JP2014070513A - Steam valve for steam turbine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a steam valve of a low cost and a high reliability by adopting a steam valve structure capable of reducing a difficulty accompanying the rotation of a valve body and a cost rise for eliminating the difficulty.SOLUTION: A steam valve for a steam turbine comprises: a valve seat 4 having an opening 7; a valve member 3 disposed to face the opening of the valve seat 4; a valve rod 2 for moving the valve body to and from the valve seat 4, and a cylindrical support member 8 for supporting the valve rod slidably. The steam valve is characterized in that the valve member 3 and the valve rod 2 engage at least partially in surface contact at the fitting portion between the valve member 3 and the valve rod 2.

Description

  The present invention relates to a steam valve installed in a steam turbine power generation facility of a power plant.

  Main steam valves in a power plant are composed of a main steam stop valve and a steam control valve of the main steam system, a reheat steam stop valve of the reheat steam system, an intercept valve, and the like. The main steam stop valve and reheat steam stop valve are installed for the purpose of shutting off the steam flowing into the turbine in an emergency, and the steam control valve and intercept valve are for the purpose of adjusting the amount of steam flowing into the turbine and controlling the turbine. is set up. The steam control valve and intercept valve also have a steam shut-off function in case of emergency.

  Among these steam valves, for example, the main steam stop valve operates the valve stem installed in the valve casing and the valve body linked to the valve stem in the axial direction of the valve stem, and the opening degree of the valve body and the valve seat is increased. It has a steam blocking function by opening and closing (Patent Document 1).

JP 2009-174324 A

  In recent years, there has been a demand for high efficiency and low cost for power plants and their facilities, and high temperature and high pressure of steam conditions and longer maintenance intervals have been implemented. However, due to the high temperature and high pressure of the steam conditions, the steam turbine power generation equipment requires materials with higher functions. In addition, there is a concern about the decrease in reliability associated with long-term operation.

  For example, in a conventional main steam stop valve, in a valve open state as shown in FIG. 5, the valve body 3 receives fluid force in a direction perpendicular to the axis with respect to the valve stem 2 by steam. Due to this fluid force, a force in the rotational direction acts on the valve body 3. When the valve body 3 rotates, wear occurs at the contact portion between the valve stem 2 and other built-in objects, causing problems with the built-in steam valve and malfunctions leading to malfunction of the steam valve.

  For the purpose of preventing the rotation of the valve body 3, a detent pin 5 has conventionally been installed. However, since the fluid force increases as the steam conditions increase in temperature and pressure, the detent pin 5 may be damaged. . For this reason, a high-functional material is applied to the detent pin 5 for the purpose of preventing damage. Moreover, as a measure for preventing reliability deterioration during long-term operation, in addition to the application of high-functional materials, measures are taken by surface treatment construction.

  Since a power plant uses a steam valve under high-temperature and high-pressure steam conditions, the structure disposed in the steam flow path is required to have erosion resistance, oxidation resistance, wear resistance, and the like. For the pin 5 for rotation prevention, since wear resistance is particularly important, materials such as 12% chromium steel and incoloy (mainly nickel-chromium-iron) are used. Further, surface treatment such as nitriding is also widely used for the purpose of improving wear resistance. Nitriding is a technique for generating a hardened layer of iron nitride by infiltrating nitrogen into the surface of the base material at a temperature of 500 to 600 ° C.

  The application of these highly functional materials and the response by surface treatment construction are factors that increase the cost of steam valves.

  Therefore, the present invention employs a steam valve structure that can suppress a problem associated with rotation of the valve body and an increase in cost due to the countermeasure, and provides a low-cost and highly reliable steam valve.

  In order to solve the above-described problems, the present invention provides a valve seat having an opening, a valve body provided to face the opening of the valve seat, and a valve that moves the valve body in a direction to contact and separate from the valve seat. In a steam valve for a steam turbine comprising a rod and a cylindrical support member that slidably supports the valve stem, the valve body and the valve stem are in surface contact at a fitting portion between the valve body and the valve stem. It is characterized by engaging.

  ADVANTAGE OF THE INVENTION According to this invention, the malfunction accompanying the rotation of a valve body and the cost increase by the countermeasure can be suppressed, and the steam valve for steam turbines of low cost and high reliability can be provided.

It is sectional drawing which showed roughly the internal structure of the main steam valve for steam turbines based on the Example of this invention. It is sectional drawing explaining the example of the valve body part of the steam valve shown in FIG. It is a perspective view explaining the example of the detent | locking structure of the valve rod of the steam valve shown in FIG. It is sectional drawing which shows schematically the internal structure of the general main steam stop valve for steam turbines. It is a figure which shows the internal structure at the time of the full open of the main steam stop valve shown in FIG.

  First, in order to facilitate understanding of the features of the present invention, a conventional general steam stop valve for a steam turbine will be briefly described with reference to FIGS. 4 is a cross-sectional view schematically showing the internal structure of the main steam stop valve for a steam turbine, and FIG. 5 is a view showing the internal structure of the main steam stop valve shown in FIG. 4 when fully opened.

  As shown in FIG. 4, the main steam stop valve includes a valve seat 4 having an opening 7, a valve body 3 provided to face the opening 7, and a direction in which the valve body 3 contacts and separates from the valve seat 4. The casing 1 is configured to accommodate a valve stem 2 to be moved to a position and a satellite casing 8 that is a cylindrical support member that supports the valve stem 2 in a slidable manner. In addition, a valve chamber partitioned up and down by a valve seat 4 is formed inside the casing 1. Although not shown, the upper side of the valve chamber is connected to the steam inlet. On the other hand, the valve chamber lower part 10 side is connected to a steam outlet (not shown).

  The valve stem 2 is driven in the vertical direction by a driving means (not shown). As shown in FIG. 5, when the valve stem moves upward, the valve body 3 interlocked with the valve stem 2 moves away from the valve seat 4, and a gap is formed between the valve body 3 and the valve seat 4. It is formed. Steam flows from the upper part of the valve chamber into the lower part 10 of the valve chamber through this gap.

  By the way, in the valve open state as shown in FIG. 5, in the upper part of the valve chamber, the steam flows from the direction perpendicular to the vertical direction as indicated by the arrow, passes through the opening 7, and descends to the lower part of the valve chamber 10. Flow into. Therefore, the valve body 3 receives a fluid force in a direction perpendicular to the axis with respect to the valve stem 2 by steam. Due to this fluid force, a force in the rotational direction acts on the valve body 3 on the valve body 3. When the valve body 3 rotates, wear occurs at the contact portion between the valve stem 2 and other built-in objects, causing problems with the built-in steam valve and malfunctions leading to malfunction of the steam valve. Therefore, conventionally, as a structure for preventing the rotation of the valve body 3, a structure in which the valve body 3 and the bush 6 inserted into the valve body 3 and the valve rod 2 are fixed to each other with a rotation pin 5 is used.

  However, the steam conditions are also increased in temperature and pressure as the efficiency of the steam turbine increases. For this reason, the fluid force increases, the rotational force acting on the valve body 3 also increases, and there is a concern about the damage of the detent pin 5. For this reason, a high-functional material is applied to the anti-rotation pin 5 for the purpose of preventing damage, and surface treatment work is taken as a measure for preventing reliability deterioration during long-term operation. These measures increase the cost of the steam valve.

  Based on the above conventional structure and its problems, embodiments of the present invention will be described below. Conventionally, a rotation prevention pin has been used to prevent the rotation of the valve body.However, in the present invention, a flat portion is installed at the fitting portion between the valve rod and the valve body, so that The valve body is engaged by surface contact, and the valve body can be prevented from rotating. In the present invention, the planar portion to be installed has a planar structure in consideration of wear resistance and oxidation resistance. More details will be described in the following examples.

  FIG. 1 is a cross-sectional view schematically showing the internal structure of a main steam stop valve for a steam turbine according to an embodiment of the present invention. 2 is a view for explaining an example of the valve body portion of the steam valve shown in FIG. 1, and is a cross-sectional view taken along the line AA of FIG. FIG. 3 is a perspective view for explaining an example of a rotation stop structure of the valve rod of the steam valve shown in FIG. The same components are denoted by the same reference symbols throughout the drawings.

  In the present embodiment, the main steam stop valve moves in a direction in which the valve seat 4 having the opening 7, the valve body 3 provided to face the opening 7, and the valve body 3 in contact with and away from the valve seat 4. It is the same as in the prior art that the valve rod 2 to be operated and the sanitary casing 8 that is a cylindrical support member that freely supports the valve rod 2 are housed in the casing 1.

  Next, the fitting part of the valve body 3 and the valve stem 2 which is the characteristic part of this invention is demonstrated. As shown in FIG. 1, the valve body 3 has a hole 12 for inserting the valve stem 2 in the center of the valve body main body. The hole 12 is formed with an upper reduced diameter portion 12a and a lower enlarged diameter portion 12b, and a cylindrical valve body bush 6 is inserted into the lower enlarged diameter portion 12b. The valve body bush 6 is fixed to the valve body 3 by an interference fit. Although not shown, stepped portions that engage with each other are provided on the surfaces of the valve body bush 6 and the valve stem 2, thereby transmitting the force of the valve stem 2 to the valve body portion.

  In the present embodiment, a flat portion 9 is formed at the tip portion of the valve stem 2 by flattening a part of the round bar-like surface. As shown in FIG. 2 (a), the flat portion 9 is formed in a pair in parallel with two locations on the surface of the valve stem 2. On the other hand, as shown in FIG. 2A, two flat portions 11 corresponding to the surface portion of the valve stem 2 are formed on the inner surface of the reduced diameter portion 12 a in the hole 12 of the valve body 3.

  When the valve stem 2 is inserted into the valve body 3 at the time of assembly, the flat portion 9 of the valve stem 2 and the flat portion 11 of the valve body 3 are fitted and fixed so as to face each other. When the flat surface portion 9 of the valve stem 2 and the flat surface portion 11 of the valve body 3 are in surface contact, the valve body 3 is prevented from rotating. Therefore, according to the present embodiment, a fluid force in a direction perpendicular to the axis is applied to the valve body 3 by steam on the valve body 3, and the rotation of the valve body 3 is prevented even if a force in the rotational direction acts on the valve body 3. I can do it. Thereby, the high reliability of the steam valve can be maintained.

  Moreover, according to this structure, since it is not necessary to use the detent | locking pin 5, use of the highly functional material for a pin and the necessity of surface treatment construction become unnecessary, and cost can be reduced.

  Therefore, according to the structure of the present embodiment, it is possible to reduce the problem associated with the rotation of the valve body and the cost due to the countermeasures, and to provide a low-cost and highly reliable steam valve.

  Another embodiment of the present invention will be described. In Example 1, although the example which provided the flat part in the valve body 3 was demonstrated, you may provide a flat part in the bush 6. FIG.

  As shown in FIG. 2 (b), a flat portion 9 is provided on the surface of the valve stem 2, a flat portion 12 facing the flat portion 9 is provided on the inner peripheral surface of the valve body bush 6, and the valve stem 2 is connected to the valve disc. 3, the flat portion 9 of the valve stem 2 and the flat portion 12 of the valve body 3 are brought into surface contact.

  FIG. 3 shows a more detailed three-dimensional structure of the valve stem 2 when the structure of FIG. The valve stem 2 has a reduced diameter portion 13 for mounting the collar 14 at a certain distance from the tip, and has a flat portion 9 a and a flat portion 9 b on the upper and lower surfaces of the reduced diameter portion 13. The collar 14, which is a ring-shaped two-part, is a part that transmits the force of the valve stem 1 to the valve body when the valve is closed, and the flat part 9 a is a flat part that needs to be provided for assembly of the valve element bush 6.

  The valve body bush 6 is a cylindrical member into which the valve rod 2 is inserted, and is fixed to the valve body 3 by an interference fit. The outer surface of the bush is provided with an enlarged diameter portion and a reduced diameter portion to form a step. On the other hand, a step corresponding to the inner surface of the hole 12 of the valve body 3 is also formed, and the step on the bush side and the step on the valve body 3 side are engaged. The force of the valve stem is transmitted from the collar 14 to the valve body bush 6, and the force on the valve stem 2 acts on the valve body 3 by engaging the step on the bush side and the step on the valve body 3 side.

  In this embodiment, when the flat surface portion 12 facing the flat surface portion 9 b of the valve stem 2 is provided on the inner surface of the valve body bush 6 and the valve rod 2 is inserted into the valve body bush 6, The flat portion 9b and the flat portion 12 on the bush side are engaged with each other so as to be in surface contact. Due to the surface contact between the flat surfaces, a fluid force in the direction perpendicular to the axis is applied to the valve body 2 by steam on the valve body 3 in the same manner as in the first embodiment, and the valve body 3 even if a rotational force acts on the valve body 3. Can prevent rotation.

  Further, when a flat surface portion is provided on the inner peripheral surface of the valve body bush 6, the contact area can be increased, wear can be reduced, and the reliability can be further improved.

  Even with the structure of the present embodiment, there is no need to use the non-rotating pin 5, and there is no fear that the non-rotating pin will be damaged, leading to improved reliability. In addition, the number of parts can be reduced, and cost reduction can be expected.

  In addition, since each plane part demonstrated in each Example becomes a site | part by which abrasion resistance and oxidation resistance are calculated | required, what is necessary is just to carry out surface treatment as needed and make it the structure which satisfy | fills these requirements. In addition, since the valve stem is a sliding part and is generally a component that requires wear resistance and oxidation resistance, use of a high-performance material or a surface treatment that improves wear resistance and oxidation resistance is used. There are many cases. For this reason, even when surface treatment is applied to the flat surface portion, the cost is not increased.

DESCRIPTION OF SYMBOLS 1 Casing 2 Valve stem 3 Valve body 4 Valve seat 5 Non-rotating pin 6 Valve body bush 7 Opening part 8 Guard casing 9, 11, 12 Plane part 10 Valve chamber lower part 13 Reduced diameter part 14 Color

Claims (3)

A valve seat having an opening, a valve body provided opposite to the opening of the valve seat, a valve rod for moving the valve body in a direction to contact and separate from the valve seat, and sliding the valve rod A cylindrical support member for free support;
In a steam valve for a steam turbine provided with
A steam valve for a steam turbine, wherein the valve body and the valve stem are engaged by surface contact at a fitting portion between the valve body and the valve stem. A steam valve for a steam turbine according to claim 1,
The valve body has a valve body body having a hole into which the valve stem is inserted at the center, and a cylindrical bush that is fitted into the hole and into which the valve stem is inserted,
The bush has a flat portion formed on the inner peripheral surface,
The said valve stem is formed in the valve stem surface, It has a plane part which surface-contacts with the plane part formed in the said bush, The steam valve for steam turbines characterized by the above-mentioned. A steam valve for a steam turbine according to claim 1,
The valve body has a hole into which the valve stem is inserted in the center, and a flat portion formed on the surface of the hole,
The said valve stem is formed in the valve stem surface, It has a plane part which surface-contacts with the plane part formed in the said hole surface, The steam valve for steam turbines characterized by the above-mentioned.