JP2002296388A - Main steam isolation valve - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent deformation of a valve body of a main steam isolation valve, large-sizing and cost rising of a device and improve safety by surely closing a steam path in emergency. SOLUTION: The self-weight and the biasing force of a compression coil spring 30 of the valve body is set to be more than twice of a mechanical resistance force, especially at a value adding a specific marginal force to the twice of the resistance force, so that the valve body 22 contacts a valve seat 17 only by the self-weight and the biasing force of a compression coil spring 30 of the valve body 22 in emergency, such as main steam line failure accident and can move to a complete closing position for completely closing a steam path 14. The complete closing force of the valve is shared by the self-weight of the valve body 22 and the repulse force of the compression coil spring 30.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a main steam isolation valve provided in a main steam pipe of a nuclear power plant to shut off a steam passage in an emergency.

[0002]

2. Description of the Related Art In a nuclear power plant, a nuclear steam generating facility for extracting heat from a nuclear reactor and generating steam by a steam generator, a so-called primary system facility, and a secondary system facility centered on a turbine generator. The steam generated by the steam generator of the primary equipment is sent to the turbine of the secondary equipment using the main steam pipe, and the steam is supplied to the main steam pipe in an emergency such as a main steam pipe breakage accident. A main steam isolation valve is provided to shut off the passage.

In a conventional main steam isolation valve, a valve body is rotatably provided in a valve box in which a steam passage is formed, and the valve body is provided between an open position for opening the steam passage and a closed position for closing the steam passage. It is movable and is urged and supported by a spring in the valve closing direction.
During operation of the nuclear power plant, the air cylinder is operated by continuously supplying air to the air cylinder, and the valve body is moved to the valve opening position against the spring to open the steam passage. On the other hand, when a main steam pipe breakage accident occurs, the supply of air to the air cylinder is stopped, the air in the air cylinder is discharged, and the valve is moved to the valve closing position by the biasing force of the spring to shut off the steam passage. I do.

[0004]

However, in the above-mentioned conventional main steam isolation valve, when a main steam pipe breakage accident occurs, the valve body is moved to the valve closing position by the urging force of a spring to open the steam passage. Although the valve is shut off, there is a possibility that the valve closing force of the valve is insufficient due to mechanical resistance of the valve element and the support portion of the spring, or the repulsive force of the packing, and the steam passage cannot be reliably shut off. . Therefore, it is conceivable to increase the urging force of the spring to secure a sufficient valve closing force of the valve body.
In this case, there is a problem that the valve body is plastically deformed when the valve body comes into contact with the valve seat of the valve box because the valve closing force is too large.

Conventionally, therefore, a manual tightening device is additionally provided to ensure the safety of the main steam isolation valve, and when the main steam pipe breaks, the valve body is closed by the urging force of the spring. After moving to the valve position, the operator used the manual tightening device to completely shut off the steam passage. For this reason, the addition of the manual tightening device increases the size of the main steam isolation valve and increases the cost, and the workability is not good.

SUMMARY OF THE INVENTION The present invention solves such a problem. In order to prevent the deformation of the valve body and to prevent the apparatus from increasing in size and the cost, the emergency operation is to surely shut off the steam passage. An object of the present invention is to provide a main steam isolation valve with improved safety.

[0007]

According to the first aspect of the present invention, there is provided a main steam isolation valve provided in a main steam pipe for shutting off a steam passage in an emergency. A valve box having a passage and a valve seat formed therein, and a valve opening position rotatably provided in the valve box and rotating upward to open the steam passage, and rotating downward to remove the steam. A valve element movable to a valve closing position for closing the passage, a spring member for urging the valve element in a valve closing direction, and opening the valve element against its own weight and the urging force of the spring member And a valve drive mechanism that moves in the direction, and in an emergency, the valve element can be brought into close contact with the valve seat only by its own weight and the urging force of the spring member to move to a completely closed position where the steam passage is completely closed. Thus, the weight of the valve body and the biasing force of the spring member are set. .

In the main steam isolation valve according to the second aspect of the present invention, the valve closing force for moving the valve body to the fully closed position is a mechanical resistance when the valve body is moved to the fully closed position. It is characterized by being set to more than twice the force.

In the main steam isolation valve according to a third aspect of the present invention, the valve closing force for moving the valve body to the fully closed position is a mechanical resistance when the valve body is moved to the fully closed position. The present invention is characterized in that a predetermined marginal force is added to a valve closing force that is twice as large as the force and set.

According to a fourth aspect of the present invention, the rigidity of the valve body and the rigidity of the valve seat are set to be substantially the same.

[0011]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a front view of a main steam isolation valve according to an embodiment of the present invention, FIG. 2 is a sectional view taken along line II-II of FIG. 1, and FIG.
FIG. 4 shows a graph for setting the valve closing force of the valve element along the III-III section.

The main steam isolation valve of the present embodiment is a main steam isolation valve for supplying and connecting steam generated by a steam generator of a primary system facility (nuclear steam generation facility) in a nuclear power plant to a turbine generator of a secondary system facility. It is provided in the steam pipe, and is configured to open the steam passage when the plant is operating, and to shut off the steam passage in an emergency such as a main steam pipe breakage accident.

In this main steam isolation valve, FIGS.
As shown in FIG. 1, the valve box 11 is formed with a steam passage 14 in which a steam inlet portion 12 and a steam outlet portion 13 are substantially linear, and an opening 1 extending upward so as to intersect the steam passage 14.
The opening 15 is closed with the valve lid 16 fixed. A ring-shaped valve seat 17 is fixed to the steam passage 14 of the valve box 11 on the steam outlet 13 side.

A housing recess 18 is formed in the opening 15 of the valve box 11 on the side of the steam outlet 13, and a spindle 19 passes through the housing recess 18 horizontally, and each end is fixed to the valve box 11. It is rotatably supported by a bearing 20. The base end of the arm 21 is fixed to the intermediate portion of the spindle 19, while the valve body 2 is fixed to the tip end of the arm 21.
2 is fixed. The valve body 22 has a disk shape whose outer diameter is substantially the same as the valve seat 17 and rotates upward to rotate the steam passage 1.
Valve opening position to open 4 (position indicated by the two-dot chain line in FIG. 3)
And a valve closing position (a position indicated by a solid line in FIG. 3) in which the steam passage 14 is closed by rotating downward. In this case, the opening 15 of the valve box 11 is
A regulating protrusion 23 is formed on the second side, and the valve body 22 is positioned by contacting the regulating protrusion 23 at the valve opening position, while being in contact with the valve seat 17 at the valve closing position to form the steam passage 14. Can be completely closed.

A spindle 19 is provided beside the valve box 11.
A valve drive mechanism 24 that opens and closes the steam passage 14 by rotating the valve body 22 through the valve is provided. That is, the valve box 1
A cylinder cover 26 having a cylindrical shape is fixed to the side outer wall of the first unit 1 via a mounting flange 25, and a cylinder 27 having a cylindrical shape having a larger diameter is fixed to a lower portion of the cylinder cover 26. A piston rod 28 penetrates the cylinder cover 26 along the up-down direction, and a piston 29 that is movably fitted to the cylinder 27 is fixed to a lower end of the piston rod 28. A compression coil spring 30 as a spring member is interposed between the cylinder cover 26 and the piston 29.

On the other hand, a lower end of a connecting lever 31 is connected to an upper end of the piston rod 28.
Is connected to one end of the spindle 19. The bearing 2 at the other end of the spindle 19
A position sensor 32 for detecting the valve opening position and the valve closing position of the valve body 22 based on the rotation angle of the spindle 19 is attached to 0. In the cylinder 27, an air chamber 33 is formed by a piston 29. An air supply valve 35 and an exhaust valve 36 are connected in parallel to the air chamber 33 via a pipe 34, and the air supply valve 35 has an accumulator. 37 and a compressor 38 are connected.

Accordingly, the air supply valve 35 is opened and the exhaust valve 36 is opened.
Compressor 38 is driven in a state where
When air is supplied to the air chamber 33 through the
9 is pushed up against the urging force of the compression coil spring 30 to move the piston rod 28 upward. Then, the spindle 19 is rotated clockwise in FIG. 3 via the connecting lever 31 and the valve body 22 is rotated upward via the arm 21 so that the steam passage 14 is opened. You can move.

On the other hand, when the air supply valve 35 is closed and the exhaust valve 36 is opened, the piston 29 is pushed up by the urging force of the compression coil spring 30, and the air in the air chamber 33 is released from the pipe 34.
And move the piston rod 28 downward. Then, the spindle 19 rotates counterclockwise in FIG. 3 via the connecting lever 31 and the valve body 22 rotates downward via the arm 21, thereby closing and opening the steam passage 14. Can be moved to a position.

A hydraulic cylinder 39 having a cylindrical shape with a smaller diameter is fixed to the lower end of the cylinder 27, and a head cover 40 is fixed to the lower part. Cylinder 2
A connecting rod 41 is connected to the lower surface of the piston 29 in the inside 7, and a lower end portion of the connecting rod 41 penetrates through the hydraulic cylinder 39 and is fixed to a piston 42 movably fitted therein. The piston 42 has two hydraulic chambers 43 and 44 inside the hydraulic cylinder 39.
The oil chambers 43 and 44 communicate with each other through an orifice hole 45 formed in the piston 42. A through hole 46 is formed in the center of the head cover 40, and a rupture disk 47 is positioned to close the through hole 46.
The through-hole 49 is formed in the holder 48 so as to face the through-hole 46.

Accordingly, the supply and discharge of air to and from the air chamber 33 and the urging force of the compression coil spring 30 move the valve body 22 through the piston 29, the piston rod 28, the connecting lever 31, the spindle 19 and the like to open and close the valve. The piston 42 moves in the hydraulic cylinder 39, and the lubricating oil flows through the oil chambers 43 and 44 through the orifice holes 45 to attenuate the opening / closing operation of the valve element. Can be. The strength of the rupture disk 47 is set so as to burst when it receives a predetermined pressure, and when the internal pressure of the oil chamber 44 rises during the closing operation of the valve body 22 and this internal pressure exceeds the predetermined pressure, The rupture disk 47 ruptures, the lubricating oil in the oil chamber 44 is discharged through the through holes 46 and 49, and the valve body 22 can be properly closed.

In the thus constructed main steam isolation valve of this embodiment, the valve body 22 is brought into close contact with the valve seat 17 only by its own weight and the urging force of the compression coil spring 30 in an emergency such as a main steam pipe breakage accident. The weight of the valve body 22 and the urging force of the compression coil spring 30 are set so that the steam passage 14 can be moved to a completely closed position where the steam passage 14 is completely closed. In this case, when the valve body 22 rotates from the valve-opening position to the completely closed position, the support portion of the valve body 22, that is, the bearing 20 of the spindle 19, the valve drive mechanism 24, or the repulsive force of the seal or the packing. Complete valve closing force is required to overcome mechanical resistance.

The mechanical resistance is set by examining the structure and material of the main steam isolation valve. In the present embodiment, as shown in FIG. 4, the valve closing force that overcomes the mechanical resistance is set to be at least twice the resistance. However, since there is a possibility that the resistance increases due to contamination of each sliding portion or deterioration of the seal due to long-term use, the valve closing force is set by adding a predetermined marginal force to twice the resistance. It is desirable that the complete valve closing force at this time is less than three times the resistance force. Therefore, the complete valve closing force set in this manner is applied to the valve body 2.
2 and the repulsive force of the compression coil spring 30.

In an emergency, it is necessary to immediately move the valve body 22 to the completely closed position, and this valve body 22 comes into contact with the valve seat 17 with a large force. for that reason,
In the present embodiment, by setting the rigidity of the valve body 22 and the rigidity of the valve seat 17 to be substantially the same, the plastic deformation of the valve body 22 when the valve body 22 comes into contact with the valve seat 17 is determined. It is trying to suppress. Specifically, by increasing the weight by increasing the thickness of the valve body 22, the rigidity of the valve seat 17 is increased.
, And the spring force is improved by increasing the wire diameter and coil diameter of the compression coil spring 30. In addition,
By increasing the size of the compression coil spring 30, the cylinder 27
However, it is desirable to provide a plurality of exhaust lines so as not to lengthen the valve closing time.

As described above, in the main steam isolation valve of the present embodiment, the valve body 22 comes into close contact with the valve seat 17 only by its own weight and the urging force of the compression coil spring 30, and the steam passage 14 is completely closed. The valve body 2 is moved so that it can be moved to the fully closed position.
2 and the biasing force of the compression coil spring 30 are set, and in this case, the valve closing force is at least twice the mechanical resistance force when the valve body 22 rotates to the valve closing position, in particular, 2 times. The valve closing force is set to a value obtained by adding a predetermined margin force to the double resistance force, and the complete valve closing force is distributed to the weight of the valve body 22 and the repulsive force of the compression coil spring 30.

Therefore, in an emergency such as a main steam pipe breakage accident, the valve body 22 moves to the completely closed position where it can be properly brought into close contact with the valve seat 17 only by its own weight and the urging force of the compression coil spring 30. The body 22 can reliably close the steam passage 14 and improve safety.

The rigidity of the valve body 22 is determined by the valve seat 1.
7 is set to be almost the same as the rigidity of the valve body 22. When the valve body 22 moves to the fully closed position, the valve body 22
Abuts against the valve seat 17, but since the rigidity and strength are almost the same, plastic deformation of the two can be suppressed, and an increase in the size and cost of the device can be prevented.

In the above-described embodiment, the compression coil spring 30 for urging the valve body 22 in the valve closing direction is provided in the valve drive mechanism 24 for moving the valve body 22 in the valve opening direction. The spring 30 may be provided on the arm 21 as a torsion coil spring.

[0029]

As described in detail in the above embodiment, according to the main steam isolation valve of the first aspect of the present invention, the steam passage is opened by pivoting upward to the valve box having the steam passage. A movable valve element is provided between a valve opening position and a valve closing position that pivots downward to close the steam passage, and a spring member that urges the valve element in the valve closing direction and a valve element that moves the valve element in the valve opening direction. A valve drive mechanism that moves, so that in an emergency, the valve body can be moved to a completely closed position where the valve body is brought into close contact with the valve seat only by its own weight and the urging force of the spring member to completely close the steam passage. The weight of the spring and the biasing force of the spring member are set to prevent deformation of the valve body and to prevent the device from increasing in size and cost. Can be planned.

According to the main steam isolation valve of the second aspect of the invention,
Since the valve closing force for moving the valve body to the fully closed position is set to be at least twice the mechanical resistance of the valve body, in an emergency, the valve body is properly moved to the valve closing position to open the steam passage. It can be reliably shut off.

According to the main steam isolation valve of the third aspect of the present invention,
Since the valve closing force for moving the valve body to the fully closed position is set by adding a predetermined margin force to the valve closing force that is twice the mechanical resistance force of the valve body, each sliding force due to long-term use is set. Even if the resistance increases due to contamination of the moving part or deterioration of the seal, the valve body can be properly moved to the valve closing position to reliably shut off the steam passage.

According to the main steam isolation valve of the fourth aspect of the present invention,
Since the rigidity of the valve body and the rigidity of the valve seat are set to be substantially the same, it is possible to suppress plastic deformation of the valve body when the valve body moves to the valve closing position and abuts on the valve seat. It is possible to prevent an increase in size and cost.

[Brief description of the drawings]

FIG. 1 is a front view of a main steam isolation valve according to an embodiment of the present invention.

FIG. 2 is a sectional view taken along line II-II of FIG.

FIG. 3 is a sectional view taken along the line III-III of FIG. 1;

FIG. 4 is a graph for setting a valve closing force of a valve body.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Valve box 14 Steam passage 17 Valve seat 19 Spindle 21 Arm 22 Valve element 24 Valve drive mechanism 30 Compression coil spring (spring member) 47 Rupture disk

Continuation of the front page (72) Inventor Tadahiko Suzuda 2-1-1, Shinhama, Arai-machi, Takasago-shi, Hyogo Prefecture Inside the Takasago Research Laboratory, Mitsubishi Heavy Industries, Ltd. (72) Inventor Masahiro Yoshida 1-1-1, Wadazakicho, Hyogo-ku, Kobe-shi, Hyogo Prefecture 1 Mitsubishi Heavy Industries, Ltd.Kobe Shipyard (72) Inventor Hiroyuki Kana No. 1-1 1-1 Wadazakicho, Hyogo-ku, Kobe, Hyogo Prefecture Mitsubishi Heavy Industries, Ltd.Kobe Shipyard (72) Inventor Yoshihisa Manabe Nishi, Amagasaki, Hyogo 5-12-1, Tachibana-cho, Toa Valve Co., Ltd. (72) Inventor Tadao Himi 5-12-1, Nishi-Tachibanacho, Amagasaki, Hyogo Prefecture, Japan Toa Valve Co., Ltd. (72) Inventor Akihiro Kawaguchi Takasago, Hyogo Prefecture 2-19, Niihama, Arai-cho, Ichigo F-term in Takaishi Engineering Co., Ltd. (reference) 3H052 AA01 BA02 BA25 EA05 EA10 3H058 AA07 BB03 BB22 CD05 CD11 DD12 DD17 EE06 EE23

Claims (4)

[Claims] 1. A main steam isolation valve provided in a main steam pipe for shutting off a steam passage in an emergency, wherein a valve box having a steam passage and a valve seat is provided, and the valve box is rotatably provided on the valve box. A valve body that is movable between an open position to open the steam passage by rotating upward and a valve closing position to rotate downward to close the steam passage; and closing the valve body in the valve closing direction. A spring member for urging, and a valve drive mechanism for moving the valve body in the valve opening direction against its own weight and the urging force of the spring member, wherein in an emergency the valve body has its own weight and the spring member. The weight of the valve body and the biasing force of the spring member are set so that the valve can be moved to a fully closed position where the steam passage is completely closed by being brought into close contact with the valve seat only by the biasing force. Steam isolation valve. 2. The main steam isolation valve according to claim 1, wherein
Main steam wherein the valve closing force for moving the valve body to the fully closed position is set to be at least twice the mechanical resistance force when the valve body moves to the fully closed position. Isolation valve. 3. The main steam isolation valve according to claim 1, wherein
A predetermined margin force is added to a valve closing force for moving the valve body to the fully closed position, to a valve closing force twice as high as a mechanical resistance force when the valve body moves to the fully closed position. A main steam isolation valve characterized by being set as follows. 4. The main steam isolation valve according to claim 1, wherein
A main steam isolation valve, wherein the rigidity of the valve body and the rigidity of the valve seat are set to be substantially the same.