JPH0560248A - Main vapor isolating valve - Google Patents

Abstract

PURPOSE:To provide long-term reliability and improve the reliability of a plant by providing a valve receiver for receiving a valve body of an integrated structure on the top end of a valve shaft, providing a small valve on the top end of the valve receiver, and providing a slave valve having a fitting groove fitted and connected to the valve body to support the valve body. CONSTITUTION:A valve body 26 is formed into an integrated structure by welding a disc valve receiver 27 with a collar 27a to the top end of a valve shaft 11, and a disc small valve 28 having a fitting groove 28b fitted and connected from the side surface of the valve receiver 27 with a free space and engagingly locked by the collar 27a is provided. Further, an A-valve body 18 and a B-valve body 19 separable into two are provided around the small valve 28 with a vertically free clearance. Since the small valve 28 is pushed to the B-valve body 19 by the collar 27a of the valve receiver 27 through its groove 28b and not fixed to the valve receiver 27, it never receives the influence of a fluctuating rotating force. Further, since the valve receiver 27 and the valve shaft 11 are also integrally formed, they never cause the mutual loosening or separation.

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 used for shutting off a main steam system in a power plant such as a nuclear power plant or a thermal power plant.

[0002]

2. Description of the Related Art As for a main steam isolation valve, when a boiling water nuclear power plant is taken as an example, as shown in the main steam system diagram of FIG. 4, a main steam for feeding steam generated in a nuclear reactor 1 to a turbine 2 A main steam isolation valve (inner valve) 5 and a main steam isolation valve (outer valve) 6 are installed inside and outside the reactor containment vessel 4, respectively, which are connected to the pipe 3. Further, in the case of having a plurality of main steam piping systems, the main steam isolation valves 5 and 6 are installed in each main steam piping system. The steam generated in the reactor 1, which is a steam generating means, passes through a main steam third valve 7 installed downstream of the main steam isolation valves 5 and 6, and is collected in a main steam header 8 and then a steam turbine. 2, it gives a rotational force, is condensed in the condenser 9 to become water, and the water supply pump 10
Is returned to the reactor 1 again.

As shown in the longitudinal sectional view of FIG. 5, a conventional main steam isolation valve 5 is provided with a valve shaft 11 having an angle of 45 degrees with the main steam pipe 3 and a valve body provided at the tip thereof. 12 is the valve shaft
The main steam isolation valve 5 is opened and closed by moving up and down in the valve box 13 along 11. That is, when the valve is fully closed, the valve body 12 is the valve box.
It sits on the valve seat 14 at the bottom of 13 to shut off the steam flow path. Further, when the valve is fully opened, the valve body 12 is pulled up by the drive mechanism 15 via the valve shaft 11 and separated from the valve seat 14 to secure a flow path in the valve box 13. In FIG. 5, reference numeral 16 indicates a guide rib of the valve body 12 inside the valve box 13. Inside the valve body 12, as shown in the enlarged sectional view of the main portion of the valve body of FIG. 6, a disc-shaped small valve 17 joined by a screw 20 is provided at the tip of the valve shaft 11,
It is composed of an A-valve element 18 and a B-valve element 19 which are arranged with a clearance above and below the periphery thereof and which can be separated into two for maintenance and assembly of the small valve 17. Further, in the central portion of the valve body 12, the seats 18a and 19a provided on the inner circumference of the A valve body 18 and the tip of the small valve 17 have a function of closing the flow path of steam when they abut.

In order to open this main steam isolation valve, the valve shaft 11 is raised by the drive mechanism 15, and the small valve 17 provided at the tip of the valve shaft 11 first separates from the A valve body 18. By opening the small valve 17 and the A valve body 18 at the seats 18a and 19a, a part of steam flows from the valve upstream side to the downstream side through the opening, and therefore acts on the valve body 12. The back pressure on the upstream side of the valve escapes to the downstream side of the valve to reduce the valve driving force required to raise the valve body 12. After that, the upper part of the small valve 17 abuts the lower part of the B valve body 19, the integrated valve body 12 composed of the B valve body 19 and the A valve body 18 is lifted, and the valve body 12 is removed from the valve seat 14. Separate them to secure a large steam flow path. Note that FIG. 6 shows a state in which the valve shaft 11 is pulled up and the valve is opened.

[0005]

When the steam turbine 2 is in operation, the main steam valves 5 and 6 are open, so the valve body 12 is exposed to the flow of steam, and the flow direction of the steam is changed by the flow of steam. It receives a fluid force in the direction perpendicular to the flow.
This fluid force not only vibrates the valve element 12 in the vertical direction, but also gives the valve element 12 a varying rotational force. B valve body 19 here
Is supported by the small valve 17, the variable rotational force of the above-mentioned valve body 12 is transmitted from the B valve body 19 to the small valve 17, and the small valve 17 is connected to the valve shaft 11 connected by the screw 20. Rotational force is repeatedly applied in the tightening direction and the loosening direction of the screw 20. Therefore,
It is conceivable that when the rotational force is repeatedly applied during long-term operation, the screw 20 of the small valve 17 starts to loosen and eventually the small valve 17 comes off the valve shaft 11. If the small valve 17 is disengaged from the valve shaft 11, the valve body 12 supported by the small valve 17 may fall out together with the small valve 17. For this reason, conventionally, a pin 21 is planted on the side surface of the screw 20 of the small valve 17 to prevent the screw 20 from loosening, and the pin 21 is regularly removed to check the looseness of the valve shaft 11 and the small valve 17. It required a complicated work of inspecting and re-assembling the pin 21 after reassembly.

An object of the present invention is to provide a valve body receiver having an integral structure at the tip of a valve shaft and attach a small valve to the valve body receiver so that the small valve comes off from the valve shaft, that is, the valve. It is to provide a main steam isolation valve that does not fall out and does not require regular inspections and has high maintainability and reliability.

[0007]

A main steam isolation valve having a small valve for reducing a driving force for raising a valve shaft when separating a valve body seated on a valve seat in a valve box from the valve seat. At
A valve body receiver for supporting a valve body having an integral structure is provided at the tip of the valve shaft, and a small valve is provided at the tip of the valve body receiver, or a valve body having an integral structure is provided at the tip of the valve shaft. A receiver is provided, and a sub-valve for supporting the valve body is provided, which is provided with a fitting groove that fits and is joined to the valve body receiver with a clearance.

[0008]

The variable rotational force which the valve body receives from the circulating steam when the valve is opened is propagated to the valve body receiver through the B valve body, but since the valve body receiver and the valve shaft have an integral structure, There is no loosening or separation between the body rest and the valve stem. Further, since the small valve is connected to the valve body receiver by a screw or the like and is not in direct contact with the B valve body, the small valve and the valve body receiver are not separated by the fluctuating rotational force.

Further, when the small valve is fitted and connected to the valve disc receiver with a clearance, the small valve is pressed against the B valve disc by the valve disc receiver integral with the valve shaft when the valve is opened. Since the body support is not fixed, the looseness of the sub-valve and the valve body support and the separation of the valve body support and the valve shaft do not occur even if a varying rotational force is applied.

[0010]

An embodiment of the present invention will be described with reference to the drawings. It should be noted that the same components as those of the above-described conventional technique are denoted by the same reference numerals and detailed description thereof will be omitted. As shown in the enlarged cross-sectional view of the main part of the valve body in FIG. 1, a disc-shaped valve body receiver 22 is integrally welded to the tip of the valve shaft 11. A small valve 24 is provided by a screw 23 provided on the lower portion of the valve body receiver 22.
Is fixedly provided, and a valve body 25 is formed by disposing A valve body 18 and B valve body 19 which are separable into two in the same manner as in the conventional case. In addition, the valve body receiver 22 is the valve shaft 11
It is also possible to have an integrated structure by carving out the same material as. Further, reference numeral 24a in the drawing denotes a seat of the small valve 24 which comes into contact with the seat 18a of the A valve body 18.

According to the above construction, the valve body is opened while the valve is open.
The varying rotational force that 25 receives from the circulating steam is propagated to the valve body receiver 22 via the B valve body 19 as in the conventional case, but since the valve body receiver 22 and the valve shaft 11 have an integral structure, Due to this fluctuating rotational force, the valve body receiver 22 and the valve shaft 11 are not loosened or separated. Since the small valve 24 is fixed to the valve body receiver 22 and the screw 23 and is not in direct contact with the B valve body 19,
The screw 23 is not loosened by the fluctuating rotational force. Further, since the valve shaft 11 and the valve body receiver 22 are integrally structured, the dimensional accuracy can be easily improved. Therefore, the precision in adjusting the seat 24a of the small valve 24 and the seat 18a of the A valve body 18 can be improved. It works well, and there is no need to disassemble it on a regular basis and carry out complicated inspections.

2 and 3 are enlarged cross-sectional views of the essential parts of a valve body showing another embodiment of the present invention. FIG. 2 (A) shows the valve open and FIG. 3 shows the valve closed state. 2B is a plan view taken along the line BB of FIG. 2A. This valve body 26 has a disc-shaped valve body receiver 27 with a collar 27a formed integrally with the tip of the valve shaft 11 by welding, and is disc-shaped with a clearance from the side surface of the valve body receiver 27. A small valve 28 is provided that has a fitting groove 28b that is fitted and coupled and that is locked by the collar portion 27a. Further, as in the conventional case, an A-valve element 18 and a B-valve element 19 which can be separated into two parts are arranged around this area with a clearance above and below. It should be noted that the valve body receiver 27 may be formed as an integral structure by cutting out the same material as the valve shaft 11. Further, reference numeral 28a in the drawing is the above A
The seat of the small valve 28 which contacts the seat 18a of the valve body 18 is shown.

According to the above construction, the changing rotational force received from the steam flowing through the valve element 26 during valve opening is transmitted to the child valve 28 via the B valve element 19, but the small valve 28 has its groove. Since it is pressed against the B valve body 19 by the flange portion 27a of the valve body receiver 27 via 28b and is not fixed to the valve body receiver 27,
It is not affected by the fluctuating torque. Also, the valve body support 27
The valve shaft 11 and the valve shaft 11 are of the same structure as in the above-described embodiment, so that they do not loosen or come off. When assembling the valve body 26, the fitting is completed by simply inserting the fitting groove 28b of the small valve 28 into the flange portion 27a of the valve body receiver 27 from the side before assembling the A valve body 18 and the B valve body 19. In addition, since it has a play, it has a structure that does not require assembling accuracy, and the assembling work is simple. Further, when the valve is opened, the small valve 28 is pressed and fixed to the upper B valve body 19 by the valve body receiver 27 as shown in FIG. 2 (A), and when the valve is closed, the valve body receiver 27 is provided as shown in FIG. It is pushed down by and is fixed to the seat 18a of the A valve body 18. At this time, when the seat 28a of the small valve 28 and the seat 18a of the A valve body 18 are lapped together, the clearance due to the fitting groove 28b is allowed between the valve body receiver 27 and the small valve 28. The optimal familiar state is secured. Therefore,
No need for complicated adjustments and inspections.

[0014]

As described above, according to the present invention, since the influence of the fluctuating rotational force exerted by the steam flowing in the valve is not exerted on the valve shaft, the child valve, etc., the complicated inspection in the periodic inspection can be omitted, and the valve body can be omitted. Also, the possibility that the sub-valve will fall off will be eliminated, and the maintainability such as disassembly and assembly will be good, which has the effect of improving the reliability of the plant along with the long-term reliability of the main steam isolation valve. ..

[Brief description of drawings]

FIG. 1 is an enlarged cross-sectional view of a main part of a valve body showing a valve open state in an embodiment of the present invention.

FIG. 2 is an enlarged sectional view of a main part of a valve body showing another embodiment of the present invention. (Fig. 2 (A) shows the valve open state. Fig. 2 (B) shows Fig. 2 (A).
FIG. 6 is a plan view taken along the line BB of FIG. )

FIG. 3 is an enlarged sectional view of a main part of a valve body showing a valve closed state according to another embodiment of the present invention.

FIG. 4 is a main steam system diagram of a boiling water nuclear power plant.

FIG. 5 is a vertical cross-sectional view showing a valve open state of a conventional main steam isolation valve.

FIG. 6 is an enlarged sectional view of a main part of a valve body showing a valve open state of a conventional main steam isolation valve.

[Explanation of symbols]

5, 6 ... Main steam isolation valve, 11 ... Valve shaft, 12, 25, 26 ... Valve body,
18 ... A valve body, 18a, 24a, 28a ... Seat, 19 ... B valve body,
22, 27 ... Valve seat, 23 ... Screw, 24,28 ... small valve, 27a ... Brim part, 28b ... Fit groove.

Claims (2)

[Claims] 1. When separating a valve body, which is installed in the middle of a main steam pipe for supplying steam from a steam generating means such as a power plant to a steam turbine and is seated on a valve seat in a valve box, from the valve seat. In the main steam isolation valve having a small valve having a function of reducing the driving force for raising the valve shaft, a valve body receiver for supporting the valve body is provided at the tip of the valve shaft with an integral structure,
A main steam isolation valve characterized in that a small valve is arranged at the tip of the valve body receiver. 2. A driving force for raising a valve shaft when separating a valve body, which is installed in the main steam pipe for supplying steam to a steam turbine and is seated on a valve seat in a valve box, from the valve seat. In a main steam isolation valve having a small valve having a function of reducing the above, a valve body receiver is integrally provided at the tip of the valve shaft, and a fitting groove for fittingly coupling the valve body receiver with a clearance is provided. A main steam isolation valve having a child valve for supporting the valve body.