Patent Publication Number: US-2021190026-A1

Title: Pressure Relief Valve and Fuel Cell Fluid Supply System Equipped with Same

Description:
This application claims priority under 35 U.S.C. § 119 to patent application no. CN 2019 1122 7789.3, filed on Dec. 4, 2019 in China, the disclosure of which is incorporated herein by reference in its entirety. 
     The disclosure relates generally to a pressure relief valve, in particular a pressure relief valve triggered on the basis of temperature. 
     BACKGROUND 
     Due to environmental protection (e.g. preventing global warming, preventing atmospheric pollution, saving energy and reducing emissions, etc.) considerations, new energy vehicles are being taken more and more seriously, and are being developed to an ever greater extent, by manufacturers. Fuel cells, as a device for supplying motive power in new energy vehicles, are receiving more and more attention from researchers and markets. 
     A fuel cell needs a gas such as high-pressure hydrogen or high-pressure air to be supplied into a battery to undergo a corresponding reaction, in order to generate electric power for driving the vehicle to travel. In general, these high-pressure gases will be stored in a high-pressure tank of the fuel cell, and are supplied into the battery as required via a supply system. Taking hydrogen as an example, this will generally be stored in a high-pressure tank at a gas pressure of more than 350 bar. The supply system comprises a high-pressure pipeline and a low-pressure pipeline, and the high-pressure tank is series-connected in the high-pressure pipeline. To ensure that the vehicle will not explode due to an excessive increase in gas pressure in the high-pressure tank caused by high temperatures in an accident, e.g. if the vehicle catches fire, thereby causing more serious personal injury, a pressure relief valve must be provided for the high-pressure tank or the high-pressure pipeline of the supply system. 
     SUMMARY 
     The disclosure proposes a pressure relief valve triggered on the basis of temperature, in order to ensure that a high-pressure tank or high-pressure pipeline can automatically decompress when a specific temperature is exceeded. 
     According to one aspect of the disclosure, a pressure relief valve is provided, comprising: 
     a valve body, with a hollow internal cavity being defined in the valve body, the hollow internal cavity having two opposite ends, which are in communication with a high-pressure side and a low-pressure side of the pressure relief valve respectively; and 
     a separating plate disposed in the valve body, the separating plate being located in the hollow internal cavity; 
     a penetrating member disposed in such a way as to be capable of sliding linearly in the valve body, the penetrating member having a force applied thereto from the low-pressure side towards the high-pressure side by an elastic component located in the internal cavity; and 
     a locking means disposed in the valve body in a fixed manner and spaced apart from the separating plate, the penetrating member being locked in a cut-off state of the pressure relief valve by means of the locking means; in the cut-off state, the high-pressure side and the low-pressure side are isolated from one another in a sealed fashion by the separating plate, and the penetrating member is configured such that the penetrating member cannot be locked when a specified temperature is exceeded, such that the penetrating member moves from the low-pressure side towards the high-pressure side under the action of the force, and finally the pressure relief valve is in an open state; in the open state, the separating plate is penetrated by the penetrating member such that the high-pressure side and the low-pressure side are in communication with each other. Thus, since the locking means is triggered on the basis of temperature, reliable protection can be provided when accidental high temperature occurs. In addition, since the locking means is disposed so as to be separate from the separating plate, it is possible to ensure that the problem of accidental leakage due to failure of the locking means will not occur. 
     Optionally, the locking means comprises a locking pin, the locking pin passing through a through-hole formed in the valve body and at least partially extending into the penetrating member, in order to lock the penetrating member in the cut-off state. 
     Optionally, the locking pin is made of a fusible alloy, so that the specified temperature is in the range of 110° C.±5° C. 
     Optionally, the penetrating member is integrally formed. 
     Optionally, the penetrating member comprises a spring seat, and a piercing component mounted on the spring seat and configured to penetrate the separating plate, and the force is applied to the spring seat. Due to the split design of the penetrating member, the cost of expensive materials used to manufacture the piercing component can be reduced. 
     Optionally, the elastic component comprises a coil spring, the coil spring being fitted round at least a partial outer surface of the spring seat, one end of the coil spring abutting a part of the valve body, and another, opposite end of the coil spring abutting a part of the spring seat. 
     Optionally, the separating plate is designed such that a part thereof in the hollow internal cavity protrudes towards the high-pressure side, and this part is shaped in such a way as to form part of a spherical surface. Thus, for a given thickness of separating plate, the separating plate is enabled to withstand a greater fluid pressure. 
     Optionally, an axially penetrating hollow first internal cavity is formed in the spring seat, an axially penetrating hollow second internal cavity is formed in the piercing component, and the internal cavity of the valve body is in communication with the first internal cavity and the second internal cavity. 
     Optionally, the piercing component has a pointed end formed by an oblique face, so that in a penetrated state of the pressure relief valve, the pointed end passes through the separating plate and causes the second internal cavity to be in communication with the high-pressure side, thereby enabling rapid relief of pressure when the separating plate is pierced. 
     Optionally, the separating plate isolates the high-pressure side and low-pressure side from one another in a sealed fashion via a sealing ring disposed in the internal cavity of the valve body, and the sealing ring is spaced apart from the locking means in an axial direction at least via the piercing component. 
     According to another aspect of the disclosure, also provided is a fluid supply system for use in a fuel cell vehicle, comprising: 
     a high-pressure fluid tank; and 
     a high-pressure pipeline in fluid communication with the high-pressure fluid tank, wherein the pressure relief valve as described above is provided in the high-pressure fluid tank and/or the high-pressure pipeline, so that the high-pressure side of the pressure relief valve is in communication with high-pressure fluid in the high-pressure fluid tank and/or the high-pressure pipeline, and the low-pressure side of the pressure relief valve is in communication with the atmosphere. 
     Using the above-described technical approach of the disclosure, it is possible to ensure that the high-pressure tank or high-pressure pipeline can be rapidly and reliably relieved of pressure at abnormally high temperatures, and the pressure-bearing ability of the pressure relief valve in conventional circumstances is somewhat improved. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A more comprehensive understanding of the principles and various aspects of the disclosure will be gained from the detailed explanation below in conjunction with the following drawings. It must be pointed out that different drawings might be drawn to different scales for the purposes of clear explanation, but this will not affect the understanding of the disclosure. In the drawings: 
         FIG. 1  shows a simplified schematic drawing of a fluid supply system equipped with the pressure relief valve according to the disclosure. 
         FIG. 2  shows schematically a pressure relief valve structure according to an embodiment of the disclosure, wherein the pressure relief valve is in a cut-off state. 
         FIG. 3  shows schematically a pressure relief valve structure according to an embodiment of the disclosure, wherein the pressure relief valve is in a pressure relief state. 
     
    
    
     DETAILED DESCRIPTION 
     In the drawings, structurally identical or functionally similar features are indicated by identical reference labels. In addition, in the drawings, hatching lines of the same component might be presented in different ways in different views, but it should not be imagined that this will have any effect on the understanding of the technical solution of the disclosure. For example, in  FIGS. 2 and 3 , the hatching lines of the same component will have different densities and lie in different directions for reasons relating to the way in which the drawings are produced, but this will not affect the understanding of the technical solution of the disclosure. 
       FIG. 1  shows schematically a part of a fluid supply system  1  that can be used in a fuel cell vehicle. For example, the fluid supply system  1  may provide a gas such as high-pressure hydrogen or high-pressure air for a battery of a fuel cell of the vehicle, but may also provide a liquid such as water for normal operation of the fuel cell. In the disclosure, the gas and liquid are collectively called fluid. The fluid supply system  1  comprises a high-pressure fluid tank  20 , with high-pressure fluid being stored therein. 
     The fluid supply system  1  is described below, taking hydrogen alone as an example. However, those skilled in the art will understand that any other suitable high-pressure fluid for ensuring normal operation of the fuel cell may also be applied to the technical content associated with the description of hydrogen and involving the following. 
     The high-pressure fluid tank  20  may be a hydrogen tank. The high-pressure fluid tank  20  is connected in a sealed fashion to a high-pressure pipeline  10   a  of the fluid supply system  1 , wherein the high-pressure pipeline  10   a  is fluid-connected via a pressure regulating valve  40  to a low-pressure pipeline  10   b  of the fluid supply system  1 . The fluid supply system  1  further comprises a supply nozzle  30  disposed in the low-pressure pipeline  10   b . Thus, high-pressure hydrogen is first of all stored in the high-pressure fluid tank  20 ; high-pressure hydrogen is outputted from the high-pressure fluid tank  20  via the high-pressure pipeline  10   a  as needed, and enters the low-pressure pipeline  10   b  after being reduced in pressure by the pressure regulating valve  40 , and is further supplied to the battery of the fuel cell via the supply nozzle  30 , in order to realize an electrochemical reaction and generate electric power. 
     When the fluid supply system  1  is damaged due to the vehicle having an accident, e.g. being involved in a collision, the high-pressure fluid tank  20  might be subjected to an abnormal high temperature, causing an abnormal increase in fluid pressure therein and in turn causing an explosion. In order to avoid the possibility of the high-pressure fluid tank  20  exploding due to this kind of accident, a pressure relief valve according to the disclosure may be disposed in the high-pressure fluid tank  20  and/or the high-pressure pipeline  10   a . For example, as indicated by the arrows  100 , such a pressure relief valve may be disposed at an outlet of the high-pressure fluid tank  20 , e.g. connected in parallel with an output valve (not shown) at the outlet; and/or such a pressure relief valve may be disposed in a wall of the high-pressure fluid tank  20 . 
     An example of the pressure relief valve  100  is now described with reference to  FIGS. 2 and 3 . As shown in the figures, the pressure relief valve  100  comprises a substantially tubular valve body component  101 . A hollow internal cavity  200  is defined by an inner wall of the valve body component  101 . The internal cavity  200  has two openings opposite each other, one of these openings being at the left side in the figures and the other being at the right side in the figures; the two openings are in communication with a high-pressure side and a low-pressure side of the pressure relief valve  100  respectively. In  FIGS. 1 and 2 , the left side is regarded as the high-pressure side of the pressure relief valve  100 , and is for example in communication with the outlet of the high-pressure fluid tank  20  or in communication with the high-pressure pipeline  10   a ; the right side is regarded as the low-pressure side of the pressure relief valve  100 , and is for example in communication with the external atmosphere or in communication with another low-pressure fluid pipeline. 
     From the high-pressure side of the valve body component  101 , a base component  102  is installed in the valve body component  101  and partially exposed. For example, a thread is formed on an outer peripheral surface of the base component  102 , and a thread is also formed on a corresponding inner peripheral surface of the valve body component  101 , in order that the two components can be screwed together. A hollow internal cavity  203  is also formed in the base component  102 . Once the base component  102  has been installed in the valve body component  101 , the internal cavity  203  can be in communication with the internal cavity  200 . In this case, an opening of the internal cavity  203  in communication with the internal cavity  200  (e.g. the left-side opening in  FIG. 2 ) is in communication with the high-pressure side of the pressure relief valve  100 . 
     An outer wall of the base component  102  is formed to have a large-diameter portion  102   a  and a small-diameter portion  102   b , wherein the outer diameter of the large-diameter portion  102   a  may be substantially the same as the outer diameter of the valve body component  101 , and an external thread is formed on the small-diameter portion  102   b , in order to engage with an internal thread formed on an inner wall of the valve body component  101 . The base component  102  and valve body component  101  form a valve body of the pressure relief valve  101  after being fitted together. 
     In the internal cavity  203  of the base component  102 , an inner wall of the base component  102  forms a step face  102   c , which is an annular face perpendicular to a longitudinal axis of the valve body. The step face  102   c  is substantially located in a region where the large-diameter portion  102   a  of the base component  102  is positioned in the direction of the longitudinal axis. An annular groove  102   d  is also formed around the step face  102   c , and is configured to have a sealing ring  108  installed therein. An inner sleeve  106  is installed in the base component  102 . An external thread is formed on an outer wall of the inner sleeve  106 , in order to engage with an internal thread formed on an inner wall of the base component  102 . The inner sleeve  106  is also substantially tubular, and has two flat end faces opposite each other. The inner sleeve  106  has a hollow internal cavity  204  defined by an inner wall thereof. 
     In addition, a separating plate  107  is clamped and fixed between the base component  102  and the inner sleeve  106 . The separating plate  107  is configured to isolate the high-pressure side and low-pressure side of the pressure relief valve  100  from one another in a sealed fashion, under the action of a securing force between the base component  102  and the inner sleeve  106 . For example, when assembly is performed, the sealing ring  108  may first of all be placed into the annular groove  102   d  of the base component  102 ; the thickness of the sealing ring  108  may be configured to be slightly greater than the axial depth of the annular groove  102   d , such that when the separating plate  107  is installed in the direction of the step face  102   c  of the base component  102 , it will first come into contact with the sealing ring  108 . The inner sleeve  106  is then screwed via the threads into the base component  102  from the side where an end face  102   e  of the base component  102  is positioned, finally causing one flat end face of the inner sleeve  106  to press against the separating plate  107  and in turn squeeze the sealing ring  108 . When the inner sleeve  106  is finally screwed into place in the base component  102 , the flat end face  106   a  of the inner sleeve  106  that is opposite the flat end face in contact with the separating plate  107  can be flush with the end face  102   e  of the base component  102 . The cooperation of the sealing ring  108  and the separating plate  107  ensures gas-tight separation of the internal cavities at the two opposite sides of the separating plate  107 , i.e. part of the internal cavity  203  located at that side of the separating plate  107  which is close to the high-pressure side of the pressure relief valve  100  (the left side in  FIGS. 1 and 2 ) and the internal cavity  204  of the inner sleeve  106  located at that side of the separating plate  107  which is close to the low-pressure side of the pressure relief valve  100  (the right side in  FIGS. 1 and 2 ). 
     The internal cavity  200  of the valve body component  101  comprises a large-diameter internal cavity portion  200   a  and a small-diameter internal cavity portion  200   b  which are defined by inner walls of the valve body component  101 , wherein the large-diameter internal cavity portion  200   a  and small-diameter internal cavity portion  200   b  are in communication with the internal cavity  204  of the inner sleeve  106  once the valve body component  101  has been fitted into place. The large-diameter internal cavity portion  200   a  is connected to the small-diameter internal cavity portion  200   b  at a step face  101   a  formed by an inner wall of the valve body component  101 . In addition, a spring seat  103  is slideably located in the internal cavity  200  of the valve body component  101 . The spring seat  103  is also a hollow structure, and an inner wall thereof defines a hollow internal cavity  201  of the spring seat  103 . Viewed from the outside, the spring seat  103  also comprises a large-diameter portion  103   a  and a small-diameter portion  103   b , wherein the large-diameter portion  103   a  further comprises an annular flange  103   c.    
     The large-diameter portion  103   a  of the spring seat  103  may be slideably supported in the large-diameter internal cavity portion  200   a  of the valve body component  101  by an inner wall of the valve body component  101  using the annular flange  103   c ; the small-diameter portion  103   b  of the spring seat  103  may be slideably supported in the small-diameter internal cavity portion  200   b  of the valve body component  101  by an inner wall of the valve body component  101 . The outer diameter of the large-diameter portion  103   a  of the spring seat  103  is smaller than the diameter of the large-diameter internal cavity portion  200   a  of the valve body component  101 , such that a coil spring  104  can be arranged between an outer diameter part of the spring seat  103 , in particular of the large-diameter portion  103   a  thereof, and an inner wall of the valve body component  101 . One end of the coil spring  104  may abut the step face  101   a  of the valve body component  101 , and another, opposite end may abut the annular flange  103   c  of the spring seat  103 . 
     Furthermore, a piercing component  105  is fixed on an end face, opposite the coil spring  104 , of the annular flange  103   c . The piercing component  105  comprises a base  105   a , and a sharp part  105   b  that is integrally formed with the base  105   a  and extends axially from the base  105   a . The piercing component  105  is also a hollow structure, and defines a hollow internal cavity  202  that runs axially through the base  105   a  and the sharp part  105   b . A through-hole may be formed in the base  105   a , in order to fix the base  105   a  to the annular flange  103   c  via a bolt, as shown in  FIGS. 2 and 3 . The sharp part  105   b  has a pointed end formed by an oblique face, for piercing the separating plate  107 . 
       FIG. 2  shows a schematic sectional view of the pressure relief valve  100  in a cut-off state; in the cut-off state, the separating plate  107  remains intact and undamaged, such that the high-pressure side and low-pressure side of the pressure relief valve  100  are isolated from one another.  FIG. 3  shows a schematic sectional view of the pressure relief valve  100  in a pressure relief state; in the pressure relief state, the separating plate  107  is pierced by the sharp part  105   b , such that the high-pressure side and low-pressure side of the pressure relief valve  100  are in communication with each other. 
     In a region where the small-diameter internal cavity portion  200   b  of the internal cavity  200  of the valve body component  101  is positioned, a radial through-hole is formed in a wall of the valve body component  101 , in which through-hole a plug member  109  can be inserted. A blind hole  119  is formed in the plug member  109 ; a locking pin  120  can be inserted in the blind hole  119  for example in a shape-fitted manner or friction-fitted manner, so as to be partially exposed through the blind hole  119 . In the cut-off state as shown in  FIG. 2 , the plug member  109  is inserted in the through-hole in a sidewall of the valve body component  101 , and the exposed part of the locking pin  120  is inserted into a radial through-hole  113  in the small-diameter portion  103   b  of the spring seat  103 , thereby locking the spring seat  103 , and thus the piercing component  105 , in place in the axial direction. 
     The outer diameter of the sharp part  105   b  of the piercing component  105  is smaller than the diameter of the hollow internal cavity  204  of the inner sleeve  106 , thus the sharp part  105   b  can extend into the internal cavity  204 . However, in the cut-off state as shown in  FIG. 2 , the pointed end of the sharp part  105   b  is spaced apart from the separating plate  107  by a certain distance, while the base  105   a  is also spaced apart from the flat end face  106   a  of the inner sleeve  106  and/or the end face  102   e  of the base component  102  by a certain distance. 
     For example, when the pressure relief valve  100  is assembled, the coil spring  104  can first be placed in the large-diameter internal cavity portion  200   a  of the valve body component  101  such that one end thereof is in contact with the step face  101   a ; the spring seat  103  with the piercing component  105  already fixed thereto is then inserted into the large-diameter internal cavity portion  200   a , such that the annular flange  103   c  of the spring seat  103  comes into contact with the other, opposite end of the coil spring  104 . Next, a special tool is used to press the spring seat  103 , such that the small-diameter portion  103   b  thereof slides axially in the small-diameter internal cavity portion  200   b  of the valve body component  101 , and finally a step face between the large-diameter portion  103   a  and small-diameter portion  103   b  of the spring seat  103  comes into contact with the step face  101   a  of the valve body component  101 , at which time the radial through-hole  113  of the spring seat  103  and the through-hole in the valve body component  101  for insertion of the plug member  109  are coaxial. Thus, the plug member  109  can be inserted into the through-hole of the valve body component  101 , in order to lock the spring seat  103  and piercing component  105  axially in place in the valve body component  101 . Next, the base component  102  with the separating plate  107  and inner sleeve  106  already fitted thereto is screwed into the valve body component  101  from the high-pressure side, such that the sharp part  105   b  of the piercing component  105  enters the hollow internal cavity  204  of the inner sleeve  106 , and the pointed end of the sharp part  105   b  is spaced apart from the separating plate  107  by a certain distance, while the base  105   a  is also spaced apart from the flat end face  106   a  of the inner sleeve  106  and/or the end face  102   e  of the base component  102  by a certain distance. 
     The axial length of the piercing component  105  may be set such that when the pressure relief valve  100  is assembled and in the cut-off state as shown in  FIG. 2 , the pointed end of the sharp part  105   b  is just out of contact with the separating plate  107 , thereby ensuring that if the piercing component  105  is merely moved towards the separating plate  107 , the pointed end of the sharp part  105   b  must be able to touch the separating plate  107 . In addition, the coil spring  104  is configured to always apply to the spring seat  103  a force tending to cause it to move from the low-pressure side of the pressure relief valve  100  towards the high-pressure side. 
     In the embodiment of the disclosure, the locking pin  120  may be made of a fusible material, e.g. a fusible alloy. For example, such a fusible alloy may be selected from any suitable fusible alloy currently available on the market, as long as the strength thereof can suddenly weaken in a specific temperature range, so that the locking pin  120  is unable to support the force of the coil spring  104  to maintain the cut-off state of the pressure relief valve  100 . Taking hydrogen as an example, the fusible alloy used to make the locking pin  120  may be selected so as to have a melting point in the range of 110° C.±5° C. The dimensions of the locking pin  120  are designed such that below this range, the locking pin  120  is able to support the force of the coil spring  104  in order to keep the pressure relief valve  100  in the cut-off state as shown in  FIG. 2 . 
     In the process of using the pressure relief valve  100 , the pressure relief valve  100  is for example installed at the outlet of the high-pressure fluid tank  20 , in the cut-off state as shown in  FIG. 2 , such that the high-pressure side of the pressure relief valve  100  is in communication with high-pressure fluid, and the low-pressure side of the pressure relief valve  100  is in communication with the atmosphere or another low-pressure pipeline. In the course of normal use, the locking pin  120  locks the spring seat  103  immovably, thus the separating plate  107  isolates the high-pressure side from the low-pressure side. When the ambient temperature of the pressure relief valve  100  reaches or exceeds some value in the range of 110° C.±5° C., the state of the locking pin  120  changes such that the strength thereof is not enough to support the force of the coil spring  104 . For example, the locking pin  120  breaks or is truncated, and under the action of the force of the coil spring  104 , the spring seat  103  is rapidly driven towards the high-pressure side, taking the piercing component  105  with it, such that the sharp part  105   b  of the piercing component  105  pierces the separating plate  107 , and finally, due to the base  105   a  coming into contact with the flat end face  106   a  and/or the end face  102   e  of the base component  102 , the piercing component  105  will be stopped, such that the pressure relief valve  100  is in the pressure relief state as shown in  FIG. 3 . In the pressure relief state, the internal cavities  203 ,  204 ,  202 ,  201  and  200  are all in communication with each other, i.e. the high-pressure side and low-pressure side of the pressure relief valve  100  are in communication with each other, such that high-pressure fluid can rapidly empty from the high-pressure fluid tank  20 , avoiding an accident. In the technical solution of the disclosure, the locking pin  120  forming a pressure relief valve locking means is configured to fail only at a specific temperature or in a temperature range, and the locking pin  120  is designed to be spaced apart from the sealing ring  108  forming a pressure relief valve sealing structure; thus, the locking means of the pressure relief valve  100  will not affect the reliability of the sealing structure. That is to say, slow leakage of high-pressure fluid from a container at the high-pressure side, e.g. the high-pressure fluid tank  20 , due to ageing of the locking means because the locking means and sealing structure have been integrated with one another will not occur. In addition, a locking means that is activated on the basis of temperature better ensures that the pressure relief valve  100  can open rapidly at an abnormally high temperature. 
     As shown in  FIGS. 2 and 3 , in an embodiment of the disclosure, the separating plate  107  is designed such that a part of the separating plate  107  that is within the hollow internal cavity  203  of the base component  102  protrudes towards the high-pressure side and is shaped in such a way as to form part of a spherical surface. In the disclosure, the expression “the separating plate protrudes towards the high-pressure side and is shaped in such a way as to form part of a spherical surface” means that the centre of the sphere is close to the low-pressure side opposite the high-pressure side. Due to this design, pressure from high-pressure fluid is in the opposite direction to that of the protrusion of the separating plate  107 , thereby ensuring that for the same thickness of separating plate  107 , the separating plate  107  of the disclosure can withstand a greater fluid pressure than a flatter separating plate. 
     In addition, in an embodiment of the disclosure, the piercing component  105  and spring seat  103  are then fitted together, thereby forming a penetrating member capable of sliding linearly in the valve body, wherein the spring seat  103  is made of a cheaper, common, machine-manufactured steel material or more lightweight aluminium alloy with no need for special heat treatment, but the piercing component  105  is made of a more expensive, special-purpose, high-hardness material with special heat treatment; thus, it is possible to ensure that the pressure relief valve according to the disclosure is manufactured at a rational cost and a light weight. Those skilled in the art will know that in an alternative embodiment, the piercing component  105  and spring seat  103  may also be made integrally as the penetrating member from a more expensive, special-purpose, high-hardness material with special heat treatment. 
     In an embodiment of the disclosure, the penetrating member applies a force from the low-pressure side towards the high-pressure side via the coil spring  104 ; however, in an alternative embodiment, the coil spring  104  may also be replaced by another elastic component having the same function. For example, in an alternative embodiment, such an elastic component may also be a hollow elastic corrugated tube structure arranged in the internal cavity of the valve body, being fitted round a part of the penetrating member, so as to apply a force, acting from the low-pressure side towards the high-pressure side, to the penetrating member relative to the valve body. 
     In the embodiment shown in the drawings, the locking pin  120  forms the locking means according to the disclosure, being configured to lock the piercing component  105  and/or spring seat  103  as part of the penetrating member in the cut-off state of the pressure relief valve  100 . However, those skilled in the art will know that the locking means is not limited to the example shown. For example, the quantity of the locking pin  120  may be one, or more than one. As another example, in an alternative embodiment, the locking means may comprise a structure of another shape made of a fusible alloy, which acts between the valve body and the spring seat  103 , in order to lock the spring seat  103  relative to the valve body. 
     Although specific embodiments of the disclosure have been described here in detail, these are provided solely for explanatory purposes, and should not be regarded as limiting the scope of the disclosure. In addition, those skilled in the art will know that the various embodiments described herein may be used in combination with each other. Various substitutions, changes and modifications can be conceived, on condition that the spirit and scope of the disclosure are not deviated from.