# Patent

## Title
Method and device for filling a tank with liquefied gas

## Abstract

A method for filling a tank (1) with liquefied gas, in particular a tank with cryogenic liquid, from a liquefied gas container (2), in particular a cryogenic liquid container (2), which container (2) is in fluid communication with the tank (1) via a filling pipe (3), wherein the method uses a pressure differential generation member (4) for transferring liquid from the container (2) to the tank (1) at a predetermined pressure, characterized in that, at or following the switching on time (M) of the pressure differential generation member (4), the method comprises a step of determining the pressure (PT4) in the tank (1) via a measurement of a first pressure in the filling pipe (3), and, following the determination of the pressure (PT4) in the tank, a step of limiting the first instantaneous pressure (PT3) to a level below a maximum pressure threshold (PT3sup), said maximum pressure threshold being defined on the basis of the determined value of the pressure (PT4) in the tank (1) and exceeding said determined value of the pressure (PT4) in the tank by two to twenty bars and preferably by two to nine bars.

## Background
CROSS REFERENCE TO RELATED APPLICATIONS
This application is a 371 of International PCT Application PCT/FR2013/052415 filed Oct. 10, 2013 which claims priority to French Patent Application No. 1261154 filed Nov. 23, 2012, the entire contents of which are incorporated herein by reference.
BACKGROUND
The present invention relates to a filling method and device.
The invention relates more particularly to a method for filling a liquefied gas tank, notably a cryogenic liquid tank, from a liquefied gas reservoir, notably a cryogenic liquid reservoir, the reservoir being fluidically connected to the tank via a filling pipe, the method using a pressure differential generating member for transferring liquid from the reservoir to the tank at a determined pressure, the pressure differential generating member being switchable between an on state and an off state, the filling pipe comprising a liquid flow regulating member positioned downstream of the pressure differential generating member, the flow regulating member being movable between a no-flow position in which the flow of liquid is interrupted and at least one flow position in which the flow of liquid is transferred to the tank at a determined flow rate, the method comprising a measurement of a first instantaneous pressure in the filling pipe downstream of the flow regulating member.
More generally, the invention may be applied to the filling of any cryogenic container (mobile or otherwise) from any other cryogenic container (mobile or otherwise).
The increasing demand from users for higher-pressure cryogenic liquid stores or reservoirs has led to the systems that fill these reservoirs being equipped with high-pressure pumps, which means to say pumps operating at pressures of between 24 bar and 40 bar. These same filling systems equipped with high-pressure pumps are called upon to fill low-pressure stores rated for pressures of 2 to 15 bar.
It is therefore necessary to fit the receiving reservoir and/or the filling device with a safety system that prevents the tank from being overfilled or overpressurized which would cause this tank to burst. Because the number of tanks to be filled is markedly higher than the number of filling devices, the safety system preferably applies to the filling devices.
There are various safety systems in existence for avoiding such a phenomenon.
Thus, one known solution is to equip the filling port of the tank with a pneumatic valve which closes when the pressure in the tank reaches a determined threshold. This solution does, however, have disadvantages which include the need to plan maintenance for this pneumatic valve and a high cost of installing it on all the tanks that require protection.
Another known solution is to provide a calibrated orifice at the tank filling port in order to keep the filling flow rate within safe ranges, typically to a flow rate that the existing safety members of the store can discharge. This solution is also installed on the tanks and penalizes filling time.
Another solution uses a rupture disk or a safety valve on the tank. This type of equipment has to be rated with care. However, this rating may be incompatible with the internal pipes of the tank. In addition, if activated, expelled liquid has to be dealt with in an area that presents no risk to the operators. Finally, rupture disks may be subject to corrosion or mechanical fatigue requiring them to be replaced by a qualified technician.
Another solution is to provide an electric overpressure detection system on the tank (if appropriate via a thermistor at the overflow gauge valve), which, in response, stops the filling pump. However, this solution requires special connectors between each tank and each filling device and, where appropriate, relies on action on the part of the operator.
Another solution (cf. for example WO2005008121A1) consists in measuring the pressure at the tank via a safety hose provided for this purpose so as to stop the pump if a problem occurs. However, this solution requires an additional hose connection and suitable circuitry on the tank.
Another solution detects any potential overconsumption of the pump and if appropriate switches it off. However, this solution can be applied only to variable-speed electric pumps and unwanted stoppages may be generated.
Another solution is to provide specific fluidic connections between filling devices and the tanks according to determined pressure ranges. This solution imposes obvious constraints in terms of logistics in particular.
The document U.S. Pat. No. 6,212,719 describes a system for automatically stopping a filling pump if the supply hose ruptures using two pressure sensors arranged at the two ends of the transfer hose. Detection of a fall in pressure triggers the stopping of the pump.
SUMMARY
One object of the present invention is to alleviate all or some of the abovementioned disadvantages of the prior art.
This object is achieved in accordance with claim 1. As an alternative, the method according to the invention, in other respects conforming to the generic definition thereof given in the above preamble, may essentially be characterized in that, at the time or after the switching on of the pressure differential generating member, the method comprises a step of determining the pressure in the tank by measuring a first pressure at the filling pipe, the method comprising, after determining the pressure in the tank, a step of limiting the first instantaneous pressure to below a maximum pressure threshold, the maximum pressure threshold being defined as a function of the determined value of the pressure in the tank and exceeding the determined value of the pressure in the tank by two to twenty bar and preferably by two to nine bar.
Moreover, some embodiments of the invention may comprise one or more of the following features:

    
    
        the step of limiting the first instantaneous pressure to below a maximum pressure threshold is performed while the flow regulating member is in the flow position,
        when the determined value for the pressure in the tank is less than or equal to a first determined level of between three and five bar, the maximum pressure threshold is a predetermined set pressure value of between 5 and 9 bar and preferably equal comprised between 5.2 and 8 bar,
        the step of limiting the first instantaneous pressure (PT3) to below a maximum pressure threshold (PT3sup) comprises at least one of the following: manual or automatic regulation of the flow rate of transferred fluid using the flow regulating member, manual or automatic regulation of the pressure differential generated by the pressure differential generating member,
        the step of limiting the first instantaneous pressure (PT3) to below the maximum pressure threshold (PT3sup) is performed during a finite determined limiting duration and when the first instantaneous pressure (PT3) remains higher than the maximum pressure threshold (PT3sup) at the end of the determined limiting duration, filling is automatically interrupted,
        during the step of determining the pressure (PT4) in the tank, this pressure (PT4) in the tank is equal to the first pressure value (PT3) measured at the filling pipe (3) (PT3=PT4), possibly corrected using a predetermined correcting coefficient,
        during the step of limiting the first instantaneous pressure (PT3), the method comprises a measurement of the quantity of fluid transferred from the reservoir to the tank and when this transferred quantity of fluid exceeds a threshold quantity before the end of the determined limiting duration, said limiting duration initially set is reduced,
        the switching on of the pressure differential generating member is preceded by a check on the stability of the first instantaneous pressure in the filling pipe, the check on the stability of the pressure being positive if at least one of the following conditions is satisfied:
        
            (i) the first instantaneous pressure (PT3) in the pipe is above a predetermined pressure of between preferably 15 and 25 bar,
            (ii) the variation in the first instantaneous pressure (PT3) during at least a determined interval of time is below a determined level of variation corresponding to a variation of between 0.005 and 0.020 bar per second, and preferably 0.01 bar per second,
        
        
    
    


the switching on of the pressure differential generating member (4) can be performed only after a positive check on the stability of the first instantaneous pressure (PT3),

    
    
        after the pressure differential generating member has been switched on and the flow regulating member has been moved from its no-flow position into a flow position, if a drop in the first instantaneous pressure (PT3) in the filling pipe at a rate of at least one bar per second is detected, the pressure differential generating member is automatically switched off,
        the method comprises a switching on of the pressure differential generating member, the operation of the pressure differential generating member being interrupted (AR) automatically in response to at least one of the following situations:
        
            the variation in the first instantaneous pressure (PT3) in the filling pipe during a determined time (T) before a flow of liquid is actually transferred to the tank is greater than a determined variation (V) (ΔPT3>V),
            a determined variation in flow rate (Q) and/or a determined variation in the first instantaneous pressure (PT3) in the pipe downstream of the pressure differential generating member is detected while the pressure differential generating member is not in the switched-on state,
            after a determined time following the switching on of the pressure differential generating member (4), the variation in the first instantaneous pressure (PT3) in the pipe remains below a determined level,
            after a determined time following the switching on of the pressure differential generating member, a determined quantity of fluid has been transferred to the tank, and the first instantaneous pressure (PT3) in the pipe remains above the maximum pressure threshold (PT3sup),
            the differential (PT2−PT3) between, on the one hand, a second instantaneous pressure (PT2) measured at the outlet of the pressure differential generating member, upstream of the flow regulating member, and, on the other hand, the first instantaneous pressure (PT3) measured in the pipe downstream of the flow regulating member (12) is less than a minimum differential preferably between 0.5 bar and 2 bar,
        
        
    
    


the flow of fluid from the reservoir to the tank remains below a determined level,

    
    
        after the step of limiting the first instantaneous pressure (PT3) to below the maximum pressure threshold (PT3sup), and during the course of the transfer of liquid to the tank, the method comprises a comparison of the first instantaneous pressure (PT3) in the filling pipe or of a mean (mPT3) of this first instantaneous pressure against a determined high threshold (Pmax) and, when the first instantaneous pressure (PT3) in the filling pipe or, as the case may be, the mean of the first instantaneous pressure (PT3) exceeds the high threshold (Pmax), a step of interrupting (AR) the filling (R), the high threshold (Pmax) being defined as the sum of, on the one hand, a first instantaneous pressure value (PT3ref) referred to as the reference value measured in the filling pipe (3) at the end of the limiting step or, as the case may be, of a mean of several measured values of the first reference instantaneous pressure (mPT3ref) measured in the filling pipe at the end of the limiting step (referred to as the “reference mean mPT3ref”) and, on the other hand, a determined pressure jump (Po) of between 0.2 and 2 bar: (Pmax=PT3ref+Po, or, as the case may be, Pmax=mPT3ref+Po),
        the value of the pressure jump (Po) is a function of the value of the first reference instantaneous pressure (PT3ref) or, as the case may be, of the reference mean mPT3ref, and when the first reference instantaneous pressure (PT3ref) or, as the case may be, the reference mean mPT3ref is below or equal to a value of between 6 and 9 bar, the pressure jump is between 0.1 and 0.9 bar and preferably between 0.3 and 0.7 bar,
        the first reference instantaneous pressure (PT3ref) or, as the case may be, the reference mean mPT3ref, is higher than a determined value of between 6 and 9 bar and lower than a determined value of between 15 and 25 bar and preferably between 18 and 22 bar, the pressure jump being between 0.8 and 1.4 bar and preferably between 0.9 and 1.2 bar,
        when the first reference instantaneous pressure (PT3ref) or, as the case may be, the reference mean (mPT3ref) is higher than a determined value of between 15 and 25 bar and preferably between 18 and 22 bar, the pressure jump is between 1.2 and 3 bar and preferably between 1.2 and 2 bar,
        during filling and after the first reference pressure (PT3ref) or a mean reference (mPT3) has been determined, the first instantaneous pressure (PT3) in the pipe (3) is measured regularly and, if the first instantaneous pressure (PT3) measured in the pipe (3) or, as the case may be, the mean (mPT3) thereof drops below the first reference instantaneous pressure (PT3ref) or, as the case may be, the reference mean (mPT3) previously adopted, a new reference instantaneous pressure (PT3refb) or, as the case may be, a new reference mean (mPT3refb) is adopted and used to define a new high threshold (Pmax=PT3refb+Po), or, as the case may be, Pmax=mPT3refb+Po,
        the determined limiting step duration may be between fifteen and two hundred and forty seconds or between fifteen and one hundred and eighty seconds or between fifteen and sixty seconds or between thirty and one hundred and eighty seconds and for example equal to ninety seconds,
        during the step of determining the pressure (PT4) in the tank, this pressure (PT4) in the tank is equal to the first pressure value (PT3) measured in the tank, corrected using a predetermined correcting coefficient comprising a dimensionless multiplicative corrective coefficient K of for example between 0.8 and 1.2 (PT4=KPT3) and/or an additive corrective coefficient C in bar of, for example, between −2 bar and +2 bar (PT4=PT3+C),
        during the step of determining the pressure (PT4) in the tank, this pressure (PT4) in the tank is equal to the first pressure value (PT3) measured at the filling pipe (PT3=PT4), or this pressure (PT4) in the tank is equal to the value of the first pressure (PT3) measured in the tank, corrected using a predetermined correcting coefficient, for example a dimensionless multiplicative corrective coefficient K of for example between 0.8 and 1.2 (PT4=KPT3) or an additive corrective coefficient C in bar of, for example, between −2 bar and +2 bar (PT4=PT3+C),
        the pressure (PT4) in the tank is determined while the flow regulating member is in the no-flow position or in the flow position,
        the step of determining the pressure (P4) in the tank is performed only by measuring the first pressure (PT3) using a first pressure sensor in the filling pipe communicating with the inside of the tank,
        when the pressure (PT4) determined in the tank is situated between the first level and a second level, the second level exceeding the first level by one to three bar, and preferably being four bar, the maximum pressure threshold (PT3sup) in bar is given by the following formula:

PT3sup=z.PT4+PA

where z is a unitless set predetermined coefficient of between 1.5 and 3 and preferably of two, and where PA is a set increase in pressure in bar of between zero and two bar and preferably of zero,

        when the pressure (PT4) determined in the tank is situated between the second level and a third level, the third level exceeding the second level by four to ten bar, and preferably being 8 bar, the maximum pressure threshold (PT3sup) in bar is given by the following formula:

PT3sup=z.PT4+PA

where z is a unitless set predetermined coefficient of between 0.80 and 1 and preferably of 0.98, and where PA is a set increase in pressure in bar of between two and four bar and preferably of four bar,

        when the pressure (PT4) determined in the tank is situated between the third level and a fourth level, the fourth level exceeding the third level by eight to fifteen bar, and preferably being between 18 and 20 bar, the maximum pressure threshold (PT3sup) in bar is given by the following formula:

PT3sup=z.PT4+PA

where z is a unitless set predetermined coefficient of between 1.00 and 1.50 and preferably of 1.20, and where PA is a set increase in pressure in bar of between one and four bar and preferably of 2.5 bar,

        when the pressure (PT4) determined in the tank is higher than the fourth level and the variation in the first pressure (PT3) is less than a determined level of variation of between 0.005 and 0.020 bar per second, the maximum pressure threshold (PT3sup) in bar is given by the following formula:

PT3sup=z.PT4+PA

where z is a unitless set predetermined coefficient of between 0.50 and 1.00 and preferably of 0.80, and where PA is a set increase in pressure in bar of between seven and 12 bar and preferably of between 8 and 10 bar,

        when the pressure (PT4) determined in the tank is higher than the fourth level and the variation in the first pressure (PT3) is greater than a determined level of variation of between 0.005 and 0.020 bar per second, the maximum pressure threshold (PT3sup) in bar is a determined set value of between 30 and 50 bar and preferably of between 32 and 40 bar,
        the method comprises a pre-check on the transfer of liquid from the reservoir to the tank via the filling pipe for a determined transfer precheck duration (TQ), and when the transfer of liquid to the tank does not reach a determined threshold (S) during the determined transfer precheck duration (TQ), the filling is interrupted and the value of the first pressure measured in the filling pipe during the step of determining the pressure (PT4) in the tank is not adopted for determining the maximum pressure threshold (PT3sup),
        the method comprises a switching on of the pressure differential generating member and a step of regulating the liquid flow rate downstream of the pressure differential generating member via at least one variable-opening valve placed on the filling pipe, upon the switching on of the pressure differential generating member, at least some of the liquid delivered by the pressure differential generating member being first of all returned at least predominantly to the reservoir via a return pipe then progressively delivered predominantly to the tank, and when the transfer of liquid to the tank does not reach a determined threshold during the determined transfer precheck duration (TQ), the method comprises a step of stopping (AR) the operation of the pressure differential generating member,
        the determining of a transfer of liquid to the tank comprises a measurement of the instantaneous liquid flow rate (Q) in the filling pipe downstream of the pressure differential generating member and upstream of the tank, a step of comparing this instantaneous liquid flow rate (Q) against a determined minimum flow rate threshold (Qmin) and, when the measured instantaneous liquid flow rate (Q) does not reach the minimum flow rate threshold (Qmin) during the determined flow rate precheck duration (TQ), a step of interrupting (AR) the operation of the pressure differential generating member (4),
        the determined minimum flow rate threshold (Qmin) is between one and fifty liters per minute and preferably between two and ten liters per minute or, more preferably still, between three and eight liters per minute,
        the determining of a transfer of liquid to the tank comprises at least one measurement of the first instantaneous pressure (PT3) in the filling pipe downstream of the pressure differential generating member and upstream of the tank, a step of comparing this first instantaneous pressure (PT3) with a reference level (PT5) and, when this measurement of the first instantaneous pressure (PT3) in the filling pipe does not reach the reference level (PT5) during the determined flow rate precheck duration (TQ), a step of interrupting (AR) the operation of the pressure differential generating member,
        the determination of a transfer of liquid to the tank comprises at least one measurement of an instantaneous pressure differential (PT3−PT5) between, on the one hand, the first pressure (PT3) and, on the other hand, the return pipe, a step of comparing this instantaneous pressure differential (PT3−PT5) with a reference differential and, when this instantaneous pressure differential (PT3−PT5) does not reach the reference differential during the determined flow rate precheck duration (TQ), a step of stopping (AR) the operation of the pressure differential generating member,
        the determined flow rate precheck duration is between twenty and two hundred and forty seconds and preferably between thirty and a hundred and twenty seconds,
        after the step of interrupting the operation of the pressure differential generating member, the latter cannot be restarted until a determined waiting time preferably of between one second and fifteen minutes has elapsed,
        the step of interrupting the filling comprises at least one of the following: stopping the pressure differential generating member, reducing or stopping the circulation of liquid in the filling pipe upstream of the pressure differential generating member, a purging of at least part of the filling pipe situated downstream of the pressure differential generating member to a discharge zone distinct from the tank, activation of a bypass returning the liquid downstream of the pressure differential generating member to the reservoir,
        the switching on of the pressure differential generating member comprises a check of the flow rate of liquid delivered by the pressure differential generating member in order to keep the instantaneous liquid flow rate (Q) in the filling pipe downstream of the pressure differential generating member above a determined minimum flow rate (Qmin),
        the at least one filling interrupting member comprises at least one of the following:
        
            a switch commanding the switching off of the pressure differential generating member,
            a purge pipe provided with a valve that is controlled and connected to the electronic logic, the purge pipe comprising a first end coupled to the filling pipe (3) downstream of the pressure differential generating member and a second end opening into a discharge zone distinct from the tank,
            a return pipe provided with a valve that is controlled and connected to the electronic logic, the return pipe comprising a first end coupled to the filling pipe downstream of the pressure differential generating member and a second end opening into the reservoir,
        
        
        a controlled isolation valve connected to the electronic logic and situated upstream of the pressure differential generating member,
        the step of measuring the first instantaneous pressure (PT3) in the filling pipe downstream of the pressure differential generating member is performed continuously or periodically,
        stopping the pressure differential generating member is performed by a switch to a passive mode, notably by stopping its drive motor in the case of a pump,
        the pressure in the reservoir is kept above a determined value by drawing liquid from the reservoir, vaporizing this drawn-off liquid and then reinjecting the vaporized liquid into the reservoir,
        during filling, the fluid pressure downstream of the pressure differential generating member is kept above the value of the pressure in the tank,
        the fluid pressure downstream of the pressure differential generating member is kept above the tank pressure value (PT4) by reducing/interrupting the direct return of fluid from the pressure differential generating member to the reservoir,
        the filling pipe comprises an upstream portion secured to the reservoir and a downstream portion, the downstream portion being preferably flexible and comprising a first end coupled in a disconnectable manner to the upstream portion and a downstream second end coupled in a disconnectable manner to a filling inlet of the tank,
        the method is implemented by an installation comprising an electronic logic receiving the measurements of instantaneous pressure (PT3) in the filling pipe, the electronic logic controlling the operation of the pressure differential generating member,
        the filling pipe is equipped with a variable-opening valve positioned downstream of the pressure differential generating member so as to regulate the flow rate of liquid delivered to the tank, said variable-opening valve positioned downstream of the pressure differential generating member preferably being of the one-way type, namely of the type that prevents reflux of fluid upstream toward the pressure differential generating member,
        the pressure differential generating member is prevented from starting when the measurement of the first instantaneous pressure (PT3) in the filling pipe downstream of the pressure differential generating member is unavailable,
        the selective purging of at least part of the filling pipe situated downstream of the pressure differential generating member to a discharge region distinct from the tank uses a discharge pipe comprising an end open to the atmosphere, said discharge pipe being fitted with a valve, said selective purging being performed for a determined purge duration of between two and sixty seconds and preferably of between five and thirty seconds,
        the bypass that selectively returns the liquid leaving the pressure differential generating member to the reservoir comprises a return pipe fitted with at least one return valve,
        the step of interrupting the filling by activating the bypass returning the liquid downstream of the pressure differential generating member to the reservoir comprises an opening of the at least one return valve for a determined duration preferably of between two and sixty seconds,
        the reservoir and the pressure differential generating member belong to a mobile installation, notably a mobile container and/or a trailer of a delivery truck.
    
    


The invention may also relate to any alternative device or method comprising any combination of the features above or below.



BRIEF DESCRIPTION OF THE DRAWINGS
Other specifics and advantages will become apparent from reading the following description given with reference to the figures in which:
FIG. 1 is a schematic and partial view illustrating a first example of a structure and operation of a device for filling a tank according to the invention,
FIG. 2 is a schematic and partial view illustrating a second example of a structure and operation of a filling device according to the invention,
FIGS. 3 to 8 depict simplified and partial schematic views respectively illustrating six other possible embodiments of the structure and operation of a filling device according to the invention,
FIG. 9 is a schematic and partial view illustrating yet another example of a structure and operation of a filling device according to the invention,
FIG. 10 illustrates a possible example of a succession of steps optionally performed during a filling according to one embodiment of the invention,
FIG. 11 illustrates an example of a succession of steps performable during a filling according to one embodiment of the invention,
FIG. 12 illustrates a third example of a succession of steps performable during a filling according to one embodiment of the invention,
FIG. 13 is a schematic, simplified and partial view similar to FIGS. 3 to 8 illustrating yet another possible embodiment of the structure and operation of a filling device according to the invention.



DESCRIPTION OF PREFERRED EMBODIMENTS
FIGS. 1 to 9 in simplified fashion illustrate one example of a filling installation that can be used according to the invention.
The filling device comprises a cryogenic liquid reservoir 2. This reservoir 2 is, for example, a double-walled reservoir the space between the walls of which is insulated by a vacuum. The reservoir 2 is, for example, mobile and transportable, if appropriate on a delivery truck such as a semitrailer.
The reservoir 2 contains liquefied gas and may be selectively fluidically connected to a tank 1 to be filled via a filling pipe 3.
The filling pipe 3 comprises an upstream end connected to the storage volume of the reservoir 2 and a downstream end that can be selectively coupled to the tank 1. The filling pipe 3 is fitted with a member 4 for generating a pressure differential in the fluid and, downstream of this member, with a valve 12 having variable opening. For example, the pressure differential generating member 4 is a pump. Of course the invention is not in any way restricted to this embodiment. Thus, the pressure differential generating member may in the conventional way comprise a vaporizer and/or a heater associated with at least one valve that allows the pressure in the reservoir 2 to be raised so that it can be transferred to a tank. Any other pressure differential generating member that allows fluid to be made to transfer from the reservoir 2 to the tank 1 may equally be used.
The variable-opening valve 12 is preferably a manually actuated valve (although this is not in any way limiting).
The device further comprises a first pressure sensor 13 positioned on the filling pipe 3 downstream of the variable-opening valve 12.
The device further comprises electronic logic 16 connected to the pump 4 and to the pressure sensor 13. The electronic logic 16 comprises for example a microprocessor and an associated memory. In instances in which the device does not comprise a pump, the electronic logic 16 may be connected to at least one controlled valve 128, 12 situated on the filling pipe 3. As illustrated notably in the example of FIG. 13, the pressure differential generating member comprises a vaporizer 11 situated in a pressurizing pipe 10 associated with a valve 128 so as to allow the pressure in the reservoir 2 to be increased. The increase in pressure is achieved by withdrawing liquid from the reservoir 2, vaporizing it and reintroducing it into the reservoir 2. This rise in pressure in the reservoir 2 generates a pressure differential that allows a flow of liquid to be created in the filling pipe 3. Actual filling and the stopping of filling may be defined by whether a valve 12 on the filling pipe 3 is in the flow or no-flow position.
The electronic logic 16 is configured to command or detect a switching on M or a switching off AR of the pressure differential generating member 4. In the case of a pump 4, the on state M or off state AR may respectively correspond to the on state or off state of its drive motor. In the case of a vaporizer system intended to increase the pressure in the reservoir 2, the on and off state may correspond to the open/closed state of at least one valve or to whether or not the reservoir 2 is actually pressurized. The description which follows covers the case of a pump but can be applied by analogy to the case of some other pressure differential generating member.
In particular, the electronic logic 16 controls the switching on A of the pump 4 (cf. step 100, FIG. 10 or step 300, FIG. 11) and may trigger an optional timed period A in order notably to allow the conditions under which liquid is transferred to the tank 1 to stabilize. In one possible alternative form, the control logic 16 receives as input parameter information concerning the switching on M of the pump and/or information concerning the opening of a controlled valve in the filling pipe 3.
An example of the stabilizing of the operating conditions of the pump 4 when it starts independently of the rest of the filling method will now be described with reference to FIG. 11.
As illustrated in FIG. 11, before the pump 4 starts M (the pump is switched off (“4=AR”, reference 300, FIG. 11)), the device may optionally make a check 301 on the stability ST of the first pressure PT3 in the filling pipe 3 (reference 301, FIG. 11). This first pressure PT3 is the pressure measured (sensor 13) while the filling pipe 3 is communicating with the inside of the tank 1. What that means to say is that this stable pressure mimics the pressure in the tank 1 that is to be filled (opening of the valves of the tank 1 downstream of the first pressure sensor 13).
For preference, the pump 4 cannot be switched on until this stability check (PT3=ST, step 301, FIG. 11) returns a positive “Y”.
For example, this check on the stability of the first pressure PT3 is positive if at least one of the following conditions is satisfied:

    
    
        (i) the first instantaneous pressure (PT3) in the pipe (3) is above a determined pressure of, for example, between 15 and 25 bar,
        (ii) the variation in the first instantaneous pressure (PT3) during at least a determined interval of time is below a determined level of variation corresponding for example to a variation, in absolute terms, of between 0.005 and 0.020 bar per second, and preferably 0.01 bar per second.
    
    


Optionally, another possible cumulative condition could be for the first measured pressure PT3 to be above atmospheric pressure.
Having the first condition (i) above satisfied indicates that the tank 1 to be filled is of the high-pressure type and therefore that it is configured to be able to withstand high pressures.
The satisfying of the second condition (ii) above can be measured in various ways. For example, the value of the first pressure PT3 can be recorded over several successive intervals of ten seconds, for example five intervals of ten seconds each. Within each ten-second time interval, the value of the first pressure PT3 must not diverge by more than 0.1 bar. For preference, the five ten-second intervals partially overlap. For example, the five ten-second intervals begin each in their turn at one-second intervals. As an alternative, a mean of this pressure may be observed. The definition of the intervals is dependent in particular on the accuracy of the pressure sensor. This check is preferably performed after the filling pipe 3 has been swept, particularly if this pipe comprises a nonreturn valve 119.
This second condition (ii) is satisfied for example if, during five sequential time intervals (which overlap where appropriate), the first pressure PT3 within each interval does not diverge by more than 0.1 bar.
For preference, if the first check 301 on the stability of the pressure is positive (“Y”, FIG. 11), the pump 4 can be switched on (“4=M”, step 100), otherwise it cannot be (“N”, step 301 and return to the previous step 300).
The switching on of the pump 4 (“4=M”, step 100) may determine a measuring of the pressure PT4 in the tank 1.
For example, at the moment of switching on M of the pump 4, the pressure PT4 in the tank 1 is determined only by measuring a first pressure (PT3→PT4) at the filling pipe 3 (step 302).
For example, this pressure PT4 in the tank 1 can be considered to be equal to the value of the first pressure PT3 measured by the sensor 13 at the pipe 3 at this moment PT3=PT4. Of course, a predetermined corrective coefficient (a multiplicative coefficient K and/or an additive coefficient C) can be used to determine the pressure PT4 in the tank 1 from the measured first pressure PT3. These coefficients can be obtained through testing; the inventors have determined that the dimensionless multiplicative corrective coefficient K may for example be between 0.8 and 1.2 (PT4=KPT3) and that the additive corrective coefficient C in bar may for example be between −2 bar and +2 bar (PT4=PT3+C).
Of course, the pressure PT4 in the tank 1 may be determined by measuring the first pressure PT3 at the filling pipe 3 (for example using the sensor 13 when all the valves between the sensor 13 and the tank 1 are open) before the pump 4 even starts.
In that case, this measurement (PT3=PT4) is preferably performed at a moment at which a check on the stability of the pressure is positive (cf. example hereinabove or any other appropriate equivalent method).
If the pressure PT4 in the tank 1 is determined before the pump is switched on (PT4=PT3) then for preference and as a security measure, this pressure PT4 in the tank may be verified once again at the time of or after the starting of the pump 4 (by measuring the pressure PT3 in the pipe 3 again as before).
The method may comprise a test on flow rate in order to determine that the flow rate supplied by the pump 4 is sufficient and that the pump 4 is not cavitating. Thus, the method may comprise a check that a minimal flow rate for example of 30 liters per minute is leaving the pump 4 for the tank (1) and/or that there is a minimum increase in pressure at the outlet of the pump 4 both at the pressure sensor 113 of the bypass pipe 8 and at the first pressure sensor 13, for example of 6 bar and 1 bar respectively (step 303, FIG. 11 and FIG. 9). If the outcome of this check is negative, the pump 4 is switched off automatically (N, return to step 300). If this condition is positive “Y” then the filling process can continue.
The method then comprises a step 304 of limiting the first instantaneous pressure PT3 to below a maximum pressure threshold PT3sup.
This step of limiting the first instantaneous pressure PT3 to below the maximum pressure threshold PT3sup is preferably performed for a finite determined limiting duration.
Limiting the first instantaneous pressure PT3 to below a maximum pressure threshold PT3sup is preferably achieved by the operator via manual regulation of the rate of flow of fluid transferred using the flow regulating member 12 and/or by regulating the pressure differential generated by the pump 4.
When the first instantaneous pressure PT3 remains above the maximum pressure threshold PT3sup at the end of the determined limiting duration, the filling is automatically interrupted AR (“N” return to step 300).
By contrast, when the first instantaneous pressure PT3 is below the maximum pressure threshold PT3sup at the end of the determined limiting duration, the filling is continued (“Y” then step 103 of keeping under a high threshold Pmax).
The determined limiting duration is, for example, between thirty and one hundred and eighty seconds and preferably equal to ninety seconds.
The limiting duration may be variable, notably according to the flow rate delivered to the store. If the flow rate is high, the duration is shorter and vice versa.
For preference, during this step of limiting the first instantaneous pressure PT3, the method comprises a measurement of the quantity Q of fluid transferred from the reservoir 2 to the tank 1. When this transferred quantity of fluid Q exceeds a threshold quantity Qs before the end of the determined limiting duration, said initially-planned limiting duration is reduced, for example, a duration of five seconds at most is granted in order to finish the limiting step 304.
The maximum pressure threshold PT3sup is defined as a function of the previously determined value of the pressure PT4 in the tank 1 (before, at the time of, or after the switching on of the pump 4).
The inventors have demonstrated that determining the pressure PT4 in the tank in this way under these stabilized pressure conditions (before, at the time of, or after the switching on of the pump 4) makes it possible to obtain a reliable value for this pressure. This pressure value PT4 then where appropriate makes it possible to define a reliable pressure threshold not be exceeded (cf. hereinafter) for this first pressure PT3.
For example, when this determined value of the pressure PT4 in the tank 1 is less than or equal to a first determined level of between three and five bar, for example of three bar, the maximum pressure threshold PT3sup is preferably a predetermined set pressure value of between 5 and 9 bar and preferably of 7 bar.
For example, when the pressure PT4 determined in the tank 1 is between three and four bar, the maximum pressure threshold PT3sup in bar may be given by the following formula:

PT3sup=z.PT4+PA

where z is a unitless set predetermined coefficient between zero and two and preferably equal to one, and where PA is a set increase in pressure in bar of between zero and eight bar and preferably of four bar.

Likewise, when the pressure PT4 determined in the tank 1 is between 4 and 8.1 bar, the maximum pressure threshold PT3sup in bar may be given by the following formula:

PT3sup=z.PT4+PA

where z is a unitless set predetermined coefficient of between 0.80 and 1 and preferably of 0.98, and where PA is a set increase in pressure in bar of between two and four bar and preferably of four bar.

When the pressure PT4 determined in the tank 1 is between 8.1 and 19.5 bar, the maximum pressure threshold PT3sup in bar may be given by the following formula:

PT3sup=z.PT4+PA

where z is a unitless set predetermined coefficient of between 1.00 and 1.50 and preferably of 1.20, and where PA is a set increase in pressure in bar of between one and four bar and preferably of 2.5 bar.

When the pressure PT4 determined in the tank 1 is higher than 19.5 bar and the variation in the first pressure PT3 is less than a determined level of variation of between 0.005 and 0.020 bar per second and preferably less than 0.01 bar per second, the maximum pressure threshold PT3sup in bar is given by the following formula:

PT3sup=z.PT4+PA

where z is a unitless set predetermined coefficient of between 0.50 and 1.00 and preferably of 0.80, and where PA is a set increase in pressure in bar of between seven and 12 bar and preferably of 9.3 bar.

By contrast, when the pressure PT4 determined in the tank 1 is higher than 19.5 bar and the variation in the first pressure PT3 is greater than the value described hereinabove, the maximum pressure threshold PT3sup in bar may be a determined set value of between 30 and 50 bar and preferably of 37 bar.
The inventors have demonstrated that this step of limiting the first pressure PT3 beforehand allows better subsequent detection of a dangerous overpressure during filling that requires filling to be stopped.
After a positive (“Y”) limiting step 304, the method may continue by then comparing the first instantaneous pressure PT3 against a high threshold Pmax and by interrupting the filling if the high threshold Pmax is crossed as described in greater detail hereinbelow with reference to FIG. 10 (steps referenced 103, 104, 105 and 106 in particular).
After the conditions for transferring liquid to the tank 1 have stabilized, and the first instantaneous pressure PT3 has optionally been limited if appropriate, actual filling R of the tank 1 can begin (cf. reference 101, FIG. 10).
The timing step A (cf. 102, FIG. 10) preferably begins when the pump 4 is switched on and has a finite duration.
After this optional timing step a, the electronic logic 16 may be configured to interrupt AR the filling R automatically as soon as the first instantaneous pressure PT3 measured in the filling pipe 3 during filling exceeds a predetermined high threshold Pmax (cf. references 103 “Y” and 104, FIG. 10).
By contrast, during the timing step A, the variations in the first pressure PT3 in the filling pipe 3 above the high threshold Pmax do not interrupt filling (reference 102, FIG. 10).
This configuration makes it possible effectively and sufficiently early on to detect an overflow at the tank 1 which could lead to an overpressure in the tank 1 during filling without the need for costly auxiliary detection or communication systems. Indeed the inventors have noticed that this configuration additionally makes it possible to avoid spurious overfill detections. In addition, the operator is not bound to perform additional operations during filling. This configuration further contributes to stabilizing the conditions of filling of the tank. This makes it possible to increase the life of the equipment by reducing detrimental pressure variations.
Instead of interrupting filling when the first instantaneous pressure PT3 exceeds the high threshold Pmax, as an alternative (or in combination), the electronic logic 16 may be configured to check a mean of first instantaneous pressures PT3max measured in the filling pipe 3. What that means to say is that the device commands the stopping of the filling as soon as this mean of first pressures PT3 exceeds a predetermined high threshold Pmax.
As illustrated in FIGS. 1 and 9, the filling device preferably comprises a return (or bypass) pipe 8 fitted with a bypass valve 5. The bypass pipe 8 comprises a first end coupled to the filling pipe 3 downstream of the pump 4 and a second end opening into the reservoir 2 in order selectively to return the pumped liquid.
As illustrated also, the filling device may comprise a pressurizing pipe 10 for selectively pressurizing the reservoir 2. The pressurizing pipe 10 may comprise two first ends which are connected to the filling pipe 3 respectively upstream and downstream of the pump 4 (cf.; FIGS. 1 and 2). The pressurizing pipe 10 comprises a second end connected to the storage volume of the reservoir 2. The pressurizing pipe 10 comprises a heat exchanger 11 for selectively vaporizing the pumped liquid before it is reintroduced into the reservoir 2.
As illustrated in FIG. 1, the filling pipe 3 may comprise an upstream portion 20 secured to the reservoir 2 and a downstream portion 30. The downstream portion 30 is preferably flexible and comprises a first end 14 coupled in a disconnectable fashion to the upstream portion 20 and a downstream second end 15 coupled in a disconnectable fashion to a filling inlet of the tank 1. The circuitry downstream 40 of the second end 15 of the downstream portion 30 may comprise a nonreturn valve 119 preventing the reflux of fluid from the tank 1 to the filling pipe 3. The circuitry 40 may next comprise two pipes 21, 22 coupled respectively to the bottom and top parts of the tank 1 via respective valves 121, 122. The tank 1 is, for example, a cryogenic tank insulated under a vacuum.
As illustrated in FIG. 1, the tank 1 further and preferably comprises a system for measuring pressure in the bottom part 25 and a system for measuring the pressure 24 at the top (or a system for measuring a pressure differential between the top and bottom parts of the tank 1).
FIG. 2 illustrates a more detailed further example of a design of filling device corresponding notably to the upstream part 20 of the filling pipe of FIG. 1.
The filling pipe 3 is connected to the bottom part of the reservoir 2 and may comprise, from upstream to downstream (namely from the reservoir 2 toward the end that can be coupled to a hose), a first 111 and a second 107 valve, which valves are arranged in series upstream of the pump 4. As depicted, a safety valve 207 and a filter 26 may be positioned upstream of the pump 4. Downstream of the pump 4, the filling pipe 3 comprises the variable-opening valve 12.
As depicted, between the pump 4 and the variable-opening valve 12, the filling pipe 3 may comprise at least one of the following: a temperature sensor 27 and a flow rate measuring member 9 such as a flow meter. Downstream of the variable-opening valve 12 the pipe preferably comprises the first pressure sensor 13 mentioned hereinabove. The filling pipe 3 may also comprise, downstream of the first pressure sensor 13, a purge pipe 60 fitted with at least one controlled valve 6 allowing liquid to be discharged to a discharge zone 18.
A bypassing pipe 28 may be provided to allow the reservoir to be pressurized via the pump 4. This bypassing pipe 28 comprises an upstream end coupled downstream of the pump 4 and a downstream end coupled to the reservoir 2. The bypassing pipe 28 comprises, for example, two pump bypassing valves 128, 228 arranged in series. As in the example of FIGS. 1 and 9, the device comprises a pressurizing pipe 10 for the selective pressurizing of the reservoir 2. The pressurizing pipe 10 comprises a first end connected between the two pump bypassing valves 128, 228 and a downstream end connected to the reservoir 2.
As depicted, the downstream end of the pressurizing pipe 10 may also be connected to a discharge line 17 comprising a discharge valve 310 and a valve 410.
As previously, a bypass pipe 8 is provided for selectively returning the pumped liquid to the reservoir 2. The bypass pipe 8 has an upstream end connected to the filling pipe 3 downstream of the pump 4 (for example between the temperature sensor 27 and the optional flow meter 9). The bypass pipe 8 has a downstream end connected to the reservoir 2.
The bypass pipe 8 comprises at least one bypass valve 5 and, in the example depicted, two bypass valves 5, 55 arranged in parallel, the valve 55 preferably being controlled.
The bypass pipe 8 may comprise a pressure sensor 113 sensing the pressure PT2 upstream of the bypass valves 5, 55. This sensor 113 in fact measures a second pressure PT2 in the filling pipe 3 upstream of the variable-opening valve 12. The bypass pipe 8 where appropriate comprises another pressure PT50 sensor 29 positioned downstream of the bypass valves 5, 55.
Downstream of the first valve 111, the circuit may comprise a pipe 211 for filling the reservoir 2 which is parallel to the filling pipe 3. This pipe 211 comprises, from upstream to downstream, a first safety valve 411, a valve 311, a second safety valve 511 and an end 611 that can be coupled to an application. This pipe 211 can be coupled to the bypass pipe 8, downstream of the bypass valves 5, 55 via a branch 31.
For preference, the operation of filling a tank 1 is at least partly manual and notably an operator can manually control the variable-opening valve 12. Of course, all or some of these actions can be automated, notably by using suitable controlled members (notably controlled valves).
For preference, in instances in which the device makes use of a pump 4, and without this however being limiting, the pump 4 is of the type that delivers a flow rate controlled by a frequency variator, notably a pump of the centrifugal type. Of course, any other type of pump is also appropriate.
Before beginning the filling, if the model of pump 4 requires it, the pump 4 is first of all cooled and stabilized for a determined interval of time. In order to do this, the operator may send the pumped liquid back to the reservoir 2 via the bypass pipe 8 (for example by opening the bypass valve 5 and keeping the variable-opening valve 12 closed).
Once the operating conditions of the pump 4 are stabilized (in order to limit the intensity of the pump), for example in terms of the temperature of the pump 4 and/or pressure downstream of the pump 4 and/or in terms of the flow rate supplied by the pump 4, the operator can progressively reduce close the bypass valve 5 again and begin the actual filling of the tank by opening the variable-opening valve 12.
During filling, the first instantaneous pressure PT3 on the filling line 3 may be measured downstream of the variable-opening valve 12 using the first sensor 13. The variations in this first measured pressure PT3 mimic the variations in pressure in the tank 1 during the course of filling.
According to one advantageous specific already mentioned hereinabove, at the end of the timing step A, abnormal increases in this pressure PT3 are defined and, when detected, cause filling to stop automatically.
The examples described hereinafter and notably the numerical values are given by way of indication and may as appropriate be adapted notably according to the performance of the filling system and the types of tanks considered.
The timing step A has a duration for example of between five and one hundred and eighty seconds and preferably between ten and ninety seconds and, more preferably still, between thirty and sixty seconds. This duration of the timing step A is preferably chosen notably as a function of the technical characteristics of the pump 4 and of the procedures required for controlling it.
At the end of the timing step A, an abnormal increase in the first pressure PT3 may be detected by monitoring the first instantaneous pressure PT3.
Thus, for example, at the end of the timing step A the device may determine a first reference instantaneous pressure PT3ref in the filling pipe 3. The high threshold Pmax may be defined as being the sum of, on the one hand, the first reference instantaneous pressure PT3ref recorded and, on the other hand, a determined pressure jump Po. What that means to say is that the high threshold Pmax (in bar) which triggers the stopping of the filling is given by:

Pmax=PT3ref+Po.

The determining of the first reference instantaneous pressure PT3ref may comprise at least a measurement of the first instantaneous pressure PT3 in the pipe 3 in a time interval of between zero and ten seconds around the end of the timing step A. This first reference instantaneous pressure PT3ref may be a spot value, a maximum or minimum value measured by the sensor 13 during the at least one measurement or a mean of several measurements.
The value of the pressure jump Po may itself be a set value (in bar) in bar and comprised between 0.1 bar and 2 bar and preferably between 0.3 and 1 bar and more preferably still, between 0.4 and 0.6 bar. For example, for preference, the value of the pressure jump Po and the duration of the timing step are adjustable as a function of the characteristics of the filling device (type of pump, type of circuit, type of tank, etc.). For preference, the value of the pressure jump is a function of the value of the first reference instantaneous pressure PT3ref.
This pressure jump Po is defined as a function of the characteristics of the filling device. Thus, for example if, after the timing step A, the device has stabilized and the first pressure PT3 downstream of the variable-opening valve 12 is reached 9.5 bar and the pressure jump is defined at 0.5 bar, then

PT3max=9.5 bar and Pmax=PT3ref+Po=9.5+0.5=10 bar.

Thus, in the continuation of the filling, if the first pressure PT3 measured by the first sensor 13 continuously reaches or exceeds this high threshold Pmax of 10 bar, the device automatically interrupts the filling.
Of course, the invention is not restricted to the example described hereinabove.
Thus, in place of (or in addition to) controlling the first instantaneous pressure PT3 downstream of the variable-opening valve 12, the device may control a mean mPT3ref of the maximum first instantaneous pressures PT3ref measured by the sensor 13. What that means to say is that the device calculates a mean mPT3ref of several maximum first instantaneous pressures PT3 measured. In that case, the high threshold Pmax is then defined by the sum, on the one hand, of the mean of the maximum first instantaneous pressures (mPT3ref) and, on the other hand, of a determined pressure jump (Po): Pmax=mPT3ref+Po.
Thus, at the end of the timing step A, if the first instantaneous pressure PT3 and/or a mean exceeds this high threshold, filling is interrupted.
For example, the mean of the first instantaneous pressure mPT3 is, for example, the mean of several instantaneous pressures PT3 measured successively over an interval of a duration of, for example, between 0.1 and 10 seconds and preferably between 0.25 second and 1 second.
Of course, overpressure control may use other parameters derived from the first measured pressure PT3.
According to one advantageous specific, for preference, if during filling, subsequently, the first measured pressure PT3 (or, as the case may be, the mean of the first pressure mPT3) were to drop below the reference value PT3ref adopted (or, as the case may be, mPT3ref), then this new reference value PT3refb replaces the previous value (cf. steps 105 and 106, FIG. 10). In this way, a new updated high threshold Pmax is recalculated Pmax=PT3refb+Po. This new high threshold which is lower in comparison with the previous high threshold thus adapts to a drop in the first pressure PT3 during filling, caused notably by the thermodynamic conditions of the filling. If not, namely if the first pressure PT3 does not decrease (“N” reference 105 in FIG. 10), the high threshold Pmax is unchanged.
What that means to say is that the first reference measured pressure PT3ref adopted is the most recently measured minimum value.
This reduction in the high threshold Pmax may be updated as often as necessary.
This calculating of the high threshold Pmax, the monitoring of whether or not the high threshold Pmax is exceeded and the stopping of the filling if required may be performed automatically by the electronic logic 16. As a non-preferred alternative it is possible to conceive of the operator being alerted to the exceeding of the high threshold Pmax and then having the task of stopping the filling.
For the sake of safety, if the signal from the first pressure sensor 13 is unavailable, the electronic logic 16 preferably commands the automatic stopping of the filling.
FIGS. 3 to 8 in a simplified manner illustrate some embodiments of the filling device. Elements identical to those described hereinabove are denoted by the same numerical references. In particular, FIG. 3 depicts the electronic logic 16 connected with the first pressure sensor 13 and with the pump 4. The electronic logic 16 is also, where appropriate, connected to a display member 7 such as a man/machine interface in order to signal all or some of the state of operation of the device during filling.
In order to interrupt filling, according to one possible feature, the operation of the pump 4 may be interrupted. What that means to say is that the setpoint to which the pump 4 is controlled is brought down to the minimum and/or the motor of the pump 4 is switched from an on state to an off state and/or a pump member 4 driven by a motor is uncoupled from the motor of the pump 4 (made to “freewheel”). Where appropriate, control of the pump 4 is achieved via a speed converter (which for the sake of simplicity has not been depicted).
According to one other possible (alternative or cumulative) feature, filling can be stopped by reducing or eliminating the circulation of liquid along the filling pipe 3 upstream of the pump 4. As illustrated in FIG. 4, that can be achieved by closing a valve 111 of the filling pipe (for example the first valve 111 or the second valve 112 in FIG. 2). This measure, used in addition to the switching off of the pump 4 makes it possible to increase the effectiveness of the stopping of the filling notably by reducing the inertia effect of the system and notably the inertia of the pump 4. This is because even after the pump 4 has been switched off, it may continue to supply liquid for a certain time. This specific feature also makes it possible to reduce any effects of a vaporization of cryogenic liquid present in the circuit. Several liters of liquid which are present in the circuit can thus be stopped upstream. In this way, the stopping of the filling is more rapid and more effective at avoiding an overpressure in the tank 1.
According to another possible (alternative or cumulative) feature, the stopping of the filling may be achieved by purging at least part of the filling pipe 3 situated downstream of the pump 4 to a discharge zone 18 distinct from the tank 1. As illustrated in FIG. 5 (and in FIG. 2), the device may for this purpose comprise, downstream of the pump 4, a purge pipe 60 fitted with at least one valve 6 controlled by the electronic logic 16 allowing liquid to be discharged to a discharge zone 18.
This feature thus allows at least the cryogenic fluid in the filling pipe 3 to be emptied into the atmosphere.
For safety reasons, this operation of purging downstream of the pump 4 is preferably performed for a limited purge duration of for example between two and sixty seconds and preferably between five and thirty seconds. The purge duration may be adapted to suit the characteristics of the purge valve (typically the coefficient of discharge Cv of the valve) and those of the piping to be purged (typically the length and the diameter). This notably makes it possible to limit the risks of hypoxia of the operators according to the nature of the gas released. This purge thus allows notably the downstream portion 30 of the filling pipe 3, notably in the flexible part, to be at least partially emptied.
According to another possible (alternative or cumulative) feature, the stopping of the filling can be achieved by actuating a bypass that returns the liquid downstream of the pump 4 to the reservoir 2. As illustrated in FIG. 6, that can be achieved by opening the bypass valve 55 of the bypass pipe 8.
This solution also increases the effectiveness and rapidity with which filling is stopped and avoids discharging a dangerous fluid around the reservoir 2.
As illustrated in FIG. 6, if the variable-opening valve 12 is of the type that prevents fluid from returning in the upstream direction, this returning of fluid to the reservoir 2 does not allow the fraction of fluid present downstream of this valve 12 to be discharged. However, this feature nonetheless makes it possible to improve the halting of the rise in pressure in the tank 1.
For preference, this opening of the bypass valve 5 of the bypass pipe 8 is preferably performed for a limited duration, for example of between two and sixty seconds and preferably between two and thirty seconds. In this way, the device avoids any risk of cavitation of the pump 4 and any risk of fluid from the tank 1 returning to the reservoir 2 if the variable-opening valve 12 is leaky.
For preference, after an interruption of the filling, the electronic logic 16 or the pump 4 itself prevents the pump 4 from restarting until a determined period of time preferably of between one second and fifteen minutes has elapsed.
While being of a simple and inexpensive structure, the device described hereinabove thus allows an abnormally high pressure in the tank 1 during the course of filling to be detected sufficiently quickly but not spuriously. The device also makes it possible to limit this abnormally high pressure by effectively stopping the filling in order to prevent the tank 1 from bursting.
A second possible and optional example of the stabilizing of the conditions of operation of the pump 4 as it starts (namely before the control of the filling described hereinabove notably in conjunction with FIG. 10) will now be described.
As illustrated in FIG. 12, the starting M of the pump 4 (reference 100) may comprise a precheck on the flow rate actually delivered by the pump 4 to the tank 1 for a determined flow rate precheck duration TQ (step 200 in FIG. 12). This flow rate precheck comprises a determining of an actual transfer of liquid to the tank 1 by the pump 4 during this flow rate precheck duration TQ. Determining that liquid is actually being transferred to the tank 1 by the pump 4 may involve determining whether the operator (or the device if it is partially automated) is beginning the actual transfer of liquid to the tank 1. Indeed, before starting the filling, the pump 4 may be cooled and stabilized for a determined interval of time during which the liquid pumped from the reservoir 2 is returned to the reservoir by the bypass pipe 8 (by opening for example the bypass valve 5 and keeping the variable-opening valve 12 closed).
What that means to say is that when the pump 4 is switched on, at least some of the liquid delivered by the pump 4 may first of all be returned at least predominantly to the reservoir 2 via a return pipe 8. Then the liquid is progressively delivered predominantly to the tank 1, notably when the pump 4 reaches a stabilized operating regime.
According to one advantageous specific, the electronic logic 16 is configured to compare the transfer of liquid to the tank 1 with a determined threshold S and, when the transfer of liquid to the tank 1 has not reached this threshold S during the flow rate precheck duration TQ, the electronic logic 16 interrupts AR the operation of the pump 4 (cf. references 201 and 202, FIG. 12). Such a switching off of the pump 4 signifies that the start is not satisfactory for continuing the process of beginning the filling.
Specifically, the inventors have noticed that this initial measure makes it possible to avoid operating conditions that detract from good subsequent filling and notably from future detection of an abnormal pressure that triggers the stopping of the filling as described hereinabove.
The determining of a transfer of liquid to the tank 1 may for example comprise a measurement 9 of the instantaneous flow rate Q of liquid in the filling pipe 3 downstream of the pump 4 and upstream of the tank 1 (cf. FIG. 8).
For that purpose, and as illustrated in FIGS. 7 and 8, the filling pipe may comprise a flow meter 9 connected to the electronic logic 16. Thus, the electronic logic 16 can compare the measured instantaneous liquid flow rate Q against a determined minimum flow rate threshold Qmin and, when the measured instantaneous liquid flow rate Q has not reached the minimum flow rate threshold Qmin during the determined flow rate precheck duration TQ, a step of interrupting AR the operation of the pump 4.
The determined minimum flow rate threshold Qmin can be chosen beforehand according to the technical characteristics of the filling device (type of pump, etc.). This minimum flow rate threshold Qmin is for example between one and fifty liters per minute and preferably between ten and forty liters per minute or between three and eight liters per minute, for example five liters per minute.
The determined flow rate precheck duration TQ may be between twenty and two hundred and forty seconds and preferably between thirty and a hundred and twenty seconds, for example ninety seconds.
Of course, alternatively or cumulatively, a transfer of liquid to the tank 1 can be determined in a different way.
For example, a transfer of liquid to the tank 1 may be determined in a way that involves measuring the first instantaneous pressure PT3 in the filling pipe 3 downstream of the pump 4 and upstream of the tank 1, notably downstream of the variable-opening valve 12, using the first pressure sensor 13 described hereinabove.
This instantaneous pressure PT3 may be compared with a predetermined reference level and, when this measurement of the first instantaneous pressure PT3 in the filling pipe 3 does not reach the reference level during the determined flow rate precheck duration TQ, the pipe 4 is switched off.
For preference though, a transfer of liquid to the tank 1 is determined by checking the changes in pressure or pressure differentials. For example, the device checks the instantaneous pressures PT3 and PT50 respectively at the filling pipe 3 downstream of the variable-opening valve 12 and at the return pipe 8 in real time.
To do that, the device may use the pressure PT50 sensor 29 upstream of the bypass valves 5, 55 (cf. FIG. 2).
For example, an increase in the first pressure PT3 above a determined threshold simultaneously with a decrease in the pressure PT50 determined in the bypass pipe 8 corresponds to a sufficient actual transfer.
If this sufficient actual transfer is not achieved during the determined flow rate precheck duration TQ then the pump 4 is switched off.
When the transfer of liquid in the tank 1 reaches this threshold (determined flow rate or pressure or pressure differential) during the determined duration TQ, operation of the pump 4 is maintained and filling R becomes effective (“Y” and reference 203, FIG. 12).
In addition, for preference, the first instantaneous pressure PT3 in the filling pipe 3 is measured downstream of the pump 4 at the moment at which the transfer of liquid to the tank 1 reaches the determined threshold S (PT3(S), cf. reference 204, FIG. 12). This value may be stored by the electronic logic 16. This value may be stored by the electronic logic 16.
For preference also, the method then comprises an additional precheck on the first pressure PT3 in the filling pipe.
More specifically, the method may then comprise a step of prechecking the first pressure PT3 in the filling pipe 3 downstream of the variable-opening valve 12 for a determined pressure precheck duration TP.
Thus, for example, when the first pressure PT3 measured by the first sensor 13 in the filling pipe 3 downstream of the pump 4 exceeds a maximum pressure threshold PT3sup or is below a minimum pressure threshold PT3min during the determined pressure precheck duration TP, the operation of the pump 4 is interrupted AR (cf. references 205 and 206, FIG. 10).
This pressure precheck is preferably designed to ensure that the pressure regulated in the filling pipe 3 downstream of the pump 4 is maintained within a determined interval. The inventors have actually determined that such an action improves the filling and notably the potential later detection of an abnormal overpressure as described previously.
The maximum pressure threshold PT3sup in bar may be identical to that described in the example of FIG. 11. The determined value of the pressure PT3=PT4 in the tank 1 may be the value of the first pressure PT3 recorded for example at the moment when the transfer of liquid to the tank 1 reaches the determined threshold of the step 204 described hereinabove.
For preference, the minimum pressure threshold PT3min is a predetermined set value which may possibly be adjustable, for example between two bar and ten bar and preferably between four and ten bar, notably five bar.
The determined pressure precheck duration TP is, for example, between five and one hundred and eighty seconds and preferably between ten and thirty seconds, for example fifteen seconds.
When this measured first pressure PT3 remains below the maximum pressure threshold PT3sup and above the minimum pressure threshold PT3min for the determined pressure precheck duration TP, the operation of the pump 4 is maintained and the filling of the tank 1 is continued.
The method may then comprise a check on the filling as described hereinabove with reference notably to FIG. 10. Thus, FIG. 12 reproduces by way of example steps 103, 104, 105 and 106 of FIG. 9. For the sake of conciseness, this process will not be described a second time.
According to a preferred but nonlimiting advantageous specific feature, the predetermined high threshold Pmax used for interrupting filling where appropriate as mentioned hereinabove is calculated or defined at the end of the determined pressure precheck duration TP. What that means to say is that the measurement or measurements of the first pressure PT3 used to define the first reference pressure PT3ref (or a mean of these pressures mPT3ref) is/are performed at the end of the determined pressure precheck duration TP (assuming of course that the pump 4 has not been stopped).
What that means to say is that the timing A mentioned hereinabove may include the checks described with reference to FIG. 12.
These processes make it possible to regulate the pressure in the filling pipe 3 downstream of the pump 4 to values close to those of the pressure PT4 prevailing in the tank 1 and for optimum operation of the pump 4. In addition, the filling performed at these pressure levels allows any overpressures in the tank 1 that require filling to stop to be better detected at the filling pipe 3. Having these overpressures better detected notably means that the potential overpressure is detected more early on and more accurately in the tank 1 only. In particular, the process described with reference to FIG. 12 makes it possible to reduce the differential in pressure between, on the one hand, the filling pipe 3 downstream of the pump 4 and, on the other hand, the inside of the tank 1.
In addition, the first reference pressure value PT3ref used to start with for calculating the first high threshold Pmax is, for example, the value of the first pressure PT3 measured at the end or at the culmination of a positive limiting step 304 of the process in FIG. 11.
Alternatively, the first reference pressure value PT3ref used to start off with for calculating the first high threshold Pmax is, for example, the first pressure value PT3 measured in the pipe 3 in a time interval of between zero and 180 s seconds after a switching on of the pump 4.
Alternatively, this first reference pressure PT3ref is measured in a determined interval of time of between zero and 180 s seconds after the actual transfer of a flow of liquid to the tank 1 has started. As previously, the first reference instantaneous pressure PT3ref is the value measured during the at least one pressure measurement or a mean of this at least one pressure measurement.
For preference, throughout the filling process (as soon as the pump 4 is switched on 100) and after the flow regulating member 12 has moved from its no-flow position into its flow position, if a drop in the first instantaneous pressure PT3 in the filling pipe 3 is detected at a rate of at least one bar per second, the pump 4 is automatically switched off (reference 400, FIG. 11).
This safety measure makes it possible to detect a fall in pressure which is synonymous with an abnormally belated opening of the valves of the tank 1. What that means to say is that if this drop in the first pressure PT3 occurs during the course of filling, that means that the tank 1 was beforehand isolated from the filling pipe 3 and that the measurements and calculations performed beforehand were erroneous, particularly the determining of the pressure PT4 in the tank.
It will be understood that many additional changes in the details, materials, steps and arrangement of parts, which have been herein described in order to explain the nature of the invention, may be made by those skilled in the art within the principle and scope of the invention as expressed in the appended claims. Thus, the present invention is not intended to be limited to the specific embodiments in the examples given above.

## Claims

1. A method for filling a liquefied gas tank from a filling device comprising a liquefied gas reservoir, the reservoir being fluidically connected to the tank via a filling pipe, the filling device comprising using a pressure differential generating member for transferring liquid from the reservoir to the tank at a determined pressure, the pressure differential generating member being switchable between an on (M) state and an off (AR) state, the filling pipe comprising a liquid flow regulating member positioned downstream of the pressure differential generating member, the flow regulating member being movable between a no-flow position in which the flow of liquid is interrupted and at least one flow position in which the flow of liquid is transferred to the tank at a determined flow rate, the method comprising a measurement of a first instantaneous pressure (PT3) in the filling pipe downstream of the flow regulating member, the method comprising a step of determining the pressure (PT4) in the tank via a measurement of the first pressure at the filling pipe, while the filling pipe is in fluidic communication with the inside of the tank, the method comprising a step of switching the flow regulating member into the flow position in order to transfer fluid from the reservoir to the tank, wherein the method comprises, after the determining of the pressure (PT4) in the tank, a step of limiting the first instantaneous pressure (PT3) to below a maximum pressure threshold (PT3sup), the step of limiting the first instantaneous pressure (PT3) to below a maximum pressure threshold (PT3sup) being performed when the flow regulating member is in the flow position, the step of limiting the first instantaneous pressure (PT3) to below a maximum pressure threshold (PT3sup) comprising at least one of the following: manual or automatic regulation of the rate of flow of fluid transferred via the flow regulating member, manual or automatic regulation of the pressure differential generated by the pressure differential generating member, the step of limiting the first instantaneous pressure (PT3) to below the maximum pressure threshold (PT3sup) being performed for a finite determined limiting duration comprised between fifteen and one hundred and eighty seconds, and in that, when the first instantaneous pressure (PT3) remains above the maximum pressure threshold (PT3sup) at the end of the determined limiting duration, filling is interrupted (AR) automatically, the maximum pressure threshold being defined as a function of the determined value of the pressure (PT4) in the tank and exceeding the determined value of the pressure (PT4) in the tank by two to twenty bar.

2. The method as claimed in claim 1, wherein the step of determining the pressure (PT4) in the tank via a measurement of the first pressure at the filling pipe is performed before the pressure differential generating member is switched on (M).

3. The method as claimed in claim 1, wherein the step of determining the pressure (PT4) in the tank via a measurement of the first pressure at the filling pipe is performed at the moment of or after the switching-on (M) of the pressure differential generating member.

4. The method as claimed in claim 1, wherein the step of determining the pressure (PT4) in the tank via a measurement of the first pressure at the filling pipe is performed after at least one of the following conditions is satisfied:
(i) the first instantaneous pressure (PT3) measured in the pipe is above a predetermined pressure,
(ii) the variation in the first instantaneous pressure (PT3) measured during at least a determined interval of time is below a determined level of variation corresponding to a variation of between 0.005 and 0.020 bar per second.

5. The method as claimed in claim 1, wherein when the determined value for the pressure (PT4) in the tank is less than or equal to a first determined level of between three and five bar, the maximum pressure threshold is a predetermined set pressure value of between five and ten bar.

6. The method as claimed in claim 1, wherein the duration of the determined limiting step is between thirty and ninety seconds.

7. The method as claimed in claim 1, wherein during the step of determining the pressure (PT4) in the tank, this pressure (PT4) in the tank is equal to the first pressure value (PT3) measured at the filling pipe (PT3=PT4).

8. The method as claimed in claim 1, wherein the switching on of the pressure differential generating member is preceded by a check on the stability of the first instantaneous pressure (PT3) in the filling pipe, the check on the stability of the pressure being positive if at least one of the following conditions is satisfied:
(i) the first instantaneous pressure (PT3) measured in the pipe is above a predetermined pressure,
(ii) the variation in the first instantaneous pressure (PT3) measured during at least a determined interval of time is below a determined level of variation corresponding to a variation of between 0.005 and 0.020 bar per second,

and in that the switching on of the pressure differential generating member can be performed only after a positive check on the stability of the first instantaneous pressure (PT3).

9. The method as claimed in claim 1, wherein after the pressure differential generating member has been switched on (M) and the flow regulating member has been moved from its no-flow position into a flow position, if a drop in the first instantaneous pressure (PT3) in the filling pipe at a rate of at least one bar per second is detected, the pressure differential generating member is automatically switched off.

10. The method as claimed in claim 1, further comprising a switching on (M) of the pressure differential generating member and in that the operation of the pressure differential generating member is interrupted (AR) automatically in response to at least one of the following situations:
the variation in the first instantaneous pressure (PT3) in the filling pipe) during a determined time (T) before a flow of liquid is actually transferred to the tank is greater than a determined variation (V) (ΔPT3>V),
a determined variation in flow rate (Q) and/or a determined variation in the first instantaneous pressure (PT3) in the pipe downstream of the pressure differential generating member is detected while the pressure differential generating member is not in the switched-on state,
after a determined time following the switching on of the pressure differential generating member, the variation in the first instantaneous pressure (PT3) in the pipe remains below a determined level,
after a determined time following the switching on of the pressure differential generating member, a determined quantity of fluid has been transferred to the tank, and the first instantaneous pressure (PT3) in the pipe remains above the maximum pressure threshold (PT3sup),
the differential (PT2−PT3) between a second instantaneous pressure (PT2) measured at the outlet of the pressure differential generating member, upstream of the flow regulating member and the first instantaneous pressure (PT3) measured in the pipe downstream of the flow regulating member (12) is less than a minimum,
the flow of fluid from the reservoir to the tank remains below a determined level.

11. The method as claimed in claim 1, wherein after the step of limiting the first instantaneous pressure (PT3) to below the maximum pressure threshold (PT3sup), and during the course of the transfer of liquid to the tank, the method comprises a comparison of the first instantaneous pressure (PT3) in the filling pipe or of a mean (mPT3) of this first instantaneous pressure against a determined high threshold (Pmax) and, when the first instantaneous pressure (PT3) in the filling pipe or the mean of the first instantaneous pressure (PT3) exceeds the high threshold (Pmax), a step of interrupting (AR) the filling (R), the high threshold (Pmax) being defined as the sum of a first instantaneous pressure value (PT3ref) or of a mean of several measured values of the first reference instantaneous pressure (mPT3ref) measured in the filling pipe (3) at the end of the limiting step and a determined pressure jump (Po) of between 0.2 and 2 bar: (Pmax=PT3ref+Po, or Pmax=mPT3ref+Po).

12. The method as claimed in claim 11, wherein the value of the pressure jump (Po) is a function of the value of the first reference instantaneous pressure (PT3ref) or of the reference mean mPT3ref, and in that, when the first reference instantaneous pressure (PT3ref) or the reference mean mPT3ref is below or equal to a value of between 6 and 9 bar, the pressure jump is between 0.1 and 0.9 bar.

13. The method as claimed in claim 12, wherein when the first reference instantaneous pressure (PT3ref) or the reference mean mPT3ref, is higher than a determined value of between 6 and 9 bar and lower than a determined value of between 15 and 25 bar the pressure jump is between 0.8 and 1.4 bar.

14. The method as claimed in claim 12, wherein when the first reference instantaneous pressure (PT3ref) or the reference mean (mPT3ref), is higher than a determined value of between 15 and 25 bar the pressure jump is between 1.2 and 3 bar.

15. The method as claimed in claim 11, wherein during filling and after the first reference pressure (PT3ref) or a reference mean (mPT3) has been determined, the first instantaneous pressure (PT3) in the pipe is measured regularly and, if the first instantaneous pressure (PT3) measured in the pipe or the mean (mPT3) thereof drops below the first reference instantaneous pressure (PT3ref) or the reference mean (mPT3) previously adopted, a new reference instantaneous pressure (PT3refb) or a new reference mean (mPT3refb) is adopted and used to define a new high threshold (Pmax=PT3refb+Po), or Pmax=mPT3refb+Po.