Stop valve and preparation method thereof

Abstract

The invention relates to the technical field of water saving, and particularly discloses a stop valve and a preparation method thereof. The stop valve comprises a valve body, a support is arranged at the top of the valve body, a valve cover is arranged at the bottom of the support, a packing pad is arranged on the inner diameter of the valve cover in a sleeved mode, and alloy rings are arranged at the contact positions of a valve clack and the valve body. The preparation method of the stop valve comprises the steps that S1, parts are machined; s2, surfacing the sealing surface; s3, heat treatment and finish machining; s4, surface treatment; s5, assembling is carried out; and S6, testing and checking. The inclined valve clack is adopted, the valve clack makes contact with the valve seat at a certain angle, a sealing face strengthening structure is matched, the technical effects that the contact area is gradually changed in the opening and closing process, and the opening and closing torque is reduced are achieved, and meanwhile abrasion of a transmission part and a sealing pair under the extreme working condition is reduced; compared with the technical scheme that a straight-through type valve clack is insufficient in adaptability under extreme working conditions in the prior art, the defects that the opening and closing torque is large, the sealing performance is unstable under the extreme working conditions, and the service life is short are overcome.

Description

Technical Field

[0001] This invention relates to the field of water-saving technology, specifically to a stop valve and its preparation method. Background Technology

[0002] Gate valves, a common type of valve, are widely used in various industrial pipeline systems to control the flow of fluids or regulate their flow rate. With the increasing level of industrial automation, higher requirements are placed on the sealing performance, pressure resistance, service life, and ease of operation of gate valves. Currently, common gate valves on the market mainly include straight-through, angle, and direct-flow types, whose core function is to cut off the flow of fluid through a tight fit between the valve disc and the valve seat.

[0003] Most gate valves in the current technology adopt a straight-through valve disc design, that is, the valve disc and the valve seat are in contact with each other in a perpendicular state. Under extreme working conditions such as high pressure, high temperature and corrosive media, this design generally suffers from unstable sealing performance, short service life and high maintenance cost. In addition, the contact area between the straight-through valve disc and the valve seat is completely adhered or separated instantaneously during the opening and closing process, resulting in the concentration of the medium force, large opening and closing torque and inconvenience of operation. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a shut-off valve and its manufacturing method, which solves the problems of large opening and closing torque, unstable sealing performance under extreme working conditions, and short service life.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a gate valve, comprising a valve body, a bracket at the top of the valve body, a valve cover at the bottom of the bracket, a sealing ring fitted on the outer diameter of the valve cover, a packing gasket fitted on the inner diameter of the valve cover, a packing layer at the top of the packing gasket, a packing pressure sleeve at the top of the packing layer, a packing pressure plate fixedly connected to the top of the packing pressure sleeve, a transmission mechanism at the top of the bracket, a second bolt threadedly connecting the transmission mechanism and the bracket, a valve disc inside the valve body, a valve disc cover fixedly connected to the inner diameter of the valve disc, a valve stem fixedly connected to the inner diameter of the valve disc cover, alloy rings at the contact points between the valve disc and the valve body, and a positioning clamp inside the bracket.

[0006] By adopting the above technical solution, when the driving device drives the valve stem to rise, the valve disc leaves the valve seat and the fluid passage opens. When the driving device drives the valve stem to fall, the valve disc and the valve seat fit tightly together and the fluid passage closes. The inclined valve disc design makes the contact area between the valve disc and the valve seat gradually change during the opening and closing process, thereby reducing the opening and closing torque and extending the service life.

[0007] Preferably, a pressure ring is fixedly connected to the top of the sealing ring, and a six-ring is provided on the top of the pressure ring, which engages with the inside of the valve body.

[0008] By adopting the above technical solution, the sealing ring is compressed evenly by the pressure ring, and the valve cover is restricted from axial displacement by the six-ring interlocking structure with the valve body. Therefore, the sealing ring compression is uniform, the valve cover assembly positioning is accurate, and the sealing performance is stable and long-lasting.

[0009] Preferably, a fourth bolt is provided between the valve body and the bracket, the fourth bolt passing through the bracket and the valve body in sequence, and the fourth bolt being threadedly connected to the bracket and the valve body.

[0010] By adopting the above technical solution, the valve body and the bracket are rigidly connected by a through-type fourth bolt. The threaded connection method facilitates disassembly and maintenance. At the same time, the bolt evenly distributes the connection stress between the valve body and the bracket. Therefore, the valve body and the bracket are firmly connected, have strong resistance to fluid pressure impact, and are easy to maintain in the later stage.

[0011] Preferably, a first bolt is provided between the bracket and the valve cover, the first bolt passes through the bracket and the valve cover in sequence, the first bolt is threadedly connected to the bracket and the valve cover, and the upper sealing area between the bottom of the valve cover and the valve stem is welded.

[0012] By adopting the above technical solution, the first bolt is used to fasten the bracket and the valve cover to ensure a tight connection. At the same time, the upper seal is welded to enhance the hardness and wear resistance of the sealing surface. Therefore, the valve cover and the bracket are connected without loosening, the upper seal has strong resistance to media erosion, and the risk of leakage is low.

[0013] Preferably, a third bolt is provided between the packing pressure plate and the bracket, the third bolt passing through the packing pressure plate and the bracket in sequence, and the third bolt being threadedly connected to the packing pressure plate and the bracket.

[0014] By adopting the above technical solution, the compression force of the packing pressure plate on the packing sleeve can be adjusted by the third bolt, and the degree of packing layer compression can be precisely controlled according to the sealing requirements. Therefore, the packing sealing performance can be adjusted, the dynamic sealing effect at the valve stem is good, and the valve stem jamming caused by excessive packing compression is avoided.

[0015] Preferably, a valve stem nut is fitted on the upper side of the valve stem surface, and bearings are fitted on both the upper and lower sides of the protrusion on the surface of the valve stem nut. A bearing cap is installed on the top of the bearing, and the bearing cap is fixed to the bracket by screws. An oil cup is provided on one side of the bracket.

[0016] By adopting the above technical solution, the frictional resistance during valve stem nut rotation is reduced by using bearings, the bearing cap fixes the bearing position to prevent movement, and the oil cup continuously provides lubrication. Therefore, the valve stem lifting and lowering operation is labor-saving and smooth, the bearing service life is long, and the transmission mechanism operates stably.

[0017] Preferably, the positioning clamp consists of two pieces connected by bolts, and the valve stem is located between the two positioning clamps.

[0018] By adopting the above technical solution, the valve stem is radially clamped and positioned by two clamping plates, and the bolt connection facilitates adjustment of the clamping force. Therefore, the valve stem movement trajectory is accurate, the valve disc sealing misalignment caused by radial displacement of the valve stem is avoided, and the opening and closing process is stable.

[0019] Preferably, the valve stem passes through the valve cover, packing pad, packing layer, packing sleeve and packing pressure plate in sequence from bottom to top.

[0020] By adopting the above technical solution, the coaxial structure in which the valve stem passes through each sealing component ensures that the sealing and guiding effects of each component on the valve stem are concentrated and coordinated. Therefore, the valve stem can move without jamming, multiple sealing defenses are superimposed, and the sealing reliability is further improved.

[0021] A method for preparing a shut-off valve, the method comprising the following steps:

[0022] S1. Parts processing: The valve body blank is cast from cast steel material and after failure treatment to eliminate internal stress, it is machined to produce the valve body flow channel, valve seat sealing surface, and various connecting flange surfaces and threaded holes. At the same time, the valve cover, bracket, valve disc gland and valve stem parts are prepared and machined.

[0023] S2. Sealing surface overlay welding: The valve seat sealing surface and valve disc sealing surface of the valve body are ground and cleaned for pretreatment. A layer of Stellite6 hard alloy is overlaid on the sealing surface using plasma arc welding or oxy-acetylene welding.

[0024] S3. Heat treatment and finishing: Stress relief heat treatment is performed on the valve seat and valve disc after overlay welding. After eliminating welding stress, the sealing surface is ground or polished.

[0025] S4. Surface treatment: Perform anti-corrosion treatment on the valve body, valve cover, and bracket;

[0026] S5. Assembly: Install the sealing ring, pressure ring, and six-open ring onto the valve cover in sequence and pre-assemble them with the valve body. Fix the valve disc to one end of the valve stem using the valve disc cover. Install the assembled valve stem and valve disc assembly into the valve body. Install the bracket and tighten the bracket to the valve cover and the bracket to the valve body using the first and fourth bolts, respectively. Install the packing pad, packing layer, and packing sleeve in sequence from the top of the valve cover and tighten them with the packing pressure plate and the third bolt to form a valve stem packing seal. Install the valve stem nut, bearing, and bearing cover and mate them with the valve stem. Install the positioning clamp inside the bracket to radially position the valve stem. Install the transmission mechanism and fix it to the bracket using the second bolt. Finally, install the oil cup on one side of the bracket.

[0027] S6. Testing and Inspection: Conduct shell tests, sealing tests, pressure tests, and opening and closing operation tests on the assembled gate valve.

[0028] By adopting the above technical solution, the aging treatment eliminates the internal stress of the casting, ensuring the dimensional stability of the parts. The valve disc and valve seat sealing surfaces are overlaid with Stellite 6 hard alloy, which improves the wear resistance and sealing performance.

[0029] Preferably, in step S2, the hard alloy overlay welding includes the following steps:

[0030] Grind the valve seat and valve disc surfaces of the valve body until they are exposed to a metallic luster, and then degrease and remove rust. After that, slowly and evenly preheat the valve body and valve disc to 350-400℃. Using Stellite6 hard alloy welding wire and a plasma arc welding torch, deposit at least two layers of welding at parameters of welding current 120-180A, arc voltage 28-32V, and welding speed 80-120mm / min. After the welding is completed, immediately wrap the workpiece with insulation cotton and slowly cool it to below 150℃, then air cool it. Then perform stress relief heat treatment, heating it to 650-700℃ and holding it for 2-3 hours before cooling it in the furnace.

[0031] This invention provides a shut-off valve and its manufacturing method. It has the following beneficial effects:

[0032] 1. This invention adopts an obliquely placed valve disc, with the valve disc contacting the valve seat at a certain angle. Combined with a reinforced sealing surface structure, it achieves the technical effect of gradually changing the contact area and reducing the opening and closing torque during the opening and closing process. At the same time, it reduces the wear of transmission components and sealing pairs under extreme working conditions. Compared with the existing straight-through valve disc technology, which has insufficient adaptability to extreme working conditions, this invention solves the shortcomings of large opening and closing torque, unstable sealing performance under extreme working conditions, and short service life.

[0033] 2. The present invention adopts an aging treatment to eliminate the internal stress of the casting and a Stellite 6 hard alloy overlay welding on the sealing surface of the valve disc and valve seat. This achieves the technical effect of ensuring the stability of the part dimensions and improving the wear resistance and sealing performance of the sealing surface. Compared with the existing technology, which does not specifically eliminate internal stress or uses ordinary materials for the sealing surface, this invention solves the shortcomings of the parts being easy to deform and the sealing surface being easy to wear, leading to leakage.

[0034] 3. The present invention adopts a multi-seal technology solution consisting of a sealing ring on the outer diameter of the valve cover, a packing layer on the inner diameter, and welding on the upper seal, to achieve a comprehensive leak-proof effect. Compared with the single-seal structure technology in the prior art, it solves the shortcomings of poor sealing reliability and easy media leakage. Attached Figure Description

[0035] Figure 1 This is a cross-sectional view of the shut-off valve of the present invention;

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

[0037] Figure 3 This is a schematic diagram of the cross-sectional structure of the valve body of the shut-off valve of the present invention;

[0038] Figure 4 This is a schematic diagram of the cross-sectional structure of the valve disc of the shut-off valve of the present invention;

[0039] Figure 5 This is a schematic diagram of the cross-sectional structure of the valve cover of the shut-off valve of the present invention;

[0040] Figure 6 This is a schematic flowchart of the preparation method of the shut-off valve of the present invention.

[0041] The components are as follows: 1. Valve body; 2. Valve disc; 3. Valve disc gland; 4. Valve stem; 5. Sealing ring; 6. Valve cover; 7. Packing gasket; 8. First bolt; 9. Packing sleeve; 10. Packing pressure plate; 11. Positioning clamp; 12. Bracket; 13. Transmission mechanism; 14. Bearing gland; 15. Second bolt; 16. Bearing; 17. Oil cup; 18. Valve stem nut; 19. Third bolt; 20. Fourth bolt; 21. Six-ring; 22. Pressure ring; 23. Alloy ring; 24. Packing layer. Detailed Implementation

[0042] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0043] Please see the appendix Figure 1 -Appendix Figure 5 This invention provides a shut-off valve, including a valve body 1, a bracket 12 at the top of the valve body 1, a valve cover 6 at the bottom of the bracket 12, a sealing ring 5 on the outer diameter of the valve cover 6, a packing gasket 7 on the inner diameter of the valve cover 6, a packing layer 24 on the top of the packing gasket 7, a packing sleeve 9 on the top of the packing layer 24, a packing pressure plate 10 fixedly connected to the top of the packing sleeve 9, a transmission mechanism 13 on the top of the bracket 12, a second bolt 15 threadedly connected between the transmission mechanism 13 and the bracket 12, a valve disc 2 inside the valve body 1, a valve disc cover 3 fixedly connected to the inner diameter of the valve disc 2, a valve stem 4 fixedly connected to the inner diameter of the valve disc cover 3, an alloy ring 23 at the contact position between the valve disc 2 and the valve body 1, and a positioning clamp 11 inside the bracket 12.

[0044] Specifically, the valve body 1 has a fluid flow channel inside, and the top flange face is rigidly connected to the bottom of the bracket 12 by the second bolt 15 to form the mounting base for the transmission components. The valve cover 6 is sandwiched between the bracket 12 and the valve body 1, which not only realizes the transition connection between the bracket 12 and the valve body 1, but also arranges dynamic and static sealing components through the inner and outer diameters respectively. At the same time, the valve stem 4 passes through the central hole of the valve cover 6, with one end connected to the valve disc 2 to perform opening and closing, and the other end extending into the bracket 12 to cooperate with the transmission mechanism 13.

[0045] A pressure ring 22 is fixedly connected to the top of the sealing ring 5. A six-open ring 21 is provided on the top of the pressure ring 22. The six-open ring 21 is engaged with the inside of the valve body 1.

[0046] Specifically, the six-slit ring 21 is a split annular structure. During assembly, it is spliced ​​and embedded in the annular groove on the inner wall of the valve body 1 to form a limiting shoulder for the axial movement of the valve cover 6. The pressure ring 22 is an annular metal part that fits against the top of the sealing ring 5. After the valve cover 6 and the valve body 1 are assembled in place, the six-slit ring 21 applies continuous and uniform axial pressure to the sealing ring 5 through the pressure ring 22, causing the sealing ring 5 to undergo elastic deformation and tightly fill the gap between the outer diameter of the valve cover 6 and the inner wall of the valve body 1, thereby achieving a static seal between the valve cover and the valve body.

[0047] A fourth bolt 20 is provided between the valve body 1 and the bracket 12. The fourth bolt 20 passes through the bracket 12 and the valve body 1 in sequence, and the fourth bolt 20 is threadedly connected to the bracket 12 and the valve body 1.

[0048] Specifically, the fourth bolt 20 is arranged in a uniform circle along the valve body 1 and the bracket 12, and is vertically inserted from the top of the bracket 12 into the threaded hole of the valve body 1 and tightened. The preload of the bolts rigidly locks the bracket 12 and the valve body 1 together, so that the connecting surfaces fit tightly. This not only resists the opening force of the fluid pressure on the connecting surfaces, but also avoids loosening of the connection due to vibration, thus ensuring the overall structural stability.

[0049] A first bolt 8 is provided between the bracket 12 and the valve cover 6. The first bolt 8 passes through the bracket 12 and the valve cover 6 in sequence. The first bolt 8 is threadedly connected to the bracket 12 and the valve cover 6. The upper sealing area between the bottom of the valve cover 6 and the valve stem 4 is welded.

[0050] Specifically, the first bolt 8 is evenly arranged along the circumference connecting the bottom of the bracket 12 and the valve cover 6. After the bolt passes through the bracket 12, it engages with the threaded hole of the valve cover 6 to achieve a tight fixation between the two. The inner surface of the bottom of the valve cover 6 that mates with the valve stem 4 is overlaid with Stellite 6 hard alloy to form a high-hardness, wear-resistant upper sealing surface. When the valve stem 4 descends to the limit position, the stepped surface of the valve stem 4 fits with the overlaid sealing surface to form an auxiliary seal, which works with the packing seal to block the medium leakage channel.

[0051] A third bolt 19 is provided between the packing plate 10 and the bracket 12. The third bolt 19 passes through the packing plate 10 and the bracket 12 in sequence, and the third bolt 19 is threadedly connected to the packing plate 10 and the bracket 12.

[0052] Specifically, the third bolt 19 is symmetrically arranged on one side of the packing pressure plate 10. After passing through the packing pressure plate 10, the bolt is connected to the threaded hole of the bracket 12. The downward pressing distance of the packing pressure plate 10 can be adjusted by rotating the bolt. The pressure is transmitted to the packing sleeve 9 through the packing pressure plate 10, and then the packing sleeve 9 applies the pressure evenly to the packing layer 24, causing the packing layer 24 to contract radially and tightly wrap the surface of the valve stem 4. By controlling the tightening of the bolt, the sealing is ensured while avoiding excessive compression of the packing, which would increase the resistance of valve stem lifting.

[0053] A valve stem nut 18 is fitted on the upper side of the valve stem 4. Bearings 16 are fitted on both the upper and lower sides of the protrusion on the surface of the valve stem nut 18. A bearing cover 14 is installed on the top bearing 16. The bearing cover 14 is fixed to the bracket 12 by screws. An oil cup 17 is provided on one side of the bracket 12.

[0054] Specifically, the valve stem nut 18 has an internal thread machined in its inner hole, which mates with the external thread of the valve stem 4 to form a lead screw nut transmission pair. A bearing 16 is installed at the upper and lower ends of the annular protrusion in the middle of the valve stem nut 18. The outer ring of the bearing 16 is respectively attached to the inner wall of the bracket 12 and the bearing cover 14. The bearing cover 14 is fixed to the top of the bracket 12 by multiple screws to restrict the axial movement of the bearing 16. The oil cup 17 is connected to the cavity of the bearing 16 through the oil passage, and grease is added regularly to reduce the rotational friction of the bearing 16 and ensure that the valve stem nut 18 rotates flexibly.

[0055] The positioning clamp 11 consists of two pieces connected by bolts, and the valve stem 4 is located between the two positioning clamps 11.

[0056] Specifically, the positioning clamp 11 consists of two semi-annular steel plates with a semi-circular groove on the inner side that matches the outer diameter of the valve stem 4. After being spliced ​​together, they form a complete guide hole. The two clamps are fixed in the mounting groove inside the bracket 12 by bolts. The valve stem 4 passes through the guide hole. The guiding effect of the clamp restricts the radial swing of the valve stem 4 during the lifting process, ensuring that the valve stem 4 always moves along the axis and avoiding misalignment and collision between the valve disc 2 and the sealing surface of the valve body 1.

[0057] The valve stem 4 passes through the valve cover 6, packing gasket 7, packing layer 24, packing sleeve 9 and packing pressure plate 10 from bottom to top.

[0058] Specifically, the valve stem 4 adopts a coaxial through-hole design, with its lower end passing through the center hole of the valve cover 6, the inner hole of the packing pad 7, the packing layer 24, the inner hole of the packing sleeve 9, and the center hole of the packing pressure plate 10 in sequence. The inner holes of each component are coaxial with the valve stem 4. The packing pad 7 is made of flexible graphite and is placed at the bottom of the packing layer 24 to provide a sealing and buffering effect. The packing layer 24 is a flexible graphite + 304 metal mesh composite structure, which has the characteristics of strong elasticity and high wear resistance.

[0059] Example 1

[0060] Please see the appendix Figure 6 This invention provides a method for preparing a shut-off valve, the method comprising the following steps:

[0061] S1. Parts processing: The valve body 1 blank is cast from cast steel material and after failure treatment to eliminate internal stress, it is machined to produce the flow channel, valve seat sealing surface, and various connecting flange surfaces and threaded holes of the valve body 1. At the same time, the valve cover 6, bracket 12, valve disc gland 3, and valve stem 4 are prepared with materials and machined.

[0062] S2, Sealing surface overlay welding: The valve seat sealing surface of valve body 1 and the sealing surface of valve disc 2 are ground and cleaned for pretreatment, and a layer of Stellite6 hard alloy is overlaid on the sealing surface using plasma arc overlay welding method.

[0063] S3. Heat treatment and finishing: The valve seat and valve disc 2 after welding are subjected to stress relief heat treatment. After eliminating the welding stress, the sealing surface is ground or polished.

[0064] S4. Surface treatment: Perform anti-corrosion treatment on the valve body 1, valve cover 6, and bracket 12.

[0065] S5. Assembly: Sequentially install the sealing ring 5, pressure ring 22, and six-open ring 21 onto the valve cover 6 and pre-assemble them with the valve body 1. Fix the valve disc 2 to one end of the valve stem 4 through the valve disc cover 3. Install the assembled valve stem 4 and valve disc 2 assembly into the valve body 1. Install the bracket 12 and tighten the bracket 12 to the valve cover 6 and the bracket 12 to the valve body 1 through the first bolt 8 and the fourth bolt 20, respectively. Install the packing gasket 7, packing layer 24, and packing sleeve 9 sequentially from the top of the valve cover 6 and tighten them through the packing pressure plate 10 and the third bolt 19 to form a packing seal for the valve stem 4. Install the valve stem nut 18, bearing 16, and bearing cover 14 and these components to cooperate with the valve stem 4. Install the positioning clamp 11 inside the bracket 12 to radially position the valve stem 4. Install the transmission mechanism 13 and fix it to the bracket 12 through the second bolt 15. Finally, install the oil cup 17 on one side of the bracket 12.

[0066] S6. Testing and Inspection: Conduct shell tests, sealing tests, pressure tests, and opening and closing operation tests on the assembled gate valve.

[0067] The S2 hard alloy surfacing process includes the following steps: grinding the valve seat of valve body 1 and the surface of valve disc 2 to be welded until the metal luster is exposed and then degreasing and rust removal are performed. Then, the valve body 1 and valve disc 2 are slowly and evenly preheated to 360°C. Using Stellite6 hard alloy welding wire, two layers are surfacing using a plasma arc welding gun at parameters of welding current 150A, arc voltage 30V, and welding speed 100mm / min. After the surfacing is completed, the workpiece is immediately wrapped with insulation cotton and slowly cooled to below 150°C before air cooling. Then, stress relief heat treatment is performed, heating to 680°C and holding for 2.5 hours before cooling with the furnace.

[0068] Example 2

[0069] Please see the appendix Figure 6 This invention provides a method for preparing a shut-off valve, the method comprising the following steps:

[0070] S1. Parts processing: The valve body 1 blank is cast from cast steel material and after failure treatment to eliminate internal stress, it is machined to produce the flow channel, valve seat sealing surface, and various connecting flange surfaces and threaded holes of the valve body 1. At the same time, the valve cover 6, bracket 12, valve disc gland 3, and valve stem 4 are prepared with materials and machined.

[0071] S2, Sealing surface overlay welding: The valve seat sealing surface of valve body 1 and the sealing surface of valve disc 2 are ground and cleaned for pretreatment, and a layer of Stellite6 hard alloy is overlaid on the sealing surface using the oxy-acetylene overlay welding method.

[0072] S3-S6: The steps are the same as those in Example 1.

[0073] The S2 hard alloy surfacing process includes the following steps: grinding the valve seat of valve body 1 and the valve disc 2 to be welded until the metal luster is exposed and then degreasing and rust removal are performed. Then, valve body 1 and valve disc 2 are slowly and evenly preheated to 380°C. Using Stellite6 hard alloy welding wire, two layers are surfacing using an oxy-acetylene welding gun under a neutral flame. After the surfacing is completed, the workpiece is immediately wrapped with insulation cotton and slowly cooled to below 150°C before air cooling. Then, stress relief heat treatment is performed, which involves heating to 660°C and holding for 2 hours before cooling with the furnace.

[0074] Example 3

[0075] Please see the appendix Figure 6 This invention provides a method for preparing a shut-off valve, the method comprising the following steps:

[0076] S1-S6: The steps are the same as those in Example 1.

[0077] The hard alloy overlay welding in S2 includes the following steps:

[0078] The surfaces of the valve seat and valve disc 2 to be welded are ground until the metal luster is exposed and degreased and rusted. Then, the valve body 1 and valve disc 2 are slowly and evenly preheated to 350°C. Using Stellite6 hard alloy welding wire, two layers are deposited using a plasma arc welding torch at a welding current of 120A, an arc voltage of 28V, and a welding speed of 80mm / min. After the deposit is completed, the workpiece is immediately wrapped with insulation cotton and slowly cooled to below 150°C before air cooling. Then, stress relief heat treatment is performed, which involves heating to 700°C and holding for 3 hours before cooling with the furnace.

[0079] The chemical composition, heat treatment, and mechanical properties of valve body 1 and bracket 12 shall conform to the specifications of ASTM A217 WC6. Molding sand, gates, risers, excess material, and oxide scale adhering to the surface and inner cavity shall be thoroughly cleaned. The surface quality of the castings shall conform to the specifications of MSSSP-55.

[0080] The material and mechanical properties of valve disc 2 conform to the specifications of ASTM A182 F11 Class 2, and the acute angle is blunted.

[0081] The machining dimensional tolerances of valve disc 2, valve disc gland 3, valve stem 4, and valve cover 6 shall comply with the requirements of GB / T1804-2000-m grade;

[0082] The chemical composition and mechanical properties of the valve stem 4 material after heat treatment shall conform to the specifications of ASTM A182F6a. The head blank and the sharp angle of the machined surface shall be cleaned and the burrs shall be removed.

[0083] The valve cover 6 forgings conform to the requirements of ASTM A82F11CL2 and must not have harmful defects such as cracks or wrinkles. The upper seal is overlaid with STL6 with a hardness ≥ HRC40.

[0084] The sealing ring 5 is made of flexible graphite + 304 stainless steel, and the filler layer 24 is made of flexible graphite.

[0085] After the bearing cap 14 and the bracket 12 are screwed together, 2-M8 saddle screws are used at the threaded part to prevent loosening.

[0086] The chemical composition and mechanical properties of valve stem nut 18 shall conform to the provisions of GB / T1176-2013.

[0087] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A shut-off valve, comprising a valve body (1), characterized in that: The valve body (1) is provided with a bracket (12) at the top, and a valve cover (6) is provided at the bottom of the bracket (12). A sealing ring (5) is fitted on the outer diameter of the valve cover (6), and a packing pad (7) is fitted on the inner diameter of the valve cover (6). A packing layer (24) is provided on the top of the packing pad (7), and a packing sleeve (9) is provided on the top of the packing layer (24). A packing pressure plate (10) is fixedly connected to the top of the packing sleeve (9). A transmission mechanism (13) is provided on the top of the bracket (12), and a second bolt (15) is threaded between the transmission mechanism (13) and the bracket (12). A valve disc (2) is provided inside the valve body (1), and a valve disc cover (3) is fixedly connected to the inner diameter of the valve disc (2). A valve stem (4) is fixedly connected to the inner diameter of the valve disc cover (3). Alloy rings (23) are provided at the contact positions between the valve disc (2) and the valve body (1). A positioning clamp (11) is provided inside the bracket (12).

2. The shut-off valve according to claim 1, characterized in that: The top of the sealing ring (5) is fixedly connected to a pressure ring (22), and the top of the pressure ring (22) is provided with a six-open ring (21), which is engaged with the inside of the valve body (1).

3. The shut-off valve according to claim 1, characterized in that: A fourth bolt (20) is provided between the valve body (1) and the bracket (12). The fourth bolt (20) passes through the bracket (12) and the valve body (1) in sequence, and the fourth bolt (20) is threadedly connected to the bracket (12) and the valve body (1).

4. The shut-off valve according to claim 1, characterized in that: A first bolt (8) is provided between the bracket (12) and the valve cover (6). The first bolt (8) passes through the bracket (12) and the valve cover (6) in sequence. The first bolt (8) is threadedly connected to the bracket (12) and the valve cover (6). The upper sealing area between the bottom of the valve cover (6) and the valve stem (4) is welded.

5. The shut-off valve according to claim 1, characterized in that: A third bolt (19) is provided between the packing plate (10) and the bracket (12). The third bolt (19) passes through the packing plate (10) and the bracket (12) in sequence, and the third bolt (19) is threadedly connected to the packing plate (10) and the bracket (12).

6. The shut-off valve according to claim 1, characterized in that: A valve stem nut (18) is fitted on the upper side of the valve stem (4). Bearings (16) are fitted on both the upper and lower sides of the protrusion on the surface of the valve stem nut (18). A bearing cover (14) is installed on the top of the bearing (16). The bearing cover (14) is fixed to the bracket (12) by screws. An oil cup (17) is provided on one side of the bracket (12).

7. The shut-off valve according to claim 1, characterized in that: The positioning clamp (11) consists of two pieces connected by bolts, and the valve stem (4) is located between the two positioning clamps (11).

8. The shut-off valve according to claim 1, characterized in that: The valve stem (4) passes through the valve cover (6), packing pad (7), packing layer (24), packing sleeve (9) and packing plate (10) from bottom to top.

9. A method for preparing a stop valve, characterized in that, For use with the shut-off valve according to any one of claims 1-8, the method comprises the following steps: S1. Parts processing: The valve body (1) blank is cast from cast steel material and then machined after aging treatment to eliminate internal stress. The flow channel, valve seat sealing surface, and various connecting flange surfaces and threaded holes of the valve body (1) are machined. At the same time, the valve cover (6), bracket (12), valve disc cover (3), and valve stem (4) parts are prepared and machined. S2, Sealing surface overlay: The valve seat sealing surface of the valve body (1) and the sealing surface of the valve disc (2) are ground and cleaned for pretreatment. A layer of Stellite6 hard alloy is overlaid on the sealing surface by plasma arc overlay or oxy-acetylene overlay. S3. Heat treatment and finishing: Stress relief heat treatment is performed on the valve seat and valve disc (2) after welding. After eliminating the welding stress, the sealing surface is ground or polished. S4. Surface treatment: Perform anti-corrosion treatment on the valve body (1), valve cover (6), and bracket (12); S5. Assembly: Install the sealing ring (5), pressure ring (22), and six-open ring (21) onto the valve cover (6) in sequence and pre-assemble them with the valve body (1). Fix the valve disc (2) to one end of the valve stem (4) through the valve disc cover (3). Install the assembled valve stem (4) and valve disc (2) assembly into the valve body (1). Install the bracket (12) and tighten the bracket (12) to the valve cover (6) and the bracket (12) to the valve body (1) with the first bolt (8) and the fourth bolt (20) respectively. Install the packing gasket from the top of the valve cover (6) in sequence. (7) The packing layer (24) and packing sleeve (9) are pressed together by the packing pressure plate (10) and the third bolt (19) to form the valve stem (4) packing seal. Install the valve stem nut (18), bearing (16) and bearing cover (14) and these components and cooperate with the valve stem (4). Install the positioning clamp (11) inside the bracket (12) to radially position the valve stem (4). Install the transmission mechanism (13) and fix it on the bracket (12) by the second bolt (15). Finally, install the oil cup (17) on one side of the bracket (12). S6. Testing and Inspection: Conduct shell test, sealing test, pressure test and opening and closing operation test on the assembled gate valve.

10. The method for preparing the shut-off valve according to claim 9, characterized in that: In step S2, the hard alloy overlay welding includes the following steps: Grind the valve seat and valve disc (2) of the valve body (1) until the metal luster is exposed and degrease and remove rust. Then, slowly and evenly preheat the valve body (1) and valve disc (2) to 350-400℃. Use Stellite6 hard alloy welding wire and plasma arc welding gun to deposit at least two layers under the parameters of welding current 120-180A, arc voltage 28-32V and welding speed 80-120mm / min. After the deposit is completed, immediately wrap the workpiece with heat insulation cotton and slowly cool it to below 150℃ and then air cool it. Then perform stress relief heat treatment, heat it to 650-700℃ and keep it for 2-3 hours and then cool it with the furnace.

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