A high pressure main steam valve for steam turbine

Abstract

The present invention relates to a high-pressure main steam valve for a steam turbine, comprising a valve body, a valve cover, a filter assembly, a main steam valve disc and a valve stem; the valve body is provided with a steam inlet, a filter assembly is installed in the valve body corresponding to the steam inlet, a valve cover fixedly connected to the valve body is arranged at one end of the filter assembly, a valve sleeve is installed in the valve body at the other end of the filter assembly, a valve stem is inserted in the valve sleeve, a valve head of the valve stem extends into the steam inlet side and a main steam valve disc is installed, a main steam valve seat for limiting is arranged on the steam outlet side of the valve body corresponding to the main steam valve disc, a steam outlet and a drain port are provided in the valve body on the steam outlet side of the main steam valve seat, a valve tail of the valve stem extends out of the valve sleeve and is connected to an oil motor through a coupling. The present invention provides a high-pressure main steam valve for a steam turbine, which can satisfy the reciprocating movement function and realize the pre-start switch function through movement coordination through the ingenious design of the main components, and has high stability.

Description

Technical Field

[0001] The invention relates to the technical field of steam turbine valve equipment, and in particular to a high-pressure main steam valve of a steam turbine. Background Art

[0002] A steam turbine is a rotary prime mover that converts thermal energy into mechanical energy using steam as a working fluid. It is mainly used to drive a generator to produce electricity. The steam inlet and exhaust of a steam turbine are mainly achieved through the coordinated action of various valves. Among them, the high-pressure main steam valve is a valve that allows the main steam to enter the steam turbine and can be closed quickly. The high-pressure main steam valve on the market is mainly composed of oil motors, valve bodies, main valve discs, pre-start valve discs, valve stems and bushings. The bushing is fixed in the valve body, and the valve stem slides in the bushing hole.

[0003] The existing main steam valve is designed with a filter screen installed to allow steam in and block impurities. However, the filter screen is processed by directly drilling a series of small holes on a round pipe. Due to the small hole diameter and the large number of holes, the filter screen processing cycle is long.

[0004] The main valve disc, pre-start valve disc and valve stem of the existing main steam valve are made of high temperature alloy or heat resistant alloy, and the sliding surface and sealing surface are nitrided to improve the Vickers hardness and wear resistance. The thickness of the nitrided layer is generally ≤0.5mm. As the valve is continuously opened and closed, the sealing surface will be worn, pitted, etched and other defects will occur, and the sealing effect cannot be guaranteed. As a result, the sliding surface is affected by the high temperature steam to produce a large amount of oxide scale, which will cause the valve stem to get stuck and cannot be closed normally. In serious cases, accidents will occur, resulting in the inability to shut down.

[0005] The existing main steam valve design uses a bushing between the valve stem and the valve body for sliding and sealing. The bushing structure is a full-length structure, and the inner hole is sprayed with Stellite alloy to slide with the valve stem. Due to the long valve stem, it is affected by long-term operation, the straightness is out of tolerance, the spray layer is not strong enough to fall off, the oxide scale is serious, and the jamming phenomenon is frequent.

[0006] The valve stem of the existing main steam valve design is required to have an anti-rotation function during the start-stop process. Usually, an anti-rotation pin is designed between the valve stem and the valve disc, and it slides in the anti-rotation keyway set in the inner hole of the valve disc. The valve disc is often switched on and off, and the temperature inside the valve body is high. After long-term operation, the sliding mating surface is severely oxidized, and often jams, causing the pre-start valve to fail. It is necessary to shut down and disassemble regularly to clean the oxide scale and restore the original design gap, which increases the workload. Summary of the invention

[0007] In order to solve the above problems, the present invention provides a high-pressure main steam valve for a steam turbine. Through the ingenious design of the main components, it can not only realize the main steam valve switching function by reciprocating movement, but also realize the pre-start switching function through movement coordination, and has high stability.

[0008] The technical solution adopted by the invention is: a high-pressure main steam valve for a steam turbine, comprising a valve body, a valve cover, a filter assembly, a main steam valve disc and a valve stem;

[0009] The valve body is provided with a steam inlet, a filter assembly is installed in the valve body corresponding to the steam inlet, a valve cover fixedly connected to the valve body is arranged at one end of the filter assembly, a valve sleeve is installed in the valve body at the other end of the filter assembly, a valve stem is inserted in the valve sleeve, the valve head of the valve stem extends into the steam inlet side and is installed with a main steam valve disc, a main steam valve seat for limiting is arranged on the steam outlet side of the valve body corresponding to the main steam valve disc, a steam outlet and a drain port are arranged in the valve body on the steam outlet side of the main steam valve seat, and the valve tail of the valve stem extends out of the valve sleeve and is connected to the oil motor through a coupling;

[0010] The main steam valve disc is slidably fitted on the stepped shaft-shaped valve head end of the valve stem through a preset stepped center hole. The steam inlet side of the main steam valve disc is coaxially installed with an axially hollow locking nut that retains a set gap with the end face of the center hole through an integrally extended flange. When the main steam valve disc is seated on the main steam valve seat and the end face of the valve head is flush with the end face of the stepped center hole of the main steam valve disc, it is the first position. When the valve stem drives the valve head to leave the first position and slide along the stepped center hole of the main steam valve disc until the end face of the valve head contacts the end face of the locking nut, it is the second position. When the valve stem drives the main steam valve disc to continue to move along the direction of the valve cover to the minimum design distance between the outer end face of the locking nut and the inner end face of the valve cover, it is the third position.

[0011] A steam inlet hole corresponding to the large end of the valve head is provided on the steam inlet side of the main steam valve disc, a steam storage chamber connected to the steam inlet hole is provided in the middle of the main steam valve disc, and cooperates with the side of the large end of the valve head to form a closed annular groove-shaped space when in the first position; a steam outlet hole corresponding to the small end of the valve head is provided on the steam outlet side of the main steam valve disc, and an auxiliary air leakage structure is processed on the side of the small end of the valve head corresponding to the steam storage chamber and the steam outlet hole; a radial through hole connected to the steam storage chamber is provided inside the valve head, and an axial through hole is provided between the radial through hole and the locking nut.

[0012] As a further limitation of the above technical solution, the filter assembly includes a cylindrical inner filter and an outer filter, the inner filter is made of seamless steel pipe, the inner filter hole is drilled on the surface of the steel pipe, and a guide angle opening outward is provided on the side of the inner filter hole adjacent to the outer filter, the outer filter is rolled from a stainless steel plate and clamped in a preset groove on the outer side of the inner filter, and the stainless steel plate is pre-formed with an outer filter hole by a stamping process; the axis of the filter assembly is arranged perpendicularly to the axis of the steam inlet.

[0013] As a further limitation of the above technical solution, the valve body is provided with two sets of filter assemblies with different apertures, including a temporary filter with a small aperture for finely filtering steam when the turbine is started and a working filter with a large aperture for filtering steam during normal operation of the turbine.

[0014] As a further limitation of the above technical solution, the valve cover is fixed to the valve body at the axial end of the filter assembly through a toothed pad, and an anti-rotation screw is provided between the filter assembly and the valve cover. The threaded portion of the anti-rotation screw is screwed into the valve cover, and the head of the anti-rotation screw is embedded in a keyway pre-opened at the axial end of the filter assembly.

[0015] As a further limitation of the above technical solution, the main steam valve seat is a ring-shaped structure clamped on a preset boss inside the valve body, the contact end faces of the main steam valve seat and the main steam valve disc are both set as Stellite alloy sealing surfaces, and the inner surface of the main steam valve seat is processed into a streamlined shape to facilitate the escape of gas to the steam outlet side.

[0016] As a further limitation of the above technical solution, the coupling includes an oil motor connecting piece, a stop washer, a coupling locking piece, a coupling sleeve and a coupling sandwich. The end of the oil motor connecting piece away from the valve tail is connected to the oil motor output shaft through threaded cooperation and a stop washer. The end of the oil motor connecting piece opposite to the valve tail and the end of the valve tail opposite to it are processed into a square shaft or two square shafts of equal size with an inwardly converging annular grooves at the distal ends. The outer sides of the ends of the oil motor connecting piece and the valve tail are buckled with two half structures of the coupling sandwich that respectively engage the annular grooves from both sides of the axis. The coupling sandwich is provided with annular guide grooves on the outer edges of the end faces at both ends of the axis. The coupling sleeve enters the guide groove at one end and is mounted on the outside of the coupling sandwich. The coupling locking piece is clamped in the guide groove at the other end of the coupling sandwich. Screws for tightening and fixing are passed through the coupling locking piece, the coupling sleeve and the coupling sandwich.

[0017] Alternatively, the coupling is a prismatic structure with threaded holes at both ends, and the two ends of the coupling are connected to the oil motor and the valve tail through threaded matching and stop washers.

[0018] As a further limitation of the above technical solution, the auxiliary air leakage structure is a structure with reduced diameter or gradually smaller diameter, or an air leakage groove is opened along the axial direction, or a combination of reduced diameter or reduced diameter and axial air leakage groove.

[0019] As a further limitation of the above technical solution, the valve sleeve includes a valve stem sleeve, a graphite gasket assembly and a sealing flange. The valve body is provided with a mounting groove, in which the valve stem sleeve and a graphite gasket assembly assembled by a plurality of graphite rings are installed in sequence from the inside to the outside along the axial direction. A sealing flange is installed at the outer end of the mounting groove, the inner side of which is embedded in the mounting groove through a guide ring and the outer side of which is provided with a flange plate, and a clamping screw for clamping the graphite gasket assembly is installed on the flange plate.

[0020] As a further limitation of the above technical solution, a heat insulation groove is provided at the outer end of the installation groove of the valve body around the sealing flange, a heat insulation material is installed in the heat insulation groove, and a first heat insulation board is fixed on the outer side of the heat insulation material;

[0021] The end surface of the coupling corresponding to one end of the valve stem is fixed to the second heat insulation plate by screws.

[0022] The oil motor is fixedly connected to the valve body through an oil motor valve column. The oil motor valve column is a hollow cylindrical structure with flanges at both ends. The oil motor valve column and the valve body, the oil motor valve column and the oil motor are centered through a stop structure and fixedly connected by bolts. A third heat insulation plate is installed between the oil motor valve column and the oil motor.

[0023] As a further limitation of the above technical solution, the steam outlet is connected to the steam inlet port of the subsequent equipment through a toothed pad with concentric annular grooves, and the inner hole of the steam outlet and the toothed pad mounting groove are provided with mutually interpenetrating hydrophobic grooves connected to the hydrophobic port.

[0024] The present invention discloses a high-stability high-pressure main steam valve design structure and control function suitable for reaction steam turbines. The main steam valve is controlled by an oil motor, and the output shaft of the oil motor reciprocates and drives the valve stem to reciprocate, and then drives the main steam valve disc to reciprocate under the guidance of the valve stem sleeve, so as to meet the steam flow control in the main steam valve, and realize the pre-start, opening and closing functions of steam under 470℃ and 49Bar working conditions. The valve stem can meet the reciprocating movement function, and the valve head of the valve stem can be regarded as a pre-start valve head, which cooperates with the movement of the main steam valve disc to realize the pre-start switch function.

[0025] Steam enters the valve body from the steam inlet, is filtered through the filter assembly to prevent impurities in the steam from entering the main steam valve disc, and then is guided out to the main steam regulating valve behind through the steam outlet under the movement of the valve stem. The moisture formed by the temperature change of the steam is guided out of the valve body through the drain port.

[0026] Through the design of the connection structure between the main steam valve disc and the valve stem, when the main steam valve is not started, the valve stem is in the first position, and the airflow at the steam inlet enters the steam storage chamber through the axial through hole of the locking nut and the radial through hole of the valve head, and then meets the airflow entering the steam storage chamber through the steam inlet hole of the main steam valve disc, so as to achieve the air pressure balance between the steam storage chamber and the steam inlet side. The valve stem can slide to the second position driven by the oil motor. During the sliding process of the valve stem, steam enters the steam outlet side from the steam inlet hole of the main steam valve disc through the auxiliary air leakage device, so that the air pressure on the steam inlet side and the steam outlet side is balanced. When the big head end of the valve stem valve head abuts against the end face of the locking nut, the pre-start opening state of the main steam valve is realized, and the valve stem is pushed to drive the main steam valve disc to leave the main steam valve seat, and the steam flows from the steam inlet side through the main steam valve seat to the steam outlet side, so as to realize the start of the main steam valve.

[0027] The invention shortens the processing cycle of the filter screen and improves the working efficiency by optimizing the processing technology of the filter screen.

[0028] The present invention provides guide holes so that the inner filter screen can achieve the function of guiding the filtered steam and the function of supporting the outer filter screen.

[0029] The present invention prevents the filter assembly from rotating through the design of the connection structure between the filter assembly and the valve cover, thereby improving the stability of the filter assembly.

[0030] The present invention limits the contact surface material of the main steam valve disc and the main steam valve seat, thereby improving the hardness and oxidation resistance of the contact surface and realizing the sealing function of the main steam valve.

[0031] The present invention effectively isolates the influence of internal high-temperature steam on the anti-rotation structure by arranging the anti-rotation structure of the valve stem outside the valve body.

[0032] The present invention provides an auxiliary air leakage structure to facilitate the discharge of the airflow inside the steam storage chamber to the steam outlet.

[0033] The design of the valve sleeve structure of the present invention utilizes the sealing structure of the middle part of the graphite gasket assembly to achieve the sealing of the valve stem under high temperature conditions. The valve stem sleeve and the sealing flange are separately installed at both ends to enhance the supporting and guiding effect on the valve stem and avoid the jamming phenomenon of the valve stem caused by long-term high-temperature operation.

[0034] The present invention improves the thermal insulation performance of the valve body by arranging three layers of thermal insulation boards. By arranging the first thermal insulation board, the heat conduction of the steam inside the valve body is effectively isolated, and a first thermal insulation layer is formed; by arranging the second thermal insulation board, the influence of the high temperature of the valve body on the coupling is eliminated, and a second thermal insulation layer is formed; by arranging the third thermal insulation board, the influence of the high temperature of the valve body on the oil motor is effectively avoided, and a third thermal insulation layer is formed. Through the design of the triple thermal insulation layer, the interior of the valve body, the coupling and the oil motor are thermally insulated and protected, and the high-temperature gas inside the valve body is isolated together, thereby reducing the influence of the high temperature on the main steam valve structure and ensuring the normal operation of the main steam valve. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is an axial cross-sectional view of the high-pressure main steam valve of the present invention;

[0036] Figure 2 for Figure 1 The enlarged view of point A in the middle;

[0037] Figure 3 for Figure 1 The enlarged view of point B in the middle;

[0038] Figure 4 for Figure 1 Enlarged view of point C in the middle;

[0039] Figure 5 for Figure 1 The enlarged view of point D in the middle;

[0040] Figure 6 It is a top view of the high-pressure main steam valve of the present invention.

[0041] In the figure: 1-valve body; 101-steam inlet; 102-main steam valve bracket interface; 103-steam outlet; 104-drain outlet; 2-valve cover; 201-toothed pad; 202-anti-rotation screw; 3-filter assembly; 301-inner filter; 302-outer filter; 303-inner filter hole; 304-outer filter hole; 305-guide angle; 306-keyway; 4-main steam valve disc; 401-steam inlet hole; 402-steam storage chamber; 403-steam outlet hole; 404-auxiliary leakage structure; 405-radial through hole; 5-main steam valve seat; 601-valve stem sleeve; 602-graphite gasket assembly; 603-sealing flange; 604-pressing screw; 605-insulating material; 606-first insulation board; 607-fixing screw; 7-valve stem; 801-oil motor connector; 802-stop washer; 803-coupling lock plate; 804-coupling sleeve; 805-coupling sandwich; 806-second insulation board; 9-oil motor; 901-oil motor valve column; 902-third insulation board; 10-locking nut; 11-pre-start stroke; 12-pressure sensor; 13-temperature sensor; 14-full-open stroke. DETAILED DESCRIPTION

[0042] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0043] Example 1

[0044] like Figure 1-6 As shown, a high-pressure main steam valve of a steam turbine is installed on a reaction steam turbine and is responsible for controlling the steam delivered by the boiler to be output to the main steam regulating valve for regulation. It is the first valve of the reaction steam turbine unit and mainly plays the role of quickly closing and cutting off the steam inlet of the steam turbine unit. It includes a valve body 1, a valve cover 2, a filter assembly 3, a main steam valve disc 4 and a valve stem 7.

[0045] The valve body 1 is a hollow cavity with openings at both ends of the horizontal axis of the valve body 1. A steam inlet 101 for introducing steam is provided at the bottom of the left side of the valve body 1. In order to enhance the stability of the high-pressure main steam valve during operation, a main steam valve bracket interface 102 is provided on one side of the steam inlet 101 of the valve body 1, which is fixedly connected to the bracket at the bottom of the steam turbine to fix the high-pressure main steam valve on the steam turbine. A horizontal steam outlet 103 is provided on the right side of the steam inlet 101 and in the middle of the side of the valve body 1. The steam outlet 103 is provided vertically outwardly with the valve body 1. A downward-opening drain port 104 is provided below the steam outlet 103 and at the bottom of the side of the valve body 1.

[0046] A cylindrical filter assembly 3 with an axis perpendicular to the steam inlet is inserted into the valve body 1 at the corresponding steam inlet 101. A valve cover 2 is installed on the left side of the filter assembly 3. A stepped hole is arranged in the valve body 1 on the right side of the filter assembly 3 and on the left side of the steam outlet 103 and the drain port 104, and a main steam valve seat 5 for limiting is installed in the stepped hole by interference fit. A valve sleeve is installed in the valve body 1 on the right side of the steam outlet 103 and the drain port 104, and a valve stem 7 is inserted in the valve sleeve, and the valve head of the valve stem 7 extends into the right side of the filter assembly 3. A main steam valve disc 4 is installed on the valve head, and the steam outlet side of the main steam valve disc 4 corresponds to the main steam valve seat 5. The steam outlet 103 and the drain port 104 are arranged on the side of the valve body 1 corresponding to the steam outlet side of the main steam valve seat 5. The valve tail of the valve stem 7 extends to the outside of the valve sleeve and is connected to the oil motor 9 through a coupling.

[0047] The structure of the filter assembly 3 is as follows Figure 4 As shown, the filter assembly 3 includes a cylindrical inner filter 301 and an outer filter 302 . The filter assembly 3 is inserted into the step groove in the valve body 1 through the opening at the left end of the valve body 1 . The side of the installed filter assembly 3 is opposite to the steam inlet 101 .

[0048] The inner filter screen 301 is made of a heat-resistant seamless steel pipe, and a matrix of inner filter holes 303 are drilled on the surface of the steel pipe. The aperture of the inner filter holes 303 is set between φ8mm and φ10mm. A guide angle 305 opening outward is provided on one side of the inner filter holes 303 adjacent to the outer filter screen 302 to achieve the function of guiding the filtered steam and supporting the outer filter screen 302.

[0049] The outer filter 302 is mounted in a slot preset on the outer side of the inner filter 301. The outer filter 302 is made of a rolled stainless steel plate, and a matrix-arranged outer filter hole 304 is pre-formed on the stainless steel plate by a stamping process. The aperture of the outer filter hole 304 is set to φ2.5 mm, so as to filter the steam and prevent impurities in the steam from entering the valve body 1.

[0050] The valve body 1 is provided with two sets of filter screen assemblies 3 with different apertures, including a temporary filter screen with a small aperture, which is used for fine filtering of steam when the steam turbine is started, and the aperture of the outer filter hole 304 of the outer filter screen 302 is φ0.2mm; and also includes a working filter screen with a large aperture, which is used for filtering steam when the steam turbine is running normally, and the aperture of the outer filter hole 304 of the outer filter screen 302 is φ2.5mm. When the steam turbine is started, a temporary filter screen is installed on the valve body 1. Since the steam of the new unit flushes the pipe, the steam impurities need to be filtered by the temporary filter screen. After the flushing is completed or it has been used for about 1 year, the valve cover is opened when the machine is shut down, and the temporary filter screen is removed and replaced with the working filter screen for long-term use.

[0051] The connection between the valve cover 2 and the filter assembly 3 is as follows Figure 4As shown, the valve cover 2 is fixedly connected to one end of the valve body 1 through bolts and seals, and abuts against the left end of the filter assembly 3. At the end face after the sealing valve cover 2 is connected to the valve body 1, the valve cover 2 is fixed to the valve body 1 at the axial end of the filter assembly 3 through a toothed pad 201. Both end faces of the toothed pad 201 are provided with annular grooves composed of concentric circles. To improve the sealing effect, the shape of the annular groove is set to be triangular. To prevent the filter assembly 3 from rotating, an anti-rotation screw 202 is provided between the filter assembly 3 and the valve cover 2. The threaded part of the anti-rotation screw 202 is screwed into the valve cover 2, and the head of the anti-rotation screw 202 is embedded in the keyway 306 pre-opened at the axial end of the filter assembly 3.

[0052] The steam outlet 103 of the high-pressure main steam valve is also sealed and connected to the main steam regulating valve through a toothed gasket. The main steam valve and the port inner holes of the main steam regulating valve and the toothed gasket mounting groove are provided with mutually interpenetrating drain grooves, and the other end of the drain groove is connected to the drain port of the high-pressure main steam valve.

[0053] Valve sleeve structure Figure 5 As shown, the valve sleeve includes a valve stem sleeve 601, a graphite gasket assembly 602, and a sealing flange 603. The valve body 1 is provided with a mounting groove opening to the right, and the valve stem sleeve 601 and a graphite gasket assembly 602 assembled with a plurality of graphite rings are sequentially installed in the mounting groove along the axial direction from left to right, so as to achieve the sealing of the valve stem 7 from leaking under high temperature conditions. The sealing flange 603 is embedded in the outer end of the right side of the mounting groove through a guide ring, and the inner side of the sealing flange 603 is embedded in the mounting groove. A flange plate is provided on the outer side of the sealing flange 603, and a clamping screw 604 for clamping the graphite gasket assembly 602 is installed on the flange plate.

[0054] The outer end of the installation groove is provided with a heat insulation groove around the sealing flange 603, and a heat insulation material 605 is installed in the heat insulation groove. The heat insulation material 605 is made of ceramic fiber rope. In order to improve the heat insulation effect, the ceramic fiber rope is radially coiled around the valve body 1. A first heat insulation board 606 is fixed outside the heat insulation material 605. The first heat insulation board 606 is L-shaped, with a vertical end attached to the heat insulation material 605 and a horizontal end fixed to the valve body 1 by a fixing screw 607.

[0055] The main steam valve disc 4 is matched with the valve head end of the valve stem 7 through the preset stepped center hole to realize the sliding setting of the main steam valve disc 4 and the valve head of the valve stem 7. The valve head is in the shape of a stepped shaft, and the left end of the valve head is divided into a large head end with a large diameter, and the right side of the large head end is a small head end with a small diameter. The main steam valve disc 4 is inserted from the valve tail and passes through the small head end, the large head end and the valve head in sequence. The steam inlet side of the main steam valve disc 4 is coaxially installed with a locking nut 10 through a flange extending outward. A gap is reserved between the locking nut 10 and the end face of the stepped center hole of the main steam valve disc 4, and the locking nut 10 is an axially hollow nut.

[0056] When the main steam valve disc 4 sits on the main steam valve seat 5 and the end face of the big end of the valve head is flush with the left end face of the stepped center hole of the main steam valve disc 4, it is the first position, that is, when the end face of the big end of the valve head is flush with the right end face of the steam storage chamber 402 of the main steam valve disc 4, it is the first position, ensuring the sealing of the steam storage chamber 402, and the first position is the main steam valve closed position; when the valve stem 7 drives the valve head to leave the first position, slide to the left along the stepped center hole of the main steam valve disc, and the end face of the big end of the valve head contacts the right end face of the locking nut, it is the second position, and the second position is the pre-start position of the main steam valve disc; when the valve stem 7 drives the main steam valve disc 4 to continue to move along the direction of the valve cover 2 to the minimum design distance between the left end face of the locking nut 10 and the right end face of the valve cover 2, it is the third position, and the third position is the main steam valve open position. The moving distance between the first position and the second position is the pre-start stroke 11. The moving distance between the second position and the third position is the full open stroke 14.

[0057] The structure of the main steam valve disc 4 is as follows Figure 2 As shown, the left end of the main steam valve disc 4 is a horizontal outward annular flange for mounting the locking nut 10; the side of the middle part of the main steam valve disc 4 is a smooth, outwardly opened arc shape for guiding the steam on the steam inlet side; the right side of the middle part of the main steam valve disc 4 has a vertical plane structure in contact with the side of the main steam valve seat 5; the right part of the main steam valve disc 4 retains a large gap with the main steam valve seat 5, and smoothly transitions to the right from the vertical plane and gradually becomes smaller and converges, so as to facilitate the steam to enter the steam outlet side from the main steam valve seat 5.

[0058] The main steam valve disc 4 is provided with a steam inlet hole 401 on the middle side, and the steam inlet hole 401 corresponds to the large end of the valve head. The main steam valve disc 4 is provided with a steam storage chamber 402 on the inner ring surface of the middle part, and the steam storage chamber 402 is connected with the steam inlet hole 401, and when the first position is matched with the large end side of the valve head, the steam storage chamber 402 is a closed annular groove-shaped space. The main steam valve disc 4 is provided with a steam outlet hole 403 on the right steam outlet side, and the steam outlet hole 403 is connected to the small hole wall of the stepped central hole of the main steam valve disc 4, corresponding to the small end of the valve head, and the number of the steam inlet hole 401 and the steam outlet hole 403 is 4-6. The valve head is processed on the side of the small end between the steam storage chamber 402 and the steam outlet hole 403, and the auxiliary leakage structure 404 is a structure with a reduced diameter or a gradually reduced diameter, or a leakage groove is provided along the axial direction, or a combination of reducing the diameter or reducing the diameter and providing a leakage groove in the axial direction. Four evenly spaced radial through holes 405 are provided inside the valve head. The radial through holes 405 are connected to the steam storage chamber 402 , and an axial through hole is provided between the radial through hole 405 and the locking nut 10 .

[0059] Before the high-pressure main steam valve is pre-started, the valve stem 7 is in the first position. Steam passes through the filter assembly 3 to block and filter the impurities in the steam pipeline, and then enters the steam storage chamber 402 from the steam inlet hole 401 of the main steam valve disc 4. This is the first airflow; the steam enters the steam storage chamber 402 from the inner hole of the locking nut 10 and the radial through hole 405 of the valve stem 7. This is the second airflow. The first airflow and the second airflow meet in the steam storage chamber 402, so that the air pressure on the steam inlet side of the valve body 1 and the steam storage chamber 402 is balanced, and the pre-start of the valve stem 7 is realized. At this time, the valve stem 7 slides from the first position to the second position driven by the oil motor 9, and the steam storage chamber 402 is no longer sealed. The steam flows from the steam inlet side to the steam outlet side through the auxiliary air leakage structure 404, so that the air pressure on the steam inlet side and the steam outlet side is balanced, and the pre-start of the main steam valve disc 4 is realized. When the valve stem 7 is in the second position, it contacts the right end surface of the locking nut 10 and pushes the valve stem 7 to the left. The valve stem 7 drives the main steam valve disc 4 to leave the main steam valve seat 5 and move to the left to the full opening stroke 14. The steam enters the steam outlet side from the steam inlet side and the main steam valve seat 5, thereby starting the main steam valve.

[0060] When the steam delivery task of the main steam valve disc 4 is completed, the valve stem 7 moves rightward to the first position under the control of the oil motor 9, and the contact surface of the main steam valve disc 4 contacts the main steam valve seat 5 to achieve the sealing of the main steam valve seat 5, and the connection between the steam storage chamber 402 and the side surface of the large end of the valve head achieves the sealing of the steam storage chamber 402, so that steam cannot enter the steam outlet side to achieve the closure of the high-pressure main steam valve.

[0061] The main steam valve seat 5 is a ring structure, and a boss is preset at the connection between the inside of the valve body 1 and the right end of the filter assembly 3. The main steam valve seat 5 is installed on the boss with an interference fit. The main steam valve seat 5 is made of heat-resistant steel. The contact end faces of the main steam valve seat 5 and the main steam valve disc 4 are both set as Stellite alloy sealing faces. The inner side surface of the main steam valve seat 5 is processed into a streamlined shape to enable the gas to escape quickly to the steam outlet side.

[0062] The valve stem 7, the main steam valve disc 4, the valve stem sleeve 601 and the sealing flange 603 are made of stainless steel. The sliding contact surfaces of the outer cylindrical surface of the valve stem 7 and the inner hole of the main steam valve disc 4, the inner hole of the valve stem sleeve 601 and the inner hole of the sealing flange 603 are all set as Stellite alloy sealing surfaces.

[0063] The connection between the coupling and the oil motor 9 and the valve tail is as follows Figure 3 As shown, the coupling includes an oil motor connecting piece 801, a stop washer 802, a coupling locking piece 803, a coupling sleeve 804 and a coupling core 805.

[0064] The end of the oil motor connector 801 away from the valve tail is connected to the output shaft of the oil motor 9 through threaded cooperation and a stop washer 802. The stop tongues of the stop washer 802 are respectively attached to the outer side surfaces adjacent to the output shaft of the oil motor 9 and the prismatic structure of the oil motor connector 801 to achieve an anti-loosening function.

[0065] The end of the oil motor connecting piece 801 opposite to the valve tail is processed into a square shaft or two square shafts, and the right part of the end of the square shaft or two square shafts is provided with an annular groove converging inwards. The end of the valve tail opposite to the oil motor connecting piece 801 is processed into a square shaft or two square shafts, and the square shafts or two square shafts are equal in size and an annular groove converging inwards is provided on the left part of the end. The square shaft or two square shafts of the oil motor are equal in size to the square shaft or two square shafts of the valve tail, and the annular grooves are also equal in size.

[0066] The coupling core 805 is buckled on the outer side of the end of the oil motor connector 801 and the valve tail. The coupling core 805 is a two-half structure. The inner hole of the coupling core 805 is provided with four square holes or two square holes to achieve the matching installation with the oil motor connector 801 and the end opposite to the valve tail. The coupling core 805 is respectively clamped with the annular grooves on both sides of the axis of the valve stem 7 to achieve the buckling of the coupling core 805.

[0067] The coupling core 805 is provided with annular guide grooves at the outer edges of the left and right end surfaces at both ends of the axis of the valve stem 7. The coupling sleeve 804 enters the outer side of the coupling core 805 along the guide groove at the left end and is sleeved on the outer side of the coupling core 805. The coupling lock piece 803 is clamped in the guide groove at the right end of the coupling core 805. The coupling core 805 is tightened by the dual effects of the coupling sleeve 804 holding and the coupling lock piece 803 pressing. The coupling lock piece 803, the coupling sleeve 804 and the coupling core 805 are penetrated and fixed with screws.

[0068] The left end surface of the coupling sleeve 804 located on one side of the valve stem 7 is fixed with a second heat insulation plate 806 by screws.

[0069] In addition, the coupling may also adopt another structure, in which the coupling is a prismatic structure with threaded holes at both ends, and the left and right ends of the coupling along the axial direction are connected to the oil motor 9 and the valve tail through threaded fitting and stop washers 802 respectively.

[0070] The shell of the oil motor 9 is fixed by the oil motor valve column 901. The oil motor valve column 901 is a hollow cylindrical structure with flanges at both ends. The oil motor valve column 901 and the valve body 1, as well as the oil motor valve column 901 and the oil motor 9 are centered by a stop structure and fixedly connected by bolts. A third heat insulation plate 902 is installed between the oil motor valve column 901 and the oil motor 9.

[0071] In order to monitor the temperature and pressure parameters of the high-pressure main steam valve in real time, a pressure sensor 12 and a temperature sensor 13 are arranged on the top of the outer side of the valve body 1 opposite to the steam inlet. Figure 4As shown, the pressure sensor 12 is electrically connected to the DEH digital electro-hydraulic control system to achieve pressure control, and the temperature sensor 13 is electrically connected to the DCS temperature control system to achieve temperature control, wherein the model of the pressure sensor is MAA20CP202, and the model of the temperature sensor can be selected from the ordinary computer display MAA20CT605, and the circuit connections of the pressure sensor, temperature sensor, DEH digital electro-hydraulic control system and DCS temperature control system all use existing technologies.

[0072] The above description is only a preferred embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any technical solution obtained by any technician familiar with the field within the technical scope disclosed by the present invention by equivalent replacement or change based on the technical concept of the present invention should be included in the protection scope of the present invention.

Claims

1. A high-pressure main steam valve for a steam turbine, characterized in that: It comprises a valve body (1), a valve cover (2), a filter assembly (3), a main steam valve disc (4) and a valve stem (7); The valve body (1) is provided with a steam inlet (101), a filter assembly (3) is installed in the valve body (1) corresponding to the steam inlet (101), a valve cover (2) fixedly connected to the valve body (1) is provided at one end of the filter assembly (3), a valve sleeve is installed in the valve body (1) at the other end of the filter assembly (3), a valve stem (7) is inserted in the valve sleeve, the valve head of the valve stem (7) extends into the steam inlet side and is installed with a main steam valve disc (4), a main steam valve seat (5) for limiting is provided in the valve body (1) at the steam outlet side corresponding to the main steam valve disc (4), a steam outlet (103) and a drain port (104) are provided in the valve body (1) on the steam outlet side of the main steam valve seat (5), and the valve tail of the valve stem (7) extends out of the valve sleeve and is connected to an oil motor (9) through a coupling; The main steam valve disc (4) is slidably fitted on the stepped shaft-shaped valve head end of the valve stem (7) through a preset stepped center hole. The steam inlet side of the main steam valve disc (4) is coaxially mounted with an axially hollow locking nut (10) which has a set gap with the end face of the stepped center hole through an integrally extended flange. When the main steam valve disc (4) is seated on the main steam valve seat (5) and the end face of the valve head is flush with the end face of the stepped center hole of the main steam valve disc (4), it is in the first position. When the valve stem (7) drives the valve head to leave the first position and slide along the stepped center hole of the main steam valve disc (4) until the end face of the valve head contacts the end face of the locking nut (10), it is in the second position. When the valve stem (7) drives the main steam valve disc (4) to continue to move along the direction of the valve cover (2) until the outer end face of the locking nut (10) and the inner end face of the valve cover (2) are at the minimum designed distance, it is in the third position. The main steam valve disc (4) has a steam inlet hole (401) corresponding to the large end of the valve head on the steam inlet side, a steam storage chamber (402) communicating with the steam inlet hole (401) and cooperating with the side of the large end of the valve head to form a closed annular groove-shaped space when in the first position on the main steam valve disc (4) is provided in the middle part, a steam outlet hole (403) corresponding to the small end of the valve head is provided on the steam outlet side of the main steam valve disc (4), and an auxiliary air leakage structure (404) is processed on the side of the small end of the valve head between the steam storage chamber (402) and the steam outlet hole (403); a radial through hole (405) communicating with the steam storage chamber (402) is provided inside the valve head, and an axial through hole is provided between the radial through hole (405) and the locking nut (10); The filter assembly (3) comprises a cylindrical inner filter (301) and an outer filter (302); the inner filter (301) is made of a seamless steel pipe, an inner filter hole (303) is drilled on the surface of the steel pipe, a guide angle (305) opening outward is provided on a side of the inner filter hole (303) adjacent to the outer filter (302); the outer filter (302) is made of a stainless steel plate and is clamped in a preset clamping groove on the outer side of the inner filter (301); the stainless steel plate is pre-formed and processed with the outer filter hole (304) by a stamping process; the axis of the filter assembly (3) is arranged to intersect and be perpendicular to the axis of the steam inlet (101); The valve cover (2) is fixed to the valve body (1) at the axial end of the filter assembly (3) via a toothed washer (201); an anti-rotation screw (202) is provided between the filter assembly (3) and the valve cover (2); a threaded portion of the anti-rotation screw (202) is screwed into the valve cover (2); and a head of the anti-rotation screw (202) is embedded in a keyway (306) pre-opened at the axial end of the filter assembly (3).

2. A steam turbine high-pressure main steam valve according to claim 1, characterized in that: The valve body (1) is provided with two sets of filter screen assemblies (3) with different apertures, including a temporary filter screen with a small aperture for finely filtering steam when the steam turbine is started, and a working filter screen with a large aperture for filtering steam when the steam turbine is in normal operation.

3. A high-pressure main steam valve for a steam turbine according to claim 1, characterized in that: The main steam valve seat (5) is a ring-shaped structure clamped on a preset boss inside the valve body (1); the contact end faces of the main steam valve seat (5) and the main steam valve disc (4) are both arranged as Stellite alloy sealing faces; the inner side surface of the main steam valve seat (5) is processed into a streamlined shape to facilitate gas escape to the steam outlet side.

4. A high-pressure main steam valve for a steam turbine according to claim 1, characterized in that: The coupling comprises an oil motor connecting piece (801), a stop washer (802), a coupling lock plate (803), a coupling sleeve (804) and a coupling sandwich (805); the end of the oil motor connecting piece (801) away from the valve tail is connected to the output shaft of the oil motor (9) through threaded engagement and a stop washer (802); the end of the oil motor connecting piece (801) opposite to the valve tail and the end of the valve tail opposite to it are processed into square axes or two square axes of equal size with inwardly converging annular grooves at the far ends; the oil motor connecting piece (801) and the valve tail are connected to the oil motor connecting piece (801) and the valve tail. The outer side of the end of the valve tail is buckled with a coupling sandwich (805) of two halves of the structure, which are respectively connected to the annular grooves on both sides of the axis. The coupling sandwich (805) is provided with annular guide grooves along the outer edges of the end faces at both ends of the axis. The coupling sleeve (804) enters along the guide groove at one end and is sleeved on the outer side of the coupling sandwich (805). The coupling locking plate (803) is clamped in the guide groove at the other end of the coupling sandwich (805). Screws for tightening and fixing are inserted between the coupling locking plate (803), the coupling sleeve (804) and the coupling sandwich (805); Alternatively, the coupling is a prism structure with threaded holes processed at both ends, and the two ends of the coupling are respectively connected to the oil motor (9) and the valve tail through threaded matching and a stop washer (802).

5. A steam turbine high-pressure main steam valve according to claim 1, characterized in that: The auxiliary air leakage structure (404) is a structure with a reduced diameter or a gradually decreasing diameter, or an air leakage groove is provided along the axial direction, or a combination of reduced diameter or reduced diameter and an air leakage groove provided along the axial direction.

6. A steam turbine high-pressure main steam valve according to claim 1, characterized in that: The valve sleeve comprises a valve stem sleeve (601), a graphite gasket assembly (602) and a sealing flange (603); a valve body (1) is provided with a mounting groove, in which the valve stem sleeve (601) and a graphite gasket assembly (602) composed of a plurality of graphite rings are sequentially mounted from the inside to the outside along the axial direction; a sealing flange (603) is mounted at the outer end of the mounting groove, the inner side of which is embedded in the mounting groove through a guide ring and the outer side of which is provided with a flange plate; a clamping screw (604) for clamping the graphite gasket assembly (602) is mounted on the flange plate.

7. A steam turbine high-pressure main steam valve according to claim 6, characterized in that: The outer end of the installation groove of the valve body (1) is provided with a heat insulation groove around the sealing flange (603), a heat insulation material (605) is installed in the heat insulation groove, and a first heat insulation board (606) is fixed on the outer side of the heat insulation material (605); The end surface of the coupling corresponding to one end of the valve stem (7) is fixed to the second heat insulation plate (806) by means of screws; The oil motor (9) is fixedly connected to the valve body (1) via an oil motor valve column (901); the oil motor valve column (901) is a hollow cylindrical structure with flanges at both ends; the oil motor valve column (901) and the valve body (1), and the oil motor valve column (901) and the oil motor (9) are centered via a stop structure and fixedly connected via bolts; a third heat insulation plate (902) is installed between the oil motor valve column (901) and the oil motor (9).

8. A high-pressure main steam valve for a steam turbine according to claim 1, characterized in that: The steam outlet (103) is connected to the steam inlet port of the subsequent equipment via a toothed pad with concentric annular grooves, and the inner hole of the steam outlet (103) and the toothed pad mounting groove are provided with mutually interpenetrating drain grooves connected to the drain port (104).

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