Assembly method of three-piece fixed ball hard-seal ball valve

Abstract

The application provides an assembling method of a three-piece fixed ball hard sealing ball valve, which comprises the following steps: firstly, pre-assembling a first valve seat assembly and a second valve seat assembly respectively, wherein the two valve seat assemblies are provided with elastic elements for applying pre-tightening force to a valve core assembly; then, sequentially assembling the first valve seat assembly, the valve core assembly and the second valve seat assembly, adjusting the compression amount of the elastic elements by a detachable adjusting tool to set the pre-tightening force, simultaneously carrying out sealing performance test, and measuring and recording the axial spacing between the two valve seat assemblies as a standard spacing after the test is qualified; then, removing the adjusting tool and the second valve seat assembly, sleeving a valve body outside the valve core assembly, adjusting the position of the valve core assembly, and keeping the shaft hole of the valve core assembly coaxial with the packing installation hole of the valve body; finally, reinstalling the second valve seat assembly, positioning and locking according to the standard spacing, and realizing the overall assembly of the ball valve. The application can complete the pre-tightening force adjustment and parameter calibration in advance, reduce the assembly rework, and improve the assembly efficiency and product quality.

Description

Technical Field

[0001] This invention relates to the field of ball valve assembly technology, and more specifically, to an assembly method for a three-piece fixed ball hard-seal ball valve. Background Technology

[0002] Three-piece fixed ball valves are widely used in harsh operating conditions such as high pressure and large diameter applications due to their compact structure, reliable sealing, and convenient maintenance. These valves typically employ a metal hard seal structure, and their sealing performance highly depends on the preload provided by the cylindrical spring at the valve seat to ensure that the valve seat sealing surface and the ball surface remain tightly fitted at all times. However, in the existing assembly process of three-piece fixed ball valves, there are generally problems of high assembly difficulty and poor precision control. Specifically, assemblers must overcome the enormous spring force during assembly, forcibly pulling the valve seat away from the ball or compressing the spring for positioning. This process is not only labor-intensive but also makes it difficult to accurately adjust the spring preload and simultaneously detect the assembly gap. Due to the lack of quantitative control methods, repeated disassembly and assembly and multiple adjustments are often required, resulting in low work efficiency and difficulty in ensuring consistent assembly quality.

[0003] Patent application number 201610393823.4 discloses an assembly process for an ultra-large diameter fully welded ball valve. This method achieves assembly by theoretically calculating the spring compression and machining the valve body and end cap to achieve "straight-mouth" positioning. While this method reduces reliance on operator experience, it is only suitable for integral, non-separable fully welded ball valves. Furthermore, this method relies entirely on theoretical data for assembly, without conducting actual testing and verification of opening / closing and sealing performance, making it unsuitable for detachable, three-piece ball valves requiring on-site dynamic adjustment of preload. Patent application number 202420635321.8 discloses a high-pressure, large-diameter, top-mounted ball valve. This method improves the valve body structure by adding an air inlet to the valve body and configuring a chain link assembly on the spring seat. It utilizes an external air source to adjust the spring compression, improving spring disassembly and preload performance. While this solution can assist in disassembly and assembly, it relies on an external air source for pressure regulation, and fluctuations in the air source pressure can lead to instability in the spring preload. In addition, this structure increases the complexity of component processing and assembly, resulting in higher manufacturing costs.

[0004] Therefore, there is an urgent need to develop an assembly method that is compatible with three-piece fixed ball metal hard seal ball valves, so as to achieve standardized assembly process and precise and controllable assembly accuracy, thereby improving assembly efficiency and product reliability while reducing the requirements of assembly operations on site and supporting facilities. Summary of the Invention

[0005] In view of this, the present invention aims to propose an assembly method for a three-piece fixed ball hard seal ball valve, so as to solve the problem that the spring preload and assembly clearance need to be repeatedly adjusted when assembling the existing large-diameter three-piece fixed ball hard seal ball valve. At the same time, the method has low requirements for assembly site and space, and can simultaneously adjust the preload and complete the valve seat seal test.

[0006] To achieve the above objectives, the technical solution of the present invention is implemented as follows:

[0007] This invention provides an assembly method for a three-piece fixed ball hard-seal ball valve, comprising the following steps:

[0008] S1: Pre-assembly

[0009] The first valve seat assembly and the second valve seat assembly are pre-assembled respectively, and both the first valve seat assembly and the second valve seat assembly include elastic elements for applying pre-tightening force to the valve core assembly.

[0010] S2: Pre-adjustment and standard spacing calibration

[0011] The first valve seat assembly, valve core assembly, and second valve seat assembly are assembled sequentially, and the first valve seat assembly and the second valve seat assembly are connected by a detachable adjusting tool. The compression of the elastic element is adjusted by the adjusting tool to set the preload. During the preload adjustment process, the sealing performance test is performed simultaneously. After confirming that it is qualified, the axial distance between the first valve seat assembly and the second valve seat assembly is measured and recorded as the standard distance.

[0012] S3: Valve body assembly and coaxial alignment

[0013] Remove the adjusting fixture and the second valve seat assembly, sleeve the valve body on the outside of the valve core assembly, and adjust the position of the valve core assembly so that the shaft hole of the valve core assembly is coaxial with the packing mounting hole of the valve body;

[0014] S4: Final Assembly Positioning

[0015] The second valve seat assembly is reinstalled on the other end of the valve body. The first and second valve seat assemblies are positioned and locked using the standard spacing to complete the ball valve assembly.

[0016] This invention divides the assembly process into four major steps: pre-assembly, pre-adjustment and spacing calibration, valve body assembly and coaxial correction, and final assembly positioning. First, the valve seat assembly is pre-assembled separately. Then, the valve seat and valve core are combined, and the compression of the elastic element and the sealing pre-tightening force are precisely controlled with the help of adjusting fixtures. At the same time, the sealing test is completed and the standard axial spacing is calibrated. After that, the valve body is assembled separately, and the coaxiality of the holes is calibrated. Finally, the overall locking assembly is completed based on the calibrated standard spacing. This effectively avoids the need for disassembly and rework of the entire valve due to unqualified sealing performance after traditional one-piece assembly.

[0017] In this invention, the axial distance between the first valve seat assembly and the second valve seat assembly is preferably the distance between the opposing surfaces of the first connecting body and the second connecting body.

[0018] Furthermore, in step S3, the valve core assembly is pressed down synchronously using a calibration fixture to adjust its axial position, thereby performing a coaxial calibration operation. After confirming coaxiality, the valve stem and stuffing box are installed so that the end face of the valve stem forms a transmission connection with the shaft hole on the valve core assembly.

[0019] It should be noted that the present invention does not limit the specific structure of the calibration fixture, as long as it can achieve the coaxial calibration function.

[0020] This invention utilizes a calibration fixture to actively achieve coaxial alignment, precisely eliminating hole misalignment and misalignment issues during assembly. This structure effectively ensures smooth transmission and engagement between the valve stem and valve core assembly, preventing valve opening and closing jamming and abnormal component wear, significantly improving the valve's operational stability and service life.

[0021] Furthermore, the calibration fixture includes a pressure plate base and a support leg disposed on the lower side of the pressure plate base. The support leg is used to abut against the support plate of the valve core assembly. Tightening the fasteners on the calibration fixture drives the pressure plate base to press down, thereby pressing down the support plate synchronously through the support leg until the shaft hole is coaxial with the packing mounting hole.

[0022] Furthermore, the pressure plate base is a plate-shaped structure, and two support legs are provided and symmetrically distributed at the bottom of the pressure plate base; the pressure plate base is provided with a channel for fasteners to pass through, and the fastener is a screw, one end of which abuts against the end face of the valve body, and the other end extends out of the channel and is locked with a nut.

[0023] In this invention, the calibration fixture has two sets of channels running vertically through it, with two channels arranged symmetrically in each set for threading the screw; two legs are respectively set at the middle position of the two channels on the same side.

[0024] Furthermore, in step S1, when pre-assembling the first valve seat assembly or the second valve seat assembly, the elastic element, the sealing assembly and the valve seat are first installed inside the connector body, and then the valve seat is evenly pressed into the connector body using a press fitting tool in conjunction with a screw and a nut.

[0025] It should be noted that the present invention does not limit the specific structure of the pressing tool, as long as it can achieve the function of uniform pressing.

[0026] This invention introduces a specialized press-fitting fixture that provides overall positioning and guidance for the valve seat, effectively preventing tilting or displacement caused by uneven force during press-fitting. This structure fundamentally avoids the valve seat compressing and damaging sealing components such as the graphite sealing ring, significantly improving the assembly accuracy and final sealing reliability of the valve seat assembly. Simultaneously, the application of this fixture enables standardized press-fitting of the valve seat assembly, unifying assembly quality standards, greatly reducing the risk of product defects due to variations in manual operation, and effectively ensuring product consistency and yield.

[0027] Furthermore, one end of the press-fitting fixture is adapted to the end face of the valve seat near the press-fitting fixture, and the other end of the press-fitting fixture is turned outward to form a fixing part; the fixing part is provided with a channel for inserting the screw.

[0028] Furthermore, the method of using the press-fitting fixture is as follows: by evenly tightening the nuts on the screw diagonally, the valve seat moves along the axial direction of the screw towards the inside of the connector body until the valve seat is completely pressed into the inside of the connector body.

[0029] In this invention, the pressing fixture adopts a cylindrical design, with one end bent outward to form a ring-shaped fixing part. Multiple holes are distributed along the circumferential direction on the fixing part for the screw to pass through. The projection contour of the end face of the other end of the pressing fixture along the length direction of the pressing fixture is consistent with the contour of the valve seat end face.

[0030] Furthermore, in step S2, the sealing performance test performed simultaneously includes opening and closing torque detection and sealing test; when the opening and closing torque value meets the set range and the sealing surface is free of scratches, the axial distance between the first valve seat assembly and the second valve seat assembly at this time is recorded as the standard distance.

[0031] This multi-dimensional comprehensive testing mechanism can identify and intercept potential assembly defects in advance, ensuring that the components entering the final assembly process are in a fully qualified state, thereby achieving strict control over product quality throughout the entire process.

[0032] Furthermore, in step S2, the adjusting fixture includes a screw passing through the periphery of the first valve seat assembly and the second valve seat assembly, and a mating nut, which is tightened to compress the elastic element.

[0033] It should be noted that the present invention does not limit the specific structure of the adjustment fixture, as long as it can adjust the distance between the first valve seat assembly and the second valve seat assembly.

[0034] In its design, this invention employs a structure with multiple screws evenly arranged circumferentially to ensure uniform force application. During the compression of the elastic element, this structure drives the valve seat assemblies on both sides to maintain parallel movement, effectively preventing deflection or tilting of the assemblies. This ensures the consistency of the elastic element's compression in the circumferential direction, resulting in a more uniform distribution of the sealing preload and significantly improving sealing reliability. Furthermore, the screws and nuts in this invention are standardized, universal parts, which not only simplifies the assembly and disassembly of the tooling but also gives it high flexibility, easily adapting to ball valves of different specifications and models. This significantly reduces tooling manufacturing costs and improves production efficiency.

[0035] Furthermore, the specific installation method of the adjustment fixture is as follows: first, assemble the first valve seat assembly and the valve core assembly, then insert the screw rod around the first valve seat assembly, then assemble the second valve seat assembly by fitting it onto the outside of the screw rod, and finally tighten the nut.

[0036] Compared with the prior art, the assembly method of the three-piece fixed ball hard seal ball valve of the present invention has the following advantages:

[0037] (1) The present invention adopts a step-by-step pre-assembly combined with special tooling assembly method. The valve seat assembly is completed separately first. The valve seat movement trajectory is constrained by the screw, nut and valve seat pressure plate. This method can effectively prevent the valve seat from tilting and deviating, avoid the graphite sealing ring from being squeezed and damaged, improve the assembly accuracy of the valve seat components from the source, and ensure the basic sealing performance.

[0038] (2) Before the valve body is fully assembled, the spring preload adjustment, assembly gap calibration, sealing test and end face distance calibration are completed in advance, which is different from the traditional mode of rework and debugging after overall assembly. This saves the tedious process of repeatedly disassembling the whole valve and adjusting the springs, greatly shortens the debugging cycle and improves assembly efficiency; at the same time, the actual measured distance is used as the basis for final assembly to ensure that the compression of the springs on both sides and the sealing preload are uniform and reasonable, which can not only meet the hard seal requirements, but also avoid scratches on the sealing surface during opening and closing, and extend the service life of the valve.

[0039] (3) This invention adds an independent coaxial alignment process, using a pressure plate tooling to adjust the position of the ball shaft hole and the valve body packing mounting hole to ensure precise alignment between the two, ensuring smooth valve stem transmission and smooth operation without jamming. The entire process uses only simple tooling, the assembly process is simple, and the requirements for site and equipment are low. It is not only suitable for mass production in factories, but also meets the needs of on-site maintenance and disassembly operations. It is especially suitable for high-pressure, large-diameter three-piece fixed ball hard seal ball valves. Attached Figure Description

[0040] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0041] Figure 1 This is a schematic cross-sectional view of the ball valve described in this invention;

[0042] Figure 2 This is a schematic diagram of the valve seat assembly using a press-fitting fixture according to the present invention;

[0043] Figure 3 This is a schematic diagram illustrating the calibration of the spacing between the first valve seat assembly and the second valve seat assembly according to the present invention.

[0044] Figure 4 This is a schematic diagram of the coaxial alignment operation performed using the alignment fixture of the present invention;

[0045] Figure 5 This is a schematic diagram of the assembly of the second valve seat assembly and the valve body according to the present invention.

[0046] Explanation of reference numerals in the attached figures:

[0047] 1. First valve seat assembly; 101. First connecting body; 102. First valve seat; 103. First end face; 2. Second valve seat assembly; 201. Second connecting body; 202. Second valve seat; 203. Second end face; 3. Valve core assembly; 301. Ball; 302. Support plate; 303. Fixing pin; 304. Bearing; 305. Shaft hole; 4. Valve stem; 5. Valve body; 6. Stuffing box; 601. Stuffing sleeve; 602. Stuffing mounting hole; 7. Sealing assembly; 701. Spacer ring; 702. Graphite sealing ring; 8. Elastic element; 9. Screw; 10. Nut; 11. Press-fitting fixture; 12. Alignment fixture. Detailed Implementation

[0048] The present invention will be further described below with reference to specific embodiments. First, it should be noted that the data in the following experimental examples were obtained by the inventors through numerous experiments. Due to space limitations, only a portion of these data is shown in the specification, and those skilled in the art can understand and implement the present invention based on this data. These embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the contents of this invention, those skilled in the art can make various modifications or alterations to the invention, and these modifications or alterations also fall within the scope of protection of this application.

[0049] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0050] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0051] Ball valves can be classified into three-piece, two-piece, and one-piece types based on their body structure. Three-piece ball valves consist of a left connecting body, a central valve body, and a right connecting body, offering convenient disassembly, assembly, and maintenance. Based on the ball support method, they can be divided into fixed-ball and floating-ball valves. In fixed-ball valves, the ball is bidirectionally limited by upper and lower support plates, bearings, and a fixing pin, allowing only rotational movement without axial floating. This results in strong overall pressure resistance, making them suitable for high-pressure, large-diameter applications. In floating-ball valves, the ball is limited only by one side of the valve stem, allowing for slight axial movement along the medium flow direction and sealing via medium pressure. These are often used in small- to medium-diameter, low-pressure applications. Based on the sealing material, they can be classified into hard-seal and soft-seal ball valves. Hard-seal ball valves use a metal ball and metal seat to form a sealing pair, offering excellent temperature, pressure, and wear resistance. Soft-seal ball valves consist of a metal ball paired with a non-metallic elastic seat such as PTFE or rubber, relying on the material's own elasticity for sealing. While offering good sealing performance, they have weaker temperature, pressure, and erosion resistance.

[0052] It should be noted that the assembly method of this invention is specifically adapted to three-piece fixed-ball hard-seal ball valves. On one hand, the valve body structure of two-piece and one-piece ball valves differs significantly from that of three-piece valves, making them unsuitable for the assembly process and tooling of this invention. On the other hand, the ball in a floating-ball valve lacks a bidirectional support and positioning structure, and the ball is allowed to float axially during operation, which is completely inconsistent with the design principles and tooling requirements of this solution regarding ball limiting, clearance calibration, and coaxial correction. Furthermore, the sealing structure and assembly process of a soft-seal ball valve differ from those of a metal hard-seal structure, making this assembly method unsuitable. Therefore, this invention can only be applied to three-piece fixed-ball hard-seal ball valves.

[0053] This type of ball valve is a conventionally designed valve. Its specific composition, connection and mating relationships, and component functions are as follows:

[0054] like Figure 1 As shown, the main body of the ball valve is composed of components such as the first valve seat assembly 1, the second valve seat assembly 2, the valve core assembly 3, the valve stem 4, the valve body 5, and the stuffing box 6. The first connecting body 101, the valve body 5, and the second connecting body 201 are sequentially connected and fastened together to form a three-piece split valve body structure of the ball valve, which serves as the load-bearing base of the entire valve.

[0055] The first valve seat assembly 1 consists of a first valve seat 102, an elastic element 8, and a sealing assembly 7. The elastic element 8 is a cylindrical spring. The sealing assembly 7 includes a spacer ring 701 and a graphite sealing ring 702, with two spacer rings 701 and two graphite sealing rings 702. The assembly sequence is two graphite sealing rings 702 followed by two spacer rings 701. This assembly is assembled inside the first connecting body 101. The elastic element 8 and the sealing assembly 7 are assembled at the mating surface of the first valve seat 102 and the first connecting body 101. The cylindrical spring uses its own elastic force to push the first valve seat 102 and the second valve seat 202 tightly against the valve core assembly 3, ensuring that the sealing pair has a stable preload. The sealing assembly 7 is used to seal the gap between the valve seat and the connecting body to prevent media leakage. The second valve seat assembly 2 consists of a second valve seat 202, an elastic element 8, and a sealing assembly 7. The structure and assembly method are the same as those of the first valve seat assembly 1. The two sets of valve seat assemblies are symmetrically arranged on both sides of the valve body 5.

[0056] The valve core assembly 3 is assembled in the internal cavity of the valve body 5. Its components include a ball 301, a support plate 302, a fixing pin 303, and a bearing 304. The bearing 304 is assembled at both ends of the ball 301, and the support plate 302 supports the bearing 304. Together with the fixing pin 303, the ball 301 is positioned bidirectionally. This structure can constrain the axial movement of the ball 301, allowing the ball 301 to only rotate, greatly enhancing the valve's pressure-bearing capacity and meeting the requirements of high-pressure and large-diameter applications. The ball 301 is machined with a shaft hole 305, and a corresponding packing installation hole 602 is opened on the top of the valve body 5, where the packing box 6 is fixed. After the valve stem 4 passes through the stuffing box 6, its lower end is connected to the shaft hole 305 of the ball 301 to form a transmission fit. By rotating the valve stem 4, the ball 301 can be rotated to realize the opening and closing operation of the valve. Among them, the first valve seat 102, the second valve seat 202 and the ball 301 adopt a metal-to-metal contact hard seal structure. The medium is cut off by precision-machined metal sealing surface, which has the characteristics of temperature resistance, pressure resistance and wear resistance.

[0057] The aforementioned three-piece split valve body, bidirectional fixed support for the ball, metal hard seal, and other structures, as well as the assembly and fit relationships between the various components, are all well-known prior art in this field and will not be described in detail further. The specific model of this ball valve can be Q347Y.

[0058] Example 1

[0059] An assembly method for a three-piece fixed ball hard-seal ball valve includes the following steps:

[0060] S1: Pre-assembly

[0061] like Figure 2As shown, the first valve seat assembly 1 and the second valve seat assembly 2 are pre-assembled using a press-fitting fixture 11. The axial contour of one end of the press-fitting fixture 11 matches the end face of the valve seat, while its other end is flanged outwards to form a fixing part. The fixing part has a hole for the screw 9 to pass through. During assembly, the nuts 10 on the screw 9 are tightened evenly diagonally, driving the valve seat to move smoothly along the axial direction of the screw 9 towards the inside of the connector body until the valve seat is fully assembled. This operation avoids valve seat skewing or offset, prevents damage to the sealing assembly 7 due to compression, and eliminates media leakage caused by assembly deviations, effectively ensuring sealing performance. The specific operating steps are as follows:

[0062] Lay the first connector 101 flat. Grooves are evenly arranged circumferentially on the inner side of the first connector 101. First, insert the elastic element 8 into the groove, and then install the graphite sealing ring 702, the spacer ring 701, and the first valve seat 102 in sequence. Then, place the press-fit fixture 11 on the upper surface of the first valve seat 102, and evenly insert the screw 9 and nut 10 along the outer circumferential direction of the press-fit fixture 11 and the first connector 101. Tighten the nut 10 evenly diagonally to press the first valve seat 102 smoothly into the first connector 101, completing the assembly of the first valve seat assembly 1. Finally, remove the screw 9, nut 10, and press-fit fixture 11. Following the same procedure, assemble the second connector 201 and the second valve seat 202 to obtain the second valve seat assembly 2.

[0063] S2: Pre-adjustment and standard spacing calibration

[0064] like Figure 3 As shown, the assembled first valve seat assembly 1 is laid flat, with the flange facing down and the first valve seat 102 facing up. A fixing pin 303 is installed on the upper end face of the first connecting body 101. After the pre-assembly of the valve core assembly 3, which consists of the ball 301, the support plate 302, and the bearing 304, the valve core assembly 3 is assembled from top to bottom onto the first valve seat assembly 1. During the descent, the holes of the support plate 302 are precisely aligned with the fixing pin 303, and then the assembly is completed. The fixing pin 303 limits the support plate 302 to prevent the valve core assembly 3 from rotating circumferentially or shifting radially.

[0065] After assembling the first valve seat assembly 1 and the valve core assembly 3, the adjusting fixture consisting of the screw 9 and the nut 10 is installed. First, the screw 9 is inserted around the outside of the first valve seat assembly 1. Then, the second valve seat assembly 2 is fitted onto the outside of the screw 9. The second valve seat assembly 2 is slowly lowered so that the second valve seat 202 in the second valve seat assembly 2 comes into contact with the ball 301 of the valve core assembly 3.

[0066] Rotate the ball 301 to the fully closed position, and evenly tighten the nuts 10 at both ends of the first valve seat assembly 1 and the second valve seat assembly 2. Adjust the sealing preload by compressing the elastic element 8 until the fit clearance between the first connecting body 101, the second connecting body 201 and the support plate 302 is zero. Then place the entire assembly horizontally.

[0067] The valve stem 4 is inserted into the shaft hole 305 of the valve core assembly 3, and the opening and closing torque test and sealing test are carried out simultaneously: the opening and closing torque of the ball 301 is detected by driving the valve stem 4, and a pressure test is performed on the assembly to verify the sealing pre-tightening effect of the first valve seat 102 and the second valve seat 202. During the test, the relative sliding of the valve seat and the ball 301 is observed to ensure that no scratches are produced on the sealing surfaces of the two.

[0068] When the opening and closing torque and sealing performance meet the design requirements, and the sealing surface is intact and free of scratches, measure and record the axial distance between the opposite end faces of the first valve seat assembly 1 and the second valve seat assembly 2, and set this value as the standard distance. After the debugging work is completed, remove the screw 9 and nut 10 of the adjusting fixture.

[0069] S3: Valve body assembly and coaxial alignment

[0070] like Figure 4 As shown, first remove the second valve seat assembly 2 as a whole, then completely fit the valve body 5 from top to bottom onto the outside of the valve core assembly 3. Manually rotate the valve body 5 to pre-adjust the installation position so that the hole on the valve body 5 for installing the packing box 6 is initially aligned with the shaft hole 305 of the valve core assembly 3, in preparation for subsequent coaxial correction work.

[0071] A calibration fixture 12, a screw 9, and a matching nut 10 are installed at the upper end of the valve body 5. The calibration fixture 12 is a dedicated coaxial calibration fixture. The main body of the fixture is a plate-shaped pressure plate base. Two legs are symmetrically arranged at the bottom of the pressure plate base, and the two legs respectively abut against the surfaces of the support plates 302 at the upper and lower parts of the valve core assembly 3. A through-hole is opened in the middle of the pressure plate base. The screw 9 passes through the hole for assembly. The bottom end of the screw 9 abuts against the upper end face of the valve body 5, and the top end of the screw 9 extends upward from the hole and is initially locked and positioned with the nut 10.

[0072] Slowly and evenly tighten the nut 10. The nut 10 moves downward along the screw 9 axis and pushes the pressure plate base to move downward as a whole. The two legs at the bottom of the pressure plate base press down the support plate 302 in sync, thereby fine-tuning the axial position of the valve core assembly 3. Continue to adjust until the shaft hole 305 of the valve core assembly 3 and the packing mounting hole 602 of the valve body 5 are completely coaxial, ensuring that their center lines coincide.

[0073] After completing the coaxiality calibration, first insert the packing sleeve 601 into the packing mounting hole 602 of the valve body 5. Then, assemble the valve stem 4 and the packing box 6 into a transmission component and install them in the designated position, ensuring that the end face of the valve stem 4 is precisely aligned with the shaft hole 305 of the valve core assembly 3 to form a stable and reliable transmission fit. After all assembly procedures are completed, remove the calibration fixture 12, screw 9, and nut 10 in sequence. This stage of the assembly operation is now complete.

[0074] S4: Final Assembly Positioning

[0075] like Figure 5 As shown, because the elastic element 8 always applies an outward elastic force, the second valve seat assembly 2 cannot stably remain in the preset assembly position under unrestrained conditions. Adjust the second valve seat assembly 2 to a flange-up position and smoothly assemble it from top to bottom to the end of the valve body 5 away from the first valve seat assembly 1;

[0076] During the assembly process, the alignment and calibration are strictly carried out in accordance with the standard spacing specified in the previous debugging stage to ensure that the assembly gap between the first valve seat assembly 1, the second valve seat assembly 2 and the valve body 5 is uniform. Then, the fasteners are tightened step by step and evenly, and the assembly stroke is precisely controlled so that the axial spacing between the two opposite end faces (first end face 103 and second end face 203) of the first valve seat assembly 1 and the second valve seat assembly 2 is completely matched with the standard spacing.

[0077] At this point, the compression of the elastic elements 8 on both sides of the valve remains uniform, the sealing pre-tightening force and the overall assembly clearance both meet the design specifications, and a reliable seal can be formed between the valve seat and the ball 301. Thus, the complete assembly of the three-piece fixed ball hard seal ball valve is completed.

[0078] Comparative Example 1

[0079] In the existing technology, the traditional three-piece fixed ball hard seal ball valve adopts an integrated assembly process. During operation, the first valve seat assembly 1, the second valve seat assembly 2, the valve core assembly 3 and the valve body 5 are directly aligned and assembled. All components are assembled in place at the same time, without the need for separate pre-adjustment, spacing calibration and coaxial correction of shaft hole 305 and packing installation hole 602. After the entire valve is assembled, a unified sealing performance test is performed. If the test result is not up to standard, the entire valve must be completely disassembled, and the installation position, arrangement and number of internal elastic elements 8 must be repeatedly adjusted, or the number of elements increased or decreased. Then, the entire valve is reassembled and the sealing performance is retested. This assembly mode not only involves a cumbersome debugging process, numerous rework attempts, and low production assembly efficiency, but also fails to accurately control the compression and sealing preload of the elastic elements 8 on both sides in advance. The assembly gap between the valve seat and the ball 301 relies entirely on the operator's experience, which can easily lead to uneven preload on both sides and large gap deviations, resulting in unstable product sealing performance. In addition, the large size and weight of the overall components of large-diameter valves make it difficult to assemble multiple components synchronously, which also places higher demands on the assembly site and operator skills.

[0080] Compared to traditional integral assembly processes, this invention pre-assembles the elastic element 8 through steps such as pre-assembly, standard spacing calibration, and coaxial correction, eliminating the need for repeated disassembly of the valve adjusting spring. This significantly reduces assembly difficulty and improves work efficiency. The assembly process effectively prevents valve seat misalignment and offset, avoids scratches on the sealing surface, and ensures stable valve sealing performance.

[0081] While the present invention has been disclosed above, it is not limited thereto. Any person skilled in the art can make various alterations and modifications without departing from the spirit and scope of the invention; therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. A method for assembling a three-piece fixed ball hard-seal ball valve, characterized in that, Includes the following steps: S1: Pre-assembly The first valve seat assembly (1) and the second valve seat assembly (2) are pre-assembled respectively. Both the first valve seat assembly (1) and the second valve seat assembly (2) include an elastic element (8) for applying a preload to the valve core assembly (3). S2: Pre-adjustment and standard spacing calibration The first valve seat assembly (1), the valve core assembly (3), and the second valve seat assembly (2) are assembled in sequence, and the first valve seat assembly (1) and the second valve seat assembly (2) are connected by a detachable adjusting fixture. The compression of the elastic element (8) is adjusted by the adjusting fixture to set the preload. During the preload adjustment process, the sealing performance test is carried out simultaneously. After confirming that it is qualified, the axial distance between the first valve seat assembly (1) and the second valve seat assembly (2) is measured and recorded as the standard distance. S3: Valve body assembly and coaxial alignment Remove the adjusting fixture and the second valve seat assembly (2), put the valve body (5) on the outside of the valve core assembly (3), adjust the position of the valve core assembly (3) so that the shaft hole (305) of the valve core assembly (3) is coaxial with the packing mounting hole (602) of the valve body (5); S4: Final Assembly Positioning The second valve seat assembly (2) is reinstalled on the other end of the valve body (5), and the first valve seat assembly (1) and the second valve seat assembly (2) are positioned and locked using the standard spacing to complete the ball valve assembly.

2. The assembly method according to claim 1, characterized in that, In step S3, the valve core assembly (3) is pressed down synchronously using a calibration fixture (12) to adjust the axial position of the valve core assembly (3) and thus perform coaxial calibration. After confirming coaxiality, the valve stem (4) and the stuffing box (6) are installed so that the end face of the valve stem (4) and the shaft hole (305) on the valve core assembly (3) form a transmission connection.

3. The assembly method according to claim 2, characterized in that, The calibration fixture (12) includes a pressure plate base and a support foot disposed on the lower side of the pressure plate base. The support foot is used to abut against the support plate (302) of the valve core assembly (3). Tighten the fasteners on the calibration fixture (12) to drive the pressure plate base to press down, thereby pressing down the support plate (302) synchronously through the support foot until the shaft hole (305) is coaxial with the packing installation hole (602).

4. The assembly method according to claim 3, characterized in that, The pressure plate base is a plate-shaped structure. Two support legs are provided and symmetrically distributed at the bottom of the pressure plate base. The pressure plate base has a channel for fasteners to pass through. The fastener is a screw (9). One end of the screw (9) abuts against the end face of the valve body (5), and the other end extends out of the channel and is locked with a nut (10).

5. The assembly method according to claim 1, characterized in that, In step S1, when pre-assembling the first valve seat assembly (1) or the second valve seat assembly (2), the elastic element (8), the sealing assembly (7) and the valve seat are first installed inside the connector body, and then the valve seat is evenly pressed into the connector body by using the press fitting tool (11) in conjunction with the screw (9) and the nut (10).

6. The assembly method according to claim 5, characterized in that, One end of the press-fitting fixture (11) is adapted to the end face of the valve seat near the press-fitting fixture (11), and the other end of the press-fitting fixture (11) is turned outward to form a fixing part; the fixing part is provided with a channel for inserting the screw (9).

7. The assembly method according to claim 6, characterized in that, The pressing tool (11) is used as follows: by evenly tightening the nuts (10) on the screw (9) diagonally, the valve seat moves along the axial direction of the screw (9) toward the inside of the connector body until the valve seat is completely pressed into the inside of the connector body.

8. The assembly method according to claim 1, characterized in that, In step S2, the sealing performance test performed simultaneously includes opening and closing torque detection and sealing test; when the opening and closing torque value meets the set range and the sealing surface is free of scratches, the axial distance between the first valve seat assembly (1) and the second valve seat assembly (2) at this time is recorded as the standard distance.

9. The assembly method according to claim 1, characterized in that, In step S2, the adjusting fixture includes a screw (9) passing through the first valve seat assembly (1) and the second valve seat assembly (2) and a matching nut (10), and the elastic element (8) is compressed by tightening the nut (10).

10. The assembly method according to claim 1, characterized in that, The specific installation method of the adjustment fixture is as follows: first, assemble the first valve seat assembly (1) and the valve core assembly (3), then insert the screw (9) around the first valve seat assembly (1), then assemble the second valve seat assembly (2) on the outside of the screw (9), and then tighten the nut (10).

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