Key points for quality control in the design, manufacture, and installation of reactors ---- Design

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Key points for quality control in the design, manufacturing, and installation of reaction vessels -- Design 1. The material used for the mixing vessel shall comply with the provisions of the \"Safety Technical Inspection Regulations for Fixed Pressure Vessels\" TSG R0004, the \"Pressure Vessels\" standards GB150.1–150.2, and the \"Steel Welded Atmospheric Pressure Vessels\" standard NB/T47003.1–2009. 2. Unless otherwise specified, the corrosion margin for carbon steel and low-alloy steel materials shall be greater than or equal to 1 mm; the corrosion margin for high-alloy steel and non-ferrous metal materials may be disregarded. 3. The interface flange and mounting cover shall comply with the following requirements: 1) When the interface flange is of the pipe connection flange type, its manufacturing, inspection, and acceptance shall conform to the provisions of \"Steel Pipe Flanges, Gaskets, and Fasteners\" HG/T20592–20615 as well as the requirements specified in the design drawings. 2) When the interface flange is of the flanged type, its manufacturing, inspection, and acceptance shall comply with the requirements of HG21564 \"Flanged Flanges for Mixing Drive Devices\". 3) The manufacturing, inspection, and acceptance of the installation bottom cover shall comply with the requirements of HG21565 \"Installation Bottom Cover for Mixing Drive Units\". 4) The joint surface between the interface flange and the mounting base cover, as well as the joint surfaces between the mounting base cover and the frame and the shaft seal, shall be perpendicular to the mixing shaft; the tolerance for this perpendicularity shall be less than or equal to 1% of the outer diameter of the interface flange. 4. The interface flange and the mounting bottom cover shall be coaxial with the axis of the frame flange and the shaft seal flange, and the coaxiality tolerance shall be selected in accordance with the accuracy requirement of grade 8 specified in \"Tolerances for shapes and positions – Unspecified tolerances\", GB/T1184. 5. When the inner surface of the mixing vessel needs to be polished according to the requirements of the process, the Ra value of the surface roughness after polishing should be between 0.1 μm and 0.8 μm ； The surfaces of other components that may come into contact with the material should also be polished; their surface roughness must meet the requirements specified in the design drawings ； The inspection and evaluation rules shall not only comply with the provisions of the “Rules for Quality Inspection and Evaluation of Polished Metal Surfaces” HG/T 4079, but also meet the requirements of the design drawings. 6. The circumferential welds connecting the pressurized jacket and the shell shall undergo 100% non-destructive testing using magnetic particle or penetrant methods; they are considered acceptable if they meet the requirements of Grade I as specified in JB/T4730.4 or JB/T4730.5 “Non-destructive Testing of Pressure Equipment”. 7. Unless otherwise specified, the unspecified dimensional tolerances of the machined surfaces of the mixer’s various components shall meet the m-grade accuracy requirements specified in GB/T1804 \"General tolerances – Tolerances for linear and angular dimensions without specification\", while the unspecified dimensional tolerances of the unmachined surfaces shall meet the c-grade accuracy requirements of GB/T1804. 8. The form and position tolerances not specified for the machined surface shall meet the K-grade accuracy requirements of GB/T1184 \"Unspecified Tolerances for Form and Position Tolerances\". 9. The unspecified dimensional tolerances for the unmachined surfaces of castings shall meet the requirements of CT14 in GB/T6414 \"Dimensional Tolerances of Castings and Machining Allowances\". 10. When a covered jacket is present at the support, the jacket should be locally avoided at the support. The distance between the weld edges of the jacket and the supports on the shell should be greater than 3 times the wall thickness of the container shell, and at least 100 mm. 11. The balance testing of the impeller and shaft assemblies shall comply with the following requirements: 1) When the speed of the mixer (shaft) is 60 r/min or higher, the impeller shall undergo a static balance test. 2) When the shaft length is 2.5 m or more, the impeller shall undergo a static balance test. 3) When the speed of the mixer (shaft) is 150 r/min or higher, a static balance test should be conducted on the mixing paddle and the shaft after they have been assembled. 4) When the shaft length is 3.6 m or more, a static balance test of the impeller and shaft after assembly shall be conducted. 5) When the speed of the mixer (shaft) is 400 r/min or higher, the mixing paddle shall undergo a dynamic balance test after assembly. 6) When designing the flexible shaft, the impeller should undergo a dynamic balance test after assembly. 12. The stirring shaft inside the mixing vessel can be designed with a segmented structure, and a rigid coupling should be used to connect the two sections of the shaft. For axles that are inserted from the top and are segmented, a shaft rest structure can be designed on the axle. 13. Unless otherwise specified, the stirring shaft shall have a solid shaft structure. When a hollow shaft structure is used, both ends of the shaft should be sealed by welding. 14. The shaft should not be joined to extend it. For shafts with a welded structure for the shaft and coupling, post-weld finishing should be carried out. 15. Unless otherwise specified, the stirring shaft shall be designed as a rigid shaft. When a flexible shaft design is used, the warning “Do not run idle” should be indicated in a prominent position on the mixer. When a flexible shaft is used, the frame and the mixing container must meet the vibration isolation requirements. 16. For the mating surfaces between the shaft and bearings, couplings, shaft seals, impellers, etc., the coaxiality tolerance shall be selected in accordance with the precision requirement of grade 8 specified in \"Tolerances for shapes and positions – Uncoded tolerances\", GB/T1184. 17. The surface roughness Ra of the shaft diameter at the mechanical seal should be less than or equal to 0.8 μm, and the fitting accuracy between the mechanical seal and the shaft, according to the base shaft system, should be F8/h7. The axial force of the stirring shaft should not be borne by the reducer bearings; otherwise, it must be calculated and verified, and approval from the buyer must be obtained. 18. If the frame is made of castings, they shall meet the mechanical properties specified for HT200 in the standard GB/T9439 for gray cast iron parts; such castings should undergo aging treatment or other mechanical and thermal treatment methods to eliminate internal stresses. The mating surfaces of the castings after processing should be free from defects such as pores, slag holes, sand inclusions, and cracks. There should be no defects in other areas that could affect the frame’s strength. 19. The coaxiality tolerance of the upper and lower bearing seats of the frame, as well as the machining surfaces of the mounting flanges, shall meet the precision requirements of grade 8 as specified in \"Tolerances for shapes and positions – Values without specification\", GB/T1184. 20. For the mounting surfaces of the frame and bearing housings, a fit tolerance of H7/f6 is recommended, with a surface roughness Ra of less than or equal to 3.2 μm. 21. The tolerance for the perpendicularity of the bottom plane of the frame to the axis line of the bearing seat hole shall meet the accuracy requirement of grade 9 as specified in \"Tolerances for shape and position – Undesignated tolerances\" GB/T1184. 22. The perpendicularity of the end face in the bearing housing that is in contact with the outer ring of the bearing to the axis of the hole shall meet the accuracy requirement of grade 7 as specified in \"Tolerances for shape and position – No specific tolerances given\", GB/T1184. 23. Intermediate and bottom bearings should not be installed inside the container. When intermediate and bottom bearings are installed inside the container, the type and size of the bearings on the stirring shaft should be selected based on factors such as the magnitude and direction of the loads transmitted to the stirring shaft, as well as the overall alignment requirements for the various supports on the drive mechanism. 24. The shaft sleeves and bearing shells of the intermediate bearings and bottom bearings shall be fixed to the shaft and the bearing housings respectively, and there shall be no relative movement between the shaft sleeves and the shaft, nor between the bearing shells and the bearing housings. The surface roughness Ra of the bearing bush inner surface should be less than or equal to 3.2 μm. The surface roughness Ra of the outer surface of the shaft sleeve should be less than or equal to 1.6 μm. 25. The reducer shall comply with the specifications of \"Vertical Reducers for Kettles\" HG/T3139.1–3139.12, and shall also meet the requirements of the design drawings. It should also have a manufacturer’s inspection certificate or quality certificate. 26. When the reducer operates under conditions of vibration and load variations, it must meet the requirements for stability and continuous operation. Gears or planetary cycloidal pinwheel reducers with higher transmission efficiency should be selected. The service factor of gear reducers should be greater than or equal to 1.6; for applications involving significant impact loads during mixing, frequent starts, or situations where the mixing paddle may get buried in solid materials, it should be greater than or equal to 2.0. 27. When a bidirectional rotation of the output shaft is required, worm gear reducers are not suitable. 28. The axial force of the stirring shaft should not be borne by the reducer bearings; otherwise, it must be calculated and verified, and approval from the buyer must be obtained. 29. The rated power of the reducer should be greater than or equal to the transmission power of the reducer’s output shaft during normal operation (the transmission power of the output shaft includes the power required to drive the mixing shaft, the frictional losses at the shaft seals, as well as the losses associated with the transmission bearings on the frame); it should also meet the requirements related to the increased shaft power needed when starting up the mixing equipment.