FR2964439A1 - AUTOMATIC PURGING DEVICE OF A TANK AND TANK COMPRISING SUCH A DEVICE - Google Patents

Abstract

Apparatus for automatically purging a pressurized gas tank comprising a discharge valve (5) having an upstream end for connection with a pressurized gas supply of a container (1) and a downstream end for be connected to a gas evacuation zone, said purge valve (5) being movable between a "closed" state closing the gas passage between the upstream and downstream ends and an "open" state allowing the passage of gas between the upstream and downstream ends, the device comprising a reserve volume (2, 3) storing a reagent (4) at a predetermined pressure, the pressure of the reagent (4) in the reserve volume (2, 3) being sensitive to the temperature, especially during fire conditions, said reserve volume (2, 3) being connected to the purge valve (5) for selectively controlling the displacement of said valve (5) purge from its "closed" state towards his state "open ert "when the reagent (4) undergoes a determined pressure variation, characterized in that the purge valve (5) comprises a pressure-sensitive inlet connected to the reserve volume (4), said inlet selectively actuating the displacement of the valve (5) for purging from its closed state to its open state in response to a pressure increase determined in the reserve volume (4)

Description

The present invention relates to a device for automatically purging a gas tank and a tank comprising such a device. The invention more particularly relates to a device for automatically purging a pressurized gas tank comprising a discharge valve having an upstream end intended to be put in relation with a pressurized gas reserve of a container and a downstream end intended to to be connected to a gas evacuation zone, said purge valve being movable between a "closed" state closing the gas passage between the upstream and downstream ends and an "open" state allowing the passage of gas between the upstream and downstream ends, the device comprising a reserve volume storing a reagent at a predetermined pressure, the pressure of the reagent in the reserve volume being sensitive to the temperature, in particular during fire conditions, said reserve volume being connected to the purge valve for selectively controlling the displacement of said purge valve from its "closed" state to its "open" state When the reagent undergoes a determined pressure variation. Some pressurized gas cylinders are equipped with a device for emptying the gaseous content of the bottle during exposure to a source of heat that could lead to a risk of bursting. Several types of known safety devices prevent such a burst.

A known solution is to directly detect overpressures in the contents of the bottle. These solutions generally use rupture discs, that is to say thin metal membranes whose function is to discharge the gas after the tearing of said membrane when a pressure threshold is exceeded.

Another known solution is to detect the surrounding temperature of the bottle or tank to anticipate any risk of pressure increase. This type of device generally comprises either a thermal fuse, that is to say a metal eutectic that melts under the action of the high temperature, or a glass bubble ("glassbulb") enclosing a liquid dilating sufficiently to the heat to break this bubble, a shape memory material that deforms beyond a defined temperature threshold. This fusion or rupture or deformation makes it possible to move a valve to open a gas passage thus releasing the pressurized gas contained in the bottle. In the context of the storage of hydrogen gas at very high pressure (for example greater than 300 bar and up to 700 bar or more), it is necessary to use bottles or reservoirs capable of withstanding very great constraints. mechanical, while minimizing their mass. For this reason, this type of application generally uses composite materials to constitute the storage volume of the gas. The latest generations of gas cylinders made of composite materials (called "type III" or "type IV") are formed of a metallic liner (made of aluminum for type III) or of polymer material (for type IV type, for example polyethylene). The function of this liner (or inner envelope) is to seal the package vis-à-vis the outside. Composite tanks also include a carbon fiber outer shell attached to the liner. This outer casing is generally embedded in epoxy resin to ensure the mechanical strength of the package with respect to the pressure of the stored gas. Finally, the orifice of the bottle comprises a base, for example metallic, intended to allow the connection of the bottle with a tap or an integrated expansion valve providing the fluid connection with the application receiving or supplying gas.

Unlike tanks made entirely of metal (steel or aluminum type I), composite bottles are highly thermally insulating. In addition, these composite bottles lose their mechanical characteristics when subjected to flames or high temperatures. As a result, the safety devices detecting an overpressure (rupture discs) do not function reliably in all dangerous situations. Indeed, often, the duration of the fire resistance of the bottle is less than the time required for the internal pressure to reach the rupture threshold of the rupture disc. On the contrary, for a type I bottle, the completely metallic structure of the bottle is much more resistant to flames and therefore tolerates a pressure rise sufficient to break the rupture disc well before bursting. The composite structure of the type III or IV tanks is therefore very sensitive to heat during a generalized fire but also and especially when there is a localized source with a high energy density (for example a flame or a " dart "of localized flame). In the latter case, the protection obtained by a thermal fuse is generally not effective enough because the heat detection of this kind of device is performed at the near perimeter of said thermal fuse.

EP2000719A1 discloses such a thermal fuse. US200908874A1 discloses a tank provided with a purge valve using a fuse connected to a metal coil formed on the entire body of the bottle to detect temperature increases remote from the fuse. This device is however expensive and does not guarantee sufficient operation of the discharge valve in all dangerous situations. EP1655533A1 discloses a device for automatically purging a pressurized gas tank comprising a pressurized coil connected to a discharge valve. In case of mechanical rupture of the coil (by temperature increase or in case of mechanical shock), the discharge valve undergoes a drop in pressure which moves an internal piston in an open position of the evacuation of the gas contained in the tank.

This device, however, does not offer all the guarantees of safety in all dangerous situations. In particular, this type of device requires the use of a coil having a low mechanical strength to ensure its rupture both because of an internal overpressure that due to a mechanical shock. These properties may be incompatible with certain hazardous situations and may either trigger unwanted purges or delay purges, which are necessary in some situations. Finally, this device is expensive and not reusable. The present invention proposes to solve this problem of delay in the activation of a security device.

An object of the present invention is therefore to overcome all or part of the disadvantages of the prior art noted above. For this purpose, the purge device according to the invention, moreover in accordance with the generic definition given in the preamble above, is essentially characterized in that the purge valve comprises a pressure-sensitive inlet connected to the volume. reserve, said input selectively actuating the displacement of the purge valve from its closed state to its open state in response to a determined pressure increase in the reserve volume. Furthermore, embodiments of the invention may comprise one or more of the following characteristics: the reagent stored in the reserve volume comprises a gas and / or a liquid; the reagent stored in the reserve volume comprises at least one chemical component generating a chemical reaction modifying its pressure when it is subjected to a determined temperature, the reagent stored in the reserve volume comprises at least one chemical component generating a chemical reaction modifying its pressure when subjected to a determined temperature, - the reagent stored in the reserve volume comprises two separate chemical components separated by a fuse barrier from a pressure and / or a predetermined temperature, the two chemical components being chosen to cause, at their mixing, a chemical reaction modifying the pressure and / or the temperature of their mixture, - the purge valve comprises a pressure sensitive input connected to the reserve volume, said input selectively actuating the displacement of the purge valve from its closed state to its open state in response to a determined pressure decrease in the reserve volume, - the reserve volume comprises a wall (3) provided with at least one frangible and / or fusible zone at a predetermined temperature, - the device is reusable after a sequence of movement of the purge valve from its closed state to its open state via a recess. filling the reserve volume with reagent at a predetermined pressure.

The invention also relates to a pressurized gas tank, in particular a pressurized gas cylinder of composite material, comprising an automatic purging device according to any one of the preceding characteristics. According to other possible particularities - the reserve volume covers at least part of the outer surface of the tank, - the reserve volume forms a sleeve covering the storage volume of the tank, - the reserve volume comprises a portion having the shape a pipe 25 surrounding at least a portion of the tank storage volume, the tank comprises a valve closing the opening of the tank, the valve being provided with a gas circuit communicating with the storage volume of the tank, said circuit being connected to the upstream end of the discharge valve for selectively discharging the contents stored in the storage volume of the tank in the event of a dangerous situation, - the purge valve comprises a movable valve biased by a return member to a closed position of the gas passage between the upstream and downstream ends, the movable valve being also subjected to pressure in the reserve volume. The invention may also relate to any alternative device or method comprising any combination of the above or below features. Other features and advantages will appear on reading the description below, with reference to the figures in which: - Figure 1 shows a longitudinal sectional view, schematic and partial, illustrating a reservoir provided with a purge device according to a first embodiment of the invention, the safety purge device being in closed position (inactive), - Figure 2 shows the reservoir of Figure 1 with the open position safety purge device (active). ) because of a first type of dangerous situation, - Figure 3 shows the tank of Figure 1 with the safety purge device in open position (active) because of a second type of dangerous situation, - the FIG. 4 represents a schematic and partial sectional view of a detail of a second exemplary embodiment of a detail of the safety device located around the bottle, comprising a multicore reagent bottle located around the bottle, FIG. 5 is a schematic and partial longitudinal sectional view illustrating a reservoir provided with a safety purge device according to a third embodiment of the invention, the device when the safety purge is in the closed (inactive) position, - FIG. 6 represents the reservoir of FIG. 5 with the open-position (active) safety venting device 20 because of a dangerous situation; FIG. a side view, schematic and partial, of a fourth embodiment of a tank provided with a safety device according to the invention. Referring now to Figures 1 to 3, the composite reservoir 25 containing pressurized gas comprises, on the majority of its outer surface, a volume 2, 3 said "reserve" delimited by inner and outer walls. The inner wall of the reserve volume is attached to or fixed on the outer wall of the tank 1. Preferably, the spare volume 2, 3 forms a thin envelope 30 (thickness for example between 3 mm and 6 mm) which covers all or almost the entire surface of the tank. For example, the volume 2, 3 covers at least 60% to at least 80% of the outer surface of the tank 1. The reserve volume 2, 3 preferably forms a sheath which covers the tank 1. The volume 2, 3 of reserve is For example, this volume 2, 3 is made of synthetic material such as a polymer / elastomer such as a nitrile, a chloroprene, an ethylene-propylene, a butyl polyamide or neoprene.

This reserve volume 2, 3 contains at least one reagent 4 distinct from gas stored in the reservoir, for example a fluid under pressure, such as liquid and / or gas. The reagent may include one of: water, carbon dioxide or any other suitable reagent.

For example, the reagent is normally at a pressure between 2 bar and 5 bar in volume 2, 3 reserve. The tank 1 further comprises a connector 7 or a valve closing the opening of the volume storing the gas under pressure. The connector 7 comprises an internal circuit connecting the gas stored in the tank 1 with a purge valve 5 which is normally closed. The purge valve 5 may comprise a movable valve biased by default to a position of closure against a seat via a spring 6. As described below, in the event of a dangerous situation, the movable valve is moved to an open position releasing the passage outward for the gas contained in the tank 1.

The volume 2, 3 reserve surrounding the tank 1 is connected to an inlet of the purge valve 5. For example, the pressure in the reserve volume 2, 3 is connected directly or indirectly to the movable valve of the purge valve 5 to move the valve to an open position in case of anomalous pressure variation in the reserve volume 2, 3. The pressure in the reserve volume 2, 3 can, if necessary, be transmitted to the valve via a pipe 8. Thus, when the pressure decreases abnormally in the volume 2, 3 reserve, the valve of the purge valve 5 is moved to an open position allowing the release of the contents of the tank 1. As illustrated in FIG. 2, this abnormal pressure drop can be the result, for example, of a hole located in the outer wall of the volume 2, 3 reserve resulting from a localized flame or hot spot (by melting or localized melting). Indeed, if the volume 2, 3 reserve is pierced, the pressure of the reagent 4 within it drops and solicits by reaction the valve 5 purge. Likewise, if the pressure within the reserve volume 2, 3 increases beyond a determined threshold, the purge valve 5 is also automatically opened. This increase in pressure is for example the result of an increase in temperature, for example due to a surrounding fire (see Figure 3). In this case again, the pressure variation is transmitted to the purge valve 5 and in particular to the movable valve which is moved to an open position. For this purpose, the steady state of the bleed valve 5 can be achieved by the balance of the forces created on the one hand by the permanent pressure of the return spring 6 and, on the other hand, by the pressure in the volume 2 , 3 reserve.

The purge valve 5 can comprise, for example, a sliding gate valve between: a closing position when the pressure in the reserve volume is at its normal level, an opening position when the pressure in the volume 2, 3 reserve falls below a low threshold, - an open position when the pressure in the reserve volume 2, 3 passes above a high threshold. The two open positions above can be distinct or identical. The opening of the valve 5 therefore occurs automatically when the balance of the surrounding forces is broken. Alternatively, it is possible to envision an electromechanical control system of the purge valve 5 in response to pressure sensing (instead of or in addition to a pneumatic or hydraulic system). In the case of FIG. 3, during a rise in ambient temperature, the force of the pressure contained in the reserve volume 2, 3 becomes greater than the restoring force of the spring 6 and thus puts the valve flap in motion. 5 purge. Conversely, when the reservoir 1 is in contact with an energy source, a wall 3 of the reserve volume is likely to be pierced. This opening puts the reagent 4 (gas and / or liquid) contained in volume 2, 3 reserve at atmospheric pressure. In this case, the return force of the spring 6 moves the valve of the purge valve 5 to the open position of the valve. Preferably, this opening is not reversible and then allows complete emptying of the gas contained inside the tank 1. The valve 5 is advantageously sized so that the emptying time of the gas contained in the tank 1 is less than the duration from which the tank 1 loses its mechanical characteristics of fire resistance. This minimizes the potential for explosion. The double wall constituting the reserve volume 2, 3 can optionally form an additional heat shield (via insulating properties of the synthetic material constituting it). FIG. 4 illustrates a detail of a longitudinal section of a reserve volume 2, 3 containing a reagent 4 comprising two chemical components 12, 13 separated by a barrier 11. The two components 12, 13 are stored on both sides. Another barrier 11. The barrier 11 comprises for example a fuse wall. In the case of a localized fire (flame or stinger as illustrated in FIG. 2) or of a surrounding temperature rise in contact with the body of the tank 1 (see FIG. 3), this barrier 11 is designed to melt at a pre-defined temperature thus making it possible to bring these two components 12, 13 into contact. These components 12, 13 are advantageously chosen to cause, during their mixing, an exothermic and preferably pressure-releasing chemical reaction. This reaction will propagate in the entire volume 2, 3 containing these components via an increase in temperature. The increase in pressure following this reaction between the components 12, 13 is transmitted to the purge valve 5 which will cause the opening (preferably non-reversible) of the latter (for example according to the same principle as previously described) . The two components 12, 13 may be chosen from: on the one hand the Isocyanates family and on the other hand the family of polyols or polyalcohols which, when they mix, form polyurethane foams.

The barrier 11 may comprise at least one of the family of polymers of low melting temperature (polyethylene, ABS, PVC, etc ...). In the embodiment of FIGS. 5 and 6, a reserve volume 2, 3 containing a reagent is also arranged around the outer surface of the tank 1. The reserve volume 2, 3 is delimited by two walls of synthetic material and / or metallic. The reagent contained in the volume 2, 3 reserve is for example a liquid under pressure. This double wall 2, 3 surrounding the tank 1 itself comprises a discharge valve 9 provided to break beyond a certain pressure threshold in the reserve volume. For example, the outer wall of the reserve volume 2, 3 comprises a rupture disc 9. As previously, a purge valve 5 is connected to the internal volume of the tank 1 via the internal circuit 8 of a connector 7. Likewise, as previously, the purge valve 5 comprises an inlet connected to the pressure prevailing in the volume 2 , 3 reserve.

Thus, in the event of localized leakage of the reserve volume 2, 3 (by a localized flame or when the discharge valve 9 is opened), a drop in pressure is transmitted to the purge valve 5. The depressurization of this reserve volume 2, 3 actuates the purge valve 5 against or with the help of the return spring 6. The valve 5 thus opens when the equilibrium of the forces (of the return spring 6 and of the pressure in the spare volume 2, 3) is broken (see Fig. 6). In the embodiment of FIG. 7, the reserve volume comprises a tubular coil 10 wound spirally around the body of the tank 1.

As before, the coil 10 contains within it one or more reactants, for example a gas or a liquid under pressure. The winding number of the coil 10 around the outer surface of the tank 1 may be chosen depending on the application.

One end of the coil 10 is fluidly connected to a purge valve 5 (for example according to the same principle as that described above with reference to FIGS. 5 and 6). Another end of the coil 10 may be fluidly connected to a relief valve 9 (for example according to, for example, the same operating principle as that of the discharge valve 9 of FIGS. 5 and 6). Thus, in the case of abnormal rise in temperature, an overpressure occurs in the coil 10 (overpressure proportional to the rise in ambient temperature). As previously, this variation of pressure actuates the opening of the discharge valve 9. The opening of the discharge valve (preferably non-reversible) causes a pressure drop in the coil 10 until a pressure in equilibrium with the atmospheric pressure. This pressure drop breaks the equilibrium of the purge valve 5 and thus allows the valve of this valve 5 to move in the open position (for example under the action of the return spring 6). Indeed, for example, the return spring 6 exerts on the valve of the purge valve 5 an antagonistic force against the force exerted by the pressure initially prevailing in the coil 10. Thus, in case of a dangerous situation (fire in particular) the content of gas under pressure in the tank 1 is automatically purged, thus limiting the risk of explosion. To increase the heat detection accuracy it is also possible to insert an additional metal plate around the bottle (between the bottle and the coil 10).

Thus, the invention proposes several architectures for detecting an abnormally high temperature in the environment of a tank. The reserve volume contains a reagent that covers a large area around the tank body. The device according to the invention makes it possible to capture and / or store a potential of energy sufficient to activate a purge valve in the event of a dangerous situation. The device can be applied to any type of tank without significantly reducing its volume and mass.

Claims (12)

REVENDICATIONS1. Apparatus for automatically purging a pressurized gas tank comprising a discharge valve (5) having an upstream end for connection with a pressurized gas supply of a container (1) and a downstream end for be connected to a gas evacuation zone, said purge valve (5) being movable between a "closed" state closing the gas passage between the upstream and downstream ends and an "open" state allowing the passage of gas between the upstream and downstream ends, the device comprising a reserve volume (2, 3) storing a reagent (4) at a predetermined pressure, the pressure of the reagent (4) in the reserve volume (2, 3) being sensitive to the temperature, especially during fire conditions, said reserve volume (2, 3) being connected to the purge valve (5) for selectively controlling the displacement of said valve (5) purge from its "closed" state towards his state "open ert "when the reagent (4) undergoes a determined pressure variation, characterized in that the purge valve (5) comprises a pressure-sensitive inlet connected to the reserve volume (4), said inlet selectively actuating the displacement of the valve (5) purge from its closed state to its open state in response to a pressure increase determined in the volume (4) reserve. 2. Device according to claim 1, characterized in that the reagent (4) stored in the volume (2, 3) reserve comprises a gas and / or a liquid. 3. Device according to claim 1 or 2, characterized in that the reagent (4) stored in the volume (2, 3) reserve comprises at least one chemical component generating a chemical reaction modifying its pressure when subjected to a determined temperature. 4. Device according to any one of claims 1 to 3, characterized in that the reagent stored in the volume (4) reserve comprises two separate chemical components (12, 13) separated by a barrier (11) fuse from a pressure and / or a predetermined temperature, the two components (12, 13) being chosen to cause, when they are mixed, a chemical reaction modifying the pressure and / or the temperature of their mixture. 5. Device according to any one of claims 1 to 4, characterized in that the purge valve (5) comprises a pressure-sensitive inlet connected to the reserve volume (4), said inlet selectively actuating the movement of the valve. (5) purging from its closed state to its open state in response to a determined pressure decrease in the reserve volume (4). 6. Device according to claim 5, characterized in that the volume (2, 3) reserve comprises a wall (3) provided with at least one zone (9) breakable and / or fusible at a predetermined temperature. 7. Device according to any one of claims 1 to 6, characterized in that the device is reusable after a sequence of movement of the valve (5) to purge its closed state to its open state via a refilling of the volume (2, 3) reserve with reagent (4) at a determined pressure. 8. Pressurized gas tank, in particular pressurized gas cylinder of composite material, comprising an automatic purge device according to any one of the preceding claims. 9. Tank according to claim 8, characterized in that the reserve volume (2, 3) covers at least a portion of the outer surface of the tank. 10. Tank according to claim 8 or 9, characterized in that the reserve volume (2, 3) forms a sleeve covering the storage volume of the tank. 11. Tank according to any one of claims 8 to 10, characterized in that the volume (2, 3) of reserve comprises a portion having the shape of a pipe (10) surrounding at least a portion of the storage volume of the tank. 12. Tank according to any one of claims 8 to 11, characterized in that it comprises a valve closing the opening of the tank, the valve (7) being provided with a circuit (17, 8) of gas communicating with the storage volume of the tank (1), said circuit (17, 8) being connected to the upstream end of the discharge valve (5, 9) for selectively discharging the contents stored in the storage volume of the tank (1) in case of dangerous situation.