Method for controlling manufacturing precision of bottom conical supporting assembly of new structure dehydrogenation device

Abstract

The present application relates to the field of chemical container manufacturing, and discloses a manufacturing precision control method for a bottom conical support assembly of a dehydrogenation device with a new structure. The method comprises the following steps: (1) dividing the conical head into an upper / lower forging transition section and a middle section conical body formed by pressing 3-4 petals, reserving a margin and checking the curvature; (2) adopting double-sided asymmetric groove welding for longitudinal seams, arranging a deformation prevention support on the inner side, and controlling the interpass temperature to be 50-100 DEG C; (3) adopting double-sided half U-shaped grooves for the catalyst connecting pipes, and ensuring the symmetry degree to be less than or equal to 1.5 mm through three-dimensional modeling numerical control processing; (4) synchronously assembling 12 connecting pipes through a template tool with positioning bolt holes, and alternately welding in groups; and (5) taking the outer circle of the upper transition section as a reference, and numerically controlling the processing of the conical body contact surface to ensure that the coaxiality is less than or equal to 1.5 mm. The method solves the problems of poor welding penetration of thick conical bodies, difficult precision control of melon petal type conical head, low positioning precision of multiple connecting pipes and difficult welding deformation control, and significantly improves the flatness and concentricity of the conical support assembly.

Description

Technical Field

[0001] This invention relates to the field of chemical container manufacturing technology, and specifically discloses a manufacturing precision control and welding deformation prevention process for a novel bottom conical support component of a dehydrogenation device. Background Technology

[0002] Propylene produced by propane dehydrogenation is widely used in high-value-added products such as polypropylene, acrylonitrile, propylene oxide, ethylene propylene rubber, nylon 66 and ABS resin. In recent years, domestic demand for propylene has continued to grow, and propane dehydrogenation (PDH) has become an important technology for increasing propylene production. It is currently the most competitive propylene production process.

[0003] The dehydrogenation reactor is the core equipment of the propane dehydrogenation unit. The equipment consists of a reduction zone, a reaction zone, an inner network, an outer network, and a guide cone. Its operating conditions are extremely harsh, with reaction temperatures between 600℃ and 700℃. The catalyst is the core of the reaction, affecting the efficiency of the reaction and the selectivity of the products. It has always faced problems such as high energy consumption and easy coking and deactivation of the catalyst.

[0004] The new dehydrogenation reactor adopts a conical support structure at the bottom. The inner and outer meshes are supported by the conical surfaces of the inner and outer mesh bases and the bottom conical head, respectively. The catalyst outlet is located in the conical section between the inner and outer meshes. This structure improves the fluidity and recycling of the catalyst and reduces the probability of coking and deactivation.

[0005] However, the development of the new structure greatly increased the manufacturing difficulty. Since both the inner and outer meshes are supported by the bottom conical support components, in order to support the inner and outer mesh components, which are more than 20 meters long and weigh about 30-40 tons, and to ensure that the top of the outer mesh and the inner wall of the shell have a uniform 16mm gap to meet the requirements of the stuffing box structure, the flatness of the bottom conical support components and their concentricity with the main axis of the equipment are extremely important. Therefore, the bottom conical support components of the new structure are the most critical components in this device. Ensuring the manufacturing precision of this component is the most critical link to maximize its supporting effect on the inner and outer meshes, ensure the verticality and straightness of the equipment, the installation accuracy of the inner and outer meshes, improve the uniformity of feed distribution, and the catalyst recovery rate.

[0006] The conical head structure differs significantly from the traditional elliptical head structure. Currently, there are generally two methods for forming conical heads: integral forging and sheet metal pressing. Due to the large taper and significant difference in diameter between the large and small openings of the conical head, and the total height exceeding 3000mm, integral forging is extremely costly, and excessive thickness of austenitic stainless steel would prevent the material properties from meeting standard requirements. Therefore, the conical head can only be manufactured through sheet metal pressing.

[0007] However, because the dimensions of each segment cannot be guaranteed to be completely consistent during the segmented forming of the cone, and there are certain assembly errors when assembling multiple segments, there is also a certain amount of welding shrinkage and deformation during the cone assembly welding process. Since the cone is the main supporting component for both the inner mesh base and the outer mesh assembly, ensuring the dimensions of the welded cone is of paramount importance. Ensuring the fit between the inner wall of the cone, formed by pressing steel plates, and the inner and outer mesh bases, formed by forging, is a key manufacturing point. Determining the concentricity of the catalyst nozzle and designing and processing the bevel also present significant challenges.

[0008] Currently, the most effective method for full penetration welding of thick stainless steel is double-sided welding or back-side root cleaning welding. However, due to the large thickness and distance limitations, it is impossible to make large-size bevels, which restricts the welder's line of sight and makes it impossible to achieve single-sided welding with double-sided forming. Alternatively, it may be too dependent on the skill of the personnel, which cannot solve the problems encountered in this project.

[0009] Austenitic stainless steel has a large coefficient of linear expansion, making it prone to welding deformation during the welding process. The catalyst outlet pipes are arranged symmetrically along the circumference and need to be connected to the pipeline on site. The traditional method of numbering and assembling pipes cannot guarantee the relative position between the pipes. The method of assembling and welding a dozen pipes separately will increase the welding deformation rate and cause the relative distance and concentricity between the pipes to exceed the tolerance. Summary of the Invention

[0010] The purpose of this invention is to provide a method for controlling the manufacturing precision of a new type of conical support component at the bottom of a dehydrogenation reactor. This method achieves high-precision manufacturing of a thick conical component through the coordinated use of four technologies: establishing a manufacturing benchmark for segmented cones, preventing deformation through longitudinal seam welding, precise positioning of the catalyst inlet pipe and bevel design, and collaborative processing of the contact surface.

[0011] Specifically, it includes:

[0012] 1. Using the upper / lower transition section of the integral forging as a reference, control the curvature of the segmented cone and the assembly accuracy;

[0013] 2. Asymmetrical bevels and combined supports are used to suppress longitudinal joint deformation;

[0014] 3. Based on template-based chemical assembly, multiple pipes are assembled simultaneously, and the problem of full penetration is solved by combining double-sided semi-U-shaped bevels;

[0015] 4. Using the outer circle of the upper transition section as a reference, machine the conical contact surface to ensure that the coaxiality with the inner and outer mesh base is ≤1.5mm.

[0016] To achieve the above objectives, the present invention includes the following technical solutions:

[0017] A method for controlling the manufacturing precision of a novel bottom conical support assembly for a dehydrogenation device includes the following steps:

[0018] (1) The conical head assembly is manufactured in three sections: the upper flanged arc transition section is formed by integral forging and has a height of 250-350mm, the lower flanged arc transition section is formed by integral forging and has a height of 200-300mm, and the two serve as the assembly and processing reference for the intermediate cone; the intermediate cone is formed by pressing 3-4 steel plates, with a thickness allowance of 10-15mm for each plate, a width allowance of 3-10mm on each side, and a height allowance of 15-20mm;

[0019] (2) The longitudinal seam of the middle cone is welded with a double-sided asymmetric bevel, with the outer side being a variable angle V-shaped bevel and the inner side being a V-shaped bevel. Anti-deformation combined support is set on the inner side of the cone 30-80mm from the upper and lower ports. The support type is selected according to the cone diameter, either cross support or star support. The interpass temperature is controlled at 50-100℃ during the welding process.

[0020] (3) The catalyst outlet pipe bevel adopts a double-sided semi-U-shaped bevel with a blunt edge size of 0.5-1.5mm, a gap of 2-4mm, a bottom R angle of 8-12mm, and a bevel depth of 40%-60% of the cone thickness.

[0021] (4) 12 catalyst outlet pipes are assembled simultaneously using a template tooling. The tooling includes a template with positioning bolt holes and a reinforcing rib. The template thickness is 50-80mm. The bolt holes are CNC machined according to the pipe position coordinates marked on the design drawings.

[0022] (5) Using the inner mesh base and outer mesh base assembly area as a reference, the upper flanged arc transition section outer circle is used as a reference on the vertical machine to CNC machine the conical contact surface to ensure that the coaxiality does not exceed 1.5mm.

[0023] Furthermore, in the above control method, in step (1), when the middle cone is pressed into segments, a special fan-shaped template is used to check the curvature, and the maximum shape deviation within the upper and lower 30-80mm range of the inner mesh base assembly area does not exceed 4mm.

[0024] Furthermore, in the above control method, in step (2), the width of the arc plate of the anti-deformation combined support is 80-150mm, the longitudinal seam gap is controlled to be 2-5mm, and welding uses a welding rod with a diameter of 2.5-4.0mm and the welding rod swing amplitude does not exceed 10mm.

[0025] Furthermore, in the above control method, in step (3), the processing of the double-sided semi-U-shaped bevel is carried out by three-dimensional modeling to generate a CNC program, and the outer circle of the straight edge section of the lower flange arc transition section is used as the reference for positioning, and the bevel symmetry deviation is ≤1.5mm.

[0026] Furthermore, in the above control method, in step (4), the template is made of 3-5 ring plates welded together. During the welding process, a double-sided alternating welding process is adopted, and the temperature between welding passes does not exceed 250°C.

[0027] Furthermore, in the above control method, in step (4), when welding the catalyst connector, first complete the two-layer argon arc welding of all connectors, then divide the 12 connectors into 2-4 groups, with 3-6 pieces in each group, and have multiple welders simultaneously weld to a bevel depth of 20%-30% before rotating the work groups.

[0028] Furthermore, in the above control method, the current for the first layer of argon arc welding is 50-100 amperes, the current for the second layer is 70-130 amperes, and the temperature is lowered to below 60°C after each layer is welded and penetration testing is performed.

[0029] Furthermore, in the above control method, in step (5), the flatness of the inner mesh base and the outer mesh base support surface after processing does not exceed 0.05mm, and the local gap with the contact surface of the cone does not exceed 1.0mm.

[0030] Furthermore, in the above control method, during the welding process of step (2) or step (3), water mist cooling is used on the back of the weld, and the water mist spraying distance is 150-400mm.

[0031] Furthermore, with the above control method, the final ellipticity of the conical head assembly port does not exceed 3mm, and all longitudinal and circumferential seams are subjected to X-ray and penetrant testing in accordance with NB / T47013 standard.

[0032] Compared with the prior art, the present invention has the following outstanding advantages:

[0033] 1. Segmented manufacturing benchmark optimization

[0034] The upper / lower integral forging transition section serves as the assembly datum, the middle section is segmented and pressed to reserve allowance, and the curvature is controlled by a special template to solve the problem of concentricity of large tapered components, with port ellipticity ≤3mm.

[0035] 2. Coordinated control of welding deformation

[0036] The double-sided asymmetric bevel design reduces the filler volume by 30%, and combined with the inner anti-deformation support and water mist cooling, the longitudinal seam deformation is reduced to ≤4mm, with a weld penetration rate of 100%.

[0037] 3. Breakthrough in pipelining positioning accuracy

[0038] The template-based chemical installation enables the synchronous positioning of 12 connecting pipes, with CNC machining error of bolt holes ≤0.1mm, and the grouped alternating welding process ensures that the concentricity deviation of the connecting pipes is ≤1.5mm.

[0039] 4. Innovative design of irregular bevels

[0040] The double-sided semi-U-shaped bevel (0.5-1.5mm blunt edge, 8-12mm radius) solves the problem of root cleaning of 125-180mm thick stainless steel, reduces the welding filler amount by 40%, and achieves a 100% pass rate in penetrant / radiographic inspection. Attached Figure Description

[0041] Figure 1 Schematic diagram of the novel dehydrogenation reactor;

[0042] Wherein: 1-reduction zone, 2-reaction zone, 3-inner mesh, 4-outer mesh, 5-guide cone, 6-bottom conical support assembly, 7-feed inlet reinforcing forging;

[0043] Figure 2 Schematic diagram of the bottom conical support component;

[0044] Among them: 201-conical head (201a-upper flanged arc transition section, 201b-middle cone, 201c-lower flanged arc transition section), 202-outer mesh base, 203-inner mesh base, 204-catalyst outlet pipe;

[0045] Figure 3 Schematic diagram of the longitudinal joint bevel of the intermediate cone;

[0046] Figure 4 Schematic diagram of rigid linkage anti-deformation support;

[0047] Among them: 401-sector plate 1, 402-sector plate 2, 403-sector plate 3, 404-center plate 1, 405-center plate 2, 406-center plate 3, 407-support tube 1, 408-support tube 2, 409-support tube 3, 410-distance tube;

[0048] Figure 5 Schematic diagram of rigid fixing of longitudinal seam welding in the middle cone;

[0049] Among them: 501-intermediate cone, 502-cone longitudinal joint, 503-arc-shaped gantry reinforcement, 504-rigid linkage anti-deformation support;

[0050] Figure 6 Schematic diagram of the upper / lower flanged arc transition section and the bevel of the middle cone circumferential joint;

[0051] Figure 7 Schematic diagram of the lower flanged arc transition section and the circumferential groove bevel of the reinforcing forging at the feed inlet;

[0052] Figure 8 Schematic diagram of the bevel joint between the intermediate cone and the catalyst outlet nozzle;

[0053] Figure 9 Schematic diagram of auxiliary tooling for welding catalyst outlet pipe;

[0054] Among them: 901 template, 902 reinforcing rib plate, 903 nut, 904 stud;

[0055] Figure 10 Schematic diagram of template joint bevel;

[0056] Figure 11 Schematic diagram of the internal anti-deformation support for the catalyst outlet pipe;

[0057] Among them: 1101-support ring, 1102-support tube, 1103-support sector plate, 1104-center plate. Detailed Implementation

[0058] The technical solutions in the embodiments of the present invention will be clearly and completely described below. 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.

[0059] Example

[0060] The dehydrogenation reactor is the core equipment of the dehydrogenation unit. New types of dehydrogenation reactors (such as...) Figure 1 (As shown) It consists of a reduction zone and a reaction zone. The reaction zone includes an inner mesh, an outer mesh, a guide cone, and a bottom conical support assembly. The bottom of the reaction zone is the core structure of the device, the bottom conical support assembly (as shown). Figure 2 As shown in the figure, it mainly includes a conical head, an outer mesh base, an inner mesh base, and a catalyst outlet pipe.

[0061] A method for controlling the manufacturing precision of a novel bottom conical support assembly for a dehydrogenation device includes the following steps:

[0062] Step 1. Segmented manufacturing of the conical head:

[0063] 1) The conical head assembly is manufactured in three sections. The upper, approximately 300mm high, flanged arc transition section and the lower, approximately 250mm high, flanged arc transition section are each formed by integral forging. This provides an assembly and machining benchmark for the high coaxiality requirements of the entire conical assembly. The middle conical section is formed by pressing steel plate, reducing costs. This method avoids the drawbacks of significantly increased costs and material properties not meeting requirements caused by integral forging. It also serves as a benchmark for subsequent assembly and machining of the entire conical head assembly, ensuring the manufacturing precision of the entire conical head assembly.

[0064] 2) The upper and lower flanged arc transition sections of the forging are machined. The straight edge of the upper flanged arc transition section is left with a 10mm height allowance and is not removed for the time being. The outer dimensions of the flanged arc side are machined to meet the requirements of the drawing, and the bevel is not machined for the time being. The lower flanged arc transition section is machined to meet the requirements of the drawing, and the bevel is not machined for the time being.

[0065] 3) The middle cone is cut into three to four segments. The thickness of the steel plate should be at least 10mm, and the height should be 20mm. Each segment should have a 5mm allowance on one side. The single cone segments are cold-pressed on a special mold to ensure that the curvature and taper of each segment meet the requirements of the drawing. The maximum shape deviation of each cross section should be controlled to be no more than 6mm for outward convexity and inward concavity. The maximum shape deviation of outward convexity and inward concavity within the assembly position of the inner and outer mesh bases and within 50mm above and below them should be no more than 3mm. The sum of outward convexity and inward concavity of the same cross section should not exceed 6mm.

[0066] Step 2. Longitudinal seam welding and deformation suppression:

[0067] 1) Mark the cone-shaped lobes with assembly lines. Based on the assembly results, mark the longitudinal seam bevel lines and inspection points for the cone-shaped lobes. Considering the linear expansion coefficient of austenitic stainless steel, leave a shrinkage allowance of 3-4 mm for each longitudinal seam when marking the lines. That is, mark the assembly lines according to the theoretical outer circumference of the two ends of the cone plus the shrinkage allowance (e.g., (3-4) mm × number of lobes). Mark any areas with excessive curvature and ellipticity and recalibrate them to ensure that the dimensions of the area where the inner and outer mesh bases are welded and within 50 mm above and below them meet the above dimensional tolerance requirements. At the same time, ensure that the ellipticity of the two ends is ≤3 mm. After marking the assembly lines and calibration, machine the width allowance of the cone-shaped lobes and machine the longitudinal seam bevel (e.g., ...). Figure 3 As shown, a double-sided asymmetrical bevel is adopted. The outer side uses a variable-angle V-shaped bevel, which requires less filler and is beneficial for both TIG welding and SMAW operations. The inner side uses a V-shaped bevel, which facilitates local grinding at the root and subsequent SMAW operations. The cone lobes are reassembled to ensure that the taper and ellipticity of the cone meet the drawing and the above tolerance requirements. Any parts that exceed the tolerances are corrected a second time.

[0068] 2) After the dimensions of the cone-shaped segments are adjusted to meet the requirements, the assembly team will adjust the cone-shaped segments, controlling the ellipticity of the two ends of the cone to ≤3mm, leaving a gap of 3-4mm for each longitudinal seam, and using rigid linkage anti-deformation supports (such as...) on the inner side of the cone at 50mm from the upper and lower ends and in the middle of the cone height. Figure 4Reinforcement is carried out (using cross supports for the small opening and the middle, and star-shaped supports for the large opening, selected according to the diameter of the cone; star-shaped supports are used for diameters of 3500mm (inclusive) and above, and cross supports are used for diameters below 3500mm), ensuring that the longitudinal seam between the lobes is located at the middle slot of the fan-shaped plate, and the remaining parts of the longitudinal seam inside the cone are reinforced with arc-shaped gantry reinforcement (such as...). Figure 5 ).

[0069] 3) Weld the longitudinal seams between the cones from the outside. The cones should be upright with the larger opening facing down and the smaller opening facing up. Weld multiple longitudinal seams simultaneously. For the root, first use manual tungsten inert gas welding (TIG) to apply two passes of root pass, then use a φ3.2mm welding rod for welding. The welding parameters are shown in Table 1 below. To reduce welding shrinkage deformation, the oscillation amplitude should be controlled to not exceed 2.5 times the core diameter during welding.

[0070] Table 1 Welding parameters

[0071]

[0072] Welding should be continuous. To control the interpass temperature, water mist should be sprayed on the back side to cool the weld. Care should be taken not to allow the weld to cool too quickly; maintaining the interpass temperature between 50 and 100°C is ideal. In colder weather, air cooling can be used on the back side. All cooling measures must be performed on the back side of the weld.

[0073] After completing the front weld using this welding method, only minor grinding and root cleaning are required on the back side. This avoids excessive shrinkage on the back side due to excessive root cleaning, which could lead to cone deformation. The inner side of the longitudinal seam of the cone is welded using shielded metal arc welding (SMAW) according to the parameters shown in Table 1 above. The welding method and interpass temperature control are the same as for the outer side.

[0074] 4) After all longitudinal seams of the cone are welded and cooled to room temperature, the internal support components and arc-shaped gantry reinforcements can be removed. The longitudinal seams of the cone should be subjected to 100% PT and 100% RT tests according to the drawings and design documents to ensure that the welded joints are free of defects exceeding the standard. If welding defects are found in the welded joints, the above-mentioned process of adding anti-deformation supports should be repeated before rework.

[0075] 5) After the intermediate cone is manufactured, use the upper and lower flanged arc transition sections on the vertical lathe as aids to mark the intermediate cone, marking the orientation of the two ends of the cone (marking every 10°) and marking them. Use chalk lines to mark the orientation of the two ends. Measure the cone dimensions and, based on the actual measurement data, lay out the cone on the drawing software at a 1:1 scale. Determine the allowance to be removed from the large and small ends of the cone based on the theoretical dimensions in the layout drawing. Then, measure the dimensions of the area where the inner and outer mesh bases will be welded based on the layout results, and correct the layout drawing based on the measurement data. Then, select the position on the layout drawing that best matches (closest to) the dimensions of the inner and outer mesh bases as the reference to determine the positions of the large and small ends. Based on the corrected layout drawing, mark the cone again, marking the machining lines and inspection lines of the large and small ends of the cone, as well as the assembly position lines of the inner and outer mesh bases, and mark them. Based on the results of the line, the two ends of the cone are leveled and the excess material is removed by machining on a vertical lathe.

[0076] 6) On the vertical lathe, using the inner surface of the lower flanged arc transition section as a reference, adjust the relative position of the intermediate cone to it. Mount a dial indicator on the tool holder of the vertical lathe and slowly rotate it to measure the dimensions of the inner and outer mesh bases of the intermediate cone at the welding positions. Adjust the relative position of the intermediate cone and the lower flanged arc transition section to ensure that the ellipticity of the same cross-section of the area to be welded for the inner and outer mesh bases does not exceed 3mm, the concentricity of different cross-sections does not exceed 2mm, and the radial deviation along the cone surface is less than or equal to 1mm. Record the final dimensions of the areas to be welded for the inner and outer mesh bases in each direction. Machine a reference ring line on the surface of the large end of the intermediate cone. Mount the intermediate cone on the vertical lathe, using the reference ring line on the surface of the large end as a reference to find the center of the intermediate cone, and machine the circumferential bevel of the large end, ensuring a minimum blunt edge dimension of 3mm, and record the diameter at this blunt edge. Machine the corresponding bevel of the upper flanged arc transition section with the same diameter as the blunt edge of the large end of the intermediate cone.

[0077] 7) Assemble the upper flanged arc transition section and the middle cone using the blunt edges of the two components as the reference, controlling the misalignment to be ≤1mm, and using a U-shaped bevel with a smaller filling amount (e.g. Figure 6 As shown in Table 2), submerged arc welding, which is more efficient, is used. The welding parameters are shown in Table 2.

[0078] Table 2 Welding parameters

[0079]

[0080] The circumferential bevel at the junction of the lower flanged arc transition section and the reinforcing forging at the feed inlet (e.g.) Figure 7As shown in the figure, the assembly group reinforces the lower flanged arc transition section and the feed port forging. Welding is performed using manual tungsten inert gas welding (TIG) combined with shielded metal arc welding (SMAW), employing a variable-angle V-groove that is more conducive to TIG welding of the root pass. Welding parameters are shown in Table 3.

[0081] Table 3 Welding parameters

[0082]

[0083] 8) After the upper flanged arc transition section and the middle cone are welded and pass inspection, use the outer circle of the upper flanged arc transition section as a reference to machine the bevel of the small end of the middle cone, ensuring a minimum blunt edge size of 3mm, and record the diameter at this blunt edge. Machine the corresponding bevel of the lower flanged arc transition section with the same diameter as the blunt edge of the small end of the middle cone.

[0084] 9) Using the blunt edge of the middle cone and the lower flanged arc transition section as a reference, assemble the middle cone and the lower flanged arc transition section, controlling the misalignment to be ≤1mm, and using a U-shaped bevel with a smaller filling amount (e.g. Figure 6 As shown in Table 2), submerged arc welding, which is more efficient, is used. The welding parameters are shown in Table 2.

[0085] The forming method, process sequence, marking method, inspection method, positioning method, and reference datum of the cone are determined as key control points.

[0086] Step 3. Catalyst outlet pipe beveling and tooling assembly:

[0087] 1) The catalyst outlet pipes are located on the middle cone, between the inner mesh base and the outer mesh base. A total of 12 pieces are evenly distributed along the circumference. The relative positions of the catalyst outlet pipes are related to the uniform flow of the catalyst and are the key to avoiding catalyst aggregation, deactivation and coking.

[0088] 2) The large thickness and taper of the intermediate cone, combined with other factors, result in a maximum bevel depth of 125mm. The cone material is austenitic stainless steel, which has a high coefficient of thermal expansion, making it highly susceptible to welding deformation. This deformation can lead to deformation of the intermediate cone itself, affecting the subsequent processing and assembly of the inner and outer mesh bases. Therefore, it is necessary to design a regularly shaped welding bevel with a smaller filler volume to reduce the amount of filler and prevent weld shrinkage deformation caused by excessive filler volume.

[0089] 3) For this purpose, the following were designed: Figure 8The welding bevel shown is a double-sided semi-U-shaped bevel symmetrical along the conical surface, with a bevel dimension of 1±0.5mm, a gap of 3±1mm, and a bottom radius of 10mm. This bevel ensures complete penetration when using argon arc welding for the root pass, and prevents defects such as weld beads and undercut on the back side. This bevel facilitates welding operations, makes it easy to ensure weld quality, and requires less filler, greatly reducing the risk of welding deformation.

[0090] 4) To ensure the coaxiality and circumferentially distributed relative positions of the 12 catalyst outlet nozzles, the outer circle of the straight edge section of the lower flanged arc transition section was used as a reference on the manufactured conical head assembly. Programming was then performed on a CNC floor-type boring and milling machine to CNC machine the openings for the 12 catalyst outlets. The conical head assembly was modeled in 3D software, based on... Figure 8 The bevel is drawn and then created using the sweep cut function in 3D software. The model file is saved in a format supported by the CNC floor-type milling machine and copied to the control computer of the CNC floor-type milling machine. Using the outer circle of the straight edge section of the lower curved transition section as a reference, the machine is started to process the bevel according to the model. The bevel created using this method has regular dimensions and precise relative positions, ensuring that the center circle of the 12 catalyst outlet openings is coaxial with the lower curved transition section, facilitating the subsequent assembly of the connecting pipes.

[0091] Step 4. Simultaneous assembly and pipe connection of template chemical equipment:

[0092] 1) The simultaneous assembly of 12 catalyst outlet pipes utilizes an advanced assembly positioning and anti-deformation tooling. This tooling consists of a 901 template, a 902 reinforcing rib, a 903 nut, and a 904 stud. (See attached image.) Figure 9 On the template, machine bolt holes matching the flanges for the theoretical positions of the 12 catalyst outlet pipes as shown in the drawings. Machine four bolt holes at each pipe location. These bolt holes are used to secure the flanges, and their dimensions should match those on the flanges. All bolt holes are CNC machined to the same reference, and their relative positions fully conform to the drawing requirements. Install anti-deformation supports (such as...) on the inner side of the intermediate cone where the welded pipe will be installed. Figure 11The anti-deformation support ring is welded 100mm below the section to be welded, and an anti-deformation support consisting of a support pipe, a support sector plate, and a center plate is welded 100mm above it. The support sector plate avoids the pipe connection position. The anti-deformation support ring is welded and fixed to the inner wall of the cone using stainless steel reinforcing plates. The flange of the catalyst outlet pipe is tightened to the template with studs and nuts. The pipe and template assembly is then assembled with the cone, ensuring the bevel gap between each catalyst outlet pipe and the cone. Since all bevels are CNC machined, ensuring the gap guarantees the coaxiality with the conical head port. After assembly to the appropriate position, the template and cone are reinforced by welding reinforcing plates. The positioning bolt holes on the template ensure the relative position of each catalyst outlet pipe. The combined effect of the reinforcing plates and bolts and nuts prevents the catalyst outlet pipe from shifting during welding.

[0093] 2) The 901 template is made of four 60mm thick ring plates welded and processed together. First, it is cut using CNC gas cutting, and then a double-sided V-shaped bevel is created, as shown below. Figure 10 As shown; deformation should be controlled during ring plate welding, mainly by using small-gauge welding rods, alternating welding on both sides, and having four people weld simultaneously to reduce deformation. The main measures are as follows: For the root pass welding, use φ3.2mm welding rods. When welding to 1 / 3 of the bevel depth on the front side, clean the root and weld from the back side. When welding to 1 / 3 of the bevel depth on the back side, flip it over and weld the middle 1 / 3 thickness on the front side. At this time, φ4.0mm welding rods can be used. Repeat this process until all welding is completed. During the welding process, care should be taken not to oscillate while welding. The thickness of each weld layer should not exceed 3mm. At the same time, use fast short arc welding and control the interpass temperature to not exceed 200℃ to prevent thermal stress and aggravate welding deformation. Secondly, the lower surface of the template (the side in contact with the sealing surface of the catalyst outlet flange) should be machined on a vertical lathe until it is flat to prevent the rough and uneven surface of the template from damaging the flange sealing surface. The outer circle of the template should be machined on a vertical lathe, and then the template should be CNC machined with the outer circle of the template as a reference to open the positioning bolt holes. The template should be machined in one step using computer programming.

[0094] 3) Welding of 12 catalyst outlet nozzles to thick stainless steel conical heads, including the following aspects: 1. The conical head is placed upright (large opening facing down), and two passes of manual tungsten inert gas (TIG) welding are performed from the outside, followed by argon purging on the back. A φ2.4mm cerium tungsten electrode and a φ2.0mm TIG welding wire are used. The welding current for the first pass is 60-80 amps, with an oscillation amplitude of less than 2mm to avoid defects such as burn-through or weld beads on the back. After the first pass, the weld bead is subjected to 100% PT testing after the temperature drops below 50℃. The welding current for the second pass is 80-110 amps. After the second pass, the weld bead is subjected to 100% PT testing again after the temperature drops below 50℃. 2. Welding is performed from the outside using φ3.2mm welding rods, with multiple layers, multiple passes, and fast welding. For rapid short arc welding, water mist cooling can be used on the back side during welding to maintain the interpass temperature between 50 and 100°C, which can minimize welding thermal stress. After the root pass, the welding position is either flat or vertical, and the vertical upward welding method is adopted. Each weld pass should be staggered from the previous weld pass by at least 30mm. The arc should be paused for 2-3 seconds at the arc initiation point to avoid arc cracking. The upward vertical welding swing amplitude should not exceed twice the diameter of the welding core. 3.12 catalyst outlet pipes should first be manually tungsten inert gas (TIG) welded for the root pass. Then, they should be divided into 3 groups, and 4 welders should weld the 4 evenly distributed pipes at the same time each time, keeping the welding progress consistent. Welding of the first group should be stopped when the bevel depth is 1 / 4, and the welding of the second and third groups of pipes should be carried out successively. This process should be repeated until the outer side is completely welded.

[0095] Step 5. Finishing of the cone contact surface

[0096] 1) Before welding the inner side, the back of the root pass should be 100% PT tested. For areas with poor fusion, use a straight grinder with an arc-shaped tip to grind the area to be welded to make the shape regular and easy to weld. Use φ3.2mm welding rods for inner side welding, and the welding sequence and control measures are the same as for outer side welding.

[0097] 2) The inner and outer mesh bases are formed by integral forging. Rough machining is performed first, with a 10mm allowance for the inner diameter of the base, a 5mm allowance for the height of the base support surface, and a 15mm allowance for the outer diameter of the base. The 10mm allowance for the contact surface with the middle cone is not machined at this time.

[0098] 3) Place the conical head assembly with the large opening facing upwards on the vertical lathe operating table and adjust it to be coaxial with the rotation center. Install a dial indicator on the tool post. Using the upper flanged arc transition section as a reference, measure the areas to be welded on the inner and outer mesh bases again. Record the dimensions every 10° and every 30mm along the conical surface in the height direction. Perform proportional layout based on the measurement data and compare it with the previous measurement data. The thickness of the intermediate cone base material in the welding area of ​​the inner and outer mesh bases was measured, the thickness data was recorded, and the thickness allowance was analyzed. Based on the layout drawing with the latest dimensional measurement data, the processing scheme for the intermediate cone in the welding area of ​​the inner and outer mesh bases was determined. Using the straight edge of the upper flanged arc transition section as a reference, the cone surface of the intermediate cone in the welding area of ​​the inner and outer mesh bases was processed, and the cone thickness was measured continuously. The processing was completed when the cone surface was smooth. Because the cone was cold-pressed, the thinning amount was approximately 1-2 mm, and the remaining thickness allowance was sufficient to compensate for dimensional tolerances caused by the ellipticity, outward convexity, and inward concavity of the cone in this area. The steps between the cone surface and the surrounding base material caused by processing were processed at a transition ratio not exceeding 1:5.

[0099] 4) Based on the machining dimensions of the conical surfaces of the inner and outer mesh bases on the intermediate cone, machine the inner and outer mesh bases respectively, removing the outer circle allowance (the allowance is determined according to the machining dimensions of the intermediate cone), and machine the outer contours to ensure that their dimensions match the dimensions of the intermediate cone. Simultaneously, remove the allowance from both the inner and outer mesh bases.

[0100] 5) For the assembly of the inner and outer mesh bases and the intermediate cone, since all mating surfaces are machined, their coaxiality and conical surface fit can be fully guaranteed. Fillet welds are made between the inner and outer mesh bases and the conical head using manual tungsten inert gas (TIG) welding. The upper circumference is welded, leaving a 20mm unwelded section at the bottom. After welding, a round-head straight grinder is used to grind the upper weld surface in contact with the catalyst, creating a smooth, concave transition, free from grooves, sharp edges, etc., that could impede catalyst flow.

[0101] 6) Perform final machining on the entire conical head assembly. Using the outer circle of the upper flanged arc transition section as a reference, remove the excess material at the large end of the flanged arc transition section and machine the bevel. Simultaneously, machine the inner circle of the inner and outer mesh bases, removing excess material, and machine the support surfaces of the inner and outer mesh bases, removing excess material, and machining until it meets the drawing requirements. The upper and lower ends of the bottom conical head assembly manufactured using this method, as well as the inner and outer mesh bases, are 100% coaxial, and the flatness of the support surfaces of the inner and outer mesh bases can be controlled to below 0.02mm.

[0102] As can be seen from the above examples:

[0103] This method involves manufacturing conical heads in segments (upper / lower integral forging reference sections + segmented pressed middle sections), using asymmetrical beveling and combined support to control longitudinal seam welding deformation, and machining the double-sided semi-U-shaped catalyst nozzle beveling using 3D CNC machining. Twelve nozzles are then assembled and welded in groups using template chemical fittings. Finally, the outer circle of the upper transition section is used as a reference to machine the conical contact surface, achieving manufacturing precision control of coaxiality ≤1.5mm and support surface flatness ≤0.05mm.

[0104] The above are merely a few preferred embodiments of the present invention, described in a relatively specific and detailed manner, but they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention.

Claims

1. A method for controlling the manufacturing precision of a novel conical support assembly at the bottom of a dehydrogenation device, characterized in that, Includes the following steps: (1) The conical head assembly is manufactured in three sections: the upper flanged arc transition section is formed by integral forging and has a height of 250-350mm, and the lower flanged arc transition section is formed by integral forging and has a height of 200-300mm. The two sections serve as the assembly and processing reference for the intermediate cone. The intermediate cone is formed by pressing 3-4 steel plates, with a thickness of 10-15mm reserved for each plate, a width of 3-10mm reserved on each side, and a height of 15-20mm reserved. (2) The longitudinal seam of the middle cone is welded with a double-sided asymmetric bevel, with the outer side being a variable angle V-shaped bevel and the inner side being a V-shaped bevel. Anti-deformation combined support is set on the inner side of the cone 30-80mm from the upper and lower ports. The support type is selected according to the cone diameter, either cross support or star support. The interpass temperature is controlled at 50-100℃ during the welding process. (3) The catalyst outlet pipe bevel adopts a double-sided semi-U-shaped bevel with a blunt edge size of 0.5-1.5mm, a gap of 2-4mm, a bottom R angle of 8-12mm, and a bevel depth of 40%-60% of the cone thickness; (4) 12 catalyst outlet pipes are assembled simultaneously using template tooling. The tooling includes a template with positioning bolt holes and reinforcing ribs. The template thickness is 50-80mm. The bolt holes are CNC machined according to the pipe position coordinates marked on the design drawings. (5) Based on the actual survey results of the inner and outer mesh base assembly areas, determine the processing scheme. On the vertical lathe, take the outer circle of the upper flange arc transition section as the reference and CNC process the conical contact surface to ensure that the coaxiality does not exceed 1.5mm.

2. The control method according to claim 1, characterized in that, In step (1), when the middle cone is pressed into segments, a special fan-shaped template is used to check the curvature, and the maximum shape deviation within the upper and lower 30-80mm range of the inner mesh base assembly area does not exceed 4mm.

3. The control method according to claim 1, characterized in that, In step (2), the width of the arc plate of the anti-deformation combined support is 100-200mm, the longitudinal seam gap is controlled at 2-5mm, and welding is carried out with a welding rod of 2.5-4.0mm in diameter and the welding rod swing amplitude does not exceed 10mm.

4. The control method according to claim 1, characterized in that, In step (3), the processing of the double-sided semi-U-shaped bevel is carried out by three-dimensional modeling to generate a CNC program, and the outer circle of the straight edge section of the lower flange arc transition section is used as the reference for positioning, and the bevel symmetry deviation is ≤1.5mm.

5. The control method according to claim 1, characterized in that, In step (4), the template is made of 3-5 ring plates welded together. The welding process is a double-sided alternating welding process, and the temperature between welding passes does not exceed 250°C.

6. The control method according to claim 1, characterized in that: In step (4), when welding the catalyst outlet pipe, first complete the two-layer argon arc welding of all pipes as the root, then divide the 12 pipes into 2-4 groups, with 3-6 pieces in each group, and have multiple welders simultaneously weld to a bevel depth of 20%-30% before rotating the work groups.

7. The control method according to claim 6, characterized in that: The argon arc welding process involves applying a current of 50-100 amperes for the first layer and 70-130 amperes for the second layer. After each layer is welded, the temperature is lowered to below 60°C and a penetration test is performed.

8. The control method according to claim 1, characterized in that: In step (5), the flatness of the inner mesh base and the outer mesh base support surface after processing shall not exceed 0.05mm, and the local gap between them and the cone contact surface shall not exceed 1.0mm.

9. The control method according to claim 1, characterized in that: During the welding process in step (2) or step (3), the back of the weld is cooled by water mist, and the water mist spraying distance is 150-400mm.

10. The control method according to claim 1, characterized in that: The final ellipticity of the conical head assembly port shall not exceed 3mm, and all longitudinal and circumferential seams shall be subjected to radiographic and penetrant testing in accordance with NB / T47013 standard.

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