Manufacturing precision control method for bottom conical supporting assembly of dehydrogenation device with novel structure

Abstract

The invention relates to the field of chemical container manufacturing, and discloses a manufacturing precision control method for a bottom conical supporting assembly of a dehydrogenation device of a novel structure. The method comprises the following steps: (1) dividing a conical end socket into an upper / lower forging transition section and 3-4 compression-molded middle-section cones, reserving allowance and checking curvature; (2) longitudinal joints are welded through double-sided asymmetric grooves, an anti-deformation support is arranged on the inner side, and the temperature between tracks is controlled to be 50-100 DEG C; (3) the catalyst connecting pipe adopts a double-sided semi-U-shaped groove, and three-dimensional modeling numerical control machining ensures that the degree of symmetry is smaller than or equal to 1.5 mm; (4) 12 connecting pipes are synchronously assembled through a template tool with positioning bolt holes, and grouped and alternately welded; and (5) the outer circle of the upper transition section serves as the reference, and the contact face of the cone is subjected to numerical control machining to ensure that the coaxiality is smaller than or equal to 1.5 mm. According to the method, the problems that a large-thickness cone is poor in welding permeability, the precision of a scalloped segment tailor-welded conical end socket is difficult to control, the positioning precision of multiple connecting pipes is low, and welding deformation is difficult to control are solved, and the planeness and concentricity of the conical supporting assembly are remarkably improved.

Description

Technical Field

[0001] The invention relates to the technical field of chemical container manufacturing technology, and particularly discloses a manufacturing precision control and welding deformation prevention process for a conical support component at the bottom of a dehydrogenation device with a new structure. Background Art

[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, the domestic demand for propylene has continued to grow. The propane dehydrogenation process (PDH) has become an important technology for increasing propylene production and 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, and the reaction temperature is between 600℃ and 700℃. The catalyst is the core of the reaction, affecting the reaction efficiency and product selectivity. It has always faced problems such as high energy consumption and easy coking and deactivation of the catalyst.

[0004] The bottom of the dehydrogenation reactor with a new structure adopts a conical support structure. The inner and outer nets are supported by the inner net base and the outer net base respectively, which are in contact with the conical surface of the bottom conical head. The catalyst outlet is located in the conical area between the inner and outer nets. This structure improves the fluidity and recycling of the catalyst and reduces the chance of its coking and deactivation.

[0005] However, the development of the new structure has greatly increased the manufacturing difficulty, because both the inner and outer nets are supported by the bottom conical support assembly. In order to support the inner and outer net assemblies that are more than 20 meters long and weigh about 30-40 tons, and ensure a uniform 16mm gap between the top of the outer net and the inner wall of the shell to meet the stuffing box structure, the flatness of the bottom conical support assembly of the structure and its concentricity with the main axis of the equipment are extremely high. Therefore, the bottom conical support assembly of the new structure is the most critical component of this device. Ensuring the manufacturing accuracy of this assembly is the most critical link to maximize its support for the inner and outer nets, ensure the verticality and straightness of the equipment, the installation accuracy of the inner and outer nets, and improve the uniformity of feed distribution and the recovery rate of the catalyst.

[0006] The structure of a conical head differs significantly from that of a traditional elliptical head. Currently, there are two common methods for forming a cone: integral forging and steel plate pressing. Due to the large taper, the large difference in diameter between the large and small openings, and the total height exceeding 3000mm, integral forging is extremely expensive. Furthermore, excessively thick austenitic stainless steel will result in material properties that fail to meet standard requirements. Therefore, the cone can only be manufactured through steel plate pressing.

[0007] However, the dimensions of each petal can't be guaranteed to be completely consistent during cone formation, and there are certain assembly errors when aligning multiple petals. The cone welding process also introduces some shrinkage and deformation. Since the cone is the primary support for the inner and outer mesh components, ensuring the correct dimensions after welding is paramount. Key manufacturing issues include ensuring the proper fit between the cone's inner wall (pressed from steel plate) and the inner and outer mesh bases (formed from forgings). Determining the concentricity of the catalyst nozzle and designing and processing the grooves also present significant challenges.

[0008] Currently, the most effective method for full penetration welding of thick stainless steel is double-sided welding or back root cleaning welding. However, due to the excessive thickness and distance limitations, large-sized grooves cannot be made, resulting in limited vision of the welders, making it impossible to achieve single-sided welding and double-sided forming, or relying too much on the skills of the personnel, and unable to solve the problems encountered in this project.

[0009] Austenitic stainless steel has a large linear expansion coefficient and is prone to welding deformation during welding. The catalyst outlet pipe is arranged symmetrically along the circumference and needs to be connected to the pipeline on site. The traditional number line and grouping method cannot ensure the relative position of the pipes. The method of assembling and welding more than a dozen pipes separately will increase the welding deformation rate and cause the relative distance and concentricity of the pipes to be out of tolerance. Summary of the Invention

[0010] The purpose of the present invention is to provide a method for controlling the manufacturing accuracy of the conical support assembly at the bottom of a new structure dehydrogenation reactor. Through the coordination of four technologies, namely, the establishment of a manufacturing benchmark for cone segments, the anti-deformation of longitudinal seam welding, the precise positioning and groove design of the catalyst pipe, and the collaborative processing of the contact surface, high-precision manufacturing of large-thickness conical assemblies can be achieved.

[0011] Specifically include:

[0012] 1. Taking the upper / lower transition section of the integral forging as the benchmark, control the curvature and assembly accuracy of the petal cone;

[0013] 2. Use asymmetric grooves and combined supports to suppress longitudinal seam deformation;

[0014] 3. Synchronously assemble multiple pipes based on template-based chemical equipment, and combine double-sided half-U-shaped grooves to solve the problem of welding penetration;

[0015] 4. Use the outer circle of the upper transition section as the reference to process the cone contact surface, ensuring that the coaxiality with the inner and outer net base is ≤1.5mm.

[0016] In order to achieve the above object, the present invention includes the following technical solutions:

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

[0018] (1) The conical head assembly is manufactured in three sections: the upper flange arc transition section is formed by integral forging and has a height of 250-350 mm, and the lower flange arc transition section is formed by integral forging and has a height of 200-300 mm. The two sections serve as the assembly and processing basis of the middle cone; the middle cone is divided into 3-4 petals pressed by steel plates, with a 10-15 mm margin reserved for the thickness of each petal, a 3-10 mm margin reserved for one side of the petal in the width direction, and a 15-20 mm margin reserved for the height direction;

[0019] (2) The longitudinal seam welding of the middle cone adopts a double-sided asymmetric groove, of which the outer side is a variable angle V-shaped groove and the inner side is a V-shaped groove. Anti-deformation combined supports are set 30-80mm away from the upper and lower ports on the inner side of the cone. The support type is selected as a cross support or a Pozigzag support according to the cone diameter. The interpass temperature during the welding process is controlled at 50-100℃;

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

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

[0022] (5) Taking the inner and outer net base assembly areas as the reference, and the outer circle of the upper flanging arc transition section as the reference on the vertical lathe, CNC machine the cone contact surface to ensure that the coaxiality does not exceed 1.5 mm.

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

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

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

[0026] Furthermore, in the above control method, in step (4), the template is welded from 3-5 ring plates, and a double-sided alternating welding process is adopted during welding, 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 pipe, first complete the two-layer argon arc welding primer for all pipes, and then divide the 12 pipes into 2-4 groups, each group of 3-6 pipes is welded synchronously by multiple welders until the groove depth reaches 20%-30%, and then the working group is rotated.

[0028] Furthermore, in the above control method, the current of the first layer of argon arc welding is 50-100 amperes, and the current of the second layer is 70-130 amperes. After each layer of welding, the temperature is lowered to below 60°C and a penetration test 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 0.05 mm, and the local gap with the cone contact surface does not exceed 1.0 mm.

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

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

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

[0033] 1. Segmented manufacturing benchmark optimization

[0034] The upper / lower integral forging transition section is used as the assembly reference, the middle section is divided into petals and pressed to reserve a margin, and the curvature is controlled in combination with a special template to solve the concentricity problem of large-taper components, and the port ovality is ≤3mm.

[0035] 2. Collaborative control of welding deformation

[0036] The double-sided asymmetric groove design reduces the filling volume by 30%. Combined with the inner anti-deformation support and water mist cooling, the longitudinal seam deformation is compressed to ≤4mm, and the welding penetration rate is 100%.

[0037] 3. Breakthrough in takeover positioning accuracy

[0038] The template chemical equipment realizes the synchronous positioning of 12 connecting pipes, the CNC machining error of the bolt holes is ≤0.1mm, and the group alternating welding process makes the concentricity deviation of the connecting pipe ≤1.5mm.

[0039] 4. Innovative design of special-shaped groove

[0040] Double-sided semi-U-shaped groove (blunt edge 0.5-1.5mm, R angle 8-12mm) solves the root cleaning problem of 125-180mm thick stainless steel, reduces welding filling volume by 40%, and has a 100% pass rate for penetration / radiographic inspection. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0042] Among them: 1-reduction zone, 2-reaction zone, 3-inner net, 4-outer net, 5-guide cone, 6-bottom cone support assembly, 7-feed port reinforcement forging;

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

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

[0045] Figure 3 Schematic diagram of the longitudinal seam groove of the middle 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 the rigid fixation of the longitudinal seam welding of the middle cone;

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

[0050] Figure 6 Schematic diagram of the upper / lower flange arc transition section and the middle cone annular seam groove;

[0051] Figure 7 Schematic diagram of the lower flanging arc transition section and the feed inlet reinforcement forging annular seam groove;

[0052] Figure 8 Schematic diagram of the annular groove between the middle cone and the catalyst outlet pipe;

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

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

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

[0056] Figure 11 Schematic diagram of the anti-deformation support inside the catalyst outlet pipe welding installation;

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

[0058] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0059] Example

[0060] The dehydrogenation reactor is the core equipment of the dehydrogenation unit. The new structure of the dehydrogenation reactor (such as Figure 1 As shown) consists of a reduction zone and a reaction zone, wherein the reaction zone includes an inner network, an outer network, 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 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 accuracy of a conical support assembly at the bottom of a novel dehydrogenation device comprises the following steps:

[0062] Step 1. Manufacturing the conical head in sections:

[0063] 1) The conical head assembly is manufactured in three sections. The upper, approximately 300mm high, curved flanging transition section and the lower, approximately 250mm high, curved flanging transition section are each formed using integral forgings, providing a benchmark for assembly and processing to meet the high coaxiality requirements of the entire conical assembly. The middle cone is pressed from steel plate to reduce costs. This method avoids the drawbacks of using integral forgings, which can lead to significant cost increases and material properties that do not meet usage requirements. It also serves as a benchmark for subsequent assembly and processing of the entire conical head assembly, ensuring the manufacturing accuracy of the entire conical head assembly.

[0064] 2) Process the upper and lower flanging arc transition section forgings, leaving a 10mm height margin on the straight side of the upper flanging arc transition section and not removing it temporarily, and process the outer dimensions of the flanging arc side to meet the requirements of the drawing, and the groove is not processed temporarily; process the lower flanging arc transition section to meet the requirements of the drawing, and the groove is not processed temporarily.

[0065] 3) The middle part of the cone is divided into three to four petals. The thickness of the steel plate should leave a margin of at least 10mm, a margin of 20mm in the height direction, and a margin of 5mm on each side for each petal. The single cone petals are cold-pressed on a special mold to ensure that the curvature and taper of each petal meet the requirements of the drawing, and the maximum shape deviation of each cross section is controlled to be no more than 6mm for convexity and concavity. The maximum shape deviation of the inner and outer mesh base assembly positions and within 50mm above and below should not be more than 3mm for convexity and concavity. The sum of the convexity and concavity of the same cross section shall not exceed 6mm.

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

[0067] 1) Perform numbering on the cone petals. According to the result of the numbering, mark the longitudinal seam bevel line and inspection points of the cone petals. Considering the linear expansion coefficient of austenitic stainless steel, leave a shrinkage allowance of 3 to 4 mm for each longitudinal seam when numbering. That is, perform numbering according to the theoretical outer circumference of the two ends of the cone plus the shrinkage allowance (for example, (3 to 4) mm × the number of petals). Mark the parts with excessive curvature and ovality, and re-calibrate them to ensure that the area for welding the inner and outer mesh bases and the dimensions within 50 mm above and below meet the above-mentioned dimensional tolerance requirements. At the same time, ensure that the ovality of the two ends is ≤3 mm. After the numbering and calibration, the width allowance of the cone petals is removed by machining, and the longitudinal seam bevel is machined (such as Figure 3 (As shown in the figure), a double-sided asymmetric groove is used. The outer side adopts a variable-angle V-shaped groove, which reduces the fill volume and is conducive to argon arc welding and metal arc welding. The inner side adopts a V-shaped groove to facilitate local root grinding and subsequent metal arc welding. The cone petals are reassembled to ensure that the cone's taper and ovality meet the drawings and the above tolerance requirements. Any areas that exceed the tolerance are re-adjusted.

[0068] 2) After the cone petal size is adjusted to meet the requirements, the assembly group aligns the cone petals, controls the ovality of the two ends of the cone to be ≤3mm, leaves a gap of 3-4mm for each longitudinal seam, and adopts a rigid linkage anti-deformation support (such as Figure 4) for reinforcement (cross support is used for the small opening and the middle, and 'P' support is used for the large opening, selected according to the diameter of the cone, 'P' support is used for diameters above 3500mm (including 3500mm), and cross support is used for diameters below 3500mm), ensuring that the longitudinal seam between the petals is located at the middle slot of the fan-shaped plate, and arc-shaped gantry bars are used to reinforce the rest of the longitudinal seam inside the cone (such as Figure 5 ).

[0069] 3) First, weld the longitudinal seams between the cones from the outside. Place the cones upright with the large opening facing downward and the small opening facing upward. Weld multiple longitudinal seams simultaneously. Use manual tungsten inert gas arc welding twice at the root, then weld with a φ3.2mm electrode. The welding parameters are shown in Table 1 below. To reduce welding shrinkage deformation, the swing amplitude should be controlled to no more than 2.5 times the core diameter during welding.

[0070] Table 1 Welding parameters

[0071]

[0072] Welding should be continuous during the process. To control the temperature between passes, spray water mist on the back of the weld to cool it. Be careful not to cool the weld too quickly. Maintain the interpass temperature between 50-100°C. In cold weather, air cooling can be used on the back. All cooling measures must be performed on the back of the weld.

[0073] After completing the front weld using this method, only minor grinding and root cleaning is required on the backside. This prevents excessive backside shrinkage and cone deformation caused by excessive root cleaning. The inside of the cone's longitudinal seam is welded using arc welding using the parameters shown in Table 1. The welding method and interpass temperature control methods are the same as those for the outside.

[0074] 4) After all longitudinal seams of the cone have been welded and cooled to room temperature, the internal supports and curved gantry reinforcements may be removed. 100% PT and 100% RT testing shall be performed on the longitudinal seams of the cone according to the drawings and design documents to ensure that the welded joints are free of defects exceeding the standard. If welded joints have welding defects, the above anti-deformation support process shall be repeated before rework.

[0075] 5) After the middle cone is manufactured, the upper and lower flanging arc transition sections are used as auxiliary components on a vertical lathe to mark the middle cone. The positions of the two ends of the cone are marked (marked every 10°) and marked. The positions of the two ends are marked with powder lines. The dimensions of the cone are measured and the cone is laid out on the drawing software at a 1:1 ratio based on the actual measured data. The allowances that need to be removed from the large and small ends of the cone are determined based on the theoretical dimensions in the lofting diagram. The dimensions of the area where the inner and outer mesh bases are to be welded are measured based on the lofting results. The lofting diagram is corrected based on the measured data. The position in the lofting diagram that is closest to the dimensions of the inner and outer mesh bases is selected as the reference to determine the positions of the large and small ends. The cone is then marked again based on the corrected lofting diagram. The processing 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, are marked and marked. According to the results of line No., the two ends of the cone are leveled and the excess is removed by vertical lathe processing.

[0076] 6) Adjust the relative position of the intermediate cone with the lower flanged curved transition section using the inner surface as a reference. Mount a micrometer on the vertical lathe toolholder and slowly rotate it to measure the dimensions of the inner and outer mesh bases of the intermediate cone where welding will be performed. Adjust the relative position of the intermediate cone with the lower flanged curved transition section to ensure that the ovality of the same section in the area where the inner and outer mesh bases will be welded does not exceed 3mm, the concentricity of different 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 area where the inner and outer mesh bases will be welded in all directions. Machine a reference line on the surface of the large end of the intermediate cone. Clamp the intermediate cone to the vertical lathe. Using the reference line on the large end surface as a reference, locate the center of the intermediate cone. Machine the circumferential groove of the large end, ensuring a minimum blunt edge dimension of 3mm. Record the diameter of this blunt edge. Machine the corresponding groove of the upper flanged curved transition section to the same diameter as the blunt edge of the intermediate cone's large end.

[0077] 7) Assemble the upper flange arc transition section and the middle cone with the blunt edge of the two parts as the reference, control the misalignment ≤1mm, and use a U-shaped groove with a small filling amount (such as Figure 6 As shown in Table 2, more efficient submerged arc welding is used. The welding parameters are shown in Table 2.

[0078] Table 2 Welding parameters

[0079]

[0080] Process the annular groove at the junction of the lower flange arc transition section and the feed inlet reinforcement forging (such as Figure 7The assembly team welded the lower flanged arc transition section and the feed port reinforcement forging using manual tungsten inert gas arc welding and stick arc welding, using a variable-angle V-groove that is more conducive to argon arc welding primer. The 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 tested, the groove of the small end of the middle cone is machined based on the outer circle of the upper flanged arc transition section, ensuring a minimum blunt edge size of 3mm and recording the diameter of the blunt edge. The corresponding groove of the lower flanged arc transition section is machined with the same size as the blunt edge diameter of the small end of the middle cone.

[0084] 9) Use the blunt edge of the middle cone and the lower flanging arc transition section as the reference to assemble the middle cone and the lower flanging arc transition section, control the misalignment ≤ 1mm, and use a U-shaped groove with a smaller filling amount (such as Figure 6 As shown in Table 2, more efficient submerged arc welding is used. The welding parameters are shown in Table 2.

[0085] Determine the cone forming method, process sequence, numbering method, detection method, positioning method, benchmark, etc. as key control points.

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

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

[0088] 2) The middle cone is thick and tapered, and these two factors combined result in a groove with a maximum cross-section depth of 125mm. The cone is made of austenitic stainless steel, which has a high coefficient of thermal expansion. This easily causes welding deformation, which in turn causes deformation of the middle cone, affecting the subsequent processing and assembly of the inner and outer mesh bases. Therefore, it is necessary to design a weld groove with a regular shape and a small filler volume to reduce the filler volume and avoid shrinkage deformation of the weld caused by excessive filler volume.

[0089] 3) For this purpose, we designed Figure 8The weld groove shown, defined by the midpoint of the cone's thickness, is a double-sided, semi-U-shaped groove symmetrical along the cone's surface. Its blunt edge dimensions are 1±0.5mm, its gap is 3±1mm, and its bottom radius is 10mm. This ensures complete penetration during argon arc welding without defects such as weld beading and undercutting on the backside. This groove facilitates welding and ensures weld quality. The low filler requirement significantly reduces the risk of weld deformation.

[0090] 4) In order to ensure the coaxiality of the 12 catalyst outlet pipes and their relative positions evenly distributed along the circumference, the outer circle of the straight edge section of the lower flanged arc transition section of the manufactured conical head assembly is used as the reference for programming on a CNC floor boring and milling machine, and the openings for the 12 catalyst outlets are CNC machined. The conical head assembly is modeled on 3D software, based on Figure 8 The groove was drawn and cut using the scan-and-cut function in the 3D software. The model file was saved in a format supported by the CNC floor-type boring and milling machine and copied to the machine's control computer. Based on the model, the machine started beveling the groove, using the outer circle of the straight edge of the lower curved transition section as a reference. This method produced grooves with regular dimensions and precise relative positioning, ensuring that the center circle of the 12 catalyst outlet openings was coaxial with the lower curved transition section, facilitating subsequent pipe assembly.

[0091] Step 4. Synchronous assembly of template and chemical equipment:

[0092] 1) 12 pieces of catalyst outlet pipes are assembled at the same time, using an advanced assembly positioning and anti-deformation tooling. The auxiliary tooling consists of 901 template, 902 reinforcement plate, 903 nut, 904 stud, see Figure 9 . According to the theoretical positions of the 12 catalyst outlet pipes on the drawing, the bolt holes that match the pipe flanges are machined on the template. 4 bolt holes are machined at each pipe position. The bolt holes are used to fix the flanges. The size of the bolt holes should be consistent with the bolt holes on the flanges. All the bolt holes are CNC machined according to the same reference. Their relative positions are in full compliance with the drawing requirements. Anti-deformation supports are welded to the inner side of the middle cone where the welded pipe is to be installed (such as Figure 11), wherein an anti-deformation support ring is welded 100mm below the position of the pipe to be welded, and an anti-deformation support composed of a support pipe, a support fan plate and a center plate is welded 100mm above the position. The support fan plate avoids the position of the pipe connection, and the anti-deformation support ring is welded and fixed to the inner wall of the cone with a stainless steel rib plate. The flange of the catalyst outlet pipe is tightened with studs and nuts to the template, and the pipe and template assembly are assembled with the cone to ensure the groove gap between each catalyst outlet pipe and the cone. Since all the grooves are CNC machined, ensuring the gap can ensure its coaxiality with the conical head port. After assembly to the appropriate position, the template and the cone are welded and reinforced with a reinforcing rib plate. The positioning bolt holes on the template can ensure the relative position of each catalyst outlet pipe. The combined effect of the reinforcing rib plate and the bolts and nuts can prevent the catalyst outlet pipe from shifting during the welding process.

[0093] 2) The 901 template is made of 4 ring plates with a thickness of 60mm, welded and processed. First, the CNC gas cutting is used to cut the material and the double-sided V-shaped groove is cut by gas cutting, as shown below Figure 10 As shown in the figure, deformation should be controlled during ring plate tailor welding. This can be reduced primarily by using small-gauge electrodes, alternating between two sides, and four people welding simultaneously. The main measures are as follows: A φ3.2mm electrode is used for the bottom welding. When the front groove reaches 1 / 3 of its depth, root cleaning and welding are performed from the back side. When the back is welded to 1 / 3 of its depth, the back side is flipped over and welded to the middle 1 / 3 of its thickness. A φ4.0mm electrode can be used at this point. This process is repeated until all welds are complete. During the welding process, care should be taken not to oscillate the welds. The thickness of each weld layer should not exceed 3mm. Rapid short-arc welding should be used, and the interpass temperature should be controlled to no more than 200°C to prevent thermal stress and increased welding deformation. Secondly, the lower surface of the template (the side that contacts the catalyst outlet pipe flange sealing surface) is machined flat on a vertical lathe to prevent roughness and unevenness on the template surface from damaging the flange sealing surface. The template's outer diameter is then machined using a vertical lathe. Positioning bolt holes are then CNC-machined using the template's outer diameter as a reference. This process is completed in a single pass using computer programming.

[0094] 3) Welding of 12 catalyst outlet pipes and thick stainless steel conical heads, including the following aspects: 1. The conical head is placed upright (large mouth facing down), and manual tungsten inert gas arc welding is performed twice from the outside, and the back is filled with argon for protection. A 2.4mm cerium tungsten electrode and a 2.0mm argon arc welding wire are used. The first layer of base welding current is 60-80 amperes, and the swing amplitude is less than 2mm, which can avoid defects such as burn-through or back weld nodules. After the first layer is welded, the base weld is subjected to 100% PT inspection after the temperature drops below 50°C; the second layer of base welding current is 80-110 amperes, and after welding, the second layer of base weld is subjected to 100% PT inspection again after the temperature drops below 50°C; 2. A 3.2mm electrode is used for welding from the outside, and multiple layers, multiple passes and fast welding are required. Fast short arc welding, water mist cooling can be used on the back during welding, and the inter-pass temperature should be kept at 50-100℃ to minimize welding thermal stress. After the base welding, the welding position is flat welding and vertical welding position, and the vertical upward welding method is adopted. Each weld should be staggered with the previous weld by at least 30mm. Staying at the arc starting position for 2-3 seconds can avoid arc starting cracks. The upward vertical welding swing amplitude should not exceed 2 times the diameter of the welding core; 3.12 pieces of catalyst outlet pipes are first completed with manual tungsten inert gas arc welding base welding, and then divided into 3 groups, each time 4 welders weld 4 evenly distributed pipes at the same time, and the welding progress is consistent; the welding is stopped when the first group is welded to 1 / 4 of the groove depth, and the welding of the second and third groups of pipes is carried out successively, and this is repeated until all the outer sides are welded.

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

[0096] 1) Before welding the inside, the back of the front base weld should be subjected to 100% PT inspection. The position where the local fusion is not good should be ground with a straight grinder with an arc surface at the top to make the shape of the surface to be welded regular and convenient for welding operation. The inside welding adopts φ3.2mm welding rod, and the welding sequence and control measures are the same as those of the outside welding.

[0097] 2) The inner and outer net bases are formed by integral forgings and are first rough-machined, 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. A 10mm allowance is left for the contact surface with the middle cone and is not machined for the time being.

[0098] 3) Place the conical head assembly with the large mouth facing upward on the vertical lathe operating table and adjust it to be coaxial with the rotation center. Clamp the dial indicator on the tool holder. Use the upper flanging arc transition section as a reference to measure the inner and outer mesh bases to be welded again. Record the dimensions every 10° and every 30mm along the cone surface in the height direction. Perform proportional lofting according to the surveying and mapping data and compare with the previous surveying and mapping data. The thickness of the middle cone parent material in the area to be welded between the inner and outer mesh bases is measured, the thickness measurement data is recorded, and the thickness allowance is analyzed. Combined with the lofting diagram of the latest dimensional surveying data, the processing plan for the middle cone in the area to be welded between the inner and outer mesh bases is determined. The straight edge section of the upper flanging arc transition section is used as the reference for processing the conical surface of the middle cone to be welded to the inner and outer mesh bases. The cone thickness is measured at any time until the cone surface is exposed to light. Because the cone is cold-formed, the thinning amount is approximately 1-2mm. The remaining thickness allowance can fully meet the dimensional tolerance compensation caused by the ovality, convexity, and concavity of the cone in this area. The steps caused by processing between the cone surface and the surrounding parent material in the two areas are processed at a transition ratio of no more than 1:5.

[0099] 4) According to the processing size of the conical surface of the inner and outer mesh bases on the middle cone, the inner circles of the inner and outer mesh bases are used as the reference to process the inner and outer mesh bases to remove the outer circle allowance (the allowance is determined according to the processing size of the middle cone) and process the outer contour to ensure that its size matches the size of the middle cone, and at the same time, the allowance of the inner and outer mesh bases is removed.

[0100] 5) The assembly team aligns the inner and outer mesh bases with the middle cone, ensuring complete coaxiality and conical fit because the mating surfaces are all machined. The fillet welds between the inner and outer mesh bases and the conical head are welded separately using manual tungsten inert gas welding. The upper portion is welded circumferentially, leaving a 20mm gap at the bottom unwelded. After welding, a round-head straight grinder is used to grind the weld surface in contact with the catalyst. The surface is polished to a concave, smooth transition, without grooves or sharp corners that could affect the flow of the catalyst.

[0101] 6) Final machining of the entire conical head assembly is performed. Using the outer circle of the upper flanged arc transition section as a reference, the large port allowance of the flanged arc transition section is removed and the groove is machined. At the same time, the inner circle of the inner and outer mesh bases are machined to remove the allowance, and the support surfaces of the inner and outer mesh bases are machined to remove the allowance and machine them to meet the requirements of the drawing. The upper and lower ports of the bottom conical head assembly manufactured using this method are 100% coaxial with the inner and outer mesh bases, and the flatness of the support surfaces of the inner and outer mesh bases can be controlled to be less than 0.02mm.

[0102] From the above embodiments, it can be seen that:

[0103] This method manufactures a conical head in sections (upper / lower integral forging reference section + petal pressed middle section), uses asymmetric grooves and combined supports to control longitudinal seam welding deformation, uses three-dimensional CNC to process double-sided semi-U-shaped catalyst nozzle grooves, uses template chemical equipment to synchronously assemble 12 nozzles and weld them in groups, and finally processes the cone contact surface based on the outer circle of the upper transition section, achieving manufacturing precision control of coaxiality ≤1.5mm and support surface flatness ≤0.05mm.

[0104] The above are only a few preferred embodiments of the present invention, and their description is relatively specific and detailed, but it should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art may make various modifications and improvements without departing from the scope of the present invention, and such modifications and improvements are within the scope of protection of the present invention.

Claims

1. A method for controlling the manufacturing accuracy of a conical support assembly at the bottom of a new structure dehydrogenation device, characterized in that: The following steps are involved: (1) The conical head assembly is manufactured in three sections: the upper flange arc transition section is formed by integral forging and has a height of 250-350 mm, and the lower flange arc transition section is formed by integral forging and has a height of 200-300 mm. The two sections serve as the assembly and processing basis of the middle cone; the middle cone is divided into 3-4 petals pressed by steel plates, with a 10-15 mm margin reserved for the thickness of each petal, a 3-10 mm margin reserved for one side of the petal in the width direction, and a 15-20 mm margin reserved for the height direction; (2) The longitudinal seam welding of the middle cone adopts a double-sided asymmetric groove, of which the outer side is a variable angle V-shaped groove and the inner side is a V-shaped groove. Anti-deformation combined supports are set 30-80mm away from the upper and lower ports on the inner side of the cone. The support type is selected as a cross support or a Pozigzag support according to the cone diameter. The interpass temperature during the welding process is controlled at 50-100℃; (3) The catalyst outlet pipe groove adopts a double-sided semi-U-shaped groove with a blunt edge size of 0.5-1.5mm, a gap of 2-4mm, a bottom R angle of 8-12mm, and a groove depth of 40%-60% of the cone thickness; (4) Synchronously assemble 12 catalyst outlet nozzles using a template tooling assembly. The tooling assembly includes a template with positioning bolt holes and a reinforcing rib plate. The template thickness is 50-80 mm. The bolt holes are CNC machined according to the nozzle position coordinates marked on the design drawings. (5) The processing plan is determined based on the actual surveying results of the inner and outer net base assembly areas. The outer circle of the upper flanging arc transition section is used as the reference on the vertical lathe to CNC machine the cone contact surface to ensure that the coaxiality does not exceed 1.5 mm.

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

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

4. The control method according to claim 1, wherein: In step (3), the processing of the double-sided semi-U-shaped groove adopts three-dimensional modeling to generate a numerical control program, and the outer circle of the straight edge section of the lower flanging arc transition section is used as the reference positioning, and the groove symmetry deviation is ≤1.5mm.

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

6. The control method according to claim 1, wherein: In step (4), when welding the catalyst pipe, first complete the two-layer argon arc welding of all pipes, then divide the 12 pipes into 2-4 groups, and each group of 3-6 pipes is welded synchronously by multiple welders until the groove depth reaches 20%-30%, and then rotate the work group.

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

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

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

10. The control method according to claim 1, characterized in that: The ovality of the final conical head assembly port does not exceed 3mm, and all longitudinal seams and circumferential seams are subjected to radiographic and penetration testing in accordance with NB / T47013 standards.

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