Patent Publication Number: US-2023160478-A1

Title: Valve

Description:
TECHNICAL FIELD 
     The present invention relates to a valve that controls a flow of a fluid. The invention relates to the valve that controls a flow of a fluid, and more particularly, to a valve that is provided in a high-pressure flow passage and that requires retightening to a packing preventing a fluid from leaking from an annular gap between a stem and a bonnet. 
     BACKGROUND ART 
     A valve disclosed in PTL 1 is a needle valve type control valve for a high-pressure fluid, and a structure of the valve is a high-pressure needle valve in which a needle portion is moved up and down without rotation with respect to a valve seat in a body having an inflow port and an outflow port so as to be able to open and close or adjust a flow rate of the high-pressure fluid. The valve seat and the needle portion strongly abut against each other to block the fluid. 
     As a control valve that can adjust a flow rate of a fluid and perform opening and closing, a control valve described in PTL 2 is known. The control valve includes a valve body that has a flow passage for a fluid, a valve element that controls a flow rate of the fluid, and an actuator that moves the valve element up and down. When the valve is closed, an abutting portion of the valve element abuts against a valve seat formed in the valve body as the valve element is lowered by the actuator, thereby blocking the fluid. The valve element is strongly pressed against the valve seat facing the valve element by moving the valve element up and down without rotation, so that these control valves can withstand a high-pressure fluid. 
     CITATION LIST 
     Patent Literature 
     
         
         PTL 1: JP-A-2016-156442 
         PTL 2: JP-A-2016-014405 
       
    
     SUMMARY OF INVENTION 
     Technical Problem 
     In this type of valve, a seal member is provided to prevent a fluid from leaking outside from a space in which a stem moves. However, since an interior of a valve chamber is used at high pressure, a seal pressing member that presses the seal member to a valve chamber side may be loosened due to long-term use. In this case, although the seal pressing member is retightened to cope with this problem, pressure may be accumulated in the seal member on the valve chamber side. When the pressure is accumulated, a problem arises that it is not possible to tighten the seal pressing member to a predetermined position only by retightening with a predetermined tightening torque, and the retightening cannot be performed using a torque wrench having a set torque. 
     When sufficient retightening cannot be performed due to the accumulated pressure, the seal pressing member is once completely loosened, the accumulated pressure is released from an upper portion to the outside, and then tightening is performed again. Since the pressure is accumulated, the seal member is raised by loosening the seal pressing member, and pressure release is completed. However, a problem arises that such work requires time and effort and may damage the seal member. 
     In recent years, a valve in an environment in which a high-pressure fluid is controlled as a fluid to be controlled is required. In such an environment, when the valve is used as a discharge valve, a throttle may be provided as a noise countermeasure on a discharge side. By providing the throttle, the pressure is not released smoothly, and a stem side (seal member side) is affected. As a result, the seal pressing member that presses the seal member may be loosened. 
     (a) of  FIG.  11    shows a state in which a seal pressing member  230  is screwed into a deep position. (b) of  FIG.  11    shows a state in which the seal pressing member  230  is loosened but pressure of a high-pressure fluid in a valve chamber  214  is still maintained. Further, when a screw of the seal pressing member  230  is loosened, at a moment when a male screw of the seal pressing member  230  is disengaged, the high-pressure fluid in the valve chamber  214  may flow to an upper seal opening space (upper side with respect to a position P), and a scratch or the like that impairs seal performance may occur in an outer seal member  232  (see (c) of  FIG.  11   ). 
     (a) of  FIG.  12    shows a state in which a seal pressing member  330  is screwed into a deep position, and a pressure accumulation portion P in which the high-pressure fluid is accumulated is formed in a gap space to a seal portion. In the seal portion, an inner seal member  331  and an outer seal member  332  abut against an outer peripheral surface of a stem  320  and an inner peripheral surface  319  of a seal space, respectively. (b) of  FIG.  12    shows a state in which the seal pressing member  330  is loosened but pressure of the high-pressure fluid in a valve chamber  314  is still maintained. At this time, pressure in the pressure accumulation portion P is maintained. Further, when a screw of the seal pressing member  330  is loosened, a male screw of the seal pressing member  330  is disengaged, the high-pressure fluid in the valve chamber  314  and the pressure accumulation portion P may flow to an upper seal opening space at a moment when the outer seal member  332  and the inner peripheral surface  319  do not abut against each other, and a scratch or the like that impairs seal performance may occur in the outer seal member  332 . 
     An object of the invention is to provide a valve with which a seal member is not damaged due to pressure release when pressure accumulated near the seal member is once released to the outside in order to retighten the seal member. 
     Solution to Problem 
     A valve according to Invention ( 1 ), which has been made to solve the above problems, includes: a valve box having a fluid inlet, a fluid outlet, and a valve chamber; a valve seat provided in the valve chamber and having a seat surface; a stem connected to an actuator and including, at a tip end of the stem, a valve element configured to abut against and move away from the seat surface due to an operation of the actuator; a seal space communicating with the valve chamber and provided with a seal member configured to prevent a fluid from leaking from the valve chamber; a seal opening space communicating with the seal space and formed outside the seal space; and a seal pressing member configured to press and fix the seal member to a valve chamber side. The valve box is formed with a leak hole through which the seal space and the outside of the valve box communicate. The seal member includes an outer seal member configured to prevent the fluid from leaking from an inner peripheral surface of the seal space and an inner seal member configured to prevent the fluid from leaking from an outer peripheral surface of the stem. The leak hole opens into the seal space that is nearer to the seal opening space than is a seal effective region in which the outer seal member is in close contact with a peripheral wall forming the seal space. 
     In the valve according to Invention ( 1 ), the valve box is formed with the leak hole through which the seal space and the outside of the valve box communicate, the seal member includes the outer seal member configured to prevent the fluid from leaking from the inner peripheral surface of the seal space and the inner seal member configured to prevent the fluid from leaking from the outer peripheral surface of the stem, and the leak hole opens into the seal space that is nearer to the seal opening space than is the seal effective region in which the outer seal member is in close contact with the peripheral wall forming the seal space. Therefore, a high-pressure fluid in the valve chamber is discharged from the leak hole before the outer seal member is exposed to the seal opening space. Since pressure in the valve chamber decreases, pressure in the seal space also decreases, so that a screw of the seal pressing member can be smoothly loosened, and the outer seal member is not damaged. In this way, retightening can be easily performed. Even when a throttle is provided as a noise countermeasure in the seal opening space, the retightening can be easily performed in the same manner. 
     A valve according to Invention ( 2 ), which has been made to solve the above problems, includes: a valve body having an inflow port and an outflow port for a fluid, and a valve chamber; a valve seat provided in the valve chamber and having a seat surface that is an open end of a flow passage communicating with the inflow port; a columnar stem connected to an actuator and including, at a tip end of the stem, a valve element configured to abut against and move away from the seat surface due to an operation of the actuator; a seal member provided in a stem insertion port that communicates with the outside from the valve chamber, fitted onto the stem, and configured to prevent the fluid from leaking from the valve chamber; and a seal pressing member configured to press and fix the seal member to a valve chamber side. The stem is formed with, in an assembled state, a pressure release portion that is nearer to the seal pressing member than is a position at which the seal member is in sliding contact. 
     In the valve according to Invention ( 2 ), an outer diameter of the pressure release portion at the stem may be smaller than an outer diameter of the other part of the stem. 
     In the valve according to Invention ( 2 ), the seal member fitted onto the stem moves along with the seal member by loosening the seal pressing member and reaches the pressure release portion of the stem, and the pressure accumulated near the seal member is released to the outside. Accordingly, the pressure accumulation between the seal members is eliminated, and the retightening can be easily performed. In addition, an outer seal member is not damaged. 
     The pressure release portion may be an inflow hole and an outflow hole that communicate with each other inside the stem. By setting the outflow hole to be nearer to the seal pressing member than be the inflow hole in an axial direction, the pressure in the pressure accumulation portion is released to the outside when an inner seal member is nearer to the seal pressing member than is the inflow hole. 
     In these cases, the seal member may be implemented by attaching the inner seal member and the outer seal member to a continuous cylindrical seal holding member having different outer diameters and inner diameters, and the inner seal member may be on an actuator side. Accordingly, it is possible to quickly complete the pressure release of the seal space. 
     Advantageous Effect 
     According to the valve in the invention, it is possible to provide a valve with which the seal member of the valve is not damaged due to pressure release when the pressure accumulated near the seal member is once released to the outside in order to retighten the seal member. Even when a throttle is provided as a countermeasure against noise, it is possible to provide a valve that can be easily retightened. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1    is a front sectional view of a partly cut-away portion showing a valve according to Invention ( 1 ). 
         FIG.  2    is a side sectional view of a partly cut-away portion showing the valve according to Invention ( 1 ) . 
         FIG.  3    is an enlarged front sectional view of a partly cut-away portion showing a state in which a seal pressing member of the valve according to Invention ( 1 ) is fastened. 
         FIG.  4    is an enlarged front sectional view of a partly cut-away portion showing a state in which the seal pressing member of the valve according to Invention ( 1 ) is loosened. 
         FIG.  5    is a cross-sectional view schematically showing a seal effective region of the valve according to Invention ( 1 ). 
         FIG.  6    is a front sectional view of a partly cut-away portion showing a valve according to Invention ( 2 ). 
         FIG.  7    shows parts of the valve according to Invention ( 2 ), in which (a) is a front view of a partly cut-away portion of a stem, (b) is a sectional perspective view before a seal holding member and a seal member are attached, and (c) is a sectional perspective view of a partly cut-away portion showing a state in which the stem is fitted in the seal holding member. The seal member is attached to the seal holding member. 
         FIG.  8    is an enlarged view of main parts of the valve according to Invention ( 2 ), and is an enlarged front sectional view of a partly cut-away portion showing a state in which the seal pressing member is fastened. 
         FIG.  9    is an enlarged front sectional view of a partly cut-away portion showing a state in which the seal pressing member of the valve according to Invention ( 2 ) is loosened. 
         FIG.  10    shows another embodiment of the valve according to Invention ( 2 ), in which (a) is a front view of a partly cut-away portion of the stem, (b) is a sectional perspective view of a partly cut-away portion showing a state in which the stem is fitted in the seal holding member, and the seal member is attached to the seal holding member, (c) is a sectional perspective view of a partly cut-away portion showing a state in which the seal pressing member is loosened and a pressure release portion functions, and (d) is a sectional perspective view of a partly cut-away portion showing still another embodiment. 
         FIG.  11    shows a state (a) in which a seal member of a valve in the related art is fastened, a state (b) in which the seal member is slightly loosened, and a state (c) in which the seal member is opened. 
         FIG.  12    is a schematic explanatory view showing pressure release of a seal member of a valve in the related art, in which (a) shows a state in which the seal member is fastened, (b) shows a state in which the seal member is slightly loosened, and (c) shows a state in which the seal member is opened. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, preferred embodiments of a valve according to the invention will be described with reference to drawings. Shapes, relative arrangements, and the like of components described in the embodiments are not intended to limit the scope of the invention unless particularly specified, and are merely illustrative examples. In addition, directions of members and the like may be referred to as, for convenience, upper, lower, left, and right depending on directions in the drawings, and these directions do not limit the scope of the invention. 
     First Embodiment of Invention (1) 
       FIGS.  1  to  5    show a first embodiment of Invention ( 1 ).  FIG.  1    is a front sectional view of a partly cut-away portion of a valve  1  according to Invention ( 1 ). A fluid inlet  11  into which a fluid flows and a fluid outlet  12  through which the fluid flows out are opened on an outer surface of a valve box  10  of the valve  1  according to Invention ( 1 ). A fluid inflow passage  16  is formed between a valve chamber  14  in which the fluid is controlled and the fluid inlet  11 , and a fluid outflow passage  17  is formed between the valve chamber  14  and the fluid inlet  11 . A valve seat  13  is formed on a lower surface of the valve chamber  14 , and abuts against and moves away from a valve element  21  formed at a lower end of a stem  20  to control opening and closing of the fluid. A seal pressing member  30  that presses a seal is provided on an upper surface side of the valve box  10 . An actuator  40  that drives the stem  20  up and down is provided above the valve box  10 . 
     A leak hole  15  that is a characteristic portion according to Invention ( 1 ) is formed in the valve box  10 , and is depicted by a dotted line. 
       FIG.  2    is a side sectional view of a partly cut-away portion of the valve  1  according to Invention ( 1 ). The leak hole  15  is depicted by the dotted line in  FIG.  1   , whereas the leak hole  15  is depicted as a through hole passing through the inside of the valve box  10  in  FIG.  2   . Invention ( 1 ) is characterized in that the leak hole  15  is formed and in a formation position of the leak hole  15 . 
       FIG.  3    is an enlarged front sectional view of a partly cut-away portion showing a state in which the seal pressing member  30  is fastened to a prescribed position in the valve  1  according to Invention ( 1 ). A male screw  31  of the seal pressing member  30  is screwed into a female screw  18  formed in an upper portion of the valve box  10 . An inner seal member  31  is provided around the stem  20  to prevent the fluid from leaking along the outer peripheral surface of the stem  20 . 
     A tapered surface is formed above a position P. A space above the position P is a seal opening space. A space below the position P and above the valve chamber  14  is a seal space in which an outer seal member  32  is provided. The outer seal member  32  is in close contact with an inner peripheral wall  19  forming the seal space, to prevent the fluid from the valve chamber  14  from leaking along the inner peripheral wall  19  forming the seal space. The inner seal member  31  and the outer seal member  32  are provided in the seal space in a state in which the inner seal member  31  and the outer seal member  32  are provided in a continuous cylindrical seal holding member  33  having different outer diameters and inner diameters. 
       FIG.  4    shows a state in which the seal member  31  and the seal member  32  move upward by loosening screwing of the male screw  31  of the seal pressing member  30 . When the male screw  31  is loosened to this state, a high-pressure fluid in the valve chamber  14  is discharged from the leak hole  15  to the outside of the valve  1 . Therefore, pressure in the valve chamber  14  decreases, and the male screw  31  of the seal pressing member  30  can be lightly loosened. In this state, since an outer periphery of the outer seal member  32  abuts against the inner peripheral wall  19  of the seal space, the outer seal member  32  is not damaged. Even when a throttle is provided as a noise countermeasure on a discharge side, the high-pressure fluid is easily discharged from the leak hole  15 , and thus subsequent retightening can be easily performed. 
     The leak hole  15  is formed nearer to the valve box  14  than is a boundary P of the seal space and the seal opening space. Therefore, the high-pressure fluid can be leaked only by loosening the seal pressing member  30  and moving an upper portion of the outer seal member  32  to the position of the leak hole  15 , and thus an amount of movement can be reduced and the work can be easily performed. 
       FIG.  5    is a cross-sectional view schematically showing a seal effective region A. The seal effective region A is a region in which the inner peripheral wall  19  of the seal space and the outer seal member  32  are in close contact with each other to prevent the high-pressure fluid from leaking. In the example shown in  FIGS.  1  to  4   , one outer seal member  32  is provided, but in a valve equipped with two or more outer seal members, the seal effective region A is a seal region of the outer seal member  32  closest to the seal opening space among the plurality of outer seal members  32 . 
     First Embodiment of Invention ( 2 ) 
       FIGS.  6  to  9    show a first embodiment in Invention ( 2 ).  FIG.  6    is a front sectional view of a partly cut-away portion of a valve  101  according to Invention ( 2 ). An inflow port  111  into which the fluid flows and an outflow port  112  through which the fluid flows out are opened on an outer surface of a valve body  110  of the valve  101  according to Invention ( 2 ). The inflow port  111  and a valve chamber  114  in which the fluid is controlled communicate with each other by a fluid inflow passage  116 , and the valve chamber  114   and the inflow port  111  communicate with each other by a fluid outflow passage  117 . A valve seat  113  is formed at an open end of the fluid inflow passage  116  of the valve chamber  114 , and abuts against and moves away from a valve element  121  formed at a lower end of a stem  120  to control opening and closing of the fluid. A seal pressing member  130  that presses a seal is screwed on an upper surface side of the valve body  110 . An actuator  140  that drives the stem  120  up and down is coupled to the stem  120 , and is provided above the valve body  110 . 
     In the stem  120  of the valve  101  according to the present embodiment, in an assembled state, an outer diameter D1 of a portion of the stem  120  that is nearer to the seal pressing member  130  than is a position at which the seal members  131  and  132  are in sliding contact is smaller than an outer diameter D of the other portions of the stem  120 , and the portion forms a pressure release portion  122 . 
     (a) of  FIG.  7    is a front view of a partly cut-away portion of the stem  120  of the valve  101  according to Invention ( 2 ). A length of the pressure release portion  122  in an axial direction is not particularly limited, but is set to be about an axial length of a portion of a seal holding member  133  that has an inner diameter d2 and in which the inner seal member  131  is housed. 
     The seal member according to Invention ( 2 ) is implemented by attaching the inner seal member  131  and the outer seal member  132  to the continuous cylindrical seal holding member  133  having different outer diameters and inner diameters, and is attached to the stem  120  such that the inner seal member  131  is on the actuator  140  side. 
     Specifically, as shown in (b) of  FIG.  7   , in the continuous cylindrical seal holding member  133  having different outer diameters and inner diameters, a portion having an outer diameter d1 and the inner diameter d2 to which the inner seal member  131  is attached and a portion having an outer diameter d3 and an inner diameter d4 to which the outer seal member  132  is attached are continuous and integrally formed. The outer diameter d1 is slightly smaller than an inner diameter of a seal space  119  of the valve body  110  that will be described later, and the inner diameter d4 is slightly larger than the outer diameter D of the stem  120 . The seal holding member  133  is fitted onto the stem  120  in a state in which the seal members  131  and  132  and a plurality of backup rings BK are attached, and is fitted into the seal space. 
       FIG.  8    is an enlarged front sectional view of a partly cut-away portion showing a state in which the seal pressing member  130  is fastened to a prescribed position in the valve  101  according to Invention ( 2 ). A male screw  130   a  of the seal pressing member  130  is screwed into a female screw  118   a   formed in a seal opening space  118  in an upper portion of the valve body  110 . The inner seal member  131  is in sliding contact with a periphery of the stem  120  to prevent the fluid from leaking along the outer peripheral surface of the stem  120 . 
     A tapered surface T is formed above the seal space  119 . The seal opening space  118  is formed above the tapered surface T. A space below the tapered surface T and above the valve chamber  114  is the seal space  119  in which an outer seal member  132  attached to the seal holding member  133  is provided. The outer seal member  132  is in close contact with an inner peripheral wall forming the seal space  119 , to prevent the fluid from the valve chamber  114  from leaking along the inner peripheral wall forming the seal space  119 . Q indicated by a thick line indicates pressure accumulation in which the high-pressure fluid from the valve chamber  114  accumulates. A space from the valve chamber  114  side to a seal portion of the inner seal member  131  and the outer seal member  132  is a space (gap) of the pressure accumulation portion Q. 
       FIG.  9    shows a state in which the inner seal member  131  and the outer seal member  132  moves upward by loosening screwing of the male screw  130   a  of the seal pressing member  130  in a pressure release step before retightening. Since the seal holding member  133  holding the seal members  131   and  132  is biased toward the seal pressing member  130  by pressure in the pressure accumulation portion Q, the seal holding member  133  is lifted together with the seal pressing member  130  by loosening the male screw  130   a . When the male screw  130   a  is loosened to the position shown in  FIG.  9   , a seal surface of the inner seal member  131  reaches the small-diameter pressure release portion  122 , and the high-pressure fluid in the pressure accumulation portion Q is discharged from the seal of the inner seal member  131 , passes through a gap between an inner surface of the seal pressing member  130  and an outer surface of the stem  120 , and is discharged to the outside of the valve  101 . Therefore, the pressure in the valve chamber  114  decreases, and when retightening is performed again, the male screw  130   a  of the seal pressing member  130  can be lightly tightened. 
     Even when the seal pressing member  130  is loosened, an outer periphery of the outer seal member  132  abuts against the inner peripheral wall of the seal space  119 , and thus the outer seal member  132  is not damaged. 
     Second Embodiment of Invention (2) 
       FIG.  10    shows a second embodiment of Invention ( 2 ). The second embodiment is the same as the first embodiment except for the structure of the pressure release portion  122 , and thus the description thereof is omitted. 
     As shown in (a) of  FIG.  10   , the pressure release portion  122  of the valve  101  according to Invention ( 2 ) has an inflow hole  122   a  and an outflow hole  122   b  that communicate with each other inside the stem  120 . 
     The inflow hole  122   a  of the pressure release portion  122  is always positioned nearer to the seal pressing member  130  than is the inner seal member  131 , and the pressure (high-pressure fluid in the pressure accumulation portion Q) in the valve chamber  114  does not leak to the outside (see (b) of  FIG.  10   ). 
     In the pressure release step before the retightening, since the seal holding member  133  holding the seal members  131  and  132  is biased toward the seal pressing member  130  by the pressure in the pressure accumulation portion Q, the seal holding member  133  is lifted together with the seal pressing member  130  by loosening the male screw  130   a . As shown in (c) of  FIG.  10   , when the seal portion of the inner seal member  131  passes over the inflow hole  122   a  as the seal holding member  133  lifts, the high-pressure fluid in the pressure accumulation portion Q is discharged from the inflow hole  122   a  to the outside through the outflow hole  122   b  via a communication passage in the stem. Accordingly, the pressure in the valve chamber  114  decreases, and when retightening is performed again, the male screw  130   a  of the seal pressing member  130  can be lightly tightened. 
     This international application claims priority based on Japanese Patent Application No. 2020-078892 filed on Apr. 28, 2020 and priority based on Japanese Patent Application No. 2020-216537 filed on Dec. 25, 2020, and entire contents of Japanese Patent Application No. 2020-078892 and Japanese Patent Application No. 2020-216537 are incorporated into this international application. 
     INDUSTRIAL APPLICABILITY 
     When the pressure accumulated near the seal member is released to the outside, the valve according to the invention can surely release the pressure even when the seal pressing member is slightly loosened and a movement distance of the seal member is reduced, and thus the valve can be suitably used as a valve in a high-pressure environment, for example, a hydrogen station. In the valve according to the invention, since it is not necessary to change the valve body by performing a modification in which a leak port called the leak hole is formed or by using the stem in which the pressure release portion is formed, the valve can be suitably used for maintenance and modification of existing equipment.  
     
       
         
           
               
               
             
               
                 Reference Sign List 
               
             
            
               
                   1 ,  101   
                 valve 
               
               
                 
                   10 
                 
                 valve box 
               
               
                 
                   11 
                 
                 fluid inlet 
               
               
                 
                   12 
                 
                 fluid outlet 
               
               
                   13 , 
                   113  valve seat 
               
               
                   14 , 
                   114  valve chamber 
               
               
                 
                   15 
                 
                 leak hole 
               
               
                   16 , 
                   116  fluid inflow passage 
               
               
                   17 , 
                   117  fluid outflow passage 
               
               
                 
                   18 
                 
                 female screw 
               
               
                 
                   19 
                 
                 inner peripheral wall 
               
               
                   20 , 
                   120  stem 
               
               
                   21 , 
                   121  valve element 
               
               
                   30 , 
                   130  seal pressing member 
               
               
                 
                   31 
                 
                 male screw 
               
               
                 
                   32 
                 
                 seal effective region 
               
               
                   40 , 
                   140  actuator 
               
               
                 
                   110 
                 
                 valve body 
               
               
                 
                   111 
                 
                 inflow port 
               
               
                 
                   112 
                 
                 outflow port 
               
               
                 
                   118 
                 
                 seal opening space 
               
               
                 
                   118 
                   a 
                 
                 female screw 
               
               
                 
                   119 
                 
                 seal space 
               
               
                 
                   122 
                 
                 pressure release portion 
               
               
                 
                   130 
                   a 
                 
                 male screw 
               
               
                 
                   131 
                 
                 inner seal member 
               
               
                 
                   132 
                 
                 outer seal member 
               
               
                 
                   133 
                 
                 seal holding member 
               
               
                 P boundary position of seal opening space and seal space 
               
               
                 Q pressure accumulation portion