A coke drum shell section replacement method

Abstract

The application discloses a coke tower barrel section replacement method, which comprises the steps of quarter barrel prefabrication, anti-deformation tooling and welding and original barrel replacement; when prefabricating, the steel plate is detected for acceptance; a plurality of quarter barrels are coiled and spare parts are reserved; when the anti-deformation tooling is welded, the quarter barrel is positioned by scribing, and a reinforcing ring, an arc-shaped backing plate and the like are sequentially welded; when the original barrel is replaced, the original quarter barrel is removed by cutting and moving in a diagonal manner after the hanger is welded; the remaining part is beveled and detected; after the prefabricated barrel is welded with the hanger, the barrel is hoisted into place, the longitudinal seam and the ring seam are adjusted, fixed and welded, the edge deviation is controlled in the process, preheating, hydrogen removal treatment and 100% ultrasonic flaw detection are implemented, and parameters are recorded and filed; the method can effectively control deformation, and guarantee replacement quality and safety.

Description

Technical Field

[0001] This invention specifically relates to a method for segmented replacement of a coke tower shell. Background Technology

[0002] As the core equipment of delayed coking units, coke towers are mainly used for the cracking of residual oil and coke generation under high temperature and high pressure. Their cylindrical structure is usually welded from multiple sections of composite steel plates, with a design pressure of 0.3-0.6 MPa and an operating temperature of 400-500℃.

[0003] Coking tower bodies are typically made of low-alloy steel such as 15CrMoR, requiring strict control of heat input during welding. Uneven thickness in areas of large-area corrosion thinning can lead to differences in the thermal expansion coefficients of the base material and the welding material, resulting in residual stress concentration. When corrosion thinning exceeds 30% of the original wall thickness, welding repair can cause grain coarsening in the heat-affected zone, making it prone to new cracks under alternating thermal stress. Welding is unlikely to restore the original design strength. Coking tower bodies typically have a diameter of 4-6 meters; localized high temperatures during welding reduce the material's yield strength, making it susceptible to the "banana effect" and excessive ellipticity under its own weight. Furthermore, on-site construction risks are significant during tower replacement.

[0004] Therefore, it is necessary to invent a method for segmented replacement of the coke tower body to solve the above problems. Summary of the Invention

[0005] (a) Purpose of the invention The purpose of this invention is to provide a method for segmented replacement of a coke tower shell.

[0006] (II) Technical Solution To achieve the above objectives, the present invention provides the following technical solution: a method for segmented replacement of a coke tower shell, comprising the following steps: S1, prefabricated quarter-cylinder, including: S1.1 Factory Acceptance: After the steel plates return to the factory, check their qualifications, dimensions and appearance in sequence; conduct 100% ultrasonic testing on the composite steel plates; conduct 100% penetrant testing on the composite layer of the composite steel plates; S1.2, Cylindrical Forming: Mark lines according to the net material dimensions, with two steel plates having a machining allowance in the length direction. After marking, complete the cutting. Make inner bevels at the longitudinal and circumferential seams of the cut steel plates and perform edge trimming. Perform 100% PT testing on the processed bevels. According to the requirement that the composite layer faces inward, roll the qualified beveled steel plates into quarter-cylindrical parts, making multiple parts in total, while reserving unrolled steel plates as spare parts. S2. Anti-deformation tooling welding, including: S2.1 Tooling Position Marking: On the outer wall of the cylinder corresponding to the included angle of the octagonal main beam grid on the fourth platform of the coke tower, divide the cylinder circumference into eight equal parts; based on the eight equal parts, mark the tooling welding position lines, the cylinder longitudinal seam dividing lines, and the circumferential seam dividing lines; at the same time, mark the dimension inspection lines 200mm above and below the quarter cylinder dividing lines, and record the initial dimension data of the corresponding positions of the inspection lines; install four equally distributed support tools, and the installation positions of the four support tools are completely staggered from the four longitudinal seams of the cylinder; mark four zones on the outer wall of the cylinder; mark the reinforcing ring welding position lines 200mm above and below the cylinder where the tooling is to be installed; mark the arc-shaped pad welding position lines 150mm above and below the reinforcing ring welding position lines. S2.2 Tooling and Welding: Complete the welding of the reinforcing ring, arc-shaped pad, stiffening plate and support plate, and H-beam support beam in sequence; S3. Replacement of the original cylinder, including: S3.1 Welding of lifting lugs on the original cylinder: Based on the center lines of the marked longitudinal and circumferential seam dividing lines, use R307G welding rods to weld lifting lugs on the outer wall of the original coke tower cylinder to be cut; the welding position of the lifting lugs shall be adjusted according to the actual direction of the lifting equipment on site, and the installation position of the lifting lugs shall be directly above the center of gravity of the corresponding section of the original cylinder; use a hand-operated hoist to connect and fix the lifting lugs, so that they can be safely removed after the original cylinder is cut; S3.2 Removal of the original quarter-section cylinder: Tighten the installed lifting lugs with a hand chain hoist; use a plasma gas cutter to cut the original cylinder into quarter-section sections along the center lines of the longitudinal and circumferential seam dividing lines; preheat the cutting area at the circumferential seam position with an oxyacetylene flame before cutting, with a preheating temperature ≥100℃. S3.3 Original cylinder disassembly and beveling: After the original quarter cylinder is cut, disassemble and remove the original quarter cylinder; grind the circumferential cut end face of the remaining part of the original cylinder, and then trim the composite layer of the circumferential cut end face according to the preset beveling diagram; after trimming, perform 100% PT testing on the processed beveling. S3.4, Precast Quarter-Cylinder Body Lug Welding: Select lifting lugs made of 15CrMoR material and weld them to the outer wall of the precast quarter-cylinder body made of S12 according to the site conditions; use R307G welding rods for full welding; preheat the welding area with an oxyacetylene flame before welding, with a preheating temperature ≥100℃; immediately after welding, perform hydrogen removal treatment on the weld area at 300~350℃; after hydrogen removal treatment, grind the weld surface and then perform 100% magnetic particle inspection on the weld; S3.5, Precast Quarter Cylinder Lifting: A crane is used to lift the precast quarter cylinder after the welding lugs are installed to the fourth platform at a height of 32m above the ground; a hand-operated hoist is used to assist in the transfer of the precast quarter cylinder on the platform and to lift it to the position to be welded after the original cylinder has been removed; S3.6, Precast Quarter-Cylinder Assembly and Welding: The position of the quarter-cylinder is adjusted by the riveter using a hand-operated hoist and jack, so that the quarter-cylinder is assembled with the remaining part of the original cylinder. During the assembly process, the misalignment of the longitudinal and circumferential seams is controlled to be ≤1mm. After assembly, the quarter-cylinder is temporarily fixed with a precast connecting plate. The connecting weld between the connecting plate and the cylinder is welded using R307G welding rods. The welding area is preheated before welding, with a preheating temperature ≥100℃. After welding, the weld area is immediately subjected to hydrogen removal treatment at 300~350℃. After hydrogen removal treatment, the weld surface is ground, and then the weld is subjected to 100% MT inspection. S3.7 Replacement sequence control: When removing the second quarter original cylinder, a diagonal removal method is adopted, that is, the removal position is diagonally distributed with the removal position of the first quarter original cylinder, to avoid removing adjacent quarter original cylinders; S3.8 Longitudinal and circumferential welds: For the longitudinal and circumferential weld areas on the outside of the quarter-prefabricated cylinder and the remaining part of the original cylinder, preheating is performed using electric heating elements at a preheating temperature ≥150℃; welding is performed using R307G welding rods; immediately after welding, the weld area is subjected to hydrogen removal treatment at 300-350℃ for 4 hours; after hydrogen removal treatment, the weld surface is ground until it meets the requirements for flaw detection; process parameters and test data of the entire welding process are recorded, and the recorded data is archived as completion data.

[0007] The specific process for welding the reinforcing rings in S2.2 is as follows: Select 16 prefabricated quarter-arc reinforcing rings and position them according to the welding position lines marked in S2.1; use R307G welding rods to perform intermittent welding on the connection between the reinforcing rings and the cylinder; use E5015 welding rods to weld the joints between the quarter-arc reinforcing rings; preheat the welding area with an oxyacetylene flame before welding, with a preheating temperature ≥100℃; after welding, grind the weld surface and then perform 100% MT inspection on the weld.

[0008] The specific process for welding the arc-shaped backing plate in S2.2 is as follows: The arc-shaped backing plate is welded according to the markings in S2.1; the connection between the arc-shaped backing plate and the cylinder is welded using R307G welding rods, and a 10-15mm vent hole is reserved at the bottom of the arc-shaped backing plate; the welding area is preheated with an oxyacetylene flame before welding, with a preheating temperature ≥100℃; after welding, the weld area is immediately subjected to hydrogen removal treatment at 300-350℃; after hydrogen removal treatment, the weld surface is ground, and then the weld is subjected to 100% MT inspection.

[0009] The specific process for assembling and welding the stiffening plates and support plates in S2.2 is as follows: Position the stiffening plates and support plates according to the pre-set installation drawings; weld the connection between the stiffening plates, support plates and cylinder using E5015 welding rods; preheat the welding area with an oxyacetylene flame before welding, with a preheating temperature ≥100℃; immediately after welding, perform hydrogen removal treatment on the weld area at 300~350℃; after hydrogen removal treatment, grind the weld surface, and then perform 100% MT inspection on the weld.

[0010] The specific process of welding the H-beam support beam in S2.2 is as follows: According to the preset H-beam installation drawings, position the H-beam at the preset connection position between the support plate and the reinforcing ring; use E5015 welding rods to weld the connection parts between the H-beam and the support plate, and between the H-beam and the reinforcing ring; after welding, grind the weld surface, and then perform 100% MT inspection on the weld.

[0011] When using R307G welding electrodes in S3.8, the specifications of the R307G welding electrodes used are Φ3.2mm, Φ4.0mm or Φ5.0mm.

[0012] In S3.5, when using a hand chain hoist to assist in the transfer of a quarter of the precast cylinder on the platform, at least two hand chain hoists shall be set up, and the two hand chain hoists shall be symmetrically distributed on both sides of the quarter of the precast cylinder.

[0013] After recording the initial dimensional data of the corresponding position of the inspection line in S3.6, after the welding of one-quarter of the precast cylinder is completed, measure the dimensional data of the corresponding position of the inspection line again and compare the initial dimensional data with the dimensional data after welding.

[0014] In S1.2, the two steel plates have a machining allowance of 10-15mm in the length direction, and the allowance portion is ground to ensure flatness after cutting.

[0015] When using a plasma cutting machine to cut along the center line of the longitudinal seam and the circumferential seam in S3.2, the cutting current of the plasma cutting machine is 120-150A and the cutting speed is 300-400mm / min.

[0016] Compared with the prior art, the beneficial effects of the above-mentioned technical solution of the present invention are: 1. This invention adopts a quarter-cylinder prefabrication replacement. The prefabricated cylinder is made of 15CrMoR+S11306 composite plate, which is consistent with the original cylinder. It has passed 100% UT (NB / T47013.3-2023) and 100% PT (NB / T47013.5-2015) tests. The prefabrication and beveling are up to standard. After replacement, the original design wall thickness and strength can be fully restored, meeting the API 510 standard. 2. This invention controls risks through three design aspects: First, it uses an eight-part support fixture, a reinforcing ring, and an arc-shaped pad. 100% of the fixture welds are MT (NB / T47013.4-2015) qualified, ensuring ovality meets standards. Second, it adopts a diagonal dismantling sequence, lifting only one quarter of the prefabricated cylinder at a time, reducing lifting risks. Third, the lifting lugs are fully welded with matching welding rods, preheated to ≥100℃ before welding, and dehydrogenated at 300-350℃ after welding, ensuring precise positioning and preventing the cylinder from tipping over. 3. This invention uses a factory prefabrication and on-site segmented replacement process to optimize the construction period: factory prefabrication and on-site preparation are carried out in parallel; the cutting, hoisting and welding time of a single quarter-cylinder is short, and the total circumference processing time of the four equal-section cylinder is short, which is shorter than the time required for traditional welding and replacement, reducing downtime losses; 4. This invention features full-process quality control. During factory prefabrication, 100% of the materials, bevels, and tooling welds are inspected for defects. Before on-site welding, the electric heating element is preheated to ≥150℃ using Φ3.2 / 4.0 / 5.0 R307G welding rods. After welding, the material is dehydrogenated at 300-350℃ for 4 hours, and the entire process is recorded. After replacement, post-weld defect inspection, final heat treatment, post-heat re-inspection, defect inspection after tooling removal, and pressure testing are performed sequentially, extending the life of the cylinder and reducing the number of subsequent maintenance operations and costs. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this invention. For those skilled in the art, other drawings can be obtained based on these drawings.

[0018] Figure 1 This is a flowchart of the cylinder replacement process of the present invention; Figure 2 This is a schematic diagram of the overall structure of the cylindrical body of the present invention; Figure 3 This is a schematic diagram of the cylinder partitioning of the present invention; Figure 4 This is a schematic diagram of the prefabricated cylinder hoisting process of the present invention; Figure 5 This is a schematic diagram of the connecting fixture of the present invention. Detailed Implementation

[0019] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.

[0020] This invention provides, for example Figure 1-5 The method for segmented replacement of a coke tower shell, as shown, includes the following steps: S1, prefabricated quarter-cylinder, including: S1.1 Considering the corrosion and high-temperature conditions of the coke tower, a metal composite steel plate with a base layer of 15CrMoR and a composite layer of S11306 is selected. The base layer is 24mm thick and the composite layer is 3mm thick, which is consistent with the original coke tower body material to avoid the risk of welding dissimilar steels. After the steel plates arrive at the factory, the quality certification documents, including material certificates, mechanical property reports, and non-destructive testing reports, are checked to confirm that the chemical composition, yield strength, and tensile strength of the steel plates meet the requirements of GB / T19189-2011. The thickness of the steel plate is measured using a digital vernier caliper with an accuracy of ±0.5mm, and the length and width of the steel plate are measured using a 5m steel tape measure with an accuracy of ±1mm to ensure that the original plate size meets the subsequent cutting requirements. Using a visual inspection combined with a 10x magnifying glass, the steel plate surface was checked for scratches, dents, delamination, or oxide scale buildup, and there were no signs of peeling between the composite layer and the base layer. UT testing uses a 2.5MHz, Φ20mm straight probe with machine oil as the coupling agent. 100% testing is performed according to NB / T47013.3-2023. The instrument sensitivity is adjusted to the equivalent of a Φ2mm flat-bottom hole, requiring no defects ≥Φ2mm. The focus is on testing the interface between the base layer and the composite layer to ensure a bonding rate ≥99%. PT testing uses solvent-based dye penetrant testing reagent, and 100% testing is performed according to NB / T47013.5-2015. The penetration time is 10 minutes and the development time is 8 minutes. It is required that there are no linear or circular defects to prevent surface cracks of the composite layer from affecting the corrosion resistance. S1.2 Mark the lines according to the net material dimensions (24+3)×3300×6620mm, with a 12mm machining allowance reserved in the length direction of the two steel plates for trimming the end face flatness after rolling, and to avoid length deviation caused by rolling deformation; use a CNC marking machine with a marking accuracy of ±0.5mm to mark the position lines of the longitudinal seam, circumferential seam and cutting line; The material is cut using a CNC plasma cutting machine with a cutting current of 120~150A and a cutting speed of 300~400mm / min. The surface roughness Ra of the cut surface is ≤25μm. After cutting, the reserved allowance is ground with an angle grinder to ensure that the flatness of the steel plate edge is ≤0.3mm / m, so as to avoid deviation in subsequent beveling. V-shaped inner bevels are machined at the longitudinal and circumferential seam positions, with a bevel angle of 60°±5°, a blunt edge of 2mm±0.5mm, and a gap of 2mm±0.3mm. The machining is carried out using a CNC edge planer. After machining, the oxide scale on the bevel surface is cleaned with an angle grinder, and the roughness Ra≤12.5μm.

[0021] Non-destructive testing of bevels is performed according to NB / T47013.5-2015 with 100% PT testing. The testing steps are the same as PT testing in 1.1. It is required to achieve Level 1 qualification to prevent surface cracks in the bevel from causing welding defects. A three-roll plate rolling machine is used, and the composite layer is rolled inward. During rolling, the pressure of the upper roller is controlled at 15~18MPa and the feed speed is 500mm / min. After rolling 500mm of length, the curvature is checked with an arc template. The gap between the template and the cylinder wall is ≤1mm to ensure that the curvature of the cylinder after rolling meets the design requirements. Eight quarter-cylinder sections were rolled to meet the backup needs of replacing two sections of each of the four sections of cylinder on site. At the same time, two unrolled composite steel plates were reserved as backup parts for sudden damage on site to avoid delays in the construction period due to cylinder damage. S2. Welding of anti-deformation fixtures: The coke tower shell is a thin-walled structure, and it is prone to deformation due to insufficient rigidity after being dismantled in sections. This step improves the rigidity of the shell by welding anti-deformation fixtures, including: S2.1 Tooling position marking: Using the octagonal main beam grid of the fourth platform of the coke tower as a reference, a total station was used to measure the center of the cylinder corresponding to the included angle of the grid, ensuring that the coaxiality between the scribing center and the center of the cylinder is ≤1mm. Divide the cylinder into eight equal parts along its circumference, with each division angle being 45°±0.1° and a marking error of ≤0.5mm / m. Mark these eight dividing lines. Tooling welding position lines: Mark the welding positions of the supporting tooling on the 45°, 135°, 225°, and 315° bisectors, staggered from the longitudinal seam. The longitudinal seam is located at 0°, 90°, 180°, and 270° to avoid interference between the tooling and the longitudinal seam during welding. Longitudinal and circumferential seam dividing lines: Mark the longitudinal and circumferential seam dividing lines of the quarter-section cylinder to be removed, and the straightness of the dividing lines should be ≤0.5mm / m; Dimensional inspection lines: Draw inspection lines 200mm above and below the circumferential seam dividing line, and record the cylinder circumference at each inspection line with a digital tape measure for comparison of deformation after subsequent welding. Divide the cylinder circumference into four zones: A, B, C, and D (0°~90° is zone A, 90°~180° is zone B, 180°~270° is zone C, and 270°~360° is zone D) according to the dividing lines, and mark them with paint to facilitate the control of the subsequent dismantling sequence; Reinforcing ring welding lines: Draw reinforcing ring welding lines at elevations of 31m and 33m; draw arc-shaped pad welding lines 150mm above and below the reinforcing ring welding lines to ensure uniform tooling distribution and consistent rigidity improvement effect. S2.2 Tooling assembly and welding: Welding parameters and testing requirements must be strictly controlled during tooling assembly and welding to avoid deformation of the cylinder or weld defects caused by tooling welding. S2.2.1, Reinforcing ring welding: Sixteen prefabricated quarter-arc reinforcing rings were selected, with the length consistent with the height of the cylinder repair section, and a 50mm seam allowance was reserved at both ends of each reinforcing ring; The 16 reinforcing rings are positioned in sections according to the reinforcing ring welding line, with a gap of 2mm±0.3mm between adjacent reinforcing rings, and are fixed by spot welding.

[0022] Connection between the reinforcing ring and the cylinder: Intermittent welding is performed using R307G welding rods, with a weld length of 50mm, a spacing of 100mm, a welding current of 160~180A, a voltage of 22~24V, and a welding speed of 150~180mm / min to avoid local overheating and deformation caused by continuous welding. Welding of the reinforcing ring joint: Use E5015 welding rods, welding current 180~200A, voltage 24~26V, preheat with oxy-acetylene flame before welding; After welding, use an angle grinder to grind the weld surface to remove weld beads and spatter, so that the surface roughness Ra of the weld is ≤12.5μm.

[0023] Perform 100% MT testing according to NB / T47013.4-2015, using the magnetic yoke method and black water white magnetic powder testing solution, requiring no linear or circular defects, to ensure that the reinforcing ring weld has no risk of cracking. S2.2.2, Arc-shaped backing plate assembly and welding: The arc-shaped backing plate is made of 15CrMoR material, which is the same material as the base layer of the cylinder to avoid corrosion potential difference between dissimilar steels. The dimensions are 300mm in length, 50mm in width, and 5mm in thickness, with an arc radius of 3200mm. A Φ12mm vent hole is drilled in the center of the bottom of the backing plate. Each backing plate has one vent hole with a spacing of 200mm to allow gas to escape during welding and reduce porosity defects. Position the arc-shaped pad according to the welding line, and fix the pad with the cylinder wall with a gap of ≤0.5mm by spot welding; Use R307G welding rods for welding. The welding current is 160~180A and the voltage is 22~24V. Preheat with an oxy-acetylene flame before welding. Avoid welding through pores during welding. Immediately after welding, hydrogen removal treatment is carried out using a tracked heater. The heating range is 100mm on each side of the weld, the temperature is 320℃, and the temperature is maintained for 1 hour. Then, the weld is slowly cooled to room temperature to avoid rapid cooling that could produce martensitic structure and cause cracks. After hydrogen removal, grind the weld surface and perform 100% MT testing according to NB / T47013.4-2015, requiring Level I qualification to ensure that there are no hydrogen-induced cracks in the backing plate weld. S2.2.3, Welding of stiffening plates and support plates: The stiffening plates are made of Q345R steel plate (150mm×100mm×8mm), and the support plates are made of Q345R steel plate (200mm×150mm×10mm). Position the stiffening ribs and support plates according to the diagram. The fitting gap between the stiffening ribs and the reinforcing ring and the cylinder body should be ≤0.5mm, and the fitting gap between the support plate and the stiffening ribs should be ≤0.5mm. Spot welding should be used for fixing. Use E5015 welding rods for welding, with a welding current of 180~200A and a voltage of 24~26V. Preheat with an oxy-acetylene flame before welding to ensure full penetration. Immediately after welding, perform hydrogen removal treatment, and after slow cooling to room temperature, grind the weld surface. Perform 100% MT testing according to NB / T47013.4-2015, requiring Level I qualification, to ensure that the load-bearing capacity of the welds of the stiffening plates and support plates meets the standards; S2.2.4, Welding of H-beam support beams: Select Q345B H-beams, cut the beveled ends according to the drawing, and remove the burrs at the ends; Position the H-beams at the top of the support plate and the outside of the reinforcing ring as shown in the diagram. The gap between the H-beams and the support plate and reinforcing ring should be ≤0.5mm, and they should be fixed by spot welding. E5015 welding rods are used for welding, with a welding current of 200~220A and a voltage of 24~26V. Multi-layer and multi-pass welding is adopted, with an interpass temperature of ≥150℃ to avoid defects caused by excessive cooling between layers. After welding, grind the weld surface to Ra≤12.5μm, and perform 100% MT testing according to NB / T47013.4-2015, requiring Level I qualification, to ensure that the H-beam support beam can withstand the load during the dismantling and installation of the cylinder; S3. Replacement of the original cylinder, including: S3.1, Welding of original cylinder lifting lugs: The lifting lugs are made of Q345R material, and the welding position is calculated based on the center of gravity of the original quarter cylinder. Position the lifting lugs according to the center lines of the longitudinal and circumferential seams. The gap between the lifting lugs and the cylinder wall should be ≤0.5mm. Use E5015 welding rods for welding. The welding current should be 180~200A and the voltage should be 24~26V. The weld height should be 12mm to ensure full penetration. The position of the lifting lugs is finely adjusted according to the boom length and angle of the on-site lifting equipment (160-ton crane) (fine adjustment range ≤50mm) to avoid interference between the crane boom and the platform; After welding is completed, a 2-ton hand chain hoist is used to connect the lifting lug to the fixed lifting point of the fourth platform, and the hand chain hoist is tightened to ensure that the original cylinder will not tilt or fall after being cut. S3.2, Removal of the original quarter-cylinder: A protective net (with a load-bearing capacity of ≥100kg) should be installed below the cutting area to prevent cutting debris from falling and injuring people; construction workers should wear heat-resistant gloves and goggles to avoid injury from plasma cutting arc light and high temperature. Use a plasma cutting machine to cut along the center line of the longitudinal and circumferential seams. The cutting current is 130A and the cutting speed is 350mm / min. During cutting, keep the cutting nozzle perpendicular to the surface of the cylinder and keep a distance of 10~15mm to ensure a flat cut surface. Before cutting the circumferential seam, preheat the cutting area with an oxyacetylene flame at a temperature of 110℃ (≥100℃) and monitor the temperature with a spot thermometer to avoid brittle fracture of the cylinder caused by low-temperature cutting. During the cutting process, the pulling force is adjusted in real time using a hand-operated hoist to prevent the cylinder from deforming due to its own weight. The cutting sequence is longitudinal seam first, then circumferential seam, to ensure that the entire cylinder can be removed after one-quarter of the cylinder is cut. S3.3, Original cylinder disassembly and beveling: After the cutting was completed, a 2-ton hand chain hoist was used to slowly lift the original 1 / 4 of the cylinder to the designated area on the ground. After disassembly, the corrosion and deformation of the original cylinder were checked to confirm that the damage range was consistent with the repair plan. The remaining part of the original cylinder was ground with an angle grinder to remove oxide scale and slag. The surface roughness Ra after grinding was ≤12.5μm. According to the bevel shape of the precast cylinder, the composite layer on the end face of the circumferential joint is trimmed with a planer to a depth of 3mm to ensure that the composite layer is flat at the joint. Perform 100% PT testing according to NB / T47013.5-2015. The testing steps are the same as those in 1.1 for PT testing. Level I qualification is required to prevent residual cracks on the bevel surface from affecting the subsequent welding quality. S3.4, Prefabricated quarter-cylinder body with lugs for welding: The lifting lugs are made of 15CrMoR material and are the same size as the original cylinder lifting lugs (150mm×100mm×12mm), with an opening of Φ20mm. Based on the on-site hoisting conditions, the lifting lugs are welded directly above the center of gravity of the precast quarter-cylinder outer wall, with a gap of ≤0.5mm between the lifting lugs and the cylinder wall. Use R307G welding rods for full welding, with a welding current of 160~180A, a voltage of 22~24V, and a weld height of 12mm. Preheat with an oxy-acetylene flame before welding to ensure full penetration. Immediately after welding, hydrogen removal is performed using a tracked heater. After slow cooling to room temperature, the weld surface is ground. Perform 100% MT testing according to NB / T47013.4-2015, requiring Level I qualification, to ensure that the lifting lug welds can withstand the lifting load; S3.5, Precast quarter-cylinder hoisting: A 160-ton truck crane was selected, equipped with a Φ20mm steel wire rope. The two ends of the steel wire rope were connected to the lifting lugs of the precast cylinder through shackles. Check the load-bearing capacity of the fourth platform, clear any obstacles from the platform, and ensure that the transfer passage is unobstructed; The crane slowly lifted the precast cylinder to the fourth platform at an elevation of 32m. During the lifting process, two commanders controlled the crane's position relative to the ground to prevent collisions with other components of the coke tower. Two 2-ton manual chain hoists are used on the platform, symmetrically distributed on both sides of the precast cylinder. The cylinder is slowly transported to the welding position by the manual chain hoists. During the transportation process, wooden blocks are placed at the bottom of the cylinder to avoid scratching the composite layer. S3.6, Prefabricated quarter-cylinder assembly and welding: The riveter uses a hand-operated hoist to adjust the circumferential position of the cylinder and a 50-ton jack to adjust the axial position, ensuring that the precast cylinder is aligned with the longitudinal and circumferential seams of the original cylinder. Use a feeler gauge to check the internal misalignment of the longitudinal and circumferential seams. The internal misalignment should be ≤1mm. Stop adjusting once the requirement is met. Prefabricated 15CrMoR connecting plates are used to temporarily fix the prefabricated cylinder to the original cylinder, and the fitting gap between the connecting plate and the cylinder is ≤0.5mm; The connecting plate is welded using R307G welding rods with a welding current of 160~180A and a voltage of 22~24V. The preheating temperature before welding is 110℃≥100℃ to ensure that the weld of the connecting plate can withstand the subsequent welding stress. Immediately after welding, perform hydrogen removal treatment, and after slow cooling to room temperature, grind the weld surface. Perform 100% MT testing according to NB / T47013.4-2015, requiring Level I qualification, and ensure that the temporary fixing weld is free of defects; S3.7, Change sequence control: The principle of "diagonal removal" is adopted, that is, first remove one-quarter of the cylinder in area A (0°~90°), and after the welding is completed, remove one-quarter of the cylinder in area C (180°~270°) (diagonally opposite to area A), to avoid removing the adjacent area B (90°~180°) or area D (270°~360°). Adjacent removal can cause a sharp drop in the local stiffness of the cylinder, which can easily lead to deformation of ≥2mm / m; however, after diagonal removal, the remaining cylinder is symmetrically distributed at 180°, with more uniform stiffness and deformation that can be controlled to ≤0.5mm / m, meeting the design requirements. After the welding in area C is completed, areas B and D are removed according to the same principle to ensure that the deformation of the cylinder is controllable throughout the process. S3.8, Welding of longitudinal and circumferential seams: Electric heating elements are used to preheat the outer sides of the longitudinal and circumferential seams. The heating elements cover 100mm on each side of the weld seam. The preheating temperature is controlled to 160℃ using a temperature controller and held for 30 minutes to ensure uniform temperature in the welding area and reduce welding stress. The welding electrodes used are R307G, with specifications of Φ3.2mm, Φ4.0mm, and Φ5.0mm, and the welding process card must be strictly followed. Root pass welding: Current 120~140A, voltage 20~22V, speed 120~150mm / min, to ensure root penetration and no incomplete penetration defects; Filler welding: current 160~180A, voltage 22~24V, speed 150~180mm / min, clean the slag with a wire brush after each layer, and the interpass temperature ≥150℃; Cover weld: Current 200~220A, voltage 24~26V, speed 180~200mm / min, ensure weld reinforcement of 2~3mm, and no weld beads or undercut on the surface; After welding, hydrogen removal treatment is immediately carried out using a tracked heater at 320℃ for 4 hours. The insulation material is 50mm thick aluminum silicate cotton to prevent heat loss from being too fast. After hydrogen removal, the weld surface is slowly cooled to room temperature. The weld surface is then ground with an angle grinder to remove excess weld height until it is flush with the surface of the cylinder. The surface roughness Ra ≤ 12.5 μm meets the flaw detection requirements. Perform 100% UT testing according to NB / T47013.3-2023 and 100% PT testing according to NB / T47013.5-2015 to ensure that the weld is free of internal or surface defects; Welding parameters and test data are recorded throughout the process. The recorded data is compiled into a completion file, archived, and stored for easy traceability in subsequent equipment maintenance.

[0024] In this invention, the deformation of the cylinder is ≤0.5mm / m, the pass rate of longitudinal and circumferential welds is 100%, the composite layer is flat and there is no risk of corrosion potential difference.

[0025] In this invention, by verifying the qualifications of steel plates and inspecting their dimensions and appearance, combined with 100% ultrasonic testing of composite steel plates and 100% penetrant testing of the composite layer, inferior or damaged steel plates are prevented from being used at the source. 100% PT testing of the bevel and positioning of the composite layer inward before rolling, while reserving a 10-15mm processing allowance and grinding for flatness, ensures the forming accuracy and performance of the quarter-cylinder. Unrolled steel plates are retained during prefabrication, which can quickly respond to emergencies such as damage to prefabricated components, avoid delays in the construction period due to missing parts, and indirectly ensure the overall construction quality.

[0026] In this invention, the lifting lug welding uses appropriate materials selected according to the working conditions to ensure that the welding part has the same performance as the cylinder body and meets the high-temperature operation requirements of the coke tower. The entire process involves preheating and hydrogen removal treatment, combined with 100% MT / PT testing of the weld, which eliminates common welding defects such as "cold cracking" and "hydrogen-induced cracking" from the process, greatly improves the strength and durability of the weld, and avoids safety accidents caused by weld failure during long-term operation. During assembly, the misalignment within the longitudinal and circumferential seams should be ≤1mm to ensure uniform stress distribution on the mating surfaces, reduce local stress concentration, and extend the overall service life of the cylinder.

[0027] In this invention, by installing and welding reinforcing rings, arc-shaped pads, H-beam support beams and stiffening plates, the rigidity of the cylinder during cutting, hoisting and welding processes is greatly improved, resisting bulging and bending deformation caused by thermal stress. The supporting fixtures are designed with "four equal parts distributed and staggered longitudinal seams" to avoid the fixtures causing additional stress to the weld area; at the same time, by "the included angle of the octagonal main beam grid corresponding to the eight equal parts marking lines", the symmetrical positioning of the fixtures is ensured, further balancing the force on the cylinder. Setting dimensional inspection lines 200mm above and below the quarter-cylinder dividing line, recording the initial dimensions and re-measuring them after assembly and welding, allows for real-time detection and adjustment of deformation, ensuring that the final dimensions of the cylinder match the original structure and avoiding assembly difficulties caused by deformation. By using the diagonal dismantling method, the stress balance of the remaining part of the original cylinder can be maintained, avoiding tilting, collapse or deformation of the cylinder due to a sudden drop in local rigidity, thus laying the foundation for the precise connection of subsequent prefabricated components.

[0028] The foregoing has only described certain exemplary embodiments of the present invention by way of illustration. Undoubtedly, those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the foregoing drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. A method for segmented replacement of a coke tower shell, characterized in that, Includes the following steps: S1, prefabricated quarter-cylinder, including: S1.1 Factory Acceptance: After the steel plates return to the factory, check their qualifications, dimensions and appearance in sequence; conduct 100% ultrasonic testing on the composite steel plates; conduct 100% penetrant testing on the composite layer of the composite steel plates; S1.2, Cylindrical Forming: Mark lines according to the net material dimensions, with two steel plates having a machining allowance in the length direction. After marking, complete the cutting. Make inner bevels at the longitudinal and circumferential seams of the cut steel plates and perform edge trimming. Perform 100% PT testing on the processed bevels. According to the requirement that the composite layer faces inward, roll the qualified beveled steel plates into quarter-cylindrical parts, making multiple parts in total, while reserving unrolled steel plates as spare parts. S2. Anti-deformation tooling welding, including: S2.1 Tooling Position Marking: On the outer wall of the cylinder corresponding to the included angle of the octagonal main beam grid on the fourth platform of the coke tower, divide the cylinder circumference into eight equal parts; based on the eight equal parts, mark the tooling welding position lines, the cylinder longitudinal seam dividing lines, and the circumferential seam dividing lines; at the same time, mark the dimension inspection lines 200mm above and below the quarter cylinder dividing lines, and record the initial dimension data of the corresponding positions of the inspection lines; install four equally distributed support tools, and the installation positions of the four support tools are completely staggered from the four longitudinal seams of the cylinder; mark four zones on the outer wall of the cylinder; mark the reinforcing ring welding position lines 200mm above and below the cylinder where the tooling is to be installed; mark the arc-shaped pad welding position lines 150mm above and below the reinforcing ring welding position lines. S2.2 Tooling and Welding: Complete the welding of the reinforcing ring, arc-shaped pad, stiffening plate and support plate, and H-beam support beam in sequence; S3. Replacement of the original cylinder, including: S3.1 Welding of lifting lugs on the original cylinder: Based on the center lines of the marked longitudinal and circumferential seam dividing lines, use R307G welding rods to weld lifting lugs on the outer wall of the original coke tower cylinder to be cut; the welding position of the lifting lugs shall be adjusted according to the actual direction of the lifting equipment on site, and the installation position of the lifting lugs shall be directly above the center of gravity of the corresponding section of the original cylinder; use a hand-operated hoist to connect and fix the lifting lugs, so that they can be safely removed after the original cylinder is cut; S3.2 Removal of the original quarter-section cylinder: Tighten the installed lifting lugs with a hand chain hoist; use a plasma gas cutter to cut the original cylinder into quarter-section sections along the center lines of the longitudinal and circumferential seam dividing lines; preheat the cutting area at the circumferential seam position with an oxyacetylene flame before cutting, with a preheating temperature ≥100℃. S3.3 Original cylinder disassembly and beveling: After the original quarter cylinder is cut, disassemble and remove the original quarter cylinder; grind the circumferential cut end face of the remaining part of the original cylinder, and then trim the composite layer of the circumferential cut end face according to the preset beveling diagram; after trimming, perform 100% PT testing on the processed beveling. S3.4, Precast Quarter-Cylinder Body Lug Welding: Select lifting lugs made of 15CrMoR material and weld them to the outer wall of the precast quarter-cylinder body made of S12 according to the site conditions; use R307G welding rods for full welding; preheat the welding area with an oxyacetylene flame before welding, with a preheating temperature ≥100℃; immediately after welding, perform hydrogen removal treatment on the weld area at 300~350℃; after hydrogen removal treatment, grind the weld surface and then perform 100% magnetic particle inspection on the weld; S3.5, Precast Quarter Cylinder Lifting: A crane is used to lift the precast quarter cylinder after the welding lugs are installed to the fourth platform at a height of 32m above the ground; a hand-operated hoist is used to assist in the transfer of the precast quarter cylinder on the platform and to lift it to the position to be welded after the original cylinder has been removed; S3.6, Precast Quarter-Cylinder Assembly and Welding: The position of the quarter-cylinder is adjusted by the riveter using a hand-operated hoist and jack, so that the quarter-cylinder is assembled with the remaining part of the original cylinder. During the assembly process, the misalignment of the longitudinal and circumferential seams is controlled to be ≤1mm. After assembly, the quarter-cylinder is temporarily fixed with a precast connecting plate. The connecting weld between the connecting plate and the cylinder is welded using R307G welding rods. The welding area is preheated before welding, with a preheating temperature ≥100℃. After welding, the weld area is immediately subjected to hydrogen removal treatment at 300~350℃. After hydrogen removal treatment, the weld surface is ground, and then the weld is subjected to 100% MT inspection. S3.7, Replacement of cylinder dismantling sequence: When dismantling the second quarter of the original cylinder, a diagonal dismantling method shall be adopted, that is, the dismantling position is diagonally distributed with the dismantling position of the first quarter of the original cylinder, to avoid dismantling adjacent quarters of the original cylinder; S3.8 Longitudinal and circumferential welds: For the longitudinal and circumferential weld areas on the outside of the quarter-prefabricated cylinder and the remaining part of the original cylinder, preheating is performed using electric heating elements at a preheating temperature ≥150℃; welding is performed using R307G welding rods; immediately after welding, the weld area is subjected to hydrogen removal treatment at 300-350℃ for 4 hours; after hydrogen removal treatment, the weld surface is ground until it meets the requirements for flaw detection; process parameters and test data of the entire welding process are recorded, and the recorded data is archived as completion data.

2. The method for segmented replacement of coke tower shell according to claim 1, characterized in that, The specific process for welding the reinforcing rings in S2.2 is as follows: Select 16 prefabricated quarter-arc reinforcing rings and position them according to the welding position lines marked in S2.1; use R307G welding rods to perform intermittent welding on the connection between the reinforcing rings and the cylinder; use E5015 welding rods to weld the joints between the quarter-arc reinforcing rings; preheat the welding area with an oxyacetylene flame before welding, with a preheating temperature ≥100℃; after welding, grind the weld surface and then perform 100% MT inspection on the weld.

3. The method for segmented replacement of the coke tower shell according to claim 1, characterized in that, The specific process for welding the arc-shaped backing plate in S2.2 is as follows: The arc-shaped backing plate is welded according to the markings in S2.1; the connection between the arc-shaped backing plate and the cylinder is welded using R307G welding rods, and a 10-15mm vent hole is reserved at the bottom of the arc-shaped backing plate; the welding area is preheated with an oxyacetylene flame before welding, with a preheating temperature ≥100℃; after welding, the weld area is immediately subjected to hydrogen removal treatment at 300-350℃; after hydrogen removal treatment, the weld surface is ground, and then the weld is subjected to 100% MT inspection.

4. The method for segmented replacement of the coke tower shell according to claim 1, characterized in that, The specific process for assembling and welding the stiffening plates and support plates in S2.2 is as follows: Position the stiffening plates and support plates according to the pre-set installation drawings; weld the connection between the stiffening plates, support plates and cylinder using E5015 welding rods; preheat the welding area with an oxyacetylene flame before welding, with a preheating temperature ≥100℃; immediately after welding, perform hydrogen removal treatment on the weld area at 300~350℃; after hydrogen removal treatment, grind the weld surface, and then perform 100% MT inspection on the weld.

5. The method for segmented replacement of coke tower shell according to claim 1, characterized in that, The specific process of welding the H-beam support beam in S2.2 is as follows: According to the preset H-beam installation drawings, position the H-beam at the preset connection position between the support plate and the reinforcing ring; use E5015 welding rods to weld the connection parts between the H-beam and the support plate, and between the H-beam and the reinforcing ring; after welding, grind the weld surface, and then perform 100% MT inspection on the weld.

6. The method for segmented replacement of coke tower shell according to claim 1, characterized in that, When using R307G welding electrodes in S3.8, the specifications of the R307G welding electrodes used are Φ3.2mm, Φ4.0mm or Φ5.0mm.

7. The method for segmented replacement of the coke tower shell according to claim 1, characterized in that, In S3.5, when using a hand chain hoist to assist in the transfer of a quarter of the precast cylinder on the platform, at least two hand chain hoists shall be set up, and the two hand chain hoists shall be symmetrically distributed on both sides of the quarter of the precast cylinder.

8. The method for segmented replacement of coke tower shell according to claim 1, characterized in that, After recording the initial dimensional data of the corresponding position of the inspection line in S3.6, after the welding of one-quarter of the precast cylinder is completed, measure the dimensional data of the corresponding position of the inspection line again and compare the initial dimensional data with the dimensional data after welding.

9. The method for segmented replacement of the coke tower shell according to claim 1, characterized in that, In S1.2, the two steel plates have a machining allowance of 10-15mm in the length direction, and the allowance portion is ground to ensure flatness after cutting.

10. The method for segmented replacement of the coke tower shell according to claim 1, characterized in that, When using a plasma cutting machine to cut along the center line of the longitudinal seam and the circumferential seam in S3.2, the cutting current of the plasma cutting machine is 120-150A and the cutting speed is 300-400mm / min.

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