JPS58165505A - Steam leak preventive device of steam valve - Google Patents

Abstract

PURPOSE:To prevent a leak of steam and effectively utilize leaked steam, by forming the shape of a valve main unit and cover unit to a mutually contactable seal surface to provide a high temperature resistant material of large hardness to said mutually contacting surface and connect a steam line to the seal surface. CONSTITUTION:A tapered main unit seal surface part 15 is formed to the opening internal peripheral edge of a steam valve main unit 11 equipped with a flow inlet 8 and flow outlet 9, and a main unit seal pressure stripe 16 made of high temperature resistant material of large hardness is embedded in the circumferential direction to said seal surface part 15. While, a spherical cover unit seal surface part 17 is formed to the internal protrusive peripheral edge of a cover unit 10 closing an opening of the unit 11, and a spherical or over sectional cover unit seal pressure stripe 18 made of high temperature resistant material of large hardness is embedded in the circumferential direction in such a manner as to be contacted to said stripe 16. Further a leak-off line 23 connecting a space 21, formed between a mutually contacted surface of said both seal pressure stripes 16, 18 and a gasket 13, to a steam line is drilled to the unit 10.

Description

[Detailed Description of the Invention] [Technical Public Expenditure of the Invention] The present invention relates to a steam leakage prevention device for a steam valve, and is a steam leakage prevention device that can extremely effectively prevent steam leakage from a main steam valve in a steam plant such as a steam power plant. It is related to the device.

[Technical background of the invention and its problems]

The steam power station that constitutes the conventional Rankin Naikrun is the first
As shown in the figure, a water supply pump IK supplies water to a water heater 2, where steam is generated, and a steam turbine 6 directly connected to a generator 5 through a steam main steam stop valve 3 and a steam control valve 4Y. The steam that has finished its work in the steam turbine C 6 is condensed in a condenser 7, and then refluxed to the water supply 4 pump 1.

In addition, the thermal efficiency of a steam power station is shown in a graph as shown in Figure 2, where the vertical axis is the thermal efficiency l of the steam power station, the horizontal axis is λ, the steam temperature t, 'g, and the inlet steam pressure PY factor. ,
It is clear that the higher the inlet steam pressure P and the inlet steam temperature t1, the better the thermal efficiency becomes. Note that the curve a shown by the dotted line in the graph of FIG. 2 is a steam saturation curve, and the lower the value, the better the thermal efficiency of the internal pressure in the condenser 7#IC.

On the other hand, the relationship between the inlet steam pressure P, the inlet steam temperature t1, and the exhaust chamber dryness X is as shown in the graph shown in Figure 3, and as is clear from this, the exhaust chamber dryness X is If the following conditions occur, water droplets will cause significant erosion of the low-pressure part of the steam turbine.

It is desired that the exhaust chamber dryness is XV high (4). However, in order to increase the thermal efficiency of the steam power plant, the inlet steam pressure P and the inlet steam temperature t0 of the steam turbine must be increased. Although it can be achieved by increasing only the input steam pressure P, the relative dryness of the turbine exhaust chamber xt
'This results in a decrease in the QK inlet steam temperature t,
1-Need to increase.

On the other hand, the reheating cycle of the MjlL power plant eliminates the decrease in exhaust chamber dryness X, and it extracts steam from the middle of the expansion of the steam turn and sends it to Zeira 2 for reheating. According to such means, not only the dryness X of the exhaust chamber increases, but also the thermal efficiency η increases, and the output per the same amount of steam can be increased.

In addition, the relationship between the steam power plant efficiency M and the inlet steam pressure P when reheating the reheated steam temperature t2 of the single-stage reheat cycle to the inlet steam temperature t is expressed by j5 of the needle 7 shown in FIG.
become. It is clear from this: 1゜541C1 The means to increase the thermal efficiency η of a steam plant is
・H.

Although it has been theoretically clarified, in the prior art, the inlet steam condition of a steam turbine is 169! in a subcritical pressure plant! /fi”N, temperature 538℃
, *sgz temperature 5 temperature 5 yang 8 In a critical pressure plant, the inlet steam pressure was limited to 240 KI/ffi" I, the temperature was 538°C, and the reheat steam temperature was limited to about 566°C. This is due to the heat resistance of materials such as the turbine casing! and the valve body (casing) of the main steam stop valve 3.

However, in today's world where high efficiency steam power stations are desired, ultra-high pressure and high temperatures (e.g. 300 to 3") are desired.

600℃/600℃) There is a strong demand for the construction of steam power plants (and along with this, progress in the development of heat-resistant materials has also been remarkable).

Furthermore, one of the problems that must be solved in the development of ultra-high pressure, high temperature plants is measures to prevent steam leakage from main steam valves.

Here, we will explain the location where steam leakage occurs in the main steam stop valve installed at the steam turn and the location where ultra-high pressure occurs.
Problems in high-temperature plants will be explained with reference to Figures 5 and 6.

In FIG. 5, 10 is the lid of the main steam stop valve, 11 is the main body of the main steam stop valve, 12 is the strainer, and 13 is the spiral gas shell (V).

When the inlet steam conditions become extremely high pressure and high temperature, there is a possibility that the steam will leak from the part indicated by the → mark in the figure.To prevent this, generally, the gasket L3t - the opening circumference of the valve body 11 * It should be placed in advance. This gasket B is formed into a spiral shape by overlapping alloy steel such as carbon steel or stainless steel with asbestos, and is made to fit into the metal surface around the opening of the valve body 11 while applying a predetermined surface pressure. It is something that

Therefore, this I-stat 13 may have a number of M depending on its type.
I-sket minimum tightening pressure design value y, gasket ia (
m = #jl/Pi, where σg = gasket M effective contact surface pressure, pi: m rest operating pressure) 1, and in order to make the seal 7 for leakage prevention possible, the tightening given by the formula below is An applied force r8 is required.

F1≧Mugmpi +F2=AgmPi +AiPi where? □=Tightening force F□=AgY Ag: J sket contact area m: I sket coefficient PiSfi body working pressure AI=effective area where internal pressure acts F2: Force that acts on the gasket when internal pressure PiQ/m'' is applied.

As is clear from this equation (assuming other conditions are the same, Pl: The higher the fluid working pressure, the higher the required clamping force proportional to the pressure ratio, the higher the required clamping force, and the higher the pressure ratio. Under ultra-high pressure, First of all, it is necessary to increase the clamping force.

This tightening force is applied by the tightening belt 14 that tightens and fixes the lid 10Y to the valve body 11.

If the number of tightening bolts 14 is the same for K in order to increase the tightening force, -/the bolt stress will increase. Furthermore, although high-temperature alloy steel is used for the tightening bolt 14, the strength of the material rapidly decreases at high temperatures. Gakatsu [.

In ultra-high pressure and high temperature plants, the tightening force increases by mK!
6d'') ffiiojllll;j,,,,,,,,,,,,,,,G,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,G,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,. It is necessary to reduce the root stress. Even if this is theoretically possible, due to the structure of the main steam stop valve,
That is, in reality, the space margin of the lid body 10 is more than llv.

In addition, as the temperature increases, the temperature often exceeds the service limit temperature of Gasket (13) (generally 500 to 550°C), so a metal-shaped gasket (130) with excellent heat resistance is used as an alternative to the spiral gasket (130). May be adopted. Special materials such as stainless steel, nickel steel, or Incoloy, which are high temperature resistant, are used as the material.
For such metal gaskets, the minimum tightening pressure design value y
and the gasket coefficient m is very large (large value), so both of them lack conformity to the metal surface of the lid body 10 and valve body 11, resulting in a very high surface pressure when installed.
Considerably large tightening force is required. This causes the problem of rotting and bruising in the same way as explained in the case of the spiral gas pipe 13.

In this way, in order to realize an ultra-high pressure, high temperature steam power plant, K
The currently used main steam stop valves of the structure shown in Figure 5 and Figure 6 have many problems, and it is clear that they need to be improved.

[Purpose of the invention]

Therefore, the present invention was created to solve the various conventional problems as described above, and is intended to reliably prevent steam leakage in a steam valve.

[Summary of the invention]

Therefore, in the present invention, the opening peripheral edge of the valve body has a 9-shaped main body sealing surface, in which the main body seal piezoelectric χ is embedded, and the spherical lid seal piezoelectrically connecting the outer periphery of the inner protrusion of the lid. By making contact in the circumferential direction of the opening of the valve body to reduce the contact surface pressure and sealing the steam, leaking steam generated from this sealing part is further guided to a low-pressure low-temperature line and vaporized. This has successfully prevented steam leakage occurring between the lid and the valve body.

[Examples of inventions]

Hereinafter, one embodiment of the present invention will be described with reference to FIG. 7.

In FIG. 7, the same members in FIG. 5 and FIG. 6 are designated by the same reference numerals, and the present invention is described.

There is no difference from the members configured in the prior art, and there are features in the shape and sealing means of the member. In other words, the inner periphery of the opening of the valve body 11 of the steam valve equipped with the inlet 8 and the outlet 9. A chi/4-shaped main body sealing surface portion 15'lk is formed in the main body sealing surface portion 15, and a main body sealing piezoelectric 16 made of a high temperature resistant material having high hardness is embedded in the main body sealing surface portion 15 in the circumferential direction. On the other hand, a spherical lid sealing surface 17 is formed on the outer peripheral edge of the inner protrusion of the lid 10 that closes the opening of the valve body 11, and this lid sealing surface s17 has a
A lid seal piezoelectric 18 made of a high temperature resistant material with high hardness and having a spherical or elliptical cross section and in point contact with the main body seal piezoelectric 16 is formed by being embedded in the lid sealing surface 1117 in the circumferential direction. It is.

Body seal piezoelectric 16. The body seal compression strips 18 are all made of a hard, high-temperature resistant material, for example, a -3A rut-base superalloy called Stellai F is used, which is conventionally used to connect the valve and valve seat of steam valves. It is often used on contact surfaces.

In addition, a storage groove 19 is recessed in the opening of the valve body 11 so as to surround this opening. Protrusions N2o that fit into the groove 19 are arranged in a cluster,
By compressing and pressing the gasket 13 housed in the housing groove 19, the sealing at the gasket 13 portion is ensured and serves as an auxiliary function to prevent steam leakage.

Furthermore, in the illustrated example, the contact surface between the body seal piezoelectric 16° and the lid body seal piezoelectric 18 is formed between the gasket 13 housed in the groove 19 between the opening stations of the valve body 11. A leaf hole 23 is bored in the lid 10 to connect the space 21 to the low-pressure low-temperature steam line n. The symbol in the diagram is the leaf seat. By doing this,
Body seal piezoelectric 16. Even if there is steam leaking from the sealing part between the lid and the piezoelectric 18, it will not be led to the downstream side as a low-pressure low-temperature steam line 4 such as a high-pressure turbine exhaust, and will not be released into the atmosphere. , its effective use can be achieved.

The present invention is constructed as described above, and therefore, the main body seal piezoelectric 16 formed on the A-shaped main body sealing surface portion 15 of the valve body U, and the spherical lid body sealing surface 1B17 of the lid body. A lid seal piezoelectric 18 formed on one side 1
6 has a planar shape and the other 18 has a spherical shape, and together with this, there is a point contact in both cross-sectional directions, that is, a line contact in the circumferential direction of the opening Q8 of the valve body U when viewed from the plane. When the lid body 10 is tightened and fixed to the main body 11 by the tightening lever 14, the tightening pressure concentrates on the contact surface between the two parts 16.18 and becomes extremely high, so steam leakage is ensured. In addition, since both 16 and 18 have a spherical cross section and are made of high-temperature resistant materials with high hardness, even if they come into contact with each other under high pressure, the possibility of damage from this is minimal. (The prevention of steam leakage is 1%,
l” It is maintained for a long period of time.

For this reason, the 13 gaskets stored in the storage groove W are high pressure,
There is no direct contact with high-temperature steam, and the conventionally used spiral gasket (13) is not only sufficient for convenient use, but the tightening surface pressure is sufficient to meet the downstream steam conditions &C. As for Jin.

Even if the steam conditions inside the valve body 11 become extremely high pressure, the only thing that will affect the tightening bolt 14 is the increase in the required tightening force due to the increase in internal pressure.
This means that the increase in the tightening force that should normally be received due to the increase in surface pressure has no effect. Therefore, an increase in the number of tightening bolts 14, an increase in their diameter, etc. can be kept to a necessary minimum.

Of course, in the event of the disaster of the present invention, the main valves 1 in a steam power station, such as steam control valves, reheat steam stop valves, etc., will be affected by the valve bodies and lids, or the various parts forming the stand. It goes without saying that the structure according to the present invention can be applied since the steam leakage prevention means are the same in terms of shape and structure.

〔Effect of the invention〕

As explained above, according to the present invention, the shape of the valve body and the lid used in the prior art are combined with the shape of the sealing surface that allows them to come into contact with each other, and the mutual contact surfaces are made of high-temperature resistant material with high hardness. By using a gasket, it is possible to reliably prevent steam leakage in the valve, and by placing a gasket in the space formed by the valve body and the lid, the space formed by the sealing surface and gasket can be used as a low-pressure, low-temperature steam line. By connecting this valve, it is possible to provide a main steam stop valve that can easily be used (and withstand) even under ultra-high pressure and high temperature steam conditions, such as by making effective use of leaked steam even if it occurs.

[Brief explanation of the drawings] 1fi is a system diagram of a steam power station that constitutes the Rankine cycle, Figures 1112 to 4 are graphs showing the relationship between inlet steam temperature thermal efficiency and inlet steam pressure in the steam power station. Fig. 5 is a sectional view of the main steam stop valve, Fig. 6 is a sectional view of the main part of the conventional example, and Fig. 7 is a sectional view of the main steam stop valve of the present invention. FIG. 3 is a sectional view of a main part in an example. 1... Water supply imp, 2... -ira, 3... Main steam stop valve, 4... Steam control valve, 5... Generator, 6...
・Steam turbine, 7... Condenser, 8... Inlet, 9
... Outlet. DESCRIPTION OF SYMBOLS 10... Lid body, 11... Valve body, 12... Strainer, 13... Gasket), 14... Tightening bolt, 15... Main body seal surface part. 16... Body seal piezoelectric, 17... Lid body sealing surface [
5,1g... Lid seal piezoelectric, 19... Storage groove, processing... Center origin, 21... Space, 22... Low pressure low temperature steam line, 23... Leaf hole. Sae... Leaf seat.

Claims (1)

[Claims] 1. In a steam valve for a steam turbine equipped with an inlet and an outlet, a tenodder-shaped main body sealing surface is formed on the inner peripheral edge of the opening of the valve body, and this main body sealing surface has a spherical cross-section. On the other hand, the main body seal pressure strip made of a hard, high temperature resistant material is embedded in the circumferential direction. A spherical lid sealing surface is formed on the outer periphery of the inner protrusion of the lid that closes the opening of the valve body, and this lid sealing surface is made of a high temperature resistant material with high hardness that contacts the main body seal protrusion. A steam leak prevention device for a steam valve characterized by providing a lid seal pressure strip. 2. The contact surface between the main body seal pressure strip and the lid body seal pressure strip is
The steam according to claim 1, wherein the lid body is provided with seven holes for connecting the space formed between the gasket housed in the storage groove around the opening of the valve body and the low-pressure low-temperature steam line. Valve steam leak prevention device. 1. The I-sket t stored in a storage groove recessed around the opening of the valve body and compressed by a protrusion protruding from the contact surface of the f& portion of the lid body according to claim 1 or 2. Steam leak prevention device for steam valves.