JP6058985B2 - safety valve - Google Patents

Description

  The present invention relates to a safety valve provided with a self-tightening membrane sheet.

  The safety valve automatically operates when the pressure on the primary side (inlet side) of the valve rises to a predetermined pressure, and when the valve body opens and the pressure drops to a predetermined value, the valve body again Has the function to close. Generally, a safety valve is used for ensuring safety of a steam or gas generator, a pressure vessel, and piping.

  As a safety valve for low-pressure gas such as LNG and LPG, a flexible membrane sheet is stretched on the valve body, and primary pressure is introduced into the gap between the valve body and this pressure is applied to the inner sheet surface of the membrane sheet. Thus, there is a self-tightening type in which the membrane sheet is brought into close contact with the sealing surface of the valve seat to maintain airtightness (for example, Non-Patent Document 1).

  As illustrated in FIG. 3, the self-tightening safety valve supports the membrane sheet 2 stretched below the valve body 1, the mounting shaft 3 protruding downward from the central hole of the membrane sheet 2, and the membrane sheet 2 from below. Thus, a seat support 4 fixed to the mounting shaft 3 and a pressure introduction path for guiding the primary side pressure to the gap 5 between the valve body 1 and the membrane sheet 2 via the inside of the mounting shaft 3 are provided. The outer periphery of the membrane sheet 2 is fixed to the valve body 1 by a secondary sheet 6. The sheet support 4 supports the center side of the membrane sheet 2. When the valve is closed, the pressure led to the gap 5 from the pressure introduction path also becomes the primary pressure, but the membrane sheet 2 is on the lower side because the pressure receiving area on the upper surface side of the membrane sheet 2 is larger than the pressure receiving area on the lower surface side. Pressed. As a result, the non-supporting portion of the membrane sheet 2 that is not supported by the seat support portion 4 and the secondary seat 6 is pressed against the valve seat 7 to keep airtight. At this time, a large force does not act on the membrane sheet 2 and the non-supporting portion is not torn.

Standard technology collection "valve" created by the JPO (especially "technical name 1-1-2-3 safety valve with pilot valve for LNG / LPG")

  Due to the nature of safety valves that do not normally operate, airtightness when the valve is closed is also important. In order to bring the non-supporting portion of the membrane sheet 2 into close contact with the valve seat 7, it is necessary to increase the flexibility by thinning the non-supporting portion.

  However, when the primary side pressure escapes when the unsupported portion of the membrane sheet 2 is opened away from the valve seat 7, the pressure distribution immediately below the valve body 1 theoretically becomes as shown in FIG. In the conventional self-tightening type safety valve, since the pressure introduction path in FIG. 3 has a downward pressure intake at the center of the lower surface of the mounting shaft 3, the stagnation point pressure, which is the pressure distribution peak in FIG. Will lead in. Therefore, the pressure in the gap 5 is considerably higher than the average pressure of the pressure distribution in FIG. As a result, a relatively high pressure acts on the upper surface side of the membrane sheet 2 in FIG. 3 and a relatively low pressure acts on the lower surface side, and the non-supported portion swells downward due to the differential pressure. The thinner the unsupported portion, the more likely it will burst when it swells. In general, after the safety valve is installed in the safety system of the facility, the operation test of the safety valve is performed.If the above-mentioned defects that lead to rupture are unfortunately not found in the operation test, There is no opportunity to find defects until periodic inspections. For this reason, even if airtightness is improved, it should be avoided to easily cause rupture.

  Therefore, the problem to be solved by the present invention is to prevent the membrane sheet from rupturing during the operation of the safety valve.

  In order to solve the above-described problems, the present invention provides a membrane sheet stretched below the valve body, an attachment shaft protruding downward from a central hole of the membrane sheet, and the attachment shaft so as to support the membrane sheet from below. A seat support portion to be fixed, and a pressure introduction path that guides the primary pressure to the gap between the valve body and the membrane sheet via the inside of the mounting shaft, and the pressure led from the pressure introduction path to the gap In the safety valve in which the membrane seat is pressed against the valve seat, a configuration is adopted in which the pressure introduction path is provided so as to take in the primary side pressure only from the outer diameter of the mounting shaft in the axial direction.

  According to this configuration, when the valve is opened, the pressure introduction path takes in the primary side pressure only from the outer diameter of the mounting shaft in the axial direction, so that the stagnation point pressure in the illustrated pressure distribution is not led to the gap. Accordingly, the force for inflating the non-supporting portion of the membrane sheet is reduced, so that the non-supporting portion can be prevented from bursting.

  In particular, the pressure inlet of the pressure introduction path is preferably closed at the lower end. The pressure intake port separated from the stagnation point in the axial direction is in a flow in which the primary pressure blows out to the secondary side. Since the pressure in the gap and the pressure introduction path is the operating pressure of the safety valve at the beginning of valve opening, the blowing flow is lower than the pressure in the gap. If the pressure intake port is closed at the lower end, an ejector effect in which the blown-out flow does not enter the pressure introduction path directly and is sucked out from the pressure intake port can be obtained. Thereby, since the pressure in the gap is reduced more than the pressure at the position of the pressure inlet in the illustrated pressure distribution, it is possible to further prevent the unsupported portion of the membrane sheet from being ruptured.

  Further, an extension member fixed to the mounting shaft is provided, and the extension member is connected from the pressure intake port located farther than the outer diameter of the mounting shaft in the axial direction to the inside of the mounting shaft, and the pressure introduction The path may take in the primary side pressure from the pressure inlet. In this case, a lower pressure can be introduced than when a pressure intake port is formed on the outer diameter surface of the mounting shaft.

  When the seat support portion has a nut screwed into a male screw portion formed on the outer diameter surface of the mounting shaft, it is preferable that the extension member is a cap nut screwed into the male screw portion. Conventionally, a nut is used to support the membrane sheet from below. The extension member screwed into the same male thread as the nut communicates with the inside of the mounting shaft, and the axial position of the pressure inlet can be set by selecting the outer diameter of the extension member. In addition, since the present invention can be realized only by adding an extension member to a mounting shaft having a conventional structure having a hollow hole opened at the male screw portion and the central portion of the lower surface, application to an existing safety valve is easy.

  By adopting the above configuration, the present invention can reduce the force for inflating the non-supported portion of the membrane sheet when the safety valve is activated, and can prevent the membrane sheet from bursting.

The partial longitudinal cross-sectional front view which showed the valve body vicinity of the safety valve which concerns on embodiment of this invention in the valve opening state (A) is a partially longitudinal front view showing the vicinity of the valve body of the safety valve of FIG. 1 in an open state, (b) is an unsupported portion of the membrane sheet showing the action of the primary pressure in the state of (a). Enlarged view Longitudinal front view showing the overall configuration of a conventional safety valve Conceptual diagram showing the pressure distribution immediately below the valve body when the safety valve of FIG. 1 or FIG. 3 is operated. 1 is a longitudinal front view of the extension member of FIG.

  A safety valve according to an embodiment of the present invention will be described with reference to the accompanying drawings. The basic structure of this safety valve is the same as that of the safety valve illustrated in FIG. That is, the safety valve includes a main valve 100 and a pilot valve 200, and is configured as a safety valve with a pilot valve that operates the main valve 100 when the pilot valve 200 is blown out.

  This safety valve opens when the primary pressure is introduced into the dome chamber 201 and the pilot valve 200 reaches a predetermined pressure, and the primary pressure in the dome chamber 201 is released to the atmosphere. While the valve is closed, the pressure load applied to the spring of the pilot valve 200 and the sense chamber diaphragm is balanced, and when the primary pressure introduced into the dome chamber 201 exceeds the set pressure of the spring, the spring of the pilot valve is pushed up, The valve body of the pilot valve 200 is displaced to the valve opening position.

  The main valve 100 includes a membrane sheet 2 stretched below the valve body 1, a mounting shaft 3 projecting downward from the central hole of the membrane sheet 2, and a seat fixed to the mounting shaft 3 so as to support the membrane sheet 2 from below. The support part 4 and the pressure introduction path which guides the primary side pressure to the gap 5 between the valve body 1 and the membrane sheet 2 via the inside of the mounting shaft 3 are provided. The outer periphery of the membrane sheet 2 is fixed to the valve body 1 by a secondary sheet 6. The secondary sheet 6 sandwiching the outer periphery of the membrane sheet 2 together with the valve body 1 is fastened to the valve body 1 with bolts and nuts.

  A shaft 8 is connected to the valve body 1. The shaft portion 8 is passed through a guide portion 10 provided in the main valve diaphragm 9, and is coupled with a diaphragm retainer and a diaphragm retainer in the dome chamber 201. The guide direction of the guide unit 10 is the up-down direction. When the pilot valve 200 is closed, the main valve diaphragm 9 has a dome chamber 201 as compared to the area (valve element pressure receiving area) where the valve element 1 is pushed by the primary pressure that has entered the inlet 12 of the main valve body 11. Since the effective area pushed by the primary side pressure is large, the downward load applied from the main valve diaphragm 9 to the valve body 1 via the shaft portion 8 exceeds the force pushed by the primary pressure flowing from the inlet 12. For this reason, when the pilot valve 200 is closed, the valve body 1 is pushed downward, and accordingly, the secondary seat 6 and the membrane seat 2 are pushed against the valve seat 7. When the primary pressure reaches or exceeds the set pressure of the pilot valve 200, the pilot valve 200 opens, the pressure in the dome chamber 201 decreases, the downward load pushing the valve body 1 also decreases, the valve body 1 lifts, and the membrane sheet 2. The secondary seat 6 leaves the valve seat 7 and the primary pressure escapes from the outlet 13 of the main valve body 11. When the pressure in the dome chamber 201 decreases to near zero, the main valve 100 is fully opened, and when the primary side pressure drops to a predetermined pressure, the pilot valve 200 and the main valve 100 are closed.

  As shown in FIG. 2A, the safety valve mounting shaft 3 is composed of a portion protruding downward from the central hole 15 of the membrane sheet 2 in the male screw part that passes through the central hole 14 of the valve body 1. The outer diameter of the mounting shaft 3 corresponds to the outer diameter at the top of the screw thread. The remaining part of the male screw part closes the central hole 14 and forms part of the valve body 1. The shaft portion 8 is connected to the head portion 16 of the male screw part.

  The sheet support portion 4 includes a retainer 17 that supports the center side of the membrane sheet 2 from below, and nuts 19 and 20 that are screwed into a male screw portion 18 formed on the outer diameter surface of the mounting shaft 3. The nuts 19 and 20 are double nuts.

  An annular spacer 21 is interposed between the periphery of the central hole 15 of the membrane sheet 2 and the periphery of the central hole 14 of the valve body 1. The valve body 1 has an outer peripheral protrusion 22 that sandwiches the membrane sheet 2 together with the secondary sheet 6. The membrane sheet 2 is stretched on the valve body 1 so that the gap 5 can be maintained by the spacer 21 and the outer peripheral projection 22.

  Inside the mounting shaft 3, a hollow hole 23 that passes through the shaft center so as to open to the center of the lower surface and a hole 24 that penetrates from the outer diameter surface of the mounting shaft 3 to the hollow hole 23 in the axial radial direction are formed. ing. A hole 25 is formed in the spacer 21 so as to communicate between the hole 24 and the gap 5.

  The safety valve includes an extension member 26 fixed to the mounting shaft 3. The extension member 26 includes a cap nut that is screwed into the male screw portion 18. As shown in FIG. 5, the extension member 26 includes a female screw portion 27, a blow hole 28 formed deeper in the axial direction from the female screw portion 27, and an axial radial direction from the outer diameter surface of the cap nut to the blow hole 28. A penetrating pressure inlet 29 is formed. The pressure intake ports 29 are formed at a plurality of locations in an arrangement facing the axial diameter direction. Since each pressure intake port 29 is closed at the lower end, it is not exposed on the lower surface of the extension member 26. As shown in FIG. 2A, when the extension member 26 is fixed to the mounting shaft 3 by screwing into the male screw portion 18, the pressure intake port 29 located on the outer diameter of the extension member 26 is attached to the mounting shaft in the axial direction. 3 is located farther than the male screw portion 18 having an outer diameter of 3, and continues from the pressure intake port 29 to the hollow hole 23 in the mounting shaft 3 through the blow-out hole 28.

  The pressure introduction path is composed of the extension member 26, the mounting shaft 3 and the spacer 21, and in order from the inlet 12 side, the inside of the extension member 26 (the pressure inlet 29, the flow passage wall surface of the blow-through hole 28), the inside of the mounting shaft 3 ( The hollow hole 23, the channel wall surface of the hole 24), the inside of the spacer 21 (the channel wall surface of the hole 25), and the gap 5 are communicated. Accordingly, when the valve is closed, the pressure introduction path takes the primary pressure from the inlet 12 only from the pressure intakes 29 and 29 and guides it to the gap 5. In FIG. 2B, the vicinity of the valve seat 7 being closed is enlarged, and the action of the primary pressure is conceptually drawn with an arrow line. As shown in the figure, since the pressure receiving area on the upper surface side of the membrane sheet 2 is larger than the pressure receiving area on the lower surface side of the membrane sheet 2, the membrane sheet 2 is pressed downward. As a result, the non-supporting portion 30 of the membrane sheet 2 that is not supported from below by the retainer 17 and the secondary seat 6 extends along the sealing surface 31 of the valve seat 7 by the primary pressure acting on the upper surface side of the membrane sheet 2. As a result, the non-supported portion 30 and the sealing surface 31 are securely adhered. In this way, the non-supporting portion 30 is pressed against the seal surface 31 of the valve seat 7 and is kept airtight. The sheet thickness at the non-supporting portion 30 is set to be sufficiently thin so as to obtain the flexibility that can realize the above-described deformation and adhesion.

  FIG. 1 shows the vicinity of the valve body 1 when the safety valve is fully opened. As shown in the figure, when the safety valve is actuated to lift the valve body 1, the primary pressure entered from the inlet 12 is communicated with the atmosphere through the gap between the secondary seat 6 and the valve seat 7. Run away to the next side. At this time, since the pressure introduction path takes in the primary side pressure only from each pressure intake port 29 located farther from the outer diameter of the mounting shaft 3 in the axial radial direction, it is lower than the stagnation point pressure in the pressure distribution of FIG. The pressure is guided to the gap 5. Accordingly, the force for expanding the non-supporting portion 30 of the membrane sheet 2 by the pressure of the gap 5 is reduced more than the stagnation point pressure. In FIG. 1, a state in which the non-supporting portion 30 is swollen is shown by a two-dot chain line. Therefore, this safety valve can prevent the burst at the non-supporting portion 30 of the membrane sheet 2 during operation even if the sheet thickness of the non-supporting portion 30 of the membrane sheet 2 is reduced. In the membrane sheet 2, there is no risk of rupture at a portion supported by the sheet support portion 4 such as the retainer 17 or the secondary sheet 6 from below.

  Each pressure intake port 29 is in a flow in which the primary pressure blows out to the secondary side. In the figure, the gas to be blown is drawn with dots, and the average streamline is drawn with arrows. Since each pressure intake port 29 is closed at the lower end, the blowing flow does not enter the pressure introduction path directly. Since the pressure in the gap 5 is the operating pressure of the safety valve at the beginning of the valve opening, the blowing flow is lower than the pressure in the gap 5. While the valve is opened, as long as the blow-out flow passing immediately adjacent to each pressure intake port 29 is lower than the pressure in the gap 5, an ejector effect that sucks the primary fluid of the gap 5 from each pressure intake port 29 is obtained. Thereby, since the pressure of the gap 5 is reduced, this safety valve can further prevent the unsupported portion 30 of the membrane sheet 2 from being ruptured. If the ejector effect is used in this way, the pressure in the gap 5 can be reduced to an average pressure just below the valve body 1.

  Further, the extension member 26 that is screwed into the same male screw portion 18 as the nut 19 necessary for the seat support portion 4 is communicated with the inside of the mounting shaft 3, and the axial diameter position of the pressure intake port 29 is selected by selecting the outer diameter of the extension member 26. Can be set. Therefore, this safety valve can be realized by simply adding the extension member 26 to the mounting shaft 3 of the conventional structure having the male screw portion 18 and the hollow hole 23 opened at the center of the lower surface. Application to existing safety valves is easy.

  If there is no allowance for the length of the male screw portion 18, the nut 20 may be omitted, and the nut 19 and the extension member 26 may constitute a double nut. Further, in order to prioritize the weight reduction of the hanging load of the shaft portion 8 in setting the operating pressure at which the safety valve opens, a pressure intake port may be formed on the outer diameter surface of the mounting shaft 3. Thus, the technical scope of the present invention is not limited to the above-described embodiment, but includes all modifications within the scope of the technical idea based on the description of the scope of claims.

DESCRIPTION OF SYMBOLS 1 Valve body 2 Membrane seat 3 Mounting shaft 4 Seat support part 5 Crevice 6 Secondary seat 7 Valve seat 8 Shaft part 9 Main valve diaphragm 10 Guide part 11 Main valve body 12 Inlet 13 Outlet 14 Central hole 15 Central hole 16 Head 17 Retainer 18 Male thread portion 19 Nut 20 Nut 21 Spacer 22 Outer peripheral projection 23 Hollow hole 24 Hole 25 Hole 26 Extension member 27 Female thread portion 28 Blow hole 29 Pressure intake port 30 Non-supporting portion 31 Seal surface

Claims (3)

A membrane sheet (2) stretched below the valve body (1), a mounting shaft (3) projecting downward from a central hole (15) of the membrane sheet (2), and the membrane sheet (2) are supported from below. And a gap between the valve body (1) and the membrane sheet (2) through the interior of the mounting shaft (3) with the seat support (4) fixed to the mounting shaft (3). A pressure introduction path leading to (5),
In the safety valve in which the membrane sheet (2) is pressed against the valve seat (7) by the pressure guided from the pressure introduction path to the gap (5),
The safety valve according to claim 1, wherein the pressure introduction path is provided so as to take in the primary side pressure only from the outer diameter of the mounting shaft (3) in the axial direction.   The safety valve according to claim 1, wherein the pressure inlet (29) of the pressure introduction path is closed at the lower end. An extension member (26) fixed to the mounting shaft (3);
The seat support portion (4) has nuts (19, 20) screwed into a male screw portion (18) formed on the outer diameter surface of the mounting shaft (3),
The extension member (26) comprises a cap nut screwed into the male screw portion (18),
The extension member (26) has a blow hole (28) formed deeper in the axial direction from the female screw portion (27), and a pressure located farther from the outer diameter of the mounting shaft (3) in the axial radial direction. Intake port (29) is formed,
When the extension member (26) is fixed to the mounting shaft (3) by screwing into the male screw portion (18), the mounting shaft (3) passes through the blow-through hole (28) from the pressure intake port (29 ). being adapted to extend into the interior of the hollow bore (23),
The safety valve according to claim 1 or 2, wherein the pressure introduction path takes in a primary side pressure from the pressure inlet (29).

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