.

The use of the verb "to include", "to understand" or "to include" and its conjugated forms does not exclude the presence of other elements or steps other than those set out in a claim. The use of the indefinite article "a" or "an" for an element or a step does not exclude, unless otherwise stated, the presence of a plurality of such elements or steps. In particular, the use of the undefined article "a" concerning the step of determining a target state defining the final filling levels of the tanks does not exclude determining several target states each defining the final filling levels of the tanks.

In the claims, any reference sign in parentheses can not be interpreted as a limitation of the claim.

Claims

A management method for managing the filling levels of a plurality of vessels (2, 3, 4, 5, 6) arranged in a vessel (1), said vessels (2, 3, 4, 5, 6) being connected so as to allow a transfer of liquid between said tanks (2, 3, 4, 5, 6), the method comprising

- providing an initial state (7) defining initial filling levels of the tanks (2, 3, 4, 5, 6),

determining a target state (8) defining final filling levels of said tanks (2, 3, 4, 5, 6),

determining a liquid transfer scenario (9), the transfer scenario defining one or more flows of liquid to be transferred between the tanks (2, 3, 4, 5, 6) during a transfer period to pass from the initial state in the target state of the tanks,

calculating a probability of damage to the tanks (10) as a function of successive filling levels of the tanks during the transfer period, the probability of damage to the tanks defining a probability that at least one tank will be damaged during the course of the transfer scenario,

generating a series of instructions for transferring the liquid between the tanks (2, 3, 4, 5, 6) in accordance with said transfer scenario if the probability of damaging the tanks satisfies an acceptance criterion.

2. Management method according to claim 1, further comprising, if the probability of damage to the tanks meets the acceptance criterion, transfer (13) the liquid between the tanks (2, 3, 4, 5, 6) in conformance with said transfer scenario.

3. Management method according to one of claims 1 to 2, further comprising providing a transfer capacity parameter defining a transfer capacity between the tanks, the transfer scenario being determined according to said transfer capacity parameter between the tanks.

4. Management method according to one of claims 1 to 3, further comprising a step of providing at least one environmental parameter defining the environmental data of the vessel, the calculation of the probability of damage to the tanks being made according to said at least one an environmental parameter.

5. Management method according to one of claims 1 to 4, wherein the calculation of the probability of damage to the tanks is made according to at least one parameter selected from the group of parameters comprising the movements of the vessel, the levels liquid impacts on the walls of the tank, the statistical behavior of the impacts of liquid movements, the resistance of the tanks as a function of the position in said tanks, the time spent in different filling levels, the rate of evaporation of gas induced by the transfer of liquid, the state of loading of the ship structure.

6. Management method according to one of claims 1 to 5, further comprising the step of determining a parameter in real time and take into account said parameter to determine the transfer scenario.

7. Management method according to one of claims 1 to 6, further comprising the step of determining a parameter in real time and take into account said parameter to determine the calculation of probability of damage to the tanks.

8. Management method according to one of claims 1 to 7, wherein the acceptance criterion is a criterion of risk of damage to the tanks during the transfer scenario.

9. Management method according to one of claims 1 to 8, wherein the calculation of the probability of damage to the tanks is carried out according to the formula:

in which tk_n represents the number of the tank n, SC represents the conditions of navigation as a function of the filling level fl_n of the tank tk_n,

surf is the internal surface impacted by the liquid, and

The management method according to claim 9, wherein the probability density Prob _tk-n (Pres _Surf > Res _Surf , tk_n, SC (fl_n)) is predefined.

The method of management according to one of claims 1 to 10, wherein the method further comprises the step of controlling (37) continuously successive real states of the tanks during the transfer period and, in response in detecting a divergence between the successive successive states of the tanks and successive predicted states of tanks determined by the transfer scenario, reiterating the method of claim 1.

12. Management method according to one of claims 1 to 1 1, further comprising:

selecting (12) a scenario from the plurality of transfer scenarios, and generating the series of instructions for transferring the liquid between the tanks (2, 3, 4, 5, 6) in accordance with the selected transfer scenario if the corresponding probability of damage to the tanks satisfies an acceptance criterion.

13. Management method according to one of claims 1 to 12, further comprising:

Determining a plurality of target states (8), each target state defining final filling levels of the tanks,

selecting (12) a scenario from the plurality of transfer scenarios, and

generating the series of instructions for transferring the liquid between the tanks (2, 3, 4, 5, 6) in accordance with the selected transfer scenario if the corresponding probability of damage to the tanks satisfies an acceptance criterion.

14. Management method according to claim 12 or 13, wherein the scenario is selected according to the acceptance criterion.

15. Computer-implemented management system with means for:

providing an initial state (7) defining initial fill levels of the tanks (2, 3, 4, 5, 6), determining a target state (8) defining final fill levels of said tanks (2, 3, 4, 5, 6),

determining a liquid transfer scenario (9), the transfer scenario defining one or more streams of liquid to be transferred between the tanks (2, 3, 4, 5, 6) during a transfer period to pass from the initial state in the target state of the tanks,

calculate a probability of damage to the tanks (10) as a function of successive filling levels of the tanks during the transfer period, the probability of damage to the tanks defining a probability that at least one tank is damaged at the heart of the scenario unfolding transfer,

generating a series of instructions for transferring the liquid between the tanks (2, 3, 4, 5, 6) in accordance with said transfer scenario if the probability of damage to the tanks satisfies an acceptance criterion.