Manufacturing method of thin-walled shell and tube heat exchanger requiring post-weld heat treatment

Abstract

The present invention relates to the fabrication of thin-walled shell-and-tube heat exchangers and discloses a method for fabricating thin-walled shell-and-tube heat exchangers requiring post-weld heat treatment. The method comprises the following steps: determining the tolerance range of tubesheet openings through process trials; decomposing the tubesheet into modular tubesheet segments for production; controlling the straightness of the four sides of the tubesheet using anti-deformation tooling; maintaining cutting gaps between adjacent tubesheet segments; and uniformly providing lifting holes on the tubesheet segments; employing a horizontal stand on an assembly platform, using dedicated adjustable supports to adjust and position the tubesheets; using detachable process load-bearing tubes to assist in tube threading; performing seal welding on the tubesheets, preheating an appropriate number of tube holes in separate areas and batches, and then performing seal welding, welding in separate passes, and inspecting for flaws; and heat treating the tubesheet segments at both ends of the seal welded segments using a local heat treatment tooling, cutting each anti-deformation tooling along the cutting gaps. The method can control the straightness of the tubesheet seams on site, meet heat treatment requirements, and control heat treatment deformation, thereby improving production efficiency and ensuring processing quality.

Description

Technical Field

[0001] The present invention relates to the manufacture of thin-walled tube-in-tube heat exchangers, in particular to the deformation control of thin-walled heat exchangers when post-weld heat treatment is required due to the selection of tube sheet materials. Background Art

[0002] Thin-walled shell and tube heat exchanger is a tube sheet + heat exchange tube structure, such as Figure 1 and Figure 2 As shown in the figure, due to its large overall size, the minimum length, width and height are more than 2500mm. Compared with the designed tube sheet thickness of 20mm and the heat exchange tube wall thickness of 2.5mm, the wall thickness of the tube sheet and the heat exchange tube are very thin, and the welding amount is large. When the material selection of the tube sheet and the heat exchange tube requires heat treatment, there will be the following difficulties in manufacturing: 1. The wall thickness of the tube sheet is thin, and the tube sheet is easily deformed during drilling, lifting and transportation; the wall thickness of the heat exchange tube is thin, and the tube end has a certain elliptical deformation during the tube cutting process; the fixed-distance tube structure is not designed in the tube box, and the rigidity of the tube sheet is insufficient. The above factors make it difficult to pass the heat exchange tube; 2. The tube sheet is thin and the welding area is large, and it is difficult to control the welding deformation, which makes it difficult to control the misalignment of the joints between the tube box modules; 3. The material selection of the tube sheet and the heat exchange tube requires preheating before welding and heat treatment after welding. The overall rigidity of the tube box is poor, and the heat treatment deformation cannot be controlled by overall heat treatment. Therefore, it is difficult to use the existing conventional shell and tube heat exchanger's erection and tube threading process for this type of heat exchanger. The manufacturing method needs to be improved to prevent various deformations during the processing from exceeding the allowable range. Summary of the Invention

[0003] In order to successfully complete the production of ultra-wide and ultra-large thin-walled shell-and-tube heat exchangers, the technical problem to be solved by the present invention is to provide a method for manufacturing thin-walled shell-and-tube heat exchangers that require post-weld heat treatment.

[0004] The technical solution adopted by the present invention to solve the technical problem is: a method for manufacturing a thin-walled shell-and-tube heat exchanger requiring post-weld heat treatment, comprising the following steps:

[0005] Step a: Conduct welding process tests and product trials based on the materials of the heat exchange tubes and tube sheets to determine the tolerance range of the tube sheet openings;

[0006] Step b: Decompose the tube sheet into two or more tube sheet segments according to the tube sheet size. Set lifting holes uniformly on the tube sheet segments. Arrange the two or more tube sheet segments at one end of the tube sheet that need to be sealed and fixed in the same anti-deformation tool to control the straightness of the four sides of the tube sheet. Keep a cutting gap between adjacent tube sheet segments.

[0007] Step c: Using the tube sheet assembled in the anti-deformation fixture as a reference, erect a frame on the assembly platform with the tube hole axis parallel to the assembly platform. Decompose the remaining tube sheets into tube sheets of the same size and set corresponding lifting holes on the tube sheets. Install them on the dedicated adjustable supports and adjust the positioning according to the tube sheet spacing and heat exchange tube coaxiality requirements.

[0008] Step d: After the tube is threaded using a detachable process load-bearing tube, another anti-deformation fixture is assembled around the tube sheet of the other end that needs to be sealed and welded. The front and rear anti-deformation fixtures are welded into a whole using connecting steel parallel to the axis of the heat exchange tube.

[0009] Step e: Perform sealing welding on the tube sheet. Divide the tube sheet into multiple set welding areas according to the size of the tube sheet. Preheat an appropriate number of tube holes in the same set area in batches and perform "tube-to-sheet" sealing welding until the first weld of the sealing weld is completed at all tube holes, and then perform flaw detection. To ensure production efficiency, it is generally recommended to perform sealing welding on both ends of the tube sheet at the same time. It is also possible to perform sealing welding on both ends of the tube sheet first or later.

[0010] Repeat step e until all the pipe holes are welded;

[0011] Step f: Use local heat treatment tooling to perform post-weld heat treatment on the tube sheets at both ends that have completed the sealing welding, cut each anti-deformation tooling along the cutting gap, and separate the tube sheets that have been connected to the heat exchange tubes.

[0012] This method solves the problem of difficult control of misaligned seams of tube sheets on site by designing a modular tube sheet and then combining multiple tube box modules together for simultaneous manufacturing, and utilizing anti-deformation tooling to control the straightness of the four sides of the tube sheet; assembles a group of tube sheet sheets into components using anti-deformation tooling and positions them with special adjustable supports, thereby facilitating subsequent tube threading operations and controlling thermal deformation during the sealing welding process, while improving production efficiency; reduces the effect of the deadweight of the tube sheet and heat exchange tube on tube threading by means of process load-bearing tubes, thereby ensuring smooth completion of tube threading; controls heat input by preheating in a small area, thereby reducing tube sheet deformation; and replaces overall heat treatment with local heat treatment, thereby improving production efficiency and reducing heat treatment deformation, thereby ensuring processing quality and construction period.

[0013] Furthermore, the localized heat treatment fixture includes a support plate with a shape and size matching that of a single tube sheet. The support plate is equipped with fixing hooks, threading holes, and lugs. An insulation layer is applied to the support plate surface, and an electromagnetic induction heating plate is applied to the insulation layer. The electromagnetic induction heating plate is secured to and compacted against the insulation layer by the fixing hooks. The wires of the electromagnetic induction heating plate pass through the threading holes and are electrically connected to the electric heating distribution control cabinet. The heat treatment fixture can be prefabricated as a single unit and, after welding, can be quickly installed on the tube sheet end face for post-weld heat treatment.

[0014] The support plate is removably secured to the anti-deformation fixture via a C-clamp. The C-clamp comprises a C-shaped clamp body and a tightening screw that extends and adjusts along the clamp body's opening and is threadedly connected to the clamp body. Multiple C-clamps can be positioned around the plate to ensure secure, reliable clamping and easy assembly and disassembly.

[0015] Furthermore, adjacent tubesheets are welded together using ribbed plates after being positioned within the same anti-deformation fixture. These ribbed plates are removed after the first weld is completed to seal all tube holes within the anti-deformation fixture. Once all tube holes in the tubesheet are welded to the heat exchange tubes, their strength is enhanced, and subsequent deformation of the tubesheet caused by welding is minimal. Therefore, the ribbed plates can be removed at this point. The ribbed plates, combined with the anti-deformation fixture, enhance the anti-deformation effect of the tubesheet during processing. The number of ribbed plates can be reduced, and the effect of removing them after welding on tubesheet deformation is far less than the anti-deformation effect they provide during processing.

[0016] Furthermore, the anti-deformation tooling used in step b includes a steel frame with an inner frame size adapted to the aligned tubesheets. Stoppers are positioned on both sides of the tubesheet surface to clamp the tubesheets. These stoppers are welded to the steel frame and staggered relative to the tube hole insertion and welding locations. This anti-deformation tooling effectively controls tubesheet deformation during machining, ultimately ensuring the straightness of all four sides of the tubesheets, ensuring that the misalignment of the on-site tubesheet seams is within the allowable range, and ensuring smooth assembly of the final product.

[0017] Furthermore, in step f, before cutting the anti-deformation tooling along the cutting gap, the steel frame is first reinforced with reinforcing steel sections arranged on the left and right sides of the cutting gap and arranged parallel to the cutting gap.

[0018] Furthermore, the dedicated adjustable support in step c includes an adjustable base, a dedicated adjustable support, and a temporary support. The adjustable base is used to adjust the vertical position of the tube sheet, the dedicated adjustable support is used to adjust the size of the tube sheet gap, and the temporary support is used to adjust the verticality of the tube sheet. Before installing the tube sheet, the bottom steel section that forms the steel frame is pre-placed on the adjustable base. Furthermore, if necessary, the left-right position of the tube sheet can be adjusted using a wedge or jack.

[0019] The present invention recommends that the adjustable base, the dedicated adjustable support and the temporary support all adopt a threaded adjustment structure to facilitate fine adjustment. The adjustment structure and principle are shown in the accompanying drawings.

[0020] The wall thickness of the tube sheet in the heat exchanger structure of the present invention is very thin. For thin tube sheets, it is necessary to consider the deformation effect of the deadweight of the heat exchange tubes after insertion, as well as the deformation effect of the lifting process on the tube sheet. For this reason, the present invention makes the following design to eliminate or reduce the above-mentioned influences: in step d, the lifting holes are set at the four corners of the single tube sheet. Before inserting the heat exchange tubes, a spacing tube is first inserted into the lifting hole to lock the spacing between the tube sheets. Then, at least one process load-bearing tube with a wall thickness greater than the heat exchange tube and 3 to 5 heat exchange tubes are inserted in the four corners and the center area of ​​the tube sheet. Then, the heat exchange tubes are inserted from bottom to top in sequence and the process load-bearing tubes are replaced with heat exchange tubes when they reach the position of the process load-bearing tubes. If necessary, the tube holes are repaired or the heat exchange tubes are replaced until the insertion of all the heat exchange tubes is completed. The phrase "grinding the tube holes when necessary" refers to situations where the tube hole tolerance cannot accommodate the oval deformation caused by cutting thin-walled heat exchange tubes. In this case, the tube hole can be partially enlarged by grinding, or the heat exchange tube can be replaced to successfully complete the tube threading process. The tubes can then be sealed by welding. Lifting holes are designed at the four corners of the tube sheet to facilitate lifting and transportation. These lifting holes can be used to install distance tubes during the tube threading and sealing welding processes without affecting the corresponding operations.

[0021] In step e, the tubesheet is divided into nine designated welding zones in a nine-square grid. Preheating and welding are performed on each zone, with the four corner zones welded first, the center zone welded second, and the four side middle zones welded last. The nine zones are further divided and subdivided as described above until no more than four tube holes are preheated simultaneously in each designated welding zone. This division is a custom division and sorting method for rectangular tubesheets that is relatively easy to perform and less prone to operational errors. Multiple divisions and sorting methods are also possible. Based on the specific tubesheet size and number of tube holes, the area corresponding to the sealing weld is divided into several designated welding zones. The order of welding is determined based on the principle of keeping the deformation caused by local preheating within a controllable range. The number of tube holes preheated simultaneously in a single session is determined based on the preheating device used, the preheating temperature, and the time required to weld a single tube hole.

[0022] The beneficial effects of the present invention are as follows: It has been verified that the method of the present invention can realize the adjustment of the tube sheet during the assembly of the tube box module, smoothly carry out the threading of the heat exchange tube, and after the modular decomposition of the tube box, multiple modules are combined and manufactured. In combination with the designed anti-deformation tooling, the purpose of controlling the straightness of the on-site joints of the tube sheet can be achieved. The use of local heat treatment tooling for post-weld heat treatment can meet the heat treatment requirements while controlling heat treatment deformation, improve production efficiency, and ensure processing quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a schematic diagram of the tube box structure of a thin-walled shell and tube heat exchanger.

[0024] Figure 2 yes Figure 1A top-down schematic diagram of .

[0025] Figure 3 Yes Figure 1 Schematic diagram of the modular decomposition of the pipe box shown (decomposed into six modules).

[0026] Figure 4 yes Figure 3 A top-down schematic diagram of .

[0027] Figure 5 This is a schematic diagram of the combined manufacturing of three tube box modules (an anti-deformation fixture accommodates three tube sheet sheets and simultaneously positions them for tube threading).

[0028] Figure 6 yes Figure 5 A top-down schematic diagram of .

[0029] Figure 7 yes Figure 5 Schematic diagram of another viewing direction.

[0030] Figure 8 Schematic diagram of the post-weld heat treatment curve required by the embodiment.

[0031] Figure 9 It is a schematic diagram of assembling tube sheets in the anti-deformation tooling.

[0032] Figure 10 yes Figure 9 Left view of .

[0033] Figure 11 yes Figure 9 A partial enlarged view of .

[0034] Figure 12 yes Figure 11 Left view after the pipe is passed through the corresponding position.

[0035] Figure 13 It is a schematic diagram of adjusting the tube sheet when the stand is erected on the assembly platform.

[0036] Figure 14 yes Figure 13 A top-down schematic diagram of .

[0037] Figure 15 yes Figure 13 Schematic diagram of a tube sheet B supported by a dedicated adjustable support.

[0038] Figure 16 yes Figure 15 Schematic diagram of the adjustable base.

[0039] Figure 17 yes Figure 16 Left view of .

[0040] Figure 18 It is a schematic diagram of the pipe box assembly connection.

[0041] Figure 19 Figure 18 A top-down schematic diagram of .

[0042] Figure 20 It is a structural diagram of the local heat treatment tooling.

[0043] Figure 21 yes Figure 20 Schematic diagram of another viewing direction.

[0044] Figure 22 It is a schematic diagram of the usage status of local heat treatment tooling.

[0045] Figure 23 yes Figure 22 A-direction view.

[0046] Figure 24 It is a schematic diagram of the electromagnetic induction heating plate of the local heat treatment tooling.

[0047] Figure 25 It is a schematic diagram of the assembly and use of local heat treatment tooling.

[0048] The markings in the figure are: 1-A tube sheet, 2-B tube sheet, 3-C tube sheet, 4-anti-deformation tooling, 5-local heat treatment tooling, 6-tension plate, 7-C-type clamp, 8-electric heating distribution control cabinet, 9-temporary support, 10-assembly platform, 11-Tube sheet A①, 12-Tube sheet A③, 13-Tube sheet A⑤, 14-Bottom steel, 15-Adjustable base, 16-Special adjustable support, 40-Cutting gap, 41-Steel frame, 42-Clamping steel, 43-Clamping block, 44-Lifting hole, 45-Connecting steel, 46-Anti-deformation tooling lifting lug, 51-Support plate, 52-Fixed hook, 53-Threading hole, 54-Lifting lug, 55-Insulation layer, 56-Electromagnetic induction heating plate, 57-Heating plate fixing hole, 58-Wire, 59-Secondary connecting wire, 101-Fixed base, 102-Special adjustable support, 150-Steel plane, 151-Base, 152-Adjustment threaded seat, 153-Inner sleeve, 154-Adjusting screw, 155-Adjusting handle, 156-Support plate, 157-Pin, 1011-Fixed support. M is the length of a set of electromagnetic induction heating sheets, and N is the width of a set of electromagnetic induction heating sheets.

[0049] The heat exchange tubes are omitted in the tube box schematic diagram. DETAILED DESCRIPTION

[0050] The present invention will be further described below with reference to the accompanying drawings and examples.

[0051] Example:

[0052] Taking the high-temperature shell-and-tube heat exchanger designed in a certain project as an example, the tube box of the heat exchanger includes tube sheets at both ends, namely A tube sheet 1, B tube sheet 2, and C tube sheet 3 located between A and B tube sheets. C tube sheet 3 mainly plays a supporting role. There is no need to weld the heat exchange tubes and C tube sheet 3. One side of A tube sheet 1 and B tube sheet 2 needs to be sealed. Figure 1 、 Figure 2 The tube sheet is nearly 8m long, 5m wide, and the heat exchange tube is nearly 4m long. The on-site operating state is vertical. The flue gas temperature is not higher than 600°C during operation. The tube sheet thickness on both sides of the tube box is 20 mm (SA-387GR91Type1), and the heat exchange tube is φ60×2.5mm (SA-213T91Type1). The sealing weld requires preheating before welding and post-weld heat treatment. It is staggered and has the characteristics of thin tube sheet, large diameter and thin wall thickness of heat exchange tube, and large welding volume.

[0053] The pipe box module is manufactured by adopting a modular processing mode and the method of the present invention.

[0054] Step a: Conduct welding process tests and product trials based on the materials of the heat exchange tubes and tube sheets to determine the tolerance range of the tube sheet opening. In this embodiment, the diameter tolerance of the tube sheet opening is Φ61. +0.2 -0.3 If the hole is too small, factors such as the roundness of the tube and the deformation of the tube sheet will make it difficult to insert the tube; if the hole is too large, the heat exchange tube will easily be welded through during sealing welding, and it is difficult to ensure the welding quality. Therefore, it is necessary to determine the reasonable tube hole size through trial production.

[0055] Step b: Decompose the tube sheet into two or more tube sheet sheets according to the tube sheet size, and arrange the two or more tube sheet sheets in a row and fix them to the same anti-deformation tool 4 to control the straightness of the four sides of the tube sheet. A cutting gap 40 is reserved between adjacent tube sheet sheets, and lifting holes 44 are uniformly set at the four corners of the single tube sheet sheet. The anti-deformation tool 4 includes a steel frame 41 with an inner frame size that matches the arranged tube sheet sheets. Limiting members are arranged on both sides of the plate surface of the tube sheet to clamp the tube sheet sheets. The limiting members on both sides are welded and fixed to the steel frame 41. The limiting members are staggered at the tube hole insertion and welding positions. Specifically, in this embodiment, a single tube sheet is decomposed into six tube sheet sheets, which are designed to be divided twice in the length direction and once in the width direction. Figure 3 and Figure 4Taking tube sheet A as an example, during production, the three tube sheets in the upper row along the length direction are manufactured together, that is, the three tube sheets are assembled in the same anti-deformation tool 4, namely the tube sheets marked as ②, ④, and ⑥ in the figure, with two cutting gaps 40 reserved. The three tube sheets in the lower row are then manufactured together separately, namely the tube sheets marked as ①, ③, and ⑤ in the figure: tube sheet A①11, tube sheet A③12, and tube sheet A⑤13 are together. "Uniformly setting lifting holes" means that after the slicing method of tube sheet A 1 is determined, tube sheets B 2 and C 3 are also divided according to the same size, retaining the same size cutting gaps. This allows the use of anti-deformation tool 4 of the same size, and lifting holes are set at the same position on each tube sheet. The lifting holes are designed on the anti-deformation tool to reduce tube sheet deformation caused by lifting.

[0056] Step c: Using the tubesheets assembled in the same anti-deformation fixture 4 as a reference, erect the tubesheets on the assembly platform 10, with the tube hole axis parallel to the assembly platform 10. Decompose the remaining tubesheets into tubesheets of the same size and similarly set corresponding lifting holes 44 on the tubesheets. Support them on dedicated adjustable supports 102, and adjust their positioning according to the tubesheet spacing and heat exchange tube coaxiality requirements. Specifically, for example, using tubesheets A①11, A③12, and A⑤13 assembled in the same anti-deformation fixture 4 on tubesheet A as a reference, erect the tubesheets on the assembly platform 10. The anti-deformation fixture 4 is assembled on the fixed base 101, and the corresponding tubesheets B①, B③, and B⑤ are assembled on the dedicated adjustable supports 102 in the basic position. The corresponding tubesheets C①, C③, and C⑤ are assembled on another dedicated adjustable support 102 in the basic position, and the other dedicated adjustable support 102 is located between the fixed base 101 and the previous dedicated adjustable support 102.

[0057] like Figure 13 、 14 As shown in Figures 15 and 15, the dedicated adjustable support 102 includes an adjustable base 15, a dedicated adjustable support 16, and a temporary support 9. The adjustable base 15 allows for fine-tuning of the vertical height of the tubesheet, i.e., the vertical position of the tubesheet. Before installing the tubesheet, the bottom steel section 14, which forms the steel frame 41, is pre-placed on the adjustable base 15. The dedicated adjustable support 16 allows for fine-tuning of the gap between the tubesheets or the front-to-back position of the tubesheets, i.e., the tubesheet spacing. The temporary support 9 is used to fine-tune the verticality of the tubesheet relative to the assembly platform 10, i.e., to adjust the parallelism of the tubesheet relative to the reference tubesheet. Alternatively, the left-right position of the tubesheet can be adjusted with the aid of a wedge or jack. Through adjustment of the dedicated adjustable support 102, the coaxiality of the corresponding tube holes on each tubesheet, as well as the parallelism and spacing between tubesheets A and C, and between tubesheets C and B, all meet the requirements for tube insertion.

[0058] Step d: After using a detachable process load-bearing tube to assist in completing the tube threading, assemble another anti-deformation tooling 4 around the tube sheet of the other end tube sheet that needs to be sealed and welded, and weld the front and rear anti-deformation tooling 4 into a whole with a connecting steel 45 parallel to the axis of the heat exchange tube. Since the weight of the heat exchange tube borne by the tube sheet continues to increase during the tube threading process, which may cause the tube sheet to deform, a detachable process load-bearing tube is designed to assist in completing the tube threading. The process load-bearing tube can be a round steel tube with a total length greater than the distance between the A and B tube sheets and a wall thickness more than twice the wall thickness of the heat exchange tube. The round steel tube and the tube hole are clearance-fitted, and the process load-bearing tube is not welded to the tube sheet. After the pipe is inserted, the other anti-deformation tooling 4 except the bottom steel section 14 is also assembled to the other end that needs to be sealed and welded to form the tube sheet of the B tube sheet 2, and the two anti-deformation toolings 4 are welded into a whole with the connecting steel section 45, so that the anti-deformation tooling 4 enhances the deformation resistance of the tube sheet during the welding process. The two ends of the connecting steel section 45 are connected to the anti-deformation tooling 4 to limit the deformation of the tube sheet. After subsequent cutting, the divided parts of the front and rear anti-deformation tooling are connected to each other as a whole, which is convenient for subsequent processing of the pipe box module that has been inserted with pipes.

[0059] Step e: Perform sealing welding on the tube sheet. Divide the tube sheet into multiple set welding areas according to the size of the tube sheet. Preheat an appropriate number of tube holes in the same set area in batches and perform "tube-sheet" sealing welding until the first weld of the sealing weld at all tube holes is completed and flaw detection is performed.

[0060] Because the sealing weld between each heat exchange tube and the tube hole on the tube sheet is designed with multiple layers of weld beads, it is necessary to repeat the above step e until all tube holes are welded. In other words, the sealing weld is performed in different areas and passes on each tube hole on the tube sheet according to a specific welding sequence.

[0061] Step f: Use the local heat treatment tool 5 to perform post-weld heat treatment on the tube sheets at both ends that have completed the sealing weld. After the post-weld heat treatment is completed, the steel frame 41 is reinforced with reinforcing steel sections arranged on the left and right sides of the cutting gap 40 and arranged parallel to the cutting gap. Then, each anti-deformation tool 4 is cut along the cutting gap to separate the tube sheets connected to the heat exchange tubes. After separation, each pipe box assembly is still protected by the steel frame, which is easy to transport and facilitates the post-weld heat treatment of the welded tube sheets. According to practice, the separation can also be performed after the sealing weld of all tube sheets in the same anti-deformation tool is completed but before the post-weld heat treatment is completed. That is, a single tube sheet can be separated from the anti-deformation tool 4 immediately after the sealing weld of the tube sheet is completed.

[0062] In order to ensure the smooth processing of the heat exchanger, Figures 3 to 7As shown, each tubesheet is broken down into two rows, each row of six, based on tubesheet dimensions. Each tubesheet carries approximately 850 to 950 heat exchange tubes. The three tubesheets in the upper and lower rows are simultaneously assembled and assembled using a combination of erection and tube threading. The three tubesheets utilize the same anti-deformation tooling to ensure the straightness of all four sides. Furthermore, due to the staggered tube layout and the poor overall rigidity of the tubebox, the tubebox undergoes localized heat treatment to control deformation.

[0063] like Figure 9 、 Figure 10 、 Figure 11 and Figure 12 As shown, the anti-deformation tooling 4 used includes a steel frame 41 whose inner frame size is adapted to the arranged tube sheets. The outer side of the steel frame 41 is provided with uniformly arranged anti-deformation tooling lifting ears 46, and the four corners of a single tube sheet are provided with uniformly arranged lifting holes 44. A cutting gap 40 is maintained between adjacent tube sheets. Limiting pieces are arranged on both sides of the plate surface of the tube sheet to clamp the tube sheet. The limiting piece on the non-sealing weld side is a clamping steel 42, and the limiting piece on the other side, i.e., the sealing weld side, is a clamping block 43. The clamping steel 42 and the clamping block 43 are welded and fixed to the steel frame 41, and all limiting pieces are staggered with the pipe hole penetration and welding positions.

[0064] The specific operation process is as follows.

[0065] First, lay out the assembly platform 10 according to the design drawings, mark the tubesheet positions, and weld the fixed base 101 and the adjustable base 15 of the dedicated adjustable support 102. A pre-buried channel steel 14 is placed on the adjustable base 15, with the outer surface of the groove of the pre-buried channel steel 14 facing upward and parallel to the assembly platform 10, serving as the load-bearing surface. The fixed base 101 can be welded from section steel, with the top surface serving as the horizontal support surface.

[0066] Second, use a laser level to level the fixed base 101 for supporting tube sheet A 1 and the two adjustable bases 15 for supporting tube sheet C 3 and tube sheet B 2 respectively. Figure 16 and Figure 17As shown, the adjustable base 15 includes two adjustment components fixed on a steel plane 150 and arranged vertically parallel to each other. A single adjustment component includes a base 151 fixedly connected to the steel plane 150. The top of the base 151 is welded to the adjustment thread seat 152. The adjustment thread seat 152 is equipped with an inner sleeve 153 rotatable relative to the base 151 through a bearing. The adjustment screw 154 passes through the internal threaded hole on the inner sleeve 153 and the corresponding through hole on the adjustment thread seat 152 from top to bottom and then extends into the base 151. The inner sleeve 153 is provided with left and right adjustment holes for the adjustment handle 1 arranged perpendicular to the axis of the adjustment screw. 55 are inserted from both sides to control the rotation of the inner sleeve 153. The top of the adjusting screw 154 is fixedly connected to the supporting plate 156. The bottom of the adjusting screw 154 is provided with a pin hole. The base 151 is provided with a long through slot corresponding to the adjustment height range and the pin hole opening orientation. The position of the inner sleeve 153 on the adjusting screw 154 can be adjusted by rotating the inner sleeve 153, thereby adjusting the height position of the supporting plate 156 relative to the steel plane 150, that is, adjusting the supporting height of the adjustable support 15. After the adjustment is in place, a pin 157 can be inserted into the pin hole and the pin 157 can be spot welded to the base 151 to lock the supporting height if necessary.

[0067] Third, press Figure 9 、 Figure 10 After welding the steel frame 41 of the anti-deformation fixture 4 and the clamping steel 42 on one side of the tube sheet, the three tube sheet segments A (A① / A③ / A⑤) of one side of the tube box (numbered ① / ③ / ⑤) are hoisted into the steel frame 41 according to the on-site installation sequence. After adjusting the cutting gap 40 between the tube sheet segments and the straightness of the joint, the clamping block 43 on the other side of the tube sheet is welded. At least four ribbed plates 6 are welded to the joint to complete the A tube sheet assembly. The anti-deformation fixture 4 uses a steel frame 41 as its main frame to ensure the straightness of each side of the tube sheet. The tube sheet and the steel frame 41 are not welded. A clamping block 43 is placed between two adjacent tube holes on one side of the tube sheet's sealing weld. A clamping steel section 42 is placed on the other side of the tube sheet. The clamping steel section 42 and the clamping block 43 are firmly welded to the steel frame 41. The clamping steel section 42 and the clamping block 43 securely fix the tube sheet in the anti-deformation fixture 4 by means of a coordinated clamping. It should be noted that the width of the clamping steel section 42 must not exceed the edge of the unperforated portion of the tube sheet to ensure smooth perforation. The size of the clamping block 43 must also not be too large to interfere with the sealing weld of the heat exchange tube. The design of the anti-deformation fixture solves the problem of high workload and poor processing quality during preheating before welding, welding deformation, and cleaning, grinding, and flaw detection of the tube sheet surface after the fixture is removed.

[0068] Fourth, hoist the A tube sheet assembly onto the fixed base 101, use the laser level to adjust its horizontal and vertical position, and press Figure 13 、 Figure 14As shown, the A tube sheet assembly is firmly supported on the assembly platform 10 and its position is maintained by means of fixed supports 1011.

[0069] Fifth, press Figure 13 、 14 As shown in FIG15 , a single tube sheet used to form the B tube sheet is hoisted onto the bottom section steel 14 pre-placed on the adjustable base 15 of the special adjustable support 102 and aligned. After adjusting the verticality of the tube sheet with a laser level, temporary supports 9 are welded on both sides of the tube sheet. One end of the temporary support 9 is welded to the assembly platform 10. The other end of the temporary support 9, which is in contact with the tube sheet, is welded with bolts and nuts for fine-tuning the verticality of the tube sheet. This end includes a nut welded to the diagonal bracing section steel. A bolt is threaded on the nut. The end face of the bolt presses the tube sheet from one side. A special adjustable support 16 is used at the bottom of the tube sheet to adjust the gap size between the A / B tube sheets, i.e. Figure 13 As shown in "L1+L2", the special adjustable support 16 includes a pair of nuts welded on the steel plane and located on both sides of the tube sheet. A bolt is threadedly connected to the nut, and the end faces of the two bolts respectively press the tube sheet from one side of the tube sheet.

[0070] Sixth, adjust the tube sheets of B tube sheet and A tube sheet assembly, and measure the dimensions until they meet the standards and product drawing requirements, then support and fix them. Use the same method to assemble C tube sheet and A tube sheet assembly corresponding tube sheets, such as Figure 13 As shown, bottom steel sections of the same specifications as the frame of the anti-deformation fixture can be used as the bottom support of each tube sheet of the C tube sheet to facilitate alignment adjustment and subsequent welding of the connecting steel sections 45.

[0071] Seventh, using tube sheet assembly A as a reference, test-thread nine process load-bearing tubes, roughly evenly spaced according to the inner frame dimensions of the anti-deformation fixture 4, and thread the spacer tubes through the lifting holes 44 to lock the tube sheet. Then, remove the temporary supports 9 that hinder the threading of the heat exchange tubes. The spacer tubes can be constructed as follows: they comprise tie rods with externally threaded sections at both ends, covered with spacer sleeves. The number and length of the spacer sleeves match the number and spacing of the tube sheets. After exiting the tube sheet, the tie rods are secured with tie rod fastening nuts at both ends. The tie rods pass from the outside of tube sheet A, pass through the front and rear of tube sheet C, and then into the interiors of two spacer sleeves, the length of which corresponds to the spacing between the tube sheets. The tie rods pass through tube sheet A, the first spacer sleeve, tube sheet C, the second spacer sleeve, and exit the outside of tube sheet B 9, where they are secured at both ends with tie rod fastening nuts.

[0072] Eighth, start threading the tubes from the A side of the tube sheet, starting with the four corners and center area. Insert 3-5 heat exchange tubes into each area. Then, thread the tubes from bottom to top, replacing the process tubes one by one. Adjust the dedicated adjustable tooling as needed during the threading process. If threading is still difficult, grind the tube holes or replace the heat exchange tubes with tubes of a diameter that matches the holes.

[0073] Ninth, assemble pipe box ③ and pipe box ⑤ according to the above method. After the three pipe box modules are threaded, use another anti-deformation tool 4 to hoop the three tube sheet segments (B① / B③ / B⑤) of the B tube sheet into a whole. That is, the part of the other anti-deformation tool 4 except the bottom steel section 14 is assembled around the tube sheet segments that make up the B tube sheet and fixed, that is, the B tube sheet assembly. Since there is no sealing weld at the C tube sheet, it is not necessary to fix it with the anti-deformation tool 4. The front and rear anti-deformation tool segments 4 are connected as a whole with the connecting steel section 45. To facilitate subsequent cutting and separation, the connecting steel section 45 should be staggered with the cutting gap 40.

[0074] 10. Seal the tube sheets at both ends according to a specific welding sequence. Weld in zones and layers. Each layer should pass the PT inspection before proceeding to the next process. Before welding, preheat 3-4 tube hole zones simultaneously according to the welding sequence. Do not preheat the entire row simultaneously.

[0075] Eleventh, as Figures 20-25 As shown, after the sealing welding is completed, the local heat treatment tool 5 is hoisted and firmly fixed with the C-type clamp 7. Figure 8 The heat treatment curve shown requires local heat treatment. The C-type clamp 7 includes a C-shaped clamp body and a tightening screw that is adjustable along the opening of the clamp body and is threadedly connected to the clamp body.

[0076] 12. Remove the local heat treatment tool 5 and conduct a PT spot check on the sealing welds.

[0077] Thirteenth, the anti-deformation tooling is cut from the joint of the tube sheets, and the pipe box is split into three pipe boxes. Before splitting, the upper and lower sides of the steel frame 41 of the single anti-deformation tooling 4 are connected to each other into a whole by reinforcing steel sections (not shown in the drawings) arranged on the left and right sides of the cutting gap and arranged parallel to the cutting gap. Obviously, in order to facilitate subsequent cutting and separation and installation of the local heat treatment tooling 5, the reinforcing steel sections should be arranged as close as possible to but avoid the cutting gap 40.

[0078] 14. After the completion inspection is passed, clean the paint and package it.

[0079] According to actual conditions, process fourteen may be adjusted to before process eleven, that is, the pipe box is disassembled first and then local heat treatment is performed.

[0080] After actual manufacturing verification, this process method can realize the assembly of tube boxes and control the straightness of tube sheets at the on-site joints of tube sheets, thus achieving the expected goals of the process plan.

[0081] like Figures 20-25As shown, the local heat treatment tooling 5 includes a support plate 51 whose shape and size match those of a single tube sheet. The support plate 51 is provided with fixing hooks 52, threading holes 53, and lugs 54. An insulation layer 55 is laid on the surface of the support plate 51, and an electromagnetic induction heating sheet 56 is laid on the insulation layer 55. The electromagnetic induction heating sheet 56 is fixed and compacted to the insulation layer 55 by the fixing hooks 52. The wires 58 of the electromagnetic induction heating sheet 56 pass through the threading holes 53 and are electrically connected to the electric heating distribution control cabinet 8. Using the tooling to fix the electromagnetic induction heating sheet 56 reduces the workload of repeatedly laying the heating sheet and connecting the wires, solving the problem of unpredictable deformation during the overall heat treatment. Since the anti-deformation fixture uses a steel clamping outer hoop, the sealing weld plane of the thin-walled tube sheet is concave, so the corresponding support plate 51 is a convex structure. The planar dimensions of the support plate 51 are slightly smaller than the outer dimensions of the tube sheet, leaving a gap of 5 to 10 mm on one side to ensure that the convex support plate 51 of the fixture can enter the concave frame of the anti-deformation fixture 4, so that the electromagnetic induction heating plate 56 can fully contact the sealing weld. According to the size of the electromagnetic induction heating plate 56 and the position of the fixing holes, the fixing hooks 52 and threading holes 53 are arranged on the support plate 51. Two layers of needle-punched insulation blanket are laid on the support plate 51 as the insulation layer 55. The insulation layer 55 is usually about 80 mm thick. Then, the electromagnetic induction heating plate 56 is laid on the insulation blanket and fixed to the fixing hooks 52 through the electromagnetic induction heating plate fixing holes. Each electromagnetic induction heating plate is fixed at least four times. When fixing, the needle-punched insulation blanket needs to be compacted to fix both the electromagnetic induction heating plate 56 and the needle-punched insulation blanket. Pass the wire 58 of the electromagnetic induction heating plate 56 through the wire hole 53, and then connect it to the electric heating distribution control cabinet 8 through the secondary connecting wire 59. The wire 58 and the secondary connecting wire 59 are wrapped with a needle-punched insulation blanket to ensure that there is no direct contact between the wire and the metal surface of the local heat treatment tooling 5 and the anti-deformation tooling 4, and between the wires to prevent short circuit. Figure 25 As shown, it is recommended to weld additional support steel to the outside of the pipe box's anti-deformation fixture 4 to position and support the local heat treatment fixture 5. During assembly, a jack or C-clamp is used to clamp the local heat treatment fixture 5 to the surface of the product to be heat treated. Alternatively, the local heat treatment fixture 5 and the anti-deformation fixture 4 can be welded together using steel sections to form a single unit. Sealing welds are typically performed simultaneously at both ends of the pipe box, and post-weld heat treatment is performed simultaneously. After heat treatment is completed, the connection is removed and the local heat treatment fixture 5 is hoisted away. There is no need to remove the electromagnetic induction heating plate 56 and secondary connecting wires 59, making it convenient to use.

[0082] Note that the local heat treatment tool 5 should be inspected before each use of the electromagnetic induction heating plate 56, and any that may affect the use should be replaced. Figure 20 and Figure 25 As shown, the multiple groups of electromagnetic induction heating plates 56 constituting the same local heat treatment tool 5 are connected in parallel, so that even if Figure 20 Even if one of the multiple sets of electromagnetic induction heating plates 56 constituting the local heat treatment fixture 5 suddenly fails during use and cannot be used normally, the post-weld heat treatment temperature and heat treatment effect of the tube sheet can be ensured by heat conduction, heat radiation, etc. For the same reason, before heat treatment, it is advisable to heat the surrounding area of ​​the corresponding tube box portion of the single tube sheet, i.e. Figure 22 、 23 The front plane, rear plane, upper plane and lower plane are all subjected to heat preservation treatment. When the power load of the local heat treatment tool 5 meets the requirements, multiple tools can be put into use at the same time to further shorten the cycle of the heat treatment process.

Claims

1. A method for manufacturing a thin-walled shell-and-tube heat exchanger requiring post-weld heat treatment, characterized in that The following steps are involved: Step a: Conduct welding process tests and product trials based on the materials of the heat exchange tubes and tube sheets to determine the tolerance range of the tube sheet openings; Step b: Decompose the tube sheet into two or more tube sheet segments according to the tube sheet size, uniformly set lifting holes (44) on the tube sheet segments, and arrange the two or more tube sheet segments of one end of the tube sheet to be sealed and fixed in a row in the same anti-deformation tool (4) to control the straightness of the four sides of the tube sheet, and retain a cutting gap (40) between adjacent tube sheet segments; Step c: Using the tube sheet assembled in the anti-deformation fixture (4) as a reference, erect a frame on the assembly platform (10), with the tube hole axis parallel to the assembly platform (10), decompose the remaining tube sheets into tube sheets of the same size, and similarly set corresponding lifting holes (44) on the tube sheets and install them on the dedicated adjustable support (102), and adjust the positioning according to the tube sheet spacing and the coaxiality requirements of the heat exchange tubes; Step d: After the pipe is threaded with the aid of a detachable process bearing tube, another anti-deformation tooling (4) is assembled around the tube sheet of the other end tube sheet that needs to be sealed and welded, and the front and rear anti-deformation tooling (4) are welded into a whole with a connecting steel (45) parallel to the axis of the heat exchange tube; Step e: Perform sealing welding on the tube sheet. The area for sealing welding is divided according to the tube sheet size and the number of tube holes to form several set welding areas. The welding sequence is determined based on the principle of keeping the deformation of local preheating within a controllable range. The number of tube holes to be preheated simultaneously is determined based on the preheating device used, the preheating temperature, and the time required to weld a single tube hole. An appropriate number of tube holes in the same set area are preheated in batches and "tube-to-sheet" sealing welding is performed until the first weld of the sealing weld is completed at all tube holes, and flaw detection is performed. Repeat step e until all the pipe holes are welded; Step f: using a local heat treatment tool (5) to perform post-weld heat treatment on the tube sheets at both ends of the sealing weld, cutting the anti-deformation tool (4) along the cutting gap (40) to separate the tube sheets connected to the heat exchange tubes.

2. The method for manufacturing a thin-walled shell-and-tube heat exchanger requiring post-weld heat treatment according to claim 1, wherein: The local heat treatment tooling (5) includes a support plate (51) whose shape and size match those of a single tube sheet. The support plate (51) is provided with a fixing hook (52), a threading hole (53) and a lifting lug (54). A thermal insulation layer (55) is laid on the surface of the support plate (51). An electromagnetic induction heating plate (56) is laid on the thermal insulation layer (55). The electromagnetic induction heating plate (56) is fixed and compacted to the thermal insulation layer (55) by the fixing hook (52). The wire (58) of the electromagnetic induction heating plate (56) passes through the threading hole (53) and is electrically connected to the electric heating power distribution control cabinet (8).

3. The method for manufacturing a thin-walled shell-and-tube heat exchanger requiring post-weld heat treatment according to claim 2, wherein: The support plate (51) is detachably fixed to the anti-deformation tooling (4) via a C-shaped clamp (7), wherein the C-shaped clamp (7) comprises a C-shaped clamp body and a tightening screw that is telescopically adjusted along an opening of the clamp body and is threadedly connected to the clamp body.

4. The method for manufacturing a thin-walled shell-and-tube heat exchanger requiring post-weld heat treatment according to claim 1, wherein: The adjacent tube sheets are positioned in the same anti-deformation tool (4) and then welded together using a ribbed plate (6). The ribbed plate (6) is removed after the first weld seam of sealing all the tube holes in the anti-deformation tool (4) is completed.

5. The method for manufacturing a thin-walled shell-and-tube heat exchanger requiring post-weld heat treatment according to claim 1, wherein: The anti-deformation tooling (4) used in step b comprises a steel frame (41) whose inner frame size is adapted to the arranged tube sheets, and stoppers are arranged on both sides of the tube sheet surface to clamp the tube sheet, and the stoppers on both sides are welded and fixed to the steel frame (41), and the stoppers are staggered with the tube hole insertion and welding positions.

6. The method for manufacturing a thin-walled shell-and-tube heat exchanger requiring post-weld heat treatment according to claim 5, wherein: In step f, before cutting the anti-deformation tool (4) along the cutting gap (40), the steel frame (41) is reinforced with reinforcement steels arranged on the left and right sides of the cutting gap (40) and arranged parallel to the cutting gap.

7. The method for manufacturing a thin-walled shell-and-tube heat exchanger requiring post-weld heat treatment according to claim 5, wherein: The dedicated adjustable support (102) in step c includes an adjustable base (15), a dedicated adjustable support (16) and a temporary support (9). The adjustable base (15) is used to adjust the upper and lower positions of the tube sheet, the dedicated adjustable support (16) is used to adjust the opening size of the tube sheet, and the temporary support (9) is used to adjust the verticality of the tube sheet. Before installing the tube sheet, the bottom steel (14) for forming the steel frame (41) is pre-placed on the adjustable base (15).

8. The method for manufacturing a thin-walled shell-and-tube heat exchanger requiring post-weld heat treatment according to claim 7, wherein: The adjustable base (15), the special adjustable support (16) and the temporary support (9) all adopt a threaded adjustment structure.

9. The method for manufacturing a thin-walled shell-and-tube heat exchanger requiring post-weld heat treatment according to claim 1, wherein: In step d, the lifting holes (44) are set at the four corners of the single tube plate. Before inserting the heat exchange tube, a spacing tube is first inserted into the lifting hole (44) to lock the spacing between the tube plates. Then, at least one process load-bearing tube with a wall thickness greater than the heat exchange tube and 3 to 5 heat exchange tubes are inserted into the four corners and the center area of ​​the tube plate. Then, the heat exchange tubes are inserted from bottom to top in sequence and the process load-bearing tube is replaced with the heat exchange tube when the process load-bearing tube is reached. If necessary, the tube hole is repaired or the heat exchange tube is replaced until all the heat exchange tubes are inserted.

10. The method for manufacturing a thin-walled shell-and-tube heat exchanger requiring post-weld heat treatment according to claim 1, wherein step e In the process, the tube sheet is divided into 9 set welding areas according to the nine-square grid. The tube holes in each area are preheated and welded in the order of welding the four corner areas first, the center area second, and the middle areas of the four sides last. The 9 areas are further divided or even subdivided according to the nine-square grid as mentioned above until the number of tube holes preheated simultaneously in each set welding area does not exceed four.

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