JPH0334537Y2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to a valve device, and particularly to a valve device configured to further enhance the sealing effect of a sealing member between a valve stem and a valve stem holder.

BACKGROUND ART In general, in a valve device, a sealing member is provided between a valve shaft having a valve body and a valve shaft holding portion that holds the valve shaft.
This seal member is compressed by a seal holder to provide a fluid-tight seal between the valve stem and the valve stem holding portion. In addition, in nuclear power plants, control rods are moved in and out between multiple fuel rods in the reactor to control the degree of nuclear fission.In an emergency, the scram valve of the water pressure control unit is opened and the water pressure control unit is activated. The pressurized water from the control rod drive mechanism is supplied to the control rod drive mechanism. Therefore, when the scram valve opens, control rods are inserted between the fuel rods to bring the reactor to an emergency shutdown. As described above, scram valves in hydraulic control units used in nuclear power plants are strictly required to operate reliably in emergencies and to not leak from each seal. For this reason, scram valves have a double seal structure between the valve stem and the valve stem holding member, and the seal member is compressed by a seal retainer to prevent the working fluid from leaking from the valve stem.

Problems to be Solved by the Invention However, in all of the above-mentioned conventional valve devices, the sealing member provided between the valve stem and the valve stem holding part is pressed by the seal retainer, so that the sealing member gradually becomes weaker. It may deform when compressed. In this case, even if the pressure of the working fluid acts on the sealing member when the valve is opened, the surface pressure necessary for liquid-tightly sealing between the valve stem and the valve stem holding portion does not act on the sealing member. Therefore, the conventional valve device has a problem in that the deformation of the sealing member may cause the working fluid to leak to the outside. In particular, in the case of a seal member having a structure in which the sealing effect is enhanced by fluid pressure, fluid tends to leak easily when the fluid pressure is low.

Therefore, an object of the present invention is to provide a valve device that solves the above problems.

Means and Effects for Solving the Problems The present invention includes a valve body having a valve seat inside, a valve shaft having a valve body that seats on and off the valve seat, and a valve shaft that slides in the direction of seating and seating of the main body. a valve stem holder for movably holding the valve stem; an annular recess formed outside the valve stem holder to surround the valve stem; In the valve device, the valve device includes a seal member for sealing between the seal member and a seal holder provided outside the seal member to press the seal member, the seal member being slidably provided near the valve stem holding portion in the recess. an annular sliding member that fits on the outer periphery of the valve shaft; an inner seal member that seals between the sliding member and the valve shaft on the inner periphery of the sliding member; An outer peripheral side sealing member is provided on the outer periphery of the sliding member to seal between the sliding member and the inner wall of the recess, and the sliding member presses the sealing member against the sealing member by the pressure of the fluid flowing inside the valve body. The sealing member is compressed by the pressure of the fluid to enhance the sealing effect.

Embodiment FIG. 1 shows an embodiment of the valve device according to the present invention. In FIG. 1, a scram valve 1 is a valve device installed in a hydraulic control unit that supplies working fluid when, for example, a control rod of a nuclear reactor is inserted into a nuclear reactor in an emergency. The valve body 2 of the scram valve 1 has an inlet 2a connected to an accumulator (not shown) and an outlet 2 that passes through a seat ring 3 and branches to both sides.
It has b, 2c. A bonnet 4 is fixed to the upper part of the valve body 2 by tightening mounting bolts 5 and nuts 6. Further, the seat ring 3 is held within the valve body 2 via a valve body holding member 7 and a disk 8, and an annular seat member 9 is sandwiched between the seat ring 3 and the disk 8. The upper part of the valve body 2 and the lower part of the bonnet 4 are liquid-tightly sealed by a seal member 10.
Further, a seal member 11 also seals between the outer periphery of the valve seat 3 and the valve body 2.

Reference numeral 12 denotes a valve body, which is integrally provided at the lower end of the valve shaft 13 and held by the valve body holding member 7. Also,
The valve stem 13 is connected to a diaphragm 15 inside the case 14 via a rod 16 and a rod receiving member 16a. Diaphragm 15 in normal case 14
There is a port 14a in the air chamber 15a defined by
Air is supplied from Therefore, the diaphragm 15 is moved downward by air pressure, and the valve body 12 is fitted into the seat member 9 to close the valve.

The valve stem 13 is inserted into the valve stem holding portion 4a of the bonnet 4 and is held slidably in the opening and closing directions. A space between the valve stem holding portion 4a and the valve stem 13 is liquid-tightly sealed by a first seal member 18 and a second seal member 19 provided in a recess 4b of the bonnet 4. That is, since the valve shaft 13 is slidably displaced by the valve opening and closing operations, it has a double seal structure, so that the working fluid does not leak to the outside when the valve is opened.

As shown in FIG. 2, the first seal member 18 is elastically displaced in the radial direction in response to the pressure of the working fluid, increasing the surface pressure on the inner and outer peripheries, and has a plurality of V gaskets 18 ₁ to 18 that maintain the sealing effect. It becomes by stacking ₅ . Further, the second seal member 19 is also formed by stacking a plurality of V gaskets 19 ₁ to 19 ₃ so that the sealing effect is enhanced by receiving the pressure of the working fluid. An annular seal presser 20 is inserted into the upper part of the first seal member 18, and the first seal member 18
positional shift is prevented. In addition, the seal presser foot 20
An annular sliding member 21 that fits onto the valve shaft 13 is provided between the valve shaft 13 and the second seal member 19 .

The lower surface of the second seal member 19 and the seal presser 20
The distance between the sliding member 21 and the sliding member 21 is larger than the thickness of the sliding member 21, and the sliding member 21 is attached to be slidable in the axial direction with a distance A between the sliding member 21 and the sliding member 21.

Therefore, when the valve is opened, the sliding member 21 is displaced upward as will be described later, the upper surface abuts the lower surface of the second seal member 19, and the lower surface is spaced apart by a distance A from the upper surface of the seal presser 20.

An O-ring (inner seal member) 26 is provided in the outer circumferential groove 21a of the sliding member 21 to seal between the inner wall of the recess 4a, and the valve shaft 1 is provided in the inner circumferential groove 21b.
An O-ring (outer peripheral side sealing member) 27 is provided to seal between the outer peripheral side and the outer peripheral side sealing member 3. Further, a groove 21c is provided on the upper inner periphery of the sliding member 21 for taking out the sliding member 21 from the recess 4b. Therefore, when replacing the first seal member 18, for example, the sliding member 21 can be easily taken out by engaging the tip of a jig (not shown) with the groove 21c. 18 replacement work can be done easily.

Note that a seal presser 22 is fitted into the upper part of the second seal member 19, and the second seal member 19 is prevented from popping out by the seal presser 22. Further, the seal presser 22 is held via a holding member 25 by tightening a nut 24 of a bolt 23 screwed onto the bonnet 4.

Here, the operation when the scram valve 1 is opened will be explained.

First, air is no longer supplied from the emergency port 14a to the air chamber 15a. Therefore, the diaphragm 15 moves upward as shown in FIG. 1 due to the pressing force of the spring 17, and the rod 16 is pulled up. Therefore, the valve body 12 and the valve shaft 13 are separated from the seat ring 9 and opened. As a result, the pressurized working fluid flows into the valve body 2 from the inlet 2a, and
It flows out from b and 2c.

Additionally, the pressure of the working fluid acts between the valve shaft 13 and the valve shaft holding portion 4a as well as the valve opening operation. That is, the first seal member 18 receives the pressure of the working fluid, and the surface pressure against the valve shaft 13 and the inner wall of the recess 4b increases, thereby preventing leakage of the working fluid.

However, even if the first seal member 18 receives the pressure of the working fluid, it may not be able to exhibit a sufficient sealing effect. Even in such a case, the fluid leaking from the first seal member 18 is reliably prevented from flowing outside by the second seal member 19.

That is, when fluid flows from the first seal member 18, the pressure of the fluid acts on the lower surface of the sliding member 21. O-rings 26 are provided on the inner and outer peripheries of the sliding member 21,
27, the sliding member 21 reliably receives the fluid pressure even when the fluid pressure is low, and presses the lower end of the second sealing member 19 with its upper surface. Second
Since the upper end of the seal member 19 is in contact with the seal presser 22, it is compressed by the pressing force of the sliding member 21. Therefore, the second seal member 19 is appropriately compressed by the fluid pressure, and the valve shaft 13
Sufficient surface pressure is maintained against the outer periphery of the recess 4b and the inner wall of the recess 4b to prevent leakage of the working fluid.

Further, since the second seal member 19 is not always compressed but is compressed by the pressure of the working fluid, it is less prone to fatigue and can appropriately prevent leakage between the valve shaft 13 and the recess 4a. Therefore, the scram valve 1 can eliminate the pressure loss of the working fluid due to leakage from the valve shaft 13 during emergency operation, so that the reliability of the hydraulic control unit during emergency operation can be further improved.

In the above explanation, the scram valve used in the water pressure control unit of a nuclear reactor was used as an example, but the invention is not limited to this, and can be applied to any valve device such as a gate valve that opens and closes by displacing the valve shaft. Of course, the present invention can be applied.

Effects of the invention As described above, in the valve device according to the present invention, the sliding member compresses the sealing member that seals between the valve shaft and the recess by the pressure of the fluid flowing inside the valve body, so that the seal is always maintained. By compressing the seal member when the valve is opened instead of compressing the member, deformation of the seal member in the compressed state can be prevented, and the life of the seal member can be extended.
Moreover, since the sealing member is provided on the inner and outer periphery of the sliding member, the sealing member can be compressed with a pressure that corresponds to the pressure of the fluid, and even if the fluid pressure is low, the sealing member can be compressed appropriately. Therefore, leakage between the valve stem and the valve stem holding member can be reliably prevented.
Furthermore, when applied to a scram valve in a water pressure control unit of a nuclear reactor, it has the advantage of eliminating loss of working fluid due to leakage from the valve stem, thereby improving reliability in emergencies.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view of an embodiment of the valve device according to the present invention, and FIG. 2 is a cross-sectional view showing an enlarged main part of the present invention. DESCRIPTION OF SYMBOLS 1... Scram valve, 2... Valve body, 4... Bonnet, 4a... Valve stem holding part, 13... Valve stem, 1
8...First seal member, 19...Second seal member, 21...Sliding member, 22...Seal presser.

Claims (1)

[Claims for Utility Model Registration] A valve body having a valve seat therein, a valve shaft having a valve body that seats and seats on the valve seat, and the valve shaft being slidably held in the direction of seating and seating on the main body. a valve stem holding part;
an annular recess formed to surround the valve shaft outside the valve shaft holding portion; a seal member provided within the recess for sealing between the valve shaft and the recess; and the seal. Provided outside of the member,
In a valve device comprising a seal holder for pressing the valve shaft, an annular sliding member is provided in the recess so as to be slidable near the valve shaft holding portion, and is fitted to the outer periphery of the valve shaft; An inner peripheral side sealing member is provided on the inner periphery of the sliding member to seal between the sliding member and the valve shaft, and an inner peripheral side sealing member is provided on the outer periphery of the sliding member to seal between the sliding member and the inner wall of the recess. A valve device comprising: an outer circumferential seal member for sealing, wherein the sliding member compresses the seal member with the seal retainer by the pressure of the fluid flowing within the valve body.