JP2017172754A - Spherical valve for cryogenic temperature - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent reduction in reliability of closing valve when a spherical valve for cryogenic temperature is used under no influence of shrinkage of a valve body due to reduction in temperature.SOLUTION: There are provided a valve case 2 of which upper opening is closed by a lid 3; a valve rod 7 of which lower end side passes through the lid 3 and inserted into the valve case 2; and a valve body 8 moved to or away from an inner valve seat 2b of the valve case 2. The valve rod 7 is made in such a way that a male thread 7a at the outer periphery is engaged in thread with a female thread 3b at the valve case 2. The valve rod 7 is rotated by a handwheel 10 and forwarded with a thrust force generated at an engaged part between the male thread 7a and the female thread 3b, and a seal pressure correcting spring 11 for biasing the valve body 8 toward the valve seat 2d is present between the valve body 8 of spherical valve for cryogenic temperature for closing the valve part and the valve rod 7 by pushing the valve body 8 against the valve seat 2d with the valve rod 7.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a cryogenic ball valve provided in a transport line for a cryogenic liquid such as liquid nitrogen or a cryogenic gas, and more specifically, a valve closed so as not to be affected by the contraction of a valve body caused by a temperature drop. The present invention relates to a cryogenic ball valve that prevents a decrease in reliability.

  The above-mentioned cryogenic ball valve is used for tank trucks that carry cryogenic liquids such as liquid nitrogen and cryogenic gases.

  As a prior art of the ball valve, for example, there are those shown in Patent Documents 1 and 2 below.

  The ball valve (stop valve) described in Patent Document 1 is for cryogenic use, and the ball valve shown in FIG. 6 of the same document is a fiber having toughness and elasticity in a cryogenic region. It is made of reinforced poly-ether-ether-ketone resin, and its valve body is pressed against a valve seat formed on the valve box to close the valve portion.

  The valve body is attached to the lower end of the valve stem, and the valve body is pushed against the valve seat by propelling the valve stem using the thrust of a screw.

  In order to propel the valve stem, a pressure-resistant pipe or tube that protects the valve stem is attached to the upper part of the valve box, and a yoke part is attached to the pressure-resistant part or the upper part of the pipe. By screwing the male screw, and operating a handle wheel (referred to as a rotary handle in Patent Document 1) attached to the valve stem, the valve stem is rotated to apply a thrust to the threaded portion of the bearing portion and the valve stem. It is done in a way that causes it.

  The ball valve of Patent Document 2 also closes the valve portion by pressing the valve body attached to the lower end of the valve stem against the valve seat of the valve box (valve case) by propelling the valve stem.

  The ball valve of Patent Document 2 has a drive sleeve that rotates by operating a handle wheel, and a male screw on the upper outer periphery of the valve rod is screwed to the drive sleeve.

  The valve stem is provided with a non-rotating ring inside the valve box and engaged with the non-rotating ring so as not to rotate relative to the non-rotating ring and to be slidable in the axial direction, thereby rotating the drive sleeve with the handle wheel. The valve stem is pushed without rotating and the valve body is pressed against the valve seat.

  In the ball valve of Patent Document 2, since the valve portion is opened and closed without the rotation of the valve stem, an increase in sliding resistance of the packing that seals the outer periphery of the valve stem is avoided.

  As a result, the rotational torque of the steering wheel wheel can be reduced and the life of the packing can be improved as compared with the ball valve of Patent Document 1. However, the valve body is directly moved by the valve rod and pushed to the valve seat. The valve closing structure to be attached is not different from the ball valve of Patent Document 1.

JP 2008-19883 A JP 7-269721 A

  In a ball valve provided in a cryogenic liquid transport pipeline, the valve body contracts due to a decrease in temperature during use, and the seal pressure against the valve seat decreases.

  The contact part of the valve element of the low temperature ball valve with respect to the valve seat is a trifluoride resin with excellent low temperature characteristics and chemical resistance (PCTFE: manufactured by Daikin Industries, Ltd., trade name: NEOFLON, etc.) (Hereinafter referred to as “soft packing”) is generally used.

  When the soft packing formed of the trifluoride resin is placed in a cryogenic environment, the soft packing shrinks and the thickness decreases. In the case of soft packing having a thickness before shrinkage of about 6 mm, the thickness reduction amount at a temperature difference of −190 ° C. is about 0.1 mm.

  Since the temperature of liquid nitrogen is −196 ° C., a temperature difference of about −190 ° C. occurs when the inside of the pipe is changed from room temperature to liquid nitrogen temperature in the case of a ball valve provided in the liquid nitrogen transport pipe. To do.

  Therefore, thickness reduction due to shrinkage due to a temperature drop of the soft packing is inevitable. Moreover, even if it is a fluorocarbon resin excellent in low-temperature characteristics, when it is exposed to an environment of −196 ° C., the elasticity decreases due to curing.

  For this reason, in the tank lorry ball valve for transporting liquid nitrogen, the sealing pressure is loosened by the soft packing.

  The looseness of the sealing pressure is due to the fact that the load applied to the sealing surface when the soft packing of the above specification before shrinkage is pressed against the valve seat in the fully closed position is now 3300 N, and the thickness of the soft packing is due to thermal shrinkage. If the thickness is reduced by 0.1 mm, the load applied to the sealing surface is reduced to 2870N. This is a numerical value that cannot be ignored and reduces the reliability of valve closing.

  Note that the ball valve of Patent Document 1 employs a valve body made of fiber-reinforced poly-ether-ether-ketone resin. However, when this valve body is also placed in a cryogenic environment, Reduced elasticity due to curing. Therefore, changing the material of the soft packing cannot be a fundamental solution to the above problem.

  In view of this, an object of the present invention is to prevent the reliability of the closed valve from being lowered during use of the cryogenic ball valve so as not to be affected by the contraction of the valve body due to the temperature drop.

In order to solve the above problems, in the present invention, a valve box whose upper opening is closed with a lid, a valve rod whose lower end passes through the lid and is inserted into the valve box, and an interior of the valve box The valve stem is connected to and separated from the valve seat, and the valve stem is screwed into a female screw at a portion where the male screw provided on the outer periphery is connected to the valve box, and the valve stem is connected to the externally exposed portion of the valve stem. A cryogenic oval valve that is rotated by an attached handle wheel and propelled by a thrust generated at the threaded portion of the male screw and the female screw, presses the valve body against the valve seat with the valve rod, and closes the valve portion is as follows. Configured as street.
That is, the valve body is mounted on the outer periphery of the tip of the valve stem in a state in which an axial relative movement larger than an assumed maximum contraction amount in the axial direction due to a temperature drop of the valve body is allowed, and the valve body and the valve stem A seal pressure correction spring for biasing the valve body toward the valve seat is interposed therebetween.

  The seal pressure correction spring employed in such a cryogenic ball valve is preferably a disc spring. Further, it is preferable that the seal pressure correcting spring is interposed by being compressed in advance rather than being interposed in a free state.

  The female screw is provided on the lid and the male screw is provided on the outer periphery of the lid penetrating portion of the valve stem, or a spherical surface is formed at the tip of the valve stem, and a plate is provided between the valve stem and the seal pressure correction spring. It is also preferable that the spherical surface at the tip of the valve stem is in point contact with the spring retainer via a spring retainer in the shape of a ring.

  The valve body may be engaged with the valve stem at an allowable upper limit position in the axial relative movement with respect to the valve stem so as to be prevented from coming off from the outer periphery of the valve stem.

  The stopper is provided with a bottomed cylindrical portion having a female thread on the inner surface at the upper part of the valve body, and the bottom end of the valve rod provided with a radially bulging portion such as a flange on the outer periphery of the tip. Inserted, and then adopts a structure in which a cylindrical valve retainer whose inner diameter is fitted to the outer periphery of the valve rod in advance is smaller than the outer diameter of the radially expanded portion is screwed into the inside of the bottomed cylindrical portion And preferred.

  The cryogenic ball valve according to the present invention is such that the valve stem is engaged with the valve box in an axially movable and non-rotatable manner, and a male screw provided on the outer periphery of the valve stem is used for rotational operation. The valve shaft is propelled by a thrust generated in the threaded portion of the male screw and the female screw by rotating the handle wheel and screwed into a female screw formed on a sleeve connected to the handle wheel, and the valve rod is used to propel the valve. The sealing pressure correction spring may be additionally provided in a ball valve having a structure in which a body is pressed against the valve seat to close the valve portion.

  The cryogenic ball valve according to the present invention pushes the valve body against the valve seat by propelling the valve rod toward the valve seat side as in the conventional ball valve. At this time, the valve stem is further pushed down even after the valve body has moved to the fully closed position.

  As a result, the seal pressure correction spring is compressed (the pre-compressed seal pressure correction spring is further compressed from the previous compression position), and in the fully closed state, the valve body is moved to the valve seat by the force of the seal pressure correction spring. Pressed.

  Further, since the valve rod is further pushed down after the valve element moves to the fully closed position, an axial movement allowance is given to the valve element. For this reason, when the valve body contracts due to a temperature drop thereafter, the reduction in the seal pressure is compensated by the force of the seal pressure correction spring, and the proper seal pressure in the fully closed state is maintained.

  The disc spring seal pressure correction spring requires less installation space in the axial direction than the coil spring, and it is easy to ensure a large spring load. If the seal pressure correction spring is compressed in advance, a larger spring load can be obtained with a small amount of compression.

  Further, in a ball valve that rotates a valve stem to generate a propulsive force, the internal thread is provided on the lid and the male screw is provided on the outer periphery of the lid penetrating portion of the valve stem. A large thrust can be applied to the rod, and the rotation operation of the steering wheel can be lightened.

  In addition, when the tip of the valve stem is a spherical surface and the spherical surface is in point contact with the spring retainer interposed between the valve stem and the seal pressure compensation spring, the contact resistance of the valve stem with respect to the spring retainer is small. Increase in rotational torque can be kept small.

  Further, the valve body engaged with the valve stem and prevented from coming off from the valve stem can be moved to the valve open position by following the valve stem.

  The valve body can be moved to the valve open position by the fluid pressure of the liquid passing through the valve when the valve rod is returned to the valve open position. With this structure, stable valve opening is guaranteed.

  In addition, the valve body that prevents the valve body from coming off from the valve stem can be connected to the valve body by a simple operation by simply screwing the valve retainer into the bottomed cylindrical portion of the valve body. Yes.

It is sectional drawing which shows an example of the lens valve for cryogenic temperatures of this invention. It is an expanded sectional view which shows the detail of the seal pressure correction spring installation part of a valve body.

  Hereinafter, an embodiment of a cryogenic ball valve according to the present invention will be described with reference to FIGS. 1 and 2 of the accompanying drawings.

  The cryogenic ball valve 1 shown in FIG. 1 includes a valve box 2, a lid 3 attached to an upper opening of the valve box 2, a union nut 4 for fixing the lid 3 to the valve box 2, and the lid 3. A relay pipe (sheath pipe) 5 connected to the upper part of the pipe, a packing box 6 attached to the upper end of the relay pipe, the packing box and the lower end inserted into the inside of the valve box 2 and inserted into the relay pipe 5 It has the valve stem 7 made.

  In addition, the valve body 8 disposed inside the valve box 2, the liquid-tight seal portion 9 on the outer periphery of the valve stem 7 installed inside the packing box 6, and the upper end outer periphery of the valve stem 7 are relatively unrotatable. It has a handle wheel 10 attached.

  Further, a seal pressure correcting spring 11 characterizing the present invention is provided between the valve stem 7 and the valve body 8.

  The valve box 2 has a cryogenic liquid inlet 2a and an outlet 2b on a horizontal axis, and further, a vertically arranged channel 2c between the inlet 2a and the outlet 2b and an upward bulge surrounding the channel. It has an extended valve seat 2d.

  Further, an opening 2e that is liquid-tightly closed by the lid 3 and the gasket 12 sandwiched between the lid 3 and the lid 3 is provided at the top.

  The lid 3 has a flange 3 a on the outer periphery for engaging the union nut 4, and has an internal thread 3 b on the inner peripheral surface at a position excluding the connection portion of the relay pipe 5.

  The relay pipe 5 is joined in a liquid-tight manner to the lid 3 and the packing box 6 into which both ends of the relay pipe are inserted using a silver brazing material 13.

  The valve stem 7 has a male screw 7 a having a diameter larger than the outer diameter of the other portion on the outer periphery of the portion inserted through the lid 3, and the male screw 7 a is screwed to the female screw formed on the inner periphery of the lid 3. I am letting. The lower end side of the valve stem 7 is a round shaft portion having a diameter smaller than the outer diameter of the male screw 7a, and a radially bulging portion having a size capable of passing through the female screw forming portion of the lid 3 on the outer periphery of the lower end of the round shaft portion (see FIG. It is provided with a flange 7b.

  A soft packing 8a made of a fluorocarbon resin that presses against the valve seat 2d is fixed to the valve body 8 by a sheet presser 16 and a nut 17 and is detachably attached.

  The valve body 8 has a bottomed cylindrical portion 8b having an upper end opening formed with an internal thread 8c on the inner surface. The bottomed cylindrical portion 8b has a concave portion 8d serving as a spring seat at the bottom center, and further has a pressure relief hole 8e extending from the inner periphery to the outer periphery of the bottomed cylindrical portion 8b at the lower portion of the bottomed cylindrical portion 8b. .

  The lower end side of the valve stem 7 is inserted inside the bottomed cylindrical portion 8b. Further, inside the bottomed cylindrical portion 8b, a cylindrical valve retainer 18 having an inner diameter fitted in advance on the outer periphery of the valve rod 7 is smaller than the outer diameter of the radially expanded portion 7b is screwed. The valve presser 18 prevents the valve body 8 from coming off from the outer periphery of the valve stem 7. Reference numeral 19 denotes a detent member for the valve presser 18, which is engaged with the valve presser 18.

  A gap G is provided between the valve retainer 18 and the bottom of the bottomed cylindrical portion 8b to allow the valve rod 7 to move in the axial direction. The gap G is larger than the assumed maximum contraction amount in the axial direction due to the temperature drop of the valve body 8.

  The liquid-tight seal portion 9 is screwed into a seal packing 9 a that is incorporated in the packing storage groove 6 a of the packing box 6 and seals between the outer periphery of the valve stem 7 and the packing box 6, and the upper outer periphery of the packing box 6. A combination of a packing pressing wheel 9b that applies a tightening force by the packing pressing nut 14 to the seal packing 9a and an adapter 9c that sandwiches the sealing packing 9a between the packing pressing wheel 9b is installed.

  The seal pressure correction spring 11 is a combination of a plurality of disc springs facing each other. The seal pressure correction spring 11 is inserted into a recess 8 d provided at the bottom of the bottomed cylindrical portion 8 b of the valve body 8.

  Reference numeral 20 denotes a plate-like spring retainer interposed between the seal pressure correction spring 11 and the valve stem 7. A spherical surface 7 c is provided at the lower end of the valve stem 7, and the spherical surface 7 c makes point contact with the spring retainer 20 so that the valve stem 8 is pressed against the valve seat 2 d by the spring retainer 20 and the seal pressure correcting spring. 11 is made through 11.

  The seal pressure correction spring 11 is compressed in advance, and when the valve body 8 is in the valve open position, the position of the valve presser 18 against the radially expanded portion 7b on the outer periphery of the lower end of the valve rod 7 by the force of the seal pressure correction spring 11 The valve body 8 is pushed down with respect to the valve rod 7.

  The exemplary cryogenic ball valve 1 configured as described above further pushes the valve rod 7 to press the valve body 8 against the valve seat 2d, and the handle portion is further closed after the valve portion is fully closed. 10 is operated to push down the valve stem 7 from the fully closed position until the movement stops. As a result, the seal pressure correction spring 11 is further compressed, the radial bulge 7b is separated from the valve retainer 18, and an axial movement allowance is generated in the valve body 8 due to the force of the seal pressure correction spring 11.

  The movement allowance is designed to be larger than the axial contraction amount of the valve body 8 due to the temperature drop. For this reason, when the valve body 8 contracts in the axial direction due to the temperature drop, the seal pressure correction spring 11 is elastically restored, The seal pressure applied to the contact portion between the valve seat 2d and the valve body 8 in the fully closed position is maintained with almost no decrease.

  The illustrated cryogenic ball valve 1 includes a valve box 2, a relay pipe 5, a valve rod 7, a seal pressure correction spring 11, a seat presser 16, a nut 17, and a nut for fixing a steering wheel made of stainless steel. The lid 3 is made of bronze, the main body of the valve body 8 (location other than the soft packing 8a), the packing box 6 and the packing retaining ring 9 are each made of brass, and the handle wheel 10 is made of zinc alloy die casting. These materials are only preferable examples.

  Further, the illustrated cryogenic ball valve 1 has the valve stem 7 screwed into the lid 3, and the diameter of the male screw 7 a on the outer periphery of the valve stem can be increased to lighten the rotating operation of the handle wheel 10. However, even when the valve stem 7 is screwed into the packing box 6, the valve stem 7 can be propelled by the rotation of the valve stem 7.

  Further, the exemplary cryogenic ball valve 1 is configured to propel the valve rod 7 by rotating the valve rod 7. The present invention is disclosed in FIG. It can also be applied to valves.

  The ball valve of FIG. 1 of Patent Document 2 has the valve stem engaged with the valve box so as to be axially movable and relatively non-rotatable, and a male screw provided on the outer periphery of the valve stem is used as a handle for rotational operation. It is screwed into the female screw of the sleeve connected to the car.

  Then, the valve stem is rotated by the handle wheel and propelled by the thrust generated in the threaded portion of the male screw and the female screw, and the valve body is pressed against the valve seat by the valve rod to close the valve portion. Yes. When this seal valve is additionally provided with the seal pressure correcting spring 11, it becomes a cryogenic bead valve of the present invention.

DESCRIPTION OF SYMBOLS 1 Cryogenic valve 2 Valve box 2a Inlet 2b Outlet 2c Flow path 2d Valve seat 2e Opening 3 Lid 3a Flange 3b Female thread 4 Union nut 5 Relay pipe 6 Packing box 6a Packing storage groove 7 Valve rod 7a Male screw 7b Radial expansion Protruding part 7c Spherical surface 8 Valve body 8a Soft packing 8b Bottomed cylindrical part 8c Female thread 8d Recess 8e Pressure release hole 9 Liquid tight seal part 9a Seal packing 9b Packing retainer wheel 9c Adapter 10 Handle wheel 11 Seal pressure correction spring 12 Gasket 13 Silver bowl Material 14 Packing retainer nut 16 Sheet retainer 17 Nut 18 Valve retainer 19 Non-rotating member 20 Spring retainer G Clearance allowing axial relative movement of the radially bulged portion of the outer periphery of the valve stem

Claims (6)

A valve box (2) whose upper opening is closed by a lid (3); a valve rod (7) whose lower end passes through the lid (3) and is inserted into the valve box (2); and the valve box The valve body (8) to be brought into and out of contact with the valve seat (2d) in (2) is provided, and the valve rod (7) has a male screw (7a) provided on the outer periphery thereof and a female screw on the valve box (2) side ( 3b), and the valve stem (7) is rotated by a handle wheel (10) attached to the externally exposed portion of the valve stem, resulting in a threaded portion of the male screw (7a) and the female screw (3b). A cryogenic ball valve that is propelled by thrust, presses the valve body (8) against the valve seat (2d) with its valve stem (7), and closes the valve portion;
The valve body (8) is mounted on the outer periphery of the tip of the valve rod (7) in a state in which an axial relative movement larger than an assumed maximum contraction amount in the axial direction due to a temperature drop of the valve body is allowed. ) And the valve stem (7), a seal pressure correction spring (11) for biasing the valve body (8) toward the valve seat (2d) is interposed.   The seal pressure correction spring (11) is a combination of a plurality of disc springs facing each other, and the seal pressure correction spring (11) is interposed between the valve body (8) and the valve stem (7). 2. A cryogenic ball valve according to claim 1, which is preliminarily compressed and interposed.   3. The cryogenic oval valve according to claim 1, wherein the female screw (3 b) is provided on the lid (3) and the male screw (7 a) is provided on an outer periphery of a lid penetrating portion of the valve rod (7). .   A spherical surface (7c) is formed at the tip of the valve stem (7), and a plate-like spring retainer (20) is interposed between the valve stem (7) and the seal pressure correction spring (11), and the valve The spherical valve for cryogenic temperature according to any one of claims 1 to 3, wherein a spherical surface (7c) of a rod tip is in point contact with the spring retainer (20).   The valve body (8) includes a bottomed cylindrical portion (8b) having an internal thread on the inner surface at the top, and the bottomed cylindrical portion (8b) is provided with a radially bulging portion (7b) on the outer periphery of the tip. The lower end side of the valve stem (7) is inserted, and a cylindrical valve retainer (18) having an inner diameter smaller than the outer diameter of the radially expanded portion (7b) is screwed into the inside of the bottomed cylindrical portion (8b). The valve body (8) is configured to be prevented from coming off from the outer periphery of the valve stem (7) by engaging the valve retainer (18). Cryogenic valve for cryogenic use. A valve box having a lid attached to the upper opening; a valve stem having a lower end inserted into the valve box; and a valve body that contacts and separates from a valve seat formed inside the valve box. Is engaged with the valve box in an axially movable and non-rotatable manner, and a male screw provided on the outer periphery of the valve stem is screwed into a female screw formed in a sleeve connected to a handle wheel for rotational operation. The valve stem is pushed by the thrust generated in the threaded portion of the male screw and the female screw by rotating the handle wheel, and the valve body is pressed by the valve stem against the valve seat to close the valve portion. There,
The valve body is mounted on the outer periphery of the tip of the valve stem in a state in which an axial relative movement larger than an assumed maximum contraction amount in the axial direction due to a temperature drop of the valve body is allowed, and between the valve body and the valve stem A cryogenic ball valve in which a seal pressure correction spring for biasing the valve body toward the valve seat is interposed.

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