Processing method of large-diameter ring-jacketed type A and B flat-welded flange

Abstract

The present application belongs to the technical field of pressure vessel manufacturing, and particularly relates to a processing method of a large-diameter ring-attached type A and type B flat-welding flange, which reduces the requirement for temperature control in the welding process, completely shields the uncertainty caused by welding deformation, and ensures that the deformation of the flange and the cylinder after assembly welding reaches a perfect repair result through the adjustment of the flange processing allowance, non-processing of the bolt hole, application of the anti-deformation tooling scheme, local heat treatment stress elimination, and one-time processing, etc. Meanwhile, the perpendicularity of the flange bolt hole is ensured, the smooth installation of the bolt fastener in the assembly process is ensured, and the uncontrollable deformation of the flange caused by the welding deformation and the flat-welding flange welding concentrated in the flange position (generally two positions) is solved.

Description

Technical Field

[0001] This invention belongs to the field of pressure vessel manufacturing technology, specifically a processing method for a large-diameter type A / B flat-welded flange with a liner ring. Background Technology

[0002] Slip-on flanges are a common structure used in many pressure vessels (such as towers, storage tanks, or heat exchangers), especially large-diameter (generally 2800mm and above) slip-on flanges, which significantly reduce procurement costs compared to weld neck flanges. Forged slip-on flanges have a larger diameter, and after processing and prolonged storage, localized dimensional deformation may occur due to stress release. This deformation is minor and has minimal impact on subsequent use. The manufacturing process of slip-on flanges, compared to weld neck flanges, presents challenges in terms of deformation and significantly increased sealing difficulty; especially for specialized equipment, special welding rings / liners are installed on carbon steel or stainless steel flanges to meet the equipment's corrosion resistance requirements. After welding, the flange components experience significant deformation due to the high welding thermal stress, combined with existing internal stresses, resulting in corrugated undulations on the flange end face. This welding stress continues to release during subsequent use, potentially leading to secondary deformation of the flange.

[0003] For many years, the manufacturing process for this type of large-diameter slip-on flange structure has involved using pre-fabricated slip-on flanges, directly assembling the welding ring and backing ring after welding them to the cylinder, and then machining the sealing surface. This existing method results in severe deformation after welding, making it impossible to guarantee the flatness of the slip-on flange after welding. Therefore, it is necessary to continuously increase the thickness of the backing ring / welding ring to meet the flatness requirements of the sealing surface after machining, resulting in the loss of a large amount of special metal. This not only increases costs but also, due to the release of welding stress during the welding process, can lead to secondary deformation after machining, easily causing bolt hole deviations, difficulty in bolt insertion, poor sealing surface flatness, and inability to seal properly, resulting in highly unstable quality. Furthermore, bolt holes may not be parallel to the cylinder axis, making subsequent bolt assembly and installation difficult and potentially impossible.

[0004] In summary, these large-diameter Type A and B slip-on flanges are the most difficult to manufacture. Because pressure vessels are pressurized during use, deformation during welding and subsequent stress release can prevent the flange from forming a seal. If there are many special materials involved, additional expensive weld rings or non-weldable bushings may need to be welded onto the large-diameter flange. Due to the unevenness of the flange after welding, the subsequent machining of the weld rings / blanks requires a significant amount of work, incurring substantial costs and posing a considerable quality risk. Summary of the Invention

[0005] In view of the above-mentioned problems in the traditional processing of slip-on flanges, the purpose of this invention is to provide a processing method for large-diameter slip-on flanges with bushings of type A and B. When the deformation caused by welding stress can only be reduced but not eliminated, by adjusting the manufacturing and processing sequence and adding some process steps, the large-diameter slip-on flanges that need to form an effective seal can be manufactured stably and with low cost.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] The processing method of the present invention includes the following steps:

[0008] Step A: Purchase blank forged flanges. Blank forged flanges are semi-finished flanges with machining allowances in both the outer diameter and thickness directions and unmachined bolt holes.

[0009] Step B: Weld a tooling reinforcing ring to the outer edge of the blank forging flange to prevent deformation;

[0010] Step C: Assemble and position the cylinder body and the blank forging flange, and then weld the two blank forging flanges together with connecting stiffeners to reduce deformation during the welding process;

[0011] Step D: Weld the weld seam;

[0012] Step E involves applying localized heat treatment to the welded flange and weld seam by wrapping them with electric heating ropes and insulating cotton to relieve stress.

[0013] Step F: Cut the welded joints of the two flanges apart, preparing them for processing;

[0014] Step G: Cut and remove the connecting stiffeners and tooling reinforcing rings on the outside of the flange, machine the upper and lower end faces of the flange, measure the thickness after one side is flat, and ensure that the thickness at the lowest point is not lower than the set thickness, and then machine the other side. After the upper and lower end faces of the flange are machined, machine the outer edge of the flange, and then machine the bolt holes.

[0015] Step H: Install the bushing on the already machined flat end face of the flange, and complete the weld between the bushing and the connecting parts as required;

[0016] Step 1: Secondary machining of the liner sealing surface.

[0017] Wherein: the diameter of the blank forged flange in step A is measured before use, and the maximum and minimum diameter deviation is one-thousandth of the diameter.

[0018] In step A, the weld seams of the blank forged flange are concentrated on the inner side near the blank forged flange to avoid weld seams on the upper surface of the blank forged flange.

[0019] In step C, before assembling and tack welding the cylinder body with the blank forging flange, the bevel positions required for assembling the blank forging flange and the cylinder body are first machined.

[0020] The heat treatment temperature and time in step E are 580℃~640℃, and the holding time is 1~3 hours.

[0021] When the bushing installed in step H is a non-weldable bushing, in step G, while marking and drilling the corresponding bolt holes, it is also necessary to drill plug holes; when the bushing installed in step H is a weldable bushing, in step G, it is only necessary to mark and drill the corresponding bolt holes.

[0022] When the bushing in step H is a non-weldable bushing, the bushing is tightened with plugs; when the bushing in step H is a weldable bushing, the bushing is welded onto the already machined flat end face of the flange.

[0023] When the bushing in step H is a non-weldable bushing, the connecting component is a sleeve, and the non-weldable bushing is welded to the sleeve; when the bushing in step H is a weldable bushing, the connecting component is a flange, and the weldable bushing is welded to the flange.

[0024] The advantages and positive effects of this invention are as follows:

[0025] Compared with traditional flat-face flange processing technology, this invention completely solves the deformation problem of large-diameter type A and B flanges, as well as the subsequent cost increases and quality instability caused by deformation, by adjusting the process sequence. Specific effects are as follows:

[0026] 1. This invention solves the problem of incomplete removal of welding deformation and uncontrollable deformation of flat-face flanges caused by welding concentrated at the flange location (usually two locations). By adjusting steps such as leaving machining allowance on the flange, not machining bolt holes, applying anti-deformation tooling schemes, local heat treatment to relieve stress, and one-time machining, the requirements for temperature control during the welding process are reduced, and the uncertainty caused by welding deformation is completely shielded, ensuring that the deformation after the flange and cylinder are welded together achieves a perfect repair result; at the same time, the perpendicularity of the flange bolt holes is guaranteed, ensuring the smooth installation of bolt fasteners during the assembly process.

[0027] 2. This invention makes uncontrollable problems controllable by simply adjusting and adding to the process sequence, and successfully ensures the manufacturing accuracy of the flat-welded flange components without significantly increasing the manufacturing difficulty; and by eliminating stress through local heat treatment, it avoids the risk of leakage during service due to uneven sealing surfaces caused by stress release after aging.

[0028] 3. This invention ensures the precision of the flange components while minimizing the machining allowance of the bushing, significantly reducing the amount of special materials used and lowering direct costs. It also provides a valuable reference for the machining of other large-diameter flat-welded flanges.

[0029] 4. After the application of this invention, during product pressure testing, workers do not need to waste a lot of time and energy on bolt tightening work, and do not need to make up for the problem of insufficient flatness of the sealing surface by tightening too many bolts. This reduces the labor intensity of workers, ensures the smooth completion of the pressure test, and greatly improves the manufacturing cycle. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the blank flange and tooling reinforcing ring of the present invention;

[0031] Figure 2 This is a schematic diagram of welding two flanges together according to the present invention;

[0032] Figure 3 This is a schematic diagram of the flange after one-time processing according to the present invention;

[0033] Figure 4 This is a schematic diagram of the present invention after the bushing is installed;

[0034] Figure 5 This is a schematic diagram of the finished component of the present invention after the final machining of the bushing sealing surface;

[0035] Wherein: 1 is the blank flange, 2 is the tooling reinforcing ring, 3 is the cylinder, 4 is the connecting stiffener, 5 is the bolt hole, 6 is the flange, 7 is the plug hole, and 8 is the bushing. Detailed Implementation

[0036] The invention will now be described in further detail with reference to the accompanying drawings.

[0037] The processing method of the large-diameter type A and B flat-face welding flange with a liner ring of the present invention includes the following steps:

[0038] Step A: Adjust the incoming material situation. Purchase the blank forged flange 1 that requires secondary processing according to the drawings. The blank forged flange 1 is a semi-finished flange with machining allowance in both the outer diameter and thickness directions and unprocessed bolt holes. The weld seams of the blank forged flange 1 are concentrated on the inner side near the blank forged flange 1. This ensures that the weld seams are not damaged after the upper surface of the blank forged flange 1 is machined, thus guaranteeing the strength of the weld. It avoids weld seams on the upper surface of the blank forged flange 1, because the upper surface of the blank forged flange 1 needs to be machined after welding, and machining may remove the weld seams, affecting the strength. Before use, measure the diameter of the blank forged flange 1. The maximum and minimum diameter deviation is one-thousandth of the diameter (7mm in this embodiment).

[0039] Step B: After the plain forged flange 1 passes inspection and is put into production, a reinforcing tooling ring 2 to prevent deformation is first welded to the outer edge of the plain forged flange 1. Figure 1 As shown, this reduces the tendency of the blank forging flange 1 itself to continue to deform during subsequent welding and heat treatment processes, and controls the roundness of the blank forging flange 1 body as much as possible.

[0040] Step C, as Figure 2 As shown, first process the bevel positions required for assembling the blank forged flange 1 and the cylinder 3, then assemble and position the cylinder 3 and the blank forged flange 1, and then weld the two blank forged flanges 1 together with connecting stiffeners 4, which plays a role in preventing deformation during welding and reducing deformation during the welding process; after completing the above work, welding can be carried out directly according to the process requirements without having to consider factors such as interpass temperature, thus ensuring the product manufacturing cycle.

[0041] Step D: Weld the weld seam according to the drawings and process requirements. Follow the welding process requirements during welding and do not need to pay special attention to the workpiece temperature.

[0042] Step E: Perform localized heat treatment on the welded flange 6 and weld seam by wrapping them with electric heating rope and insulation cotton to relieve stress. The heat treatment temperature and time are 580℃~640℃ and the holding time is 1~3 hours. The holding time can be adjusted according to the flange thickness. Do not remove the insulation cotton after the heat treatment is completed to avoid rapid cooling.

[0043] Step F: Cut the weld joints of the two flanges 6 apart to prepare for processing;

[0044] Step G: Cut and remove the connecting stiffener 4 and tooling reinforcing ring 2 from the outside of flange 6; machine the upper and lower end faces of flange 6, measure the thickness after flattening one side, ensuring that the thickness at the lowest point is not lower than the set thickness, and then machine the other side; after the upper and lower end faces of flange are machined, machine the outer edge of flange, and then machine the bolt holes 5; after machining, as shown... Figure 3 As shown;

[0045] Step H: Install (by welding or tightening with plugs) the bushing 8 on the flat end face of the flange 6 that has been processed, and complete the weld between the bushing 8 and the connecting parts according to the drawings and welding process (at this time, the amount of welding is small and there will be no deformation again).

[0046] Step I involves a second machining of the sealing surface of the bushing 8. Due to effective control in the initial machining stage and the single-stage machining, the unevenness will be very small, generally below 2mm. The machining cycle and the amount of special material removed are also very small. After machining, the sealing surface will not deform again, ensuring a sufficient sealing effect. The finished product is as follows: Figure 5 As shown.

[0047] When the bushing 8 installed in step H is a non-weldable bushing, in step G, while drilling the corresponding bolt holes 5, it is also necessary to drill the plug holes 7. The assembled condition is as follows. Figure 4 As shown; when the bushing 8 installed in step H is a weldable bushing, in step G only the corresponding bolt holes 5 need to be drilled.

[0048] When the bushing in step H is a non-weldable bushing, the bushing 8 is tightened with a plug; when the bushing in step H is a weldable bushing, the bushing 8 is welded onto the flat end face of the already machined flange 6.

[0049] When the bushing 8 in step H is a non-weldable bushing, the connecting component is a sleeve, and the non-weldable bushing is welded to the sleeve; when the bushing in step H is a weldable bushing, the connecting component is a flange 6, and the weldable bushing is welded to the flange 6.

Claims

1. A method for processing a large-diameter type A / B flat-face welding flange with a liner ring, characterized in that: Includes the following steps Step A: Purchase blank forged flanges. Blank forged flanges are semi-finished flanges with machining allowances in both the outer diameter and thickness directions and unmachined bolt holes. Step B: Weld a tooling reinforcing ring to the outer edge of the blank forging flange to prevent deformation; Step C: Assemble and position the cylinder body and the blank forging flange, and then weld the two blank forging flanges together with connecting stiffeners to reduce deformation during the welding process; Step D: Weld the weld seam; Step E involves applying localized heat treatment to the welded flange and weld seam by wrapping them with electric heating ropes and insulating cotton to relieve stress. Step F: Cut the welded joints of the two flanges apart, preparing them for processing; Step G: Cut and remove the connecting stiffeners and tooling reinforcing rings on the outside of the flange, machine the upper and lower end faces of the flange, measure the thickness after one side is flat, and ensure that the thickness at the lowest point is not lower than the set thickness, and then machine the other side. After the upper and lower end faces of the flange are machined, machine the outer edge of the flange, and then machine the bolt holes. Step H: Install the bushing on the already machined flat end face of the flange, and complete the weld between the bushing and the connecting parts as required; Step 1: Secondary machining of the bushing sealing surface; In step A, the welds of the blank forging flange are concentrated on the inner side near the blank forging flange, avoiding welds on the upper surface of the blank forging flange. In step C, before assembling and tack welding the cylinder body with the blank forging flange, the bevel positions required for assembling the blank forging flange and the cylinder body are first machined.

2. The processing method of the large-diameter type A / B flat-face welding flange with a liner ring according to claim 1, characterized in that: Before use, the diameter of the blank forged flange in step A is measured, and the maximum and minimum diameter deviation is one-thousandth of the diameter.

3. The processing method of the large-diameter type A / B flat-face welding flange with a liner ring according to claim 1, characterized in that: The heat treatment temperature and time in step E are 580℃~640℃, and the holding time is 1~3 hours.

4. The processing method of the large-diameter type A / B flat-face welding flange with a liner ring according to claim 1, characterized in that: When the bushing installed in step H is a non-weldable bushing, in step G, while marking and drilling the corresponding bolt holes, it is also necessary to drill plug holes; when the bushing installed in step H is a weldable bushing, in step G, it is only necessary to mark and drill the corresponding bolt holes.

5. The processing method of the large-diameter type A / B flat-face welding flange with a liner ring according to claim 4, characterized in that: When the bushing in step H is a non-weldable bushing, the bushing is tightened with plugs; when the bushing in step H is a weldable bushing, the bushing is welded onto the already machined flat end face of the flange.

6. The processing method of the large-diameter type A / B flat-face welding flange with a liner ring according to claim 4, characterized in that: When the bushing in step H is a non-weldable bushing, the connecting component is a sleeve, and the non-weldable bushing is welded to the sleeve; when the bushing in step H is a weldable bushing, the connecting component is a flange, and the weldable bushing is welded to the flange.

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