Main valve for pilot operated safety valve

Abstract

The main valve comprises a valve body, the upper end of the valve body is connected with a valve deck, a support is installed at the upper end of the valve deck through a bolt assembly, and the support is provided with a valve opening and closing position and opening degree detection mechanism; a valve seat is arranged on the valve body, a valve clack assembly is arranged in a valve cavity located above the valve seat, a valve clack connector is arranged at the upper end of the valve clack assembly, a valve rod is connected into the valve clack connector, and the top end of the valve rod penetrates through a spring mechanism and extends out of the upper end of the valve deck to reach the position of the support. Pressure tapping holes are respectively formed in the front and back of the valve body; pilot control holes are formed in the front, back and side surfaces of the valve body; the main valve for the pilot-operated safety valve adopts a pilot-operated medium self-driving structural form with a built-in piston cylinder, and the stress change of a piston is formed under the condition that the pressure of an internal medium and the pressure of a pilot loop of an upper cavity of the piston are changed, so that the opening and closing control of the main valve is realized. The whole main valve has the advantages of being reasonable in space layout, compact in structure, high in reliability and high in anti-seismic performance.

Description

Technical Field

[0001] The present invention relates to a main valve for a pilot-operated safety valve, which is a supporting valve for the pressure relief valve of the pressurizer in a pressurized water reactor nuclear power plant, and belongs to the technical field of valves. Background Art

[0002] The main valve for the pilot-operated safety valve is the main part of the pilot-operated safety valve, which is a supporting main valve for the pressure relief valve of the pressurizer in the advanced third-generation "Hualong One" pressurized water reactor nuclear power plant. Since the pressure relief valve of the pressurizer has a large diameter, high temperature and pressure, and higher requirements for the control and reliability of the valve, it is necessary to design a new type of pilot-operated pressure relief valve for the pressurizer that takes into account the following performance requirements while being compact in structure, easy to disassemble and assemble, integrating pressure taking and control, adjustable setting pressure, with signal feedback, having multiple redundant controls (dual redundant automatic control, manual and automatic remote control, pure manual control), high reliability, and high seismic performance, and being able to perform functions such as hot overpressure protection, cold overpressure protection, charging and discharging functions, and manual pressure relief after an accident. In order to meet the above requirements simultaneously, the main valve for the pilot-operated safety valve needs to be specifically designed for the overall scheme and layout. Summary of the Invention

[0003] In view of the above technical problems, the object of the present invention is to provide a main valve for a pilot-operated safety valve that is compact in structure, easy to disassemble and assemble, with signal feedback, and has multiple redundant controls, and the whole has the characteristics of reasonable space layout, compact structure, high reliability, and high seismic performance.

[0004] In order to achieve the above object, the technical solution adopted by the present invention is: the main valve for the pilot-operated safety valve includes: a valve body, a medium inlet flow channel, a valve cavity and a medium outlet flow channel are formed inside the valve body, and the three are connected; the upper end of the valve body is connected to the valve cover through a bolt assembly, a bracket is installed on the upper end of the valve cover through a bolt assembly, and the bracket is provided with a valve opening and closing position and opening degree detection mechanism; a valve seat is welded on the valve body, a valve flap assembly is arranged in the valve cavity above the valve seat, a valve flap connector is arranged at the upper end of the valve flap assembly, a spring mechanism is installed at the upper end of the valve flap connector, a valve stem is connected in the valve flap connector, and the top end of the valve stem passes through the spring mechanism and extends to the position of the bracket above the valve cover; a temperature detection device is arranged on the valve body located in the medium inlet flow channel; the outer surface of the valve body corresponding to the temperature detection device is the outer inclined surface of the valve body, the two planes adjacent to the outer inclined surface of the valve body are the front and rear surfaces of the valve body, and the plane opposite to the outer inclined surface of the valve body is the side surface of the valve body; pressure taking holes are respectively arranged on the front and rear surfaces of the valve body, and pilot control holes are arranged on the front, rear and side surfaces of the valve body; Furthermore, the pressure taking holes and pilot control holes arranged on the front and rear surfaces of the valve body as the dual redundant automatic control loop are of a symmetric mirror structure.

[0005] Furthermore, positioning pin holes and fastening threaded holes are arranged near the pressure taps at the front and rear of the valve body, and near the pilot control holes at the front, rear and sides of the valve body. Furthermore, the valve body adopts an integral forging structure with the inlet medium flow channel and the outlet medium flow channel forming a 45° angle; Furthermore, the valve body's medium outlet flow channel has a gradually enlarging structure.

[0006] Furthermore, the valve body inlet and outlet are respectively provided with inlet flange and outlet flange. The inlet flange opposite to the valve body inlet is connected to the valve body by butt welding to form the main body of the valve body. The inlet flange is connected to the inlet mating flange by bolt assembly, and the valve body outlet and outlet flange are connected by bolt assembly.

[0007] Furthermore, spiral wound gaskets are provided between the inlet flange and the inlet mating flange, and between the valve body and the outlet flange, to ensure the sealing performance of the flange connection. Specifically, grooves for accommodating sealing gaskets are provided on the end faces of the inlet mating flange and the outlet flange. A first spiral wound gasket is placed in the groove of the inlet mating flange, and a second spiral wound gasket is placed in the groove of the outlet flange. The first spiral wound gasket, the inlet mating flange, and the bolt assembly are connected to the inlet flange, and the second spiral wound gasket, the outlet flange, and the bolt assembly are connected to the outlet of the valve body.

[0008] Furthermore, a spiral wound gasket is provided at the junction of the upper end of the valve body and the valve cover. A groove is provided on the upper surface of the valve body to accommodate the third spiral wound gasket. The third spiral wound gasket is pressed into the sealing groove on the upper surface of the valve body by the valve cover through a bolt assembly. Furthermore, the valve disc assembly includes: a valve disc, a piston cylinder, a stainless steel wear-resistant ring, an anti-loosening washer, and an internal hexagonal head screw; the lower part of the valve disc is a large end, and the top part is a small end connected to the valve disc connector. The outer diameter of the large end of the valve disc mates with the piston cylinder, and the outer diameter of the piston cylinder mates with the inner wall of the valve body; the upper end face of the piston cylinder is connected to the valve cover by a bolt assembly, and the valve cover has a cavity in the center to accommodate the valve disc, the valve disc connector, and the spring mechanism above it; the small end of the valve disc mates with the cavity of the valve cover through a valve stem guide sleeve; the valve disc has a medium flow channel, which includes a radially bent channel penetrating the lower and upper surfaces of the large end of the valve disc and an axial channel penetrating the horizontal ends of the large end of the valve disc; The lower section of the radially bent channel is equipped with an internal hexagonal head screw. The internal hexagonal head screw is set in the lower section by an anti-loosening washer, and a throttling hole for controlling the flow rate of the medium is opened in the center of the internal hexagonal head screw. Based on the above scheme, the valve disc integrates the functions of a normal valve disc and a piston, with the lower base part (large end) of the valve disc serving as the functional part of the normal valve disc. Furthermore, wear-resistant components are respectively provided between the outer diameter of the large end of the valve disc and the inner diameter of the piston cylinder, and between the small end of the valve disc and the inner diameter of the valve stem guide sleeve. These components include a first stainless steel wear-resistant steel ring and a second stainless steel wear-resistant steel ring, and both stainless steel wear-resistant steel rings are installed in the grooves opened on the valve disc. Furthermore, a wear-resistant part, namely a third stainless steel wear-resistant ring, is also provided between the outer diameter of the piston cylinder and the inner wall of the valve body, and the third stainless steel wear-resistant ring is installed in a groove opened on the outer diameter of the piston cylinder. Based on the wear-resistant component set between the outer diameter of the large end of the valve disc and the inner diameter of the piston cylinder, the first stainless steel wear-resistant steel ring has two strips set on the outer diameter surface of the large end of the valve disc, one above the other.

[0009] Furthermore, the valve stem guide sleeve is made of wear-resistant material and is screwed into the valve cover by threads for assembly and mating; the valve stem guide sleeve and the piston cylinder together play a role in positioning the valve disc and guiding its reciprocating motion.

[0010] Furthermore, the valve seat is welded to the valve body according to a water seal structure layout, and the valve seat is configured with a gradually enlarging structure; the valve seat and the valve body are welded together.

[0011] Furthermore, a sealing contact surface is formed between the upper end of the valve seat and the lower part of the valve disc, and the sealing contact surface between the two is treated with hard alloy overlay welding.

[0012] Furthermore, the spring mechanism includes: a spring seat disposed on the valve disc connector and a spring located on the spring seat; the spring seat is connected to the valve disc through the valve disc connector, so that the spring seat can move up and down and reciprocate with the valve disc; one end of the spring contacts and is positioned with the spring seat, and the other end contacts and is positioned with the valve cover.

[0013] Furthermore, the valve stem is installed between the valve disc connector and the spring seat, and moves up and down with the valve disc, and leads the valve disc opening and closing position status to the outside of the valve. The valve opening and closing position and opening degree detection mechanism detects and provides signal feedback. Furthermore, a packing seal assembly is provided between the valve stem and the valve cover. The packing seal assembly includes a packing pressure plate, a packing sleeve, packing, and a packing pad. The packing pressure plate is located on the valve stem above the valve cover. A packing cavity is provided between the valve stem and the valve cover below the packing pressure plate. The packing is pressed into the packing cavity by the packing sleeve, and a packing pad is provided at the bottom of the packing cavity. Furthermore, the packing seal assembly is secured above by a fastening assembly, which consists of a stud, a disc spring indicator needle, a disc spring indicator plate, a disc spring sleeve, a disc spring, a gasket, and a nut. This ensures the sealing reliability of the valve stem packing under temperature and pressure changes and enables visual control of the fastening force.

[0014] Furthermore, the valve switch position and opening degree detection mechanism includes: a valve position indicator, an indicator rod, and a limit switch; the indicator rod is fixed to the upper end of the valve stem by a nut and an anti-loosening washer, the main body of the valve position indicator is fixed on the bracket, the magnetic head is fixed on the indicator rod, and the limit switch is fixed on the bracket by an internal hexagonal head screw and a limit switch seat.

[0015] Furthermore, the temperature detection device is an embedded non-penetrating temperature sensor; the bolt assemblies mentioned above all adopt a combination structure of studs, nuts, and anti-loosening washers.

[0016] In the above structure of this solution, the front, rear and side of the valve body are connected by four pilot holes to form the pilot circuit of the safety valve. The pilot circuit is connected to the upper chamber area of ​​the piston cylinder in the main valve. The main valve adopts a pilot-operated self-driven structure with an internal piston cylinder. The change in the pressure of the medium inside the main valve and the pilot circuit pressure in the upper chamber of the piston creates a change in the force on the piston, thereby realizing the opening and closing of the main valve. In the main valve body, the upper part of the valve disc's large end, together with the inner wall of the piston cylinder and the lower end face of the valve cover, forms a cavity gap. When the pressure difference between the medium pressure entering the main valve inlet and the medium pressure in the pilot circuit of the upper piston chamber changes, it forces the valve disc assembly to reciprocate up and down. When the pressure inside the main valve body is greater than the pressure in the pilot circuit, the valve disc assembly moves upward, causing the cavity gap located at the upper part of the valve disc's large end to gradually disappear, thereby causing the lower end of the valve disc to detach from the valve seat and form a gap, thus opening the valve. Conversely, when the pressure in the pilot circuit is close to or equal to the medium pressure of the main valve body, the valve disc assembly moves downward, causing the lower end of the valve disc to move closer to the valve seat, gradually restoring the cavity gap located at the upper part of the valve disc's large end, thus closing the valve.

[0017] The beneficial effects of this invention are: The main valve of the pilot-operated safety valve adopts a self-driven structure with a built-in piston cylinder. Changes in the internal medium pressure and the pilot circuit pressure in the upper chamber of the piston create changes in the force on the piston, thereby controlling the opening and closing of the main valve. The overall design features a rational spatial layout, compact structure, high reliability, and high seismic resistance. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the main valve assembly (closed position) for the pilot-operated safety valve of the present invention.

[0019] Figure 2 for Figure 1 Enlarged view of point A.

[0020] Figure 3 for Figure 1 Enlarged view of point B.

[0021] Figure 4 for Figure 1 Enlarged view of point C.

[0022] Figure 5 for Figure 1 Enlarged view of point D.

[0023] Figure 6 for Figure 1 Enlarged view of point E.

[0024] Figure 7 for Figure 1 Enlarged view of point F.

[0025] Figure 8 for Figure 1 Enlarged view of point G.

[0026] Figure 9 This is a schematic diagram of the open position of the main valve used in the pilot-operated safety valve of the present invention.

[0027] Figure 10 This is a front view of the main valve used in the pilot-operated safety valve of the present invention.

[0028] Figure 11 This is a rear view of the main valve used in the pilot-operated safety valve of the present invention.

[0029] Figure 12 for Figure 11 The left view.

[0030] Figure 13 for Figure 11 The right view.

[0031] Figure 14 This is a three-dimensional structural diagram of the main valve for the pilot-operated safety valve of the present invention.

[0032] Figure 15 This is a three-dimensional structural diagram of the main valve for the pilot-operated safety valve of the present invention from another perspective.

[0033] In the diagram, 1 is the valve body; 101 is the outer inclined surface of the valve body; 102 is the front; 103 is the rear; 104 is the side; 105 is the locating pin hole; and 106 is the fastening threaded hole. 2. Valve cover; 3. Bracket; 4. Valve seat; 5. Valve disc connector; 6. Valve stem; 7. First pressure tap; 8. Second pressure tap; 9. First pilot hole; 10. Second pilot hole; 11. Third pilot hole; 12. Fourth pilot hole; 13. Inlet flange; 14. Outlet flange; 15. Inlet mating flange; 16. First spiral wound gasket; 17. Second spiral wound gasket; 18. Third spiral wound gasket; 19. Valve disc; 191. Throttling orifice; 20. Piston cylinder; 21. Anti-loosening gasket; 22. Socket head cap screw; 23. Valve stem guide sleeve; 24. First stainless steel wear-resistant steel ring; 25. Second stainless steel wear-resistant steel ring; 26. Third stainless steel wear-resistant steel ring; 27. Spring seat; 28. Spring; 29. ​​Packing pressure plate; 30. Packing sleeve; 31. Packing; 32. Packing gasket; 33. Fastening assembly; 34. Valve position indicator; 35. Indicator rod; 36. Limit switch; 37. Nut; 38. Socket head cap screw a; 39. Temperature sensor; 40. Cavity clearance. Detailed Implementation

[0034] To make the structure and function of the present invention clearer, the technical solutions in the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0035] like Figure 1-15 The pilot-operated safety valve shown includes: a valve body 1, which internally forms a medium inlet channel, a valve cavity, and a medium outlet channel, all three being interconnected; the upper end of the valve body 1 is connected to a valve cover 2 via a bolt assembly, and a bracket 3 is mounted on the upper end of the valve cover 2 via the bolt assembly, the bracket 3 housing a valve opening / closing position and opening degree detection mechanism; a valve seat 4 is welded onto the valve body 1, and a valve disc assembly is disposed in the valve cavity above the valve seat 4; a valve disc connector 5 is disposed on the upper end of the valve disc assembly, and a spring mechanism is mounted on the upper end of the valve disc connector 5; a valve stem 6 is connected to the valve disc connector 5. The top of the valve stem 6 passes through the spring mechanism and extends out of the upper end of the valve cover 2 to the support 3; a temperature detection device is installed on the valve body 1 located in the medium inlet flow channel; the outer surface of the valve body 1 corresponding to the temperature detection device is the outer inclined surface 101 of the valve body, the two planes adjacent to the outer inclined surface 101 of the valve body are the front 102 and the rear 103 of the valve body, and the plane opposite to the outer inclined surface 101 of the valve body is the side 104 of the valve body; pressure tapping holes are respectively provided on the front 102 and the rear 103 of the valve body, and pilot control holes are provided on the front 102, the rear 103 and the side 104 of the valve body 1; Based on the above scheme, the valve body 1 of the main valve is equipped with pressure tapping and pilot control holes, which can realize dual redundant automatic control, manual and automatic remote control, and pure manual control. Furthermore, the pressure tapping and pilot control holes arranged at the front 102 and rear 103 of the valve body 1 as a dual redundant automatic control circuit are symmetrical mirror structures, which facilitates the balance of the weight center of gravity of the whole machine and improves the seismic performance.

[0036] Specifically, the valve body 1 has a first pressure tapping hole 7 and a second pressure tapping hole 8 on the front 102 and rear 103; the valve body 1 has a first pilot hole 9 and a second pilot hole 10 on the front 102 and rear 103, and a third pilot hole 11 and a fourth pilot hole 12 on the side 104. Furthermore, positioning pin holes 105 and fastening threaded holes 106 are arranged near the pressure tapping holes at the front 102 and rear 103 of the valve body 1, and near the pilot control holes at the front 102, rear 103 and side 104 of the valve body 1. All the complete set of control accessories can be fastened to the valve body 1 by bolt assemblies (bolts, nuts and anti-loosening washers), so as to achieve the characteristics of compact structure and easy disassembly and assembly of the whole machine.

[0037] Furthermore, the valve body 1 adopts an integral forging structure with the inlet medium flow channel and the outlet medium flow channel forming a 45° angle; the overall layout of the pressure regulator dome structure facilitates the field, which not only saves the overall space layout of the pilot-operated pressure regulator safety valve, but also makes the overall system structure compact and has a high space utilization rate.

[0038] Furthermore, the valve body's medium outlet flow channel has a gradually enlarging structure, a design feature tailored to the valve's ability to increase volume and flow rate after steam discharge.

[0039] Furthermore, the valve body 1 is provided with an inlet flange 13 and an outlet flange 14 at its inlet and outlet, respectively. The inlet flange 13, which is opposite to the inlet of the valve body 1, is connected to the valve body 1 by butt welding to form the main body of the valve body 1. The inlet flange 13 is connected to the inlet mating flange 15 by a bolt assembly. The outlet of the valve body 1 is connected to the outlet flange 14 by a bolt assembly, which facilitates the disassembly and installation of the valve.

[0040] Furthermore, spiral wound gaskets are provided between the inlet flange 13 and the inlet mating flange 15, and between the valve body 1 and the outlet flange 14, to ensure the sealing performance of the flange connection. Specifically, grooves for accommodating sealing gaskets are provided on the end faces of the inlet mating flange 15 and the outlet flange 14. A first spiral wound gasket 16 is provided in the groove of the inlet mating flange 15, and a second spiral wound gasket 17 is provided in the groove of the outlet flange 14. The first spiral wound gasket 16, the inlet mating flange 15, and the bolt assembly are connected to the inlet flange 13, and the second spiral wound gasket 17, the outlet flange 14, and the bolt assembly are connected to the outlet of the valve body 1.

[0041] Furthermore, a spiral wound gasket is installed at the junction of the upper end of the valve body 1 and the valve cover 2. A groove is formed on the upper surface of the valve body 1 to accommodate a third spiral wound gasket 18. The third spiral wound gasket 18 is pressed into the sealing groove on the upper surface of the valve body 1 by the valve cover 2 through a bolt assembly. This ensures sealing performance under different pressure changes and temperature expansion changes, and the sealing performance is better as the pressure increases. This sealing structure, in which the spiral wound gasket is installed in the groove, facilitates installation and fixed positioning, and will not be damaged due to excessive pressure or disassembly of valve parts. It can also be reused multiple times, thereby reducing costs. At the same time, this sealing structure will not bring impurities into the valve cavity and pipeline when replacing the spiral wound gasket or disassembling the valve, thus preventing foreign objects from entering the pipeline. Meanwhile, the sealing principle and effect of the first spiral wound gasket 16 and the second spiral wound gasket 17 in this solution are the same as those of the third spiral wound gasket 18.

[0042] Furthermore, the valve assembly includes: a valve disc 19, a piston cylinder 20, a stainless steel wear-resistant ring, an anti-loosening washer 21, and an internal hexagonal head screw 22; the lower part of the valve disc 19 is a large end, and the top part is a small end connected to the valve disc connector 5. The outer diameter of the large end of the valve disc 19 mates with the piston cylinder 20, and the outer diameter of the piston cylinder 20 mates with the inner wall of the valve body 1; the upper end face of the piston cylinder 20 is connected to the valve cover 2 by a bolt assembly, and the valve cover 2 has a cavity in the center to accommodate the valve disc 19, the valve disc connector 5, and the spring mechanism above them; a medium flow channel is provided in the middle of the valve disc 19, which includes a radially bent channel that passes through the lower and upper surfaces of the large end of the valve disc, and an axial channel that passes through the horizontal ends of the large end of the valve disc. The axial channel serves to balance the medium. The lower section of the radially bent channel is equipped with an internal hexagonal head screw 22. The internal hexagonal head screw 22 is set in the lower section through an anti-loosening washer 21, and the center of the internal hexagonal head screw 22 has a throttling orifice 191 for controlling the flow rate of the medium. The opening and closing time of the valve can be adjusted by controlling the size of the throttling orifice 191.

[0043] Based on the above scheme, the valve disc 19 integrates the normal valve disc function and the piston function, and the lower base part (large end) of the valve disc 19 serves as the functional part of the normal valve disc. Furthermore, wear-resistant parts are respectively provided between the outer diameter of the large end of the valve disc 19 and the inner diameter of the piston cylinder 20, and between the small end of the valve disc 19 and the inner diameter of the valve stem guide sleeve 23, which are applicable to the auxiliary support and guiding movement of the piston function; including a first stainless steel wear-resistant steel ring 24 and a second stainless steel wear-resistant steel ring 25, and both stainless steel wear-resistant steel rings are installed in the groove opened on the valve disc 19. Furthermore, a wear-resistant component, namely a third stainless steel wear-resistant ring 26, is also provided between the outer diameter of the piston cylinder 20 and the inner wall of the valve body 1. The third stainless steel wear-resistant ring 26 is installed in a groove opened on the outer diameter of the piston cylinder 20. The third stainless steel wear-resistant ring 26 is installed in the groove of the piston cylinder 20 and fastened to the valve cover 2 by bolt assembly, and can be removed from the valve body 1 along with the valve cover 2 as a whole.

[0044] With the above design, the valve can be removed entirely from the valve by disassembling only the bolt assembly (studs, nuts, and lock washers) in the middle cavity, which facilitates the disassembly, maintenance, and inspection of the valve.

[0045] Based on the wear-resistant component set between the outer diameter of the large end of the valve disc 19 and the inner diameter of the piston cylinder 20, the first stainless steel wear-resistant steel ring 24 is provided with two strips on the outer diameter surface of the large end of the valve disc 19, one above the other.

[0046] Furthermore, the valve stem guide sleeve 23 is made of wear-resistant material and is screwed into the valve cover 2 by threads for assembly and cooperation with the valve cover 2; the valve stem guide sleeve 23 and the piston cylinder 20 together play a role in positioning the valve disc 19 and guiding its reciprocating motion.

[0047] Furthermore, the valve seat 4 is welded to the valve body 1 according to a water seal structure layout to ensure the valve's sealing requirements; and the valve seat 4 is designed with a gradually enlarging structure to meet the characteristics of the fluid medium in steam discharge; the valve seat 4 is welded to the valve body 1, and if the medium exerts a large impact force on the valve seat, the valve seat 4 can be cut from the weld joint of the valve body 1, replaced or repaired, and then reinstalled and welded back to normal operating condition.

[0048] Furthermore, a sealing contact surface is formed between the upper end of the valve seat 4 and the lower part of the valve disc 19. The sealing contact surface between the two is treated with hard alloy overlay welding to improve the impact resistance, media erosion resistance and wear resistance of the sealing surface.

[0049] Furthermore, the spring mechanism includes: a spring seat 27 disposed on the valve disc connector 5 and a spring 28 located on the spring seat 27; the spring seat 27 is connected to the valve disc 19 through the valve disc connector 5, so that the spring seat 27 can move up and down and reciprocate with the valve disc 19; one end of the spring 28 contacts and is positioned with the spring seat 27, and the other end contacts and is positioned with the valve cover 2; the spring 28 serves as an auxiliary force for the valve disc 19 to close, so that the valve disc 19 and other related components tend to close automatically under their own weight.

[0050] Furthermore, the valve stem 6 is installed between the valve disc connector 5 and the spring seat 27, and moves up and down with the valve disc 19, and leads the valve disc 19 to the outside of the valve, and the valve switch position and opening degree are detected and signaled by the valve switch position and opening degree detection mechanism. Furthermore, a packing seal assembly is provided between the valve stem 6 and the valve cover 2. The packing seal assembly includes a packing pressure plate 29, a packing pressure sleeve 30, packing 31, and a packing pad 32. The packing pressure plate 29 is located on the valve stem 6 above the valve cover 2. A packing cavity is provided between the valve stem 6 and the valve cover 2 below the packing pressure plate 29. The packing 31 is pressed into the packing cavity by the packing pressure sleeve 30, and a packing pad 32 is provided at the bottom of the packing cavity. The setting of this packing seal assembly ensures the sealing reliability between the valve cover 2 and the valve stem 6, and also ensures the sealing reliability of the valve stem 6 during reciprocating motion under temperature and pressure changes. Furthermore, the packing sealing assembly is fastened above by a fastening assembly 33, which is composed of a stud, a disc spring indicator needle, a disc spring indicator plate, a disc spring sleeve, a disc spring, a gasket, and a nut. This ensures the sealing reliability of the valve stem 6 packing when the temperature and pressure change, and enables visual control of the fastening force.

[0051] Furthermore, the valve switch position and opening degree detection mechanism includes: a valve position indicator 34, an indicator rod 35, and a limit switch 36; the indicator rod 35 is fixed to the upper end of the valve stem 6 by a nut 37 and an anti-loosening washer, the main body of the valve position indicator 34 is fixed on the bracket 3, the magnetic head part is fixed on the indicator rod 35, and the limit switch 36 is fixed on the bracket 3 by an internal hexagonal head screw a38 and a limit switch seat.

[0052] The valve position indicator 34 is a magnetostrictive non-contact valve position indicator, which realizes the detection and signal feedback of the valve opening and closing position; the limit switch 36 is an open and closed mechanical limit switch, which realizes the detection and signal feedback of the valve opening and closing position.

[0053] Furthermore, the temperature detection device is an embedded non-penetrating temperature sensor 39, which realizes the detection and signal feedback of the medium temperature at the inlet of valve 1, and reduces external leakage points.

[0054] It should be noted that the bolt assemblies mentioned in this article all adopt a combination structure of studs, nuts, and lock washers.

[0055] In the above structure, the front 102, rear 103, and side 104 of the valve body are connected through four pilot holes to form the pilot circuit of the safety valve. The pilot circuit is connected to the upper chamber area of ​​the piston cylinder in the main valve body 1. The main valve adopts a pilot-operated self-driven structure with an internal piston cylinder. The change in pressure of the medium inside the main valve and the pilot circuit pressure in the upper chamber of the piston cylinder creates a change in the force on the piston, thereby realizing the opening and closing of the main valve. In the main valve body 1, the upper part of the large end of the valve disc 19, together with the inner wall of the piston cylinder 20 and the lower end face of the valve cover 2, forms a cavity gap 40. When the pressure difference between the medium pressure entering the main valve inlet and the medium pressure in the pilot circuit of the upper chamber of the piston changes, the valve disc assembly is forced to reciprocate up and down. When the pressure inside the main valve body 1 is greater than the pressure in the pilot circuit, the valve disc assembly moves upward, causing the cavity gap 40 located at the upper part of the large end of the valve disc 19 to gradually disappear, thereby causing the lower end of the valve disc 19 to separate from the valve seat 4 to form a gap, thus opening the valve. Conversely, when the pressure in the pilot circuit is close to or equal to the medium pressure of the main valve body 1, the valve disc assembly moves downward, causing the lower end of the valve disc 19 to move closer to the valve seat 4, causing the cavity gap 40 located at the upper part of the large end of the valve disc 19 to gradually recover, thus closing the valve.

[0056] It should be noted that the parts of this invention not described in detail are prior art.

[0057] The above examples are merely preferred embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments, and many variations are possible. All variations that can be directly derived or conceived by those skilled in the art from the disclosure of the present invention should be considered within the scope of protection of the present invention.

Claims

1. A main valve for a pilot operated safety valve, characterized in that include: The valve body internally forms a medium inlet channel, a valve cavity, and a medium outlet channel, all three of which are interconnected. The upper end of the valve body is connected to the valve cover via a bolt assembly. A bracket is mounted on the upper end of the valve cover via the bolt assembly, and the bracket houses the valve's open / close position and opening degree detection mechanism. A valve seat is welded onto the valve body. A valve disc assembly is located in the valve cavity above the valve seat. A valve disc connector is located at the upper end of the valve disc assembly, and a spring mechanism is mounted at the upper end of the valve disc connector. The valve stem is connected to the valve disc connector, and the top of the valve stem passes through the spring mechanism and extends out of the upper end of the valve cover to reach the bracket position. A temperature detection device is installed on the valve body located in the medium inlet channel. The outer surface of the valve body corresponding to the temperature detection device is an external inclined surface. Two planes adjacent to the external inclined surface are the front and rear of the valve body, and the plane opposite to the external inclined surface is the side of the valve body. Pressure taps are located at the front and rear of the valve body, and pilot control holes are located at the front, rear, and side of the valve body. The main valve adopts a pilot-operated, self-driven medium structure with an internal piston cylinder. The valve disc assembly includes: a valve disc, a piston cylinder, and a stainless steel wear-resistant steel ring; the lower part of the valve disc is a large end, and the top part is a small end connected to the valve disc connector. The outer diameter of the large end of the valve disc mates with the piston cylinder, and the outer diameter of the piston cylinder mates with the inner wall of the valve body; the upper end face of the piston cylinder is connected to the valve cover by a bolt assembly, and the valve cover has a cavity in the center to accommodate the valve disc, the valve disc connector, and the spring mechanism above it; the small end of the valve disc is fitted into the cavity of the valve cover by a valve stem guide sleeve. The valve disc integrates the functions of a normal valve disc and a piston. The valve disc is provided with a medium guiding channel, which includes a radially bent channel that passes through the lower part and upper surface of the large end of the valve disc, and an axial channel that passes through the two horizontal ends of the large end of the valve disc. The lower section of the radially bent channel is equipped with an internal hexagonal head screw. The internal hexagonal head screw is positioned inside the lower section by an anti-loosening washer, and a throttling orifice for controlling the flow rate of the medium is opened at the center of the internal hexagonal head screw.

2. The pilot operated safety valve main valve according to claim 1, characterized in that: The pressure taps and pilot control holes arranged at the front and rear of the valve body as dual redundant automatic control loops are symmetrical mirror structures; locating pin holes and fastening threaded holes are arranged near the pressure taps at the front and rear of the valve body, and near the pilot control holes at the front, rear and sides of the valve body.

3. The main valve for a pilot-operated safety valve according to claim 1, characterized in that: The valve body is provided with an inlet flange and an outlet flange, respectively. The inlet flange opposite to the valve body inlet is connected to the valve body by butt welding to form the main body of the valve body. The inlet flange is connected to the inlet mating flange by a bolt assembly. The valve body outlet is connected to the outlet flange by a bolt assembly. Spiral wound gaskets are also provided between the inlet flange and the inlet mating flange, and between the valve body and the outlet flange for sealing.

4. The main valve for a pilot-operated safety valve according to claim 3, characterized in that: Grooves for accommodating sealing gaskets are provided on the end faces of the inlet mating flange and the outlet flange. A first spiral wound gasket is placed in the groove of the inlet mating flange, and a second spiral wound gasket is placed in the groove of the outlet flange. The first spiral wound gasket, the inlet mating flange, and the bolt assembly are connected to the inlet flange, and the second spiral wound gasket, the outlet flange, and the bolt assembly are connected to the outlet of the valve body.

5. The main valve for a pilot-operated safety valve according to claim 1, characterized in that: Wear-resistant components are respectively provided between the outer diameter of the large end of the valve disc and the inner diameter of the piston cylinder, and between the small end of the valve disc and the inner diameter of the valve stem guide sleeve. These components include a first stainless steel wear-resistant steel ring and a second stainless steel wear-resistant steel ring, and both stainless steel wear-resistant steel rings are installed in grooves opened on the valve disc.

6. The main valve for a pilot-operated safety valve according to claim 1, characterized in that: The spring mechanism includes: a spring seat disposed on the valve disc connector and a spring located on the spring seat; the spring seat is connected to the valve disc through the valve disc connector, so that the spring seat can move up and down and reciprocate with the valve disc; one end of the spring contacts and is positioned with the spring seat, and the other end contacts and is positioned with the valve cover.

7. The main valve for a pilot-operated safety valve according to claim 1, characterized in that: The valve switch position and opening degree detection mechanism includes: a valve position indicator, an indicator rod, and a limit switch; the indicator rod is fixed to the upper end of the valve stem by a nut and an anti-loosening washer, the main body of the valve position indicator is fixed on the bracket, the magnetic head is fixed on the indicator rod, and the limit switch is fixed on the bracket by an internal hexagonal head screw and a limit switch seat.

8. The main valve for a pilot-operated safety valve according to any one of claims 1-7, characterized in that: The front, rear, and side of the valve body are connected by four pilot holes to form the pilot circuit of the safety valve. The pilot circuit is connected to the upper chamber of the piston cylinder in the main valve. In the valve body, the upper part of the valve disc, the inner wall of the piston cylinder, and the lower end face of the valve cover together form a cavity gap. When the pressure difference between the medium pressure entering the main valve inlet and the medium pressure in the pilot circuit of the upper chamber of the piston causes a pressure difference, the valve disc assembly is forced to reciprocate up and down. When the pressure inside the valve body is greater than the pressure in the pilot circuit, the valve disc assembly moves upward, causing the cavity gap located at the upper part of the valve disc's large end to gradually disappear, thereby causing the lower end of the valve disc to detach from the valve seat and form a gap, thus opening the valve. Conversely, when the pressure in the pilot circuit is close to or equal to the medium pressure in the valve body, the valve disc assembly moves downward, causing the lower end of the valve disc to move closer to the valve seat, causing the cavity gap located at the upper part of the valve disc's large end to gradually recover, thus closing the valve.

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