JP4088457B2 - Safety valve for pressure vessel - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a safety valve attached to a fuel gas pressure vessel for a natural gas vehicle, and more specifically, when a gas escape path is securely sealed at a temperature lower than a set operating temperature, and the temperature is raised to a set operating temperature or higher. The present invention relates to a safety valve for a pressure vessel that can quickly open a gas escape path to prevent bursting of the pressure vessel and is free from environmental pollution.
[0002]
BACKGROUND OF THE INVENTION
For example, an automobile using natural gas as a fuel is equipped with a gas cylinder (pressure vessel) filled with natural gas as a fuel at a high pressure (for example, 20 MPa). This pressure vessel has a predetermined pressure resistance, but is provided with a pressure vessel safety valve so that it does not rupture when the temperature rises due to a fire or the like at the time of an accident. This safety valve is, for example, about 100 to 135 ° C. When the temperature rises above a predetermined temperature set within the range, the gas in the pressure vessel is operated to escape to the outside.
[0003]
[Prior art]
The pressure valve safety valve that operates when the temperature rises above the predetermined temperature usually has a gas escape passage that communicates the internal space and external space of the pressure vessel, and this gas escape passage can be opened. It has a closure for sealing.
The closed body is held in a sealing posture in which the gas escape path is sealed with a low-melting-point alloy in a solid phase at a temperature lower than the set operating temperature. When the temperature rises above the set operating temperature, the closed body moves to the open posture due to the melt flow of the low melting point alloy, and the gas escape path is opened. As a result, the high-pressure gas in the pressure vessel is discharged to the external space, and the pressure vessel is prevented from bursting. In addition, said closure body may be comprised with the case where this closure body itself is comprised with a low melting-point alloy, and the case where it is comprised with the piston-shaped backup member supported by another low melting-point alloy.
[0004]
When the above-mentioned low melting point alloy reaches the set operating temperature or higher, it needs to melt and flow quickly, move the closed body to the open posture, and open the gas escape path. On the other hand, until the set operating temperature is reached, the low-melting-point alloy not only maintains a solid state but also causes a so-called creep that causes fluid deformation under high pressure, thereby moving the closed body to an open position. Must not be.
[0005]
Conventionally, the low melting point alloy includes, for example, 54 % by weight of bismuth (Bi), 26 % by weight of tin (Sn), and 20 % by weight of cadmium (Cd). The operating temperature is about 106 ° C.
[0006]
[Problems to be solved by the invention]
The above-mentioned conventional safety valve for a pressure vessel can hold the closed body in a sealed posture at a temperature lower than a set temperature, and when reaching a set temperature or higher, the low melting point alloy can melt and flow to move the closed body to an open posture. Although there is an advantage that the gas escape passage can be surely opened, the low melting point alloy contains harmful cadmium, so there is a concern that the environment may be polluted during safe operation or disposal.
[0007]
The present invention solves the above-mentioned problems, reliably seals the gas escape path at a temperature lower than the set operating temperature, and quickly opens the gas escape path when the temperature rises above the set operating temperature, thereby rupturing the pressure vessel. It is a technical problem to provide a safety valve for a pressure vessel that can be prevented and that is free from environmental pollution.
[0008]
[Means for Solving the Problems]
In order to solve the above-described problems, the present invention will be described with reference to FIGS. 1 and 2 showing an embodiment of the present invention, for example, and a pressure vessel safety valve is configured as follows.
That is, the present invention includes a gas escape passage (13) attached to the pressure vessel (4), which communicates the internal space (4a) of the pressure vessel (4) and the external space, and the gas escape passage (13). A closing body (17) for releasably sealing, and the closing body (17) includes the gas escape path (13) by a low melting point alloy (16) in a solid state at a temperature lower than a set operating temperature. ) Is maintained in a sealing posture, and when the temperature rises above the set operating temperature, the pressure that moves to the open posture due to the melt flow of the low melting point alloy (16) and opens the gas escape passage (13). a container safety valve, said low melting point alloy (16), indium (in) and 32 to 34 wt%, you characterized by containing bismuth (Bi) 66 to 68 wt%.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a partially broken elevation view of a gas cylinder valve device equipped with a pressure vessel safety valve, showing a first embodiment of the present invention.
[0010]
As shown in FIG. 1, in this valve device (1), a leg screw part (3) of a housing (2) is screwed and fixed to a neck part (5) of a gas cylinder (4) as a pressure vessel. The housing (2) is provided with a gas inlet (6), an inlet passage (7), an on-off valve (8), an outlet passage (9), and a gas outlet (10) in this order. Reference numeral (11) denotes an overflow prevention valve.
[0011]
In FIG. 1, a safety valve (12) is attached to the right side surface of the housing (2). The safety valve (12) includes a gas escape path (13), an alloy housing part (14), and a gas discharge path (15). The gas escape passage (13) communicates with the internal space (4a) of the gas cylinder (4) via the inlet passage (7), and the gas cylinder (4) via the gas discharge passage (15). ) Communicated with the external space. The alloy housing portion (14) is filled with a low melting point alloy (16), and the low melting point alloy (16) constitutes a closing body (17) for sealing the gas escape path (13). Yes. The gas escape path (13) may be directly communicated with the internal space (4a) of the gas cylinder (4) without passing through the inlet path (7).
[0012]
The above low melting point alloy (16) is indium (In) and bismuth (Bi) or Rannahli a solid state at a low temperature (e.g., 94.5 ° C.) than the set operating temperature. Therefore, the closing body (17) made of the low melting point alloy (16) is held in a sealing posture for sealing the gas escape passage (13) at a temperature lower than the set operating temperature.
[0013]
When the gas cylinder (4) is heated to a temperature higher than the set operating temperature, such as when a fire occurs, the low melting point alloy (16) melts. For this reason, the closing body (17) made of the low melting point alloy (16) is pressed and flows by the compressed gas in the gas cylinder (4), and is pushed out from the gas discharge passage (15). As a result, the gas escape passage (13) is opened, and the compressed gas in the gas cylinder (4) is discharged from the gas escape passage (13) to the outside through the gas discharge passage (15). Can be prevented from bursting.
[0014]
In the first embodiment, the closing body is formed of a low melting point alloy. However, the closing body used in the present invention may be formed separately from the low melting point alloy.
That is, in the second embodiment shown in FIG. 2, the pressure vessel safety valve (12) is attached to a valve device attached to a pressure vessel (not shown), and the gas escape passage (13) and the gas escape passage (13 ) In a releasable manner, a gas discharge passage (15), an alloy container (14), and a low melting point alloy (16) housed in the alloy container (14), And an alloy discharge path (18).
[0015]
The gas escape passage (13) communicates with the internal space of the pressure vessel (not shown) as in the first embodiment. The closing body (17) is formed in a piston shape, and is held in a sealing posture to seal the gas escape passage (13) with the low melting point alloy as shown in FIG. It is repressed by the opening direction (left direction in FIG. 2) by (19).
[0016]
The low melting point alloy (16) is in a solid state at a temperature lower than the set operating temperature, and holds the closed body (17) in a sealed posture, but melts when the temperature is raised to the set operating temperature. And discharged from the alloy discharge passage (18). As a result, the closing body (17) moves in the opening direction, the gas escape passage (13) is opened, and the gas in the pressure vessel passes through the gas discharge passage (15) from the gas escape passage (13). It is discharged to the outside and the rupture of the pressure vessel is prevented.
[0017]
Next, a specific composition of the low melting point alloy will be described.
[0018]
[Example 1]
An alloy having a metal composition containing 33 % by weight of indium (In) and 67 % by weight of bismuth (Bi) was prepared and filled in the alloy housing part (14) of the safety valve (12) of the second embodiment. The piston-like closing body (17) was supported.
The low melting point alloy (16) has a crystallization temperature of 109 ° C, and when it reaches 113 ° C, it melts and is quickly discharged from the alloy discharge passage (18), thereby opening the closing body (17). The gas escape passage (13) was smoothly opened.
Further, in order to investigate the creep characteristics, when heated to 94.5 ° C., which is lower than the set operating temperature, under a pressure of 32.5 MPa, the low melting point alloy (16) is slightly deformed even after 500 hours. The gas escape passage (13) was kept sealed by the closed body (17) without being pushed out of the alloy discharge passage (18) .
[0019]
Since the low melting point alloy used in the present invention has a melting / flowing temperature between 100 and 135 ° C., the safety valve for pressure vessel of the present invention is particularly suitable for a pressure vessel of fuel gas for natural gas vehicles. However, it goes without saying that the safety valve of the present invention can also be applied to other pressure vessels such as general-purpose gas cylinders.
[0020]
【The invention's effect】
Since the low melting point alloy used in the present invention does not contain harmful metals such as cadmium and lead, even if the low melting point alloy is discharged during safe operation or disposal, there is no possibility of polluting the environment. Moreover, since this low melting point alloy melts and flows at a predetermined set operating temperature, the gas escape path can be quickly opened to prevent the pressure vessel from rupturing, and there is little creep deformation at a lower temperature than the set operating temperature. The gas escape path can be reliably sealed.
[Brief description of the drawings]
FIG. 1 is a partially cutaway elevational view of a gas cylinder valve device equipped with a pressure vessel safety valve, showing a first embodiment of the present invention.
FIG. 2 is a longitudinal sectional view of a safety valve showing a second embodiment.
[Explanation of symbols]
4 ... Pressure vessel (gas cylinder)
4a… Internal space
12 ... Safety valve
13… Gas escape route
16 ... Low melting point alloy
17 ... Closed body

Claims (1)

A gas escape passage (13) that is attached to the pressure vessel (4) and communicates between the internal space (4a) and the external space of the pressure vessel (4) and seals the gas escape passage (13) so as to be openable. A closure (17),
The closed body (17) is held in a sealing posture in which the gas escape path (13) is sealed by a low melting point alloy (16) in a solid phase at a temperature lower than the set operating temperature, and is equal to or higher than the set operating temperature. A safety valve for a pressure vessel that moves to an open posture by the melt flow of the low-melting-point alloy (16) and opens the gas escape passage (13) when heated to
The above low melting alloy (16), indium (In) and 32 to 34 wt%, bismuth (Bi) 66 to 68, characterized in that it contains% by weight, the pressure vessel safety valve.

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