JPH08218805A - Four-valve type steam governing valve for turbine - Google Patents

Abstract

PURPOSE: To reduce oscillations of a piping and a GV valve by reducing pressure fluctuation in a downstream area of a throat of the steam governing valve(GV). CONSTITUTION: This system is composed of bilateral main steam stopping valves(MSV) and center two GV valves. In the GV valve, a throat 7 is integrated with a body casing in which a GV valve body 2, a bonnet 3, a valve bar guide 5, and a valve bar 4 are assembled. An output of a steam turbine on the downstream side is adjusted by vertically moving the GV valve body 2. In such a four-valve type steam governing valve, eight nozzles 6 are integrated with the body casing 1 between the body casing 1 on an inlet of the throat 7, the valve body 2 and the bonnet 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a four-valve steam control valve for turbines.

[0002]

2. Description of the Related Art Generally, a boiler is installed on the upstream side of a steam turbine, and a four-valve steam control valve is installed between the boiler and the steam turbine. The function of the four-valve steam control valve is to control the inflow steam (or the outflow steam amount from the turbine) into the turbine to control the rotation speed of the turbine. It also has a function to prevent the turbine unit from overspeeding during transient conditions such as when the load is cut off.
In addition, this valve has an integrated structure of two steam control valves (hereinafter abbreviated as GV valves) and two main steam stop valves (hereinafter abbreviated as MSV valves) for stopping main steam.

The valve element is installed at two places on the turbine inlet side and is called a four-valve type steam control valve. MSV valves are arranged on both sides of the steam upstream side and two GV valves are arranged on the inner side of the downstream side. There is. Then, the steam discharged from the GV valve is guided to the turbine inlet through the four steam pipes.

FIG. 5 shows an overall view of the conventional four-valve type steam control valve described above. As shown in the figure, steam flows in from the left and right steam inlet pipes 10, passes through the MSV valve, and two GV
The steam flow rate is adjusted by the valve and introduced into the turbine body.

FIG. 5 is a detailed view of the A portion of the GV valve. The bonnet 3 is fixed to the main body casing 1, and the GV is inside it.
The structure in which the valve body 2 is supported by the valve rod 4 is
When is moved up and down, the GV valve body 2 makes the same movement. By lowering the GV valve body 2 until it contacts the body casing 1,
The steam flow is stopped. On the contrary, when the GV valve body 2 is raised, the gap between the GV valve body 2 and the main body casing 1 is widened and the steam flow rate is increased.

[0006]

However, the conventional GV valve described above has a structure in which the steam flow rate is controlled by opening and closing the GV valve body 2, and the flow rate is controlled widely from a small flow rate to a large flow rate, and high temperature ( It is used in a high pressure (250 atg) field and is operated under extremely severe conditions.
Vibration may occur in the V valve body 2.

Further, in this state (the steam controlled by the GV valve 2) sometimes causes pipe vibration in the downstream pipe. This is because the GV valve body 2 is caused to vibrate due to the presence of a drift in the lower portion of the throat of the GV valve 2. It was found that the uneven flow was caused by the pressure difference around the GV valve body immediately before the throat.

An object of the present invention is to provide a four-valve steam control valve for a turbine which can reduce pipe vibration and GV valve disc vibration by reducing pressure fluctuations in the downstream region of the GV valve throat.

[0009]

A four-valve steam control valve for turbine of the present invention comprises a left and right main steam stop valve (MSV valve) and two central steam control valves (GV valve). GV
The valve has a throat portion integrally formed with a body casing, and a GV valve body, a bonnet, a valve rod guide, and a valve rod are incorporated in the body casing, and the output of a downstream steam turbine is adjusted by vertically adjusting the GV valve body. The four-valve steam control valve is characterized in that eight nozzles are integrally provided on the main body casing side between the main body casing at the throat inlet and the GV valve body and bonnet.

[0010]

In the present invention, the eight nozzles 6 are provided in the space space so that the difference in the circumferential pressure distribution between the main body casing 1 on the inlet side of the throat portion 7 and the GV valve body 2 and the bonnet 3 becomes small.
I put it in. As a result, the steam inflow area around the GV valve body 2 on the upstream side of the throat section 7 is divided into eight equal parts, and the steam inflow area gradually becomes smaller and is connected to the throat section 7.

This reduces the pressure distribution difference in the circumferential direction,
The flow rate of steam flowing from the throat section 7 is evenly distributed and flows. As a result, the pressure fluctuation in the downstream region of the throat portion becomes small, the vibration of the steam outlet pipe becomes small, and the GV valve body 2
Also reduces the vibration.

[0012]

Embodiments of the present invention will be described below with reference to FIGS. FIG. 1 shows a nozzle 6 according to a first embodiment of the present invention.
2 is a sectional view when the GV valve body is closed, FIG. 2 is a partial sectional view when the GV valve body 2 is open, FIG. 3 is a sectional view of a nozzle mounting surface, and FIG. 4 is a nozzle shape view of the first embodiment.

As shown in FIG. 5, the four-valve steam control valve for turbine of the present invention is composed of left and right MSV valves 9 and two GV valves 8 in the center. The present invention relates to this GV valve 8.

The GV valve 8 has a throat portion 7 formed integrally with the main body casing 1, and further the GV valve body 2, the bonnet 3, the valve rod guide 5 and the valve rod 4 are incorporated into the main body casing 1 to form a GV valve. By adjusting the body 2 up and down, the output of the downstream steam turbine is adjusted.

In the embodiment, eight nozzles 6 are attached between the main body casing 1 at the inlet of the throat portion 7, the GV valve body 2 and the bonnet 3 on the main body casing side by integral casting or welding structure.

Next, the operation of the above embodiment will be described.
The steam flows toward the central two GV valves 8 through the left and right MSV valves, and the above-mentioned 8 of the present invention fixed to the upstream of the throat portion 7.
When it flows into the nozzle 6, the pressure distribution difference in the inlet circumferential direction of the throat portion 7 becomes small, and the flow rate of steam flowing from the throat portion 7 is evenly distributed and flows.

As a result, pressure fluctuations in the downstream region of the throat are reduced, vibration of the steam outlet pipe is reduced, and G
The vibration of the V valve body 2 also becomes small.

[0018]

According to the present invention, as shown in FIG. 1, by disposing eight nozzles 6 in the circumferential direction in the upper portion of the throat portion 7, that is, around the steam inlet side GV valve body 2, the throat portion 7 is provided. The throat area 7 is gradually reduced by reducing the flow area.
As a result, the pressure distribution difference in the upper portion of the throat portion 7 becomes smaller, and the pressure fluctuation in the downstream region of the throat portion 7 becomes smaller, so that the pipe vibration and the GV valve body 2 vibration can be reduced.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a G equipped with a nozzle according to a first embodiment of the present invention.
Sectional drawing of the GV valve at the time of closing the V valve body.

FIG. 2 is a sectional view of the GV valve when the same GV valve body is opened.

FIG. 3 is a sectional view taken along the line BB in FIG.

FIG. 4 is a shape diagram of a nozzle 6 according to the first embodiment.

FIG. 5 is an overall partial sectional view of a conventional four-valve steam control valve.

6 is an enlarged view of part A in FIG.

FIG. 7 is a sectional view showing a steam flow of a conventional GV valve.

[Explanation of symbols]

1 ... Main body casing, 2 ... GV valve body, 3 ... Bonnet,
4 ... Valve rod, 5 ... Valve rod guide, 6 ... Nozzle, 7 ... Throat part, 8 ... Steam control valve (GV valve), 9 ... Main steam stop valve (M
SV valve), 10 ... Steam inlet pipe.

Claims (1)

[Claims] 1. A left and right main steam stop valve (MSV valve) and two steam control valves (GV valves) in the center, the GV
The valve has a throat portion integrally formed with a body casing, and a GV valve body, a bonnet, a valve rod guide, and a valve rod are incorporated in the body casing, and the output of a downstream steam turbine is adjusted by vertically adjusting the GV valve body. A four-valve steam control valve, wherein eight nozzles are integrally provided on the main body casing side between the main body casing at the throat inlet, the GV valve body and the bonnet.