Construction plan for the modification of non-standard equipment

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1. Project Overview 1.1 The XXXX methanol project plans to use four used equipment units, including a shift gas desulfurization tower transferred from XX, to manufacture some of the atmospheric and pressure vessels required for this project. The specifications of these four used equipment units are shown in the table below: Name, Specifications, Main Material, Quantity, Remarks; Shift Gas Desulfurization Tower: φ2200×31160×25, 16MnR, 1 unit; First Desulfurization Tower: φ1800×29145×20, 16MnR, 1 unit; Second Desulfurization Tower: φ1800×32314×22, 16MnR, 1 unit; Reaction Tank: φ2200×7144, 1 unit. 1.2 Due to having been stored for many years, these four used equipment units are severely corroded; therefore, they need to be thoroughly cleaned and carefully inspected before being put into use. 1.3 The parameters of the new equipment to be manufactured by modifying old equipment are as follows: Name, Location, Specifications, Main Materials, Quantity, Name of Old Equipment Used: Atmospheric pressure tower, Methanol distillation, φ1800×44888, 16MnR, 1; First and second desulfurization towers, Upper-stage condensate circulation tank, Cooling drum and electrostatic precipitator, φ2200×4000×10, Q235-A, 1; Conversion gas desulfurization tower, Lower-stage condensate circulation tank, Cooling drum and electrostatic precipitator, φ2200×4000×10, Q235-A, 1; Conversion gas desulfurization tower, Mist collector, Cooling drum and electrostatic precipitator, φ2600×5500×10, Q235-A, 1; Conversion gas desulfurization tower, Waste liquid collection tank, Cooling drum and electrostatic precipitator, φ2600×3000×8, Q235-A, 1; Conversion gas desulfurization tower, Condensate water tank, Cooling drum and electrostatic precipitator, φ2000×2000×8, Q235-A, 1; Conversion gas desulfurization tower, Discharge tank, Methanol distillation, φ2600×5500×10, Q235-A, 1; Conversion gas desulfurization tower, Sump, Desulfurization and sulfur recovery, φ2000×2000×8, Q235-A, 1; Conversion gas desulfurization tower, Oil-water separator, Benzene washing and extraction, φ1800×4000×8, Q235-A, 1; First desulfurization tower, Pre-cooling reflux tank, Methanol distillation, φ1600×4000, Q235-A, 1; First desulfurization tower, Impure alcohol storage tank, Methanol distillation, φ1600×4000, Q235-A, 1; First desulfurization tower, Atmospheric pressure filter, Methanol desulfurization, Reaction tank.

2. Basis for preparation
2.1 JB/T4735 “Welded atmospheric pressure steel vessels”
2.2 HG20584 “Technical requirements for manufacturing steel chemical industry vessels”
2.3 JB4710 “Steel tower-type vessels”
2.4 SH3505 “Safety technical regulations for petrochemical construction”
2.5 Technical parameters of old equipment and drawings of new equipment provided by the project owner.

3. Preparation work
3.1 Technical preparation
3.1.1 Inspect the old equipment, and prepare all necessary drawings, relevant technical documents, standards, specifications, and record forms for the manufacture of the new equipment ； 3.1.2 Determine the correspondence table between new and old equipment based on Party A’s suggestions and the actual conditions on site, and decide on the inspection ratio, cutting locations, etc. according to this correspondence ； 3.1.3 If replacing old equipment with new equipment results in changes to the specifications of the new equipment (mainly referring to diameter, height, etc.), it is necessary to contact the design institute for record-keeping, and check whether the foundation of the original equipment is suitable for the installation dimensions of the new equipment. Before feeding according to Equation 3.1.4, it is necessary to verify based on the drawings and actual conditions and prepare a layout diagram. 3.1.5 Before inspecting old equipment and modifying new equipment, technical personnel must provide technical instructions to all personnel involved in the construction, clearly specifying the requirements. 3.2 Preparation of construction resources 3.2.1 Equip sufficient construction machinery and equipment according to actual conditions ； 3.2.2 Non-destructive testing personnel shall hold a qualification certificate for non-destructive testing of boilers and pressure vessels corresponding to the relevant category” ； 3.2.3 All welders must hold a welder’s certificate issued by the Technical Supervision Bureau before they can carry out welding work on the appropriate locations and with the appropriate materials for the designated tasks. 3.2.4 A platform shall be set up at the construction site, and the surface irregularity of this platform must be less than 2 mm/m. 3.3 Acceptance of foundations 3.3.1 The construction quality of foundations shall be in accordance with the relevant rules specified in the HGJ210—83 standard. 3.3.2 During the initial receipt of the foundations, the civil engineering team and the installation team shall issue a \"Interim Handover Certificate for Foundations\". 3.3.3 When inspecting the foundations, it is necessary to keep proper records of re-measurements, paying special attention to whether the vertical and horizontal center lines as well as the elevation are clearly marked on the foundations. 4. Inspection of used equipment 4.1 Before inspection, the used equipment should be thoroughly cleaned to remove rust; sandblasting should be carried out inside the equipment to achieve the Sa2 standard specified in GB8923-88. This means that there should be no visible oils or dirt on the surface of the steel, and no loosely attached oxides, rust, paint layers, or other contaminants. Mechanical rust removal is performed on the outside of the equipment to meet the St2 standard. 4.2 Inspection 4.2.1 Thickness measurement: Use a metal thickness gauge to measure the thickness of the tower walls and the thickness at the pipe openings. Four measurements are taken for each pipe opening, with the measurement points distributed evenly around the circumference; 6 measurements are taken per square meter of the tower wall. The results should be recorded in accordance with the layout diagram provided by the equipment. 4.2.2 Radiographic inspection: 4.2.2.1 For the original welds of the old towers to be used in atmospheric pressure vessels, radiographic testing shall be carried out on 10% of them (including the welded pipe ends). 4.2.2.2 For the original weld joints of old towers to be used in pressure vessels, radiographic or ultrasonic testing shall be conducted on at least 20% of them, over a length of not less than 250 mm. All areas at the weld intersections and below shall be inspected: a) First, assemble the plates, and then inspect all joint connections on the convex head ； b) The weld joint enclosed within a circle with the center of the opening as its center and 1.5 times the diameter of the opening as its radius ； c) Welded joint of embedded nozzle connected to cylinder or head ； d) Welded joints of nozzles with a nominal diameter of not less than 250 mm connected to long-neck flanges, and nozzles connected to each other. 4.2.3 Chemical composition analysis: Two samples are taken from each tower (one additional sample per head) to conduct chemical analysis of the carbon, manganese, iron, sulfur, and phosphorus contents in the material of the tower body; materials whose chemical composition does not meet the requirements shall not be used. 4.2.4 Penetrant testing of some welds can be added as required. 4.2.5 Non-destructive testing standards: Welded joints shall be inspected in accordance with JB4730. 4.2.6 The dimensional tolerances of tower rings, heads, etc. shall be inspected in accordance with the requirements specified for new equipment manufacturing. 4.2.7 For those that fail the inspection, the inspection ratio should be increased and the construction unit should be informed; it is up to the construction unit to decide whether to use them. 5. Cutting of the old tower 5.1 Determine the cutting location on site based on the table that relates new and old equipment as identified on site, as well as the specific conditions of the new and old equipment ； 5.2 Since the old towers are all made of carbon steel, they can be cut using an oxygen-acetylene flame; after cutting, they are ground with a grinder to create the bevels required for welding. 6. Dimension inspection of prefabricated or used equipment components 6.1 Cylinder sections 6.1.1 The misalignment amount b of the longitudinal welds should be less than or equal to 10%S. 6.1.2 The corners formed at the buttweld joints shall be inspected using inner and outer gauges with a chord length of 1/6Dg and not less than 300 mm; the variation in height between them shall not exceed 0.1S + 2 mm. 6.1.3 The difference between the maximum and minimum diameters at the same cross-section shall not exceed 1% of Dg, nor be greater than 30 mm. When internal components are present, the requirements specified in the drawings shall be followed ； For sections reinforced with openings, measurements should be taken 100 mm away from the edge of the reinforcement ring. 6.1.4 The allowable tolerance for the outer circumferential length of the tube sections is as specified in Table 2; the specific values shall be determined based on the requirements for ensuring proper alignment of the ring joints. The end-face unevenness at the segmentation point shall not exceed 1‰ of Dg, and shall not be greater than 2 mm. Table 2 Nominal diameter: 800–1600, 2600–3000, 3200–4000, 4200–6000; Tolerances: ±7, ±13, ±15, ±18. Cutting is done using a 6.2-mark system (for parts that are not made from recycled materials). 6.2.1 Select appropriate sheet material based on the layout diagram or design drawings, and cut it in such a way as to minimize material waste. 6.2.2 For lofting and material marking, welding shrinkage allowance and machining allowance for cutting and grinding should be reserved in accordance with the process requirements. 6.2.3 For the cutting of carbon steel and the processing of welds, mechanical processing is preferred, but flame cutting can also be used. 6.2.4 For cutting stainless steel plates and processing weld grooves, mechanical or plasma cutting shall be used. 6.2.5 The allowable tolerances for the cutting of parts and marking on the material lines are as follows: ±2 mm for manual cutting, and ±1 mm for mechanical cutting. 6.2.6 The width of the wall panels should not be less than 500 mm, their length should not be less than 1000 mm, and the minimum chord length of the conical panels must be at least 200 mm. 6.2.7 Before cutting, the rust and oil on the surface of the steel in the cutting area must be removed thoroughly; after cutting, any weld spurs and splashes on the cut surface should also be cleared away. 6.3 Prefabrication 6.3.1 Before rounding the wall panels, pre-bending at both ends is advisable. 6.3.2 Measures shall be taken to prevent iron contamination before rolling stainless steel plates into a circle. 6.3.3 The thickness of the wall at each ring shall not be less than the thickness specified in the design for the corresponding height of the tank. 6.3.4 The longitudinal welds on the tank wall should be offset in the same direction by one-third of the plate length, and this offset shall not be less than 500 mm. 6.3.5 The openings in the tank wall and tank roof (or the edges of the reinforcement plates) shall be at least 100 mm away from the welds. 6.3.6 The dimensions of the welding groove and the allowable tolerances shall comply with the requirements specified in the drawings and GB985—88 \"Basic Forms and Dimensions of Grooves for Carbon Steel and Low-Alloy Welds\". 6.3.7 During storage and transportation, prefabricated components shall be secured using jigs or other measures to prevent deformation and damage. 6.4 Inspection of prefabricated parts or old tower components 6.4.1 The fabricated parts must pass inspection before being assembled; the wall panels, corner members, roof panels, and conical panels should be checked for their curvature using arc-shaped templates, while their flatness and straightness should be verified using straight-line templates. 6.4.2 The arc length of the curved template shall be greater than 1.5 mm, and the length of the straight template shall be greater than or equal to 1 mm. 6.4.3 The rolled wall panels shall be inspected using an arc-shaped template; the gap should not exceed 3 mm. In the width direction of the wall panels, a straight-line template shall be used to check the gap, which should not be greater than 1 mm. The curved edges of the cone and top plate shall also be inspected using a template; the gap here must not exceed 3 mm. Local irregularities shall be checked using a straight-line template, with the allowable gap being no more than 5 mm. 6.4.5 The radial gap of the angle plate in radians should not exceed 4 mm, the warping degree should not exceed 10 mm, and the angular deviation should not be more than 2.5 degrees. 7. Technical requirements for the assembly of storage tank-type equipment 7.1 Assembly of the bottom plate 7.1.1 When laying the bottom plate, a cross center line should first be marked on the foundation; then, in accordance with the layout plan, the plates should be installed from the center toward the middle and edge plates, and fixed using clamps. 7.1.2 The distance between any two welds on the bottom plate of the groove shall be no less than 200 mm. 7.1.3 For the lap structure of the trough bottom plates, the allowable tolerance for the lap width between the two plates is ±5 mm, and the maximum gap between their lap surfaces shall not exceed 1 mm ； For the local three-layer lap areas, the corners should be cut according to the drawing requirements. 7.1.4 For the butting welds between the bottom edge plates, the lower gasket plate must be in close contact with the edge plate, and it is necessary to ensure that the misalignment between the joints is less than 1 mm. 7.2 Assembly of the tank wall 7.2.1 During assembly, separate assembly plans can be prepared based on its structural form and specifications ； Inverted or normal orientation can be used. 7.2.2 Once the wall panels have been inspected and their curvature meets the requirements, assembly can proceed ； Those that do not meet the requirements should be retried with a new circle. 7.2.3 The minimum distance between the longitudinal seam of the bottom ring groove wall and the joint of the edge plate shall be not less than 200 mm ； The longitudinal seams in each row of the groove walls should be offset in the same direction by 1/3 of the plate length, and this offset should not be less than 500 mm. 7.2.4 For the bottom ring wall panels of storage tanks or the top ring wall panels constructed by the inverted method, the horizontal deviation at their upper edges shall be less than 2 mm; two measurement points shall be taken for each wall panel. 7.2.5 When construction is carried out using the inverted method, after the top ring wall panels are assembled, their circularity, horizontality at the upper edge, perimeter, and verticality should be checked. 7.2.6 The verticality of the tank wall shall not exceed 3‰ of the total height. 7.2.7 The local roughness on the inner side of the tank wall shall not exceed 13 mm. 7.3 Installation of the tank top and its accessories 7.3.1 Before installing the tank top, it is necessary to check the levelness, perimeter, and verticality of the upper edge of the top ring wall plate ； 7.3.2 The maximum gap in the lap joint between the edge steel and the top ring wall panel shall not exceed 2 mm, with a local tolerance of ±4 mm for areas that protrude above the wall panel ； The minimum distance between the butted weld of the edge steel and the longitudinal weld of the wall panel shall be not less than 200 mm. 7.3.3 When installing components such as manholes on the groove walls, measures to prevent deformation such as using temporary protective plates should be taken ； The distance between the openings in the groove wall and the welds between the edges of those openings and the tank wall plates should be greater than 200 mm. 8 Assembly of tower-type equipment: After assembly, the dimensional tolerances of tower-type equipment shall comply with the specifications in Table 8.1. Table 8.1 Allowable dimensional tolerances for tower components. Sequence number, Inspection item, Allowable tolerance: 1. Roundness; 2. Straightness – the tolerance for any 3000 mm long cylindrical section shall not exceed 3 mm ； When the cylinder length L is less than or equal to 15,000 mm, the deviation is not greater than L/1000 ； When the length L is greater than 15,000 mm, the deviation shall not be greater than (0.5L/1000 + 8). 3 The distance between the outer sides of the upper and lower end caps is ±1.5 mm/m, and shall not exceed ±50. 4 The distance from the bottom surface of the foundation ring to the weld joint where the lower end cap of the tower is connected to the tower shell is 1000 mm; the deviation shall not be greater than 2.5 mm, with a maximum value of 6 mm. 5 The inclination of the pipe flange relative to the outer wall of the tower and the flange itself is ±5 mm, with an inclination limit of ≤0.5. 6 The elevation of the pipes or manholes: ±6 mm for pipes, and ±12 mm for manholes. 7 The distance between the interfaces corresponding to the level gauge is ±3 mm. 8 The distance from the center line of the pipe to the tower tray surface is ±3 mm. 9 The circumferential deviation of the interface corresponding to the level gauge is 1 mm. 10 The inclination of the flange surface of the level gauge is 0.3 mm. 11 The difference in length between the two pipes connected to the level gauge is 5 mm. 9. Welding and inspection 9.1 Welding 9.1.1 Welding grooves a. Welding grooves shall be selected as standard grooves in accordance with the requirements specified in the drawings or the process conditions. b. Groove preparation can be done by mechanical methods; for carbon steel, flame cutting can also be used. However, the surface layer that affects the welding quality must be removed using mechanical means. c. The groove should be smooth, free from defects such as cracks, delamination, and inclusions, and its dimensions should meet the requirements. d. The area within 20 mm on either side of the groove surface must be cleaned of water, rust, oil, and other harmful impurities. e. Paint should be applied within 100 mm on both sides of the stainless steel groove to prevent adhesion of welding spatter. 9.1.2 Welding electrodes a. The welding electrodes used shall be accompanied by a certificate of quality. b. Welding electrodes should be dried as specified before use. c. After drying, the welding electrodes should be stored in an incubator at 80–120°C and retrieved as needed. If they are not used within four hours after being taken out of the incubator, they need to be dried again. However, the number of repeated drying cycles should not exceed two. d. The selection of welding electrodes shall meet the following requirements: For 0Cr18Ni9: A102 ； Between 00Cr19Ni10: A002 ； Between Q235-A: J422 ； Between stainless steel and carbon steel: A302 9.2 Welding procedures and methods. 9.2.1 Welding operating procedure: tack welding (spot welding) → welding → inspection. 9.2.2 The electrodes and welding procedures used for tack welding shall be the same as those for the actual welding. 9.2.3 Welders shall weld in accordance with the process parameters specified in the welding procedure specification (procedure card). 9.2.4 When environmental conditions are unfavorable for welding, such as: wind speed greater than 10 m/s; relative humidity greater than 90% ； In rainy or snowy conditions, effective protective measures must be taken before welding can proceed. 9.2.5 All welds shall be inspected visually; they must be free from defects such as cracks, pores, cratering, and slag inclusions, as well as from any slag or spatter. The weld shall have a smooth transition to the geometry of the base metal. 9.2.6 When welding stainless steel, use a low current and weld quickly, minimizing lateral movement; the width of such movement should not exceed 3 times the diameter of the welding rod. 9.2.7 To clean stainless steel welds, special grinding wheels and austenitic stainless steel brushes must be used; the use of carbon steel tools is strictly prohibited. 9.2.8 When welding stainless steel, chalk powder should be applied within a range of not less than 100 mm on both sides of the groove to prevent spatter from contaminating the weldment. 9.2.9 Welding inspections and non-destructive testing of welds must be carried out in close coordination with the welding work itself, in order to ensure project progress and welding quality. 9.2.10 During welding, it is necessary to ensure proper penetration at the root of the weld, as well as good fusion between layers and on both sides of the weld. The areas between each welding layer should be cleaned thoroughly; only after confirming that the layer is defect-free can the next layer be welded. 9.2.11 Arc striking and test currents are not permitted on the surface of any welded parts; arc striking must take place within the groove. When welding stainless steel, the grounding wire must be securely fixed to the welded part using stainless steel clamps. 9.3 Local repair of welds a. For defects present locally in the weld, the inspector shall clearly mark the location of the defects on the weld, specify the type of defect, and determine its depth and length. b. For repairs carried out more than twice, approval from the chief technical officer is required, and repair records must be kept. 9.4 Welding inspection: 9.4.1 All welds shall be inspected visually and must meet the requirements specified in the drawings as well as the following criteria: The surface of the welds shall be free from cracks, pores, slag inclusions, spatter, and surface depressions. The root gap depth shall not exceed 0.5 mm, the length shall not be more than 10% of the total length of the weld seam nor more than 100 mm, and the surface reinforcement height shall be between 1.5 and 3 mm. The welding dimensions of fillet welds shall comply with the design specifications; their appearance shall be smoothly continuous, and the root gap depth shall be less than 0.5 mm. 9.4.2 The proportion of non-destructive testing for all welds and the acceptance criteria shall comply with the requirements specified in the construction drawings; the locations for testing shall be determined by the inspector on-site. 10. Testing and Inspection: Determine the kerosene leakage inspection, water filling leak test, and other inspection methods as specified in the drawings. 11. Safety technical measures 11.1 All personnel entering the construction site must keep in mind the principle of \"safety first, prevention foremost\" and avoid any sense of complacency. 11.2 Safety helmets must be worn when entering the construction site; safety belts must be used for work at heights, and a permit for working at heights must be obtained. Isolation measures are required for work in multi-level intersections. 11.3 All types of construction equipment must be under the supervision of a designated person, regularly inspected, and kept in good condition. 11.4 Practice civilized construction, ensure proper electrical management at the site, and prevent electric shock accidents. 11.5 During lifting, the clamps must be securely in place; no one is allowed to rise or fall along with the load. When lifting heavy objects, workers are strictly prohibited from staying or passing under the load. 11.6 When performing hot work at the construction site, it is necessary to strictly comply with the factory’s regulations regarding the use of fire and fire prevention. 11.7 A full-time safety officer should be on site to oversee safety measures and correct any workers who are acting in violation of safety rules; construction workers must obey instructions. 11.8 All personnel involved in the construction work must also strictly comply with the various provisions outlined in the \"Safety Technical Regulations for Petrochemical Construction.\"