LU88646A1 - Filling device for a liquefied gas tank - Google Patents

Description

Device for filling a liquefied gas tank.

The present invention relates to a device for filling a liquefied gas tank. It relates more particularly to a device for filling large tanks of liquefied gas, such as stationary tanks.

The filling of stationary liquefied gas tanks is done by tanker trucks. To this end, the tank truck is connected by a flexible hose with an internal diameter of the order of 2 "to a tank filling device. On tanks currently in service, this filling device essentially comprises a coupling sleeve for the flexible hose and a non-return valve.

For safety reasons the tank should never be filled more than 80%. In fact, a gas zone must be kept above the liquefied gas which can act as a buffer in the event of the tank heating up. To ensure compliance with this safety rule, the stationary tank is equipped with a fixed gauge. The latter essentially comprises a dip tube fitted with a tap. The dip tube has a terminal mouth in the tank which is at the height of the maximum filling level, that is to say the highest level admissible for the liquid / gas interphase. If the liquid phase is clearly below this mouth, the fixed gauge delivers a colorless gas phase. If the liquid phase approaches this mouth, the fixed gauge begins to deliver a mist of whitish gas, which becomes thicker as the level rises.

When filling the tank, the operator of the tank truck constantly observes the fixed gauge and gradually closes a stop valve on the filling line when fog begins to escape the fixed gauge, and this until closing the stopcock completely completes the filling operation.

It is important to note that the closing of the stop valve should not be done abruptly. In fact, too abrupt closing of the shut-off valve risks producing a significant water hammer in the flexible filling pipe of the tank truck, since this flexible pipe has a fairly large inside diameter and length. However, a heavy water hammer in the filling line can, for example, cause a connection to be broken, which produces a gas leak and can cause serious accidents.

For gas cylinders and small liquefied gas tanks for motor cars, which are filled at filling stations using flexible pipes of small internal diameter and short length, filling devices are known which instantly interrupt the filling of the tank when a filling height limit is reached. To this end, these known filling devices are provided with a float which acts by means of a cam on a level valve to close the latter when the float is in a predetermined position. This level valve controls the instantaneous closing of a shut-off valve which is integrated in the device and which is capable of almost instantaneously interrupting the flow of liquefied gas in the tank. The shut-off valve comprises a seat, a closure piston axially movable relative to said seat and a closing spring associated with the piston so as to exert on the latter a closing force in the direction of the seat. The piston axially delimits in the body of the device a pressure chamber which is placed in communication with the reservoir by opening the level valve. A gas passage passes axially through the piston so as to present a mouth in the front surface of the piston and to connect this mouth to the pressure chamber. As long as the level valve is open, the pressure in the pressure chamber is lower than the pressure in the mouth in the front surface of the piston, and the obturator piston undergoes during filling a result of pressure forces which acts against the closing spring to hold the piston in the open position. If the high level of the liquid phase in the tank is reached, the float abruptly authorizes the closing of the level valve, and the pressure in the pressure chamber reaches almost instantaneously the same value as upstream of the piston. There is no longer any significant pressing force which opposes the closing force of the spring, and the latter now pushes the obturator piston on its seat to interrupt the flow of liquefied gas almost instantaneously when the high level of the phase liquid in the tank is reached.

On small tanks, such as gas cylinders and small liquefied gas tanks for motor vehicles, the devices described above have been used successfully for about fifteen years. However, devices of this kind have never been constructed for filling flows greater than 50 l / min, that is to say with diameters of passage at the level of the seats greater than 10 mm. Indeed, the principle of operation of these known devices necessarily implies a very abrupt interruption of the flow of liquefied gas, so that they would inevitably cause water hammer in the flexible filling pipes of large diameter and length, when would be built with passage diameters larger than 10 mm to allow filling of large tanks with liquefied gas flows greater than 50 l / min.

A problem underlying the present invention is to provide a device for filling large liquefied gas tanks with a liquefied gas flow rate greater than 50 l / min, which automatically interrupts the filling of the tank reliably when the level of liquid phase in the tank reaches the safety limit (80% filling), while avoiding causing water hammer in a flexible filling pipe of large diameter and length. This problem is solved in a device according to the first claim.

The device according to the invention is perfectly capable of automatically interrupting, that is to say without human intervention, flow rates of liquefied gas far greater than 50 l / min, without causing water hammer in a flexible filling pipe. of large diameter and length. It will be noted that in the device according to the invention, the level valve closes instantaneously when a threshold level is reached in the tank, which guarantees the reliability of the device. However, the closing movement of the stop valve, which is triggered by the abrupt closing of the level valve, is significantly decelerated. This is possible by using means to control, after closing of said level valve, the result of the pressure forces acting on the piston, so that this result of pressure forces opposes the action of the spring. closing to decelerate the closing movement of said sealing piston and thus avoid a water hammer in a filling pipe connected to said fitting. It is an indisputable merit of the present invention to have understood that the speed of the closing movement of the stop valve can be limited by very simple means without affecting the reliability of the device. This makes it possible to effectively control the problem of water hammer when using flexible filling pipes with a large internal diameter and a long length. It will therefore be appreciated that the present invention provides the first filling device with automatic interruption of filling, which is perfectly suited for use on large volume liquefied gas tanks which are filled which are filled with flow rates greater than 50 l / min.

To limit the speed of the closing movement of the shut-off valve, for example, one of the following measures can be used: • increased pressure drop in the gas in said passage through the piston; • increase in the volume of the pressure chamber; • controlled gas leak from the pressure chamber to the tank when the level valve is closed; • design of the piston of the stop valve of the device in the form of a stepped piston, so that the result of the pressure forces, which act on the piston when the pressure in said pressure chamber is substantially equal to the pressure of filling, opposes the spring until the shut-off valve is completely closed.

The invention will be described in more detail below, with reference to the accompanying drawings by way of illustration, in which: - Figure 1 is a vertical section through a filling device according to the present invention; - Figure 2 is a vertical section through an alternative embodiment of the lower part of the filling device according to Figure 1.

Figure 1 shows a filling device according to the invention which is mounted on a stationary tank 12 for liquefied gas. The reference 14 indicates the liquid phase of the liquefied gas in this tank 12. It will be noted that the device comprises two main parts, namely: a coupling sleeve 16 and a stop valve 18 controlled by a float 20.

The connection sleeve 16 comprises a first thread 22 to which a complementary connection (not shown) of a flexible filling pipe of a tanker truck can be tightly connected (for example screwed). These flexible pipes generally have an inside diameter of around 2 ”and the filling flow rates are well above 50 l / min.

In FIG. 1, the coupling sleeve 16 is shown with a protective cap 24 which is screwed onto the first thread 22. Before connecting a flexible hose to it, it is naturally necessary first to unscrew this protective cap 24. At the using a thread 26, the connection sleeve 16 is mounted in leaktight manner in a threaded pipe 28 of the reservoir 12. In the connection sleeve 16 is preferably integrated a non-return valve 30. The latter comprises a closure element 32 which is pushed by a closing spring 34 sealingly against its seat 36. The closing spring 34 is dimensioned so that when filling the reservoir 12 the filling pressure upstream of the seat 36 keeps the non-return valve 30 open .

The shut-off valve 18, which is controlled by the float 20, comprises a tubular body 38 which is preferably screwed into the coupling sleeve 16, so as to extend the latter inside the reservoir 12. The tubular body 38 comprises , at a certain distance from the non-return valve 30, a seat 42.

The seats 36 and 42 have a passage section adapted to the desired filling rate. For filling tanks with flow rates on the order of 100 l / min, a diameter of the passage section of the seats on the order of 15 mm would be perfectly suitable.

Below this seat 42, the tubular body 38 is provided with lateral mouths in the reservoir 12. These mouths are preferably produced in the form of two windows which are arranged symmetrically with respect to the plane of FIG. 1, that is to say ie symmetrically with respect to the pivot plane of the float 20, in order to influence the operation of this float as little as possible. Neither of these two windows is visible in the longitudinal section shown in Figure 1, since the rear window is hidden by the piston 46. A shutter piston 46 is adjusted in a chamber arranged in the tubular body 38 below the seat 42 This obturator piston 46, which is able to slide axially in this chamber and to seal the seat 42, is subjected to the action of a spring 48 which acts in the direction of the seat 42. An annular seal 47 ensures the sealing between the piston 46 and the wall of the chamber below the side windows, so that the piston delimits axially upwards, below the side windows, a pressure chamber 44.

The lower end of the tubular body 38 is closed by a control valve 50, also called level valve 50. It comprises a shutter member 52 with which is associated a seat 54. The shutter member 52 is able to move axially in a housing arranged above the seat 54. In the closed position, the closure member 52 is held in a sealed manner with a substantially spherical sealing surface resting on its seat 54, which is preferably equipped with '' an O-ring made of elastomeric material. In the open position of the level valve 50, the closure member 52 is held in the raised position above its seat 54, so as to define an annular passage through which said pressure chamber 44 is in communication with the reservoir. 12.

The shutter member 52 is extended by a foot 60 through the seat 54 of the level valve 50, so as to be able to cooperate with a cam 62, which is pivotally mounted in a yoke 64. This cam 62 comprises a contoured contour 66, 68 on which the foot 60 of the shutter member 52 is supported. The pivoting of the cam 62 is generated by the float 20 under the effect of the rise or fall of the level of liquefied gas in the tank 12.

As long as the float 20 is below the position which corresponds to the maximum filling level, the closure member 52 of the level valve is in the raised position, bearing with its foot 60 on a cylindrical profile 66 of the cam 62 whose center of curvature is located on the pivot axis of the cam 62. The level valve is open, and said pressure chamber 44 is in communication with the interior of the reservoir 12 through an annular orifice of almost constant section. When the float 20 reaches the position which corresponds to the maximum filling level of the reservoir 12, the foot 60 of the closure member 52, which can adopt a slightly inclined position in its housing, slides almost instantaneously along a slope 68 of the cam 62, and the shutter member 52 seals against its seat 54 using its substantially spherical sealing surface. The level valve 52 therefore closes instantly when the limit filling threshold is reached.

In order to fill the tank 12, a flexible hose for filling a tank truck is connected to the connection sleeve 16. The liquefied gas enters under pressure in the connection sleeve 16 where it opens the non-return valve 30 to fill the tubular body 38 upstream of the seat 42 closed in leaktight manner by the piston 46. The latter is pushed by the pressure of the gas against the action of the spring 48 in an open position, in which it opens the seat 42 to release the 'access to the two side windows. The liquefied gas can now flow through these two side windows into the reservoir 12. It will be noted that in said pressure chamber 44 only a slight back pressure is established, since this chamber is in direct communication with the inside the tank 12 through the level valve 52 in the open position.

When the liquid phase rises in the tank, the float 20 and the cam 62 integral with the float 20 pivot in the direction of the arrow 21 to finally reach the angular position shown in FIG. 1, which corresponds to the moment or the high level of the liquid phase is almost reached. In this position, the shutter body 52, which is subjected to a result of downward pressure forces, is supported with its foot 60 in an unstable equilibrium position between the two profiles 66 and 68 of the cam 60 The instant afterwards, the foot 60 slides along the slope 68 of the cam 62 and the shutter body 52 abruptly presses tightly against its seat 54. The shutter body 52 is then in a stable equilibrium position in which it is not very sensitive to oscillations of the float 20, which are possibly produced by waves on the surface of the liquid phase. The level valve 50 therefore closes almost instantaneously when the high level in the tank is reached.

In the device according to the invention shown in FIG. 1, the piston 46 reacts only very gently to this abrupt closure of the level valve 50. It will be noted that the piston 46 comprises, like the pistons of the float filling devices Known gas bottles or liquefied gas tanks for cars, a communication passage 70 which communicates the second pressure chamber 44 with the pressure prevailing directly upstream of the piston. However, according to the present invention, this passage is dimensioned so as to present a much greater pressure drop in order to allow only a slow increase in the pressure inside said pressure chamber 44 after closing the pressure relief valve. level 50. It follows that the result of the pressure forces exerted on the piston, which is oriented downwards and opposes the spring 48, decreases only slowly, and that the spring 48 produces only a moderate acceleration of the piston 46. By creating a sufficiently high pressure drop in the communication passage 70, there is therefore obtained a sufficiently slow closing movement of the piston 46 to avoid a water hammer in the flexible filling pipe. However, in certain applications, a sufficiently high pressure drop to avoid water hammer would require a free section that is too small for the passage 70, which would risk becoming blocked.

In such a case, it is possible, for example, to increase the volume of said pressure chamber 44. This results in a slower increase in the back pressure in said pressure chamber 44 and a slower decrease in the result of the pressure forces which s opposes the action of the spring 48. Alternatively or additionally, it is also possible to create, using an additional communication orifice between the pressure chamber 44 and the reservoir 12, a leakage flow rate from said pressure chamber 44 towards the inside of the reservoir 12, which makes it possible to further slow down the increase in the back pressure in said pressure chamber 44 when the level valve 50 is closed.

Figure 2 shows an alternative embodiment in which a sufficiently slow closing movement of the piston 46 is obtained to avoid a water hammer in the filling pipe, without necessarily having recourse to a communication passage 70 with a very narrow passage section .

In the execution of FIG. 2 the obturator piston is a stepped piston 46 ’, which comprises a first stage of cross section S1 and a second stage of cross section S2 smaller than the cross section S1. The first stage of the piston 46 ′ forms at its end a shutter cone capable of sitting in a sealed manner on the seat 42, which has a free section SO. An annular seal 47 ’seals between the piston 46’ and the wall of the chamber below the side windows, so that the piston axially upwards defines a chamber 45 below the side windows. The chamber 45 is in communication with the interior of the reservoir 12 through lateral orifices 49. The second stage of the piston 46 'is tightly adjusted one of cross section S2, and delimits therein a pressure chamber 44' , which corresponds functionally to the pressure chamber 44 in FIG. 1. A second seal 47 ", which is arranged on the second stage of the piston 46 ', delimits the chamber 44' axially in a sealed manner from room 45.

Through a communication passage 70 'in the piston 46', the chamber 44 'is in communication with the liquefied gas upstream from the piston 46'. When the level valve 50 closes, the pressure in the chamber 44 'increases to reach substantially the same value as the pressure upstream of the piston 46'. Since the pressure in the reservoir prevails in chamber 45, it follows that the piston 46 ′ remains exposed to a result of pressure forces which is oriented downwards and whose modulus is substantially equal to the product (p-pO) ( S1-S2), where p is the pressure upstream of the piston and pO is the pressure in the chamber 45. This pressure force continues to oppose the closing force of the spring 48 'and thus significantly reduces the speed of movement closing the piston 46 '. When the piston is finally sealed against its seat, the piston 46 'is exposed to a result of pressure forces, the module of which is equal to the product (p-p0) (S2-S0) if the level valve is closed . This result of pressure forces is oriented upwards if S2> S0, so that it contributes to keeping the piston 46 ’pressing on its seat until the non-return valve 30 is closed.

Claims (8)

1. Device for filling a large tank of liquefied gas sized for filling flow rates greater than 50 l / min, comprising a connection for filling pipes of large diameter, as well as a non-return valve integrated in a tubular body penetrating into said tank, characterized: by a shut-off valve comprising in said tubular body a seat, a closure piston displaceable axially with respect to said seat and a closing spring associated with the piston so as to exert on the latter a closing force in the direction of the seat, said closure piston being arranged in said tubular body so as to delimit there axially a pressure chamber, and being provided with a passage connecting a mouthpiece in the front surface of the piston on the seat side to said pressure chamber, by a level valve in communication with said pressure chamber, this level valve being able to establishing communication between said pressure chamber and the interior of the reservoir when the level of the liquid phase in the reservoir is below a threshold level, respectively instantaneously closing said communication between said pressure chamber and the interior of the reservoir when said threshold level is reached, so that the closing of said level valve triggers a closing movement of said obturatron piston by pressurization of said pressure chamber; and by means for controlling, after closing of said level valve, the result of the pressure forces acting on the piston so that this result of pressure forces opposes the action of the closing spring to decelerate the movement of closing of said sealing piston and thus avoiding a water hammer in a filling pipe connected to said fitting. 2. Device according to claim 1, characterized by first means for controlling the rate of increase of the pressure in said pressure chamber after closing of said level valve. 3. Device according to claim 2, characterized in that said first means comprise means for creating a high pressure drop in said passage through the piston. 4. Device according to claim 2 or 3, characterized in that said first means comprise means for increasing the volume of said pressure chamber, so as to slow the increase in pressure in said pressure chamber after closing of said valve level. 5. Device according to claim 2, 3 or 4, characterized by means for producing a controlled leak for the gas from the pressure chamber to the tank when the level valve is closed. 6. Device according to any one of claims 1 to 5, characterized in that said shutter piston is produced in the form of a stepped piston, having directly downstream of its seat a transverse surface S1, which is exposed to the pressure directly downstream of its seat, having in said pressure chamber a transverse surface S2 <S1, which is exposed to the pressure in said pressure chamber, and having in an intermediate chamber which is in communication with the reservoir an annular surface S1 -S2, which is exposed to tank pressure. 7. Device according to claim 7, characterized in that the seat has a free section SO <S2. 8. Device according to any one of claims 1 to 7, characterized in that the seat of said stop valve has a passage diameter greater than 12 mm.