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Many designers have no concept of standard shell-and-tube heat exchangers, and the length of the heat exchanger shell as well as the thickness of the tube sheet are chosen arbitrarily. In fact, Luoyang Institute published a series of catalogues on standard shell-and-tube heat exchangers quite early on, to facilitate the replacement of tube bundles in chemical and petroleum refining plants (the service life of tube bundles is 3 years, while that of heat exchangers is usually 10 years). Therefore, a series of dimensions such as the length of the heat exchanger shell and the thickness of the tube sheet are selected based on the nominal pressure of the heat exchanger. 1. Heat exchanger pressure difference design: Pressures on both the tube side and the shell side act simultaneously under conditions such as pressure testing, startup and shutdown, abnormal operation, and normal operation. Voltage withstand test method: First, apply pressure to the shell side by pressing the differential value, while simultaneously checking the tube ends of the heat exchange tubes ； Then, the tube side and shell side are pressurized simultaneously, with the pressure difference remaining within extreme limits during the pressure increase and decrease process. 2. Points to note in the design of the baffle rod tube bundle: ① The first baffle plate in the baffle rod tube bundle should be arranged horizontally (to serve as a support plate). ② Baffle rods should avoid interfering with the holes for tie rods; otherwise, it will lead to an increased spacing between the baffle rings during manufacturing. Note: During factory production, the baffle rods should be welded in advance before the tubes are inserted, as forced insertion of the tubes can result in cumulative errors in the baffle rings (optimal manufacturing practice: weld the baffle rods simultaneously while inserting the tubes). ③ The maximum size of the baffle rings in the tube bundle should not exceed the length of the shell, otherwise, it will limit the space available for installing and removing the bolts on the side of the baffle rings, as well as for thermal expansion and contraction of those bolts. ④For single-pass baffled tube sheets, the spacing between the baffle grooves (arranged at 45°) should not be specified, otherwise errors will accumulate and it will be impossible to insert the tubes properly. 3. Tube arrangement: For four-pass systems (φ19), remove the innermost heat exchange tube; the MA value must be specified for the gaskets in the four-pass tube boxes. 4. Process medium flow direction: Cold fluid (heating)↑ ； Hot fluid (cooling): ↓ BJS structure: Reboiler medium↑ ； Condenser medium ↓ 5. The smaller the baffle spacing, the greater the pressure drop in the shell side. 6. In floating-head condensers, when the heat exchange tubes are subjected to axial compressive forces and the baffle spacing is large, the value often exceeds cr; however, since the instability of the heat exchange tubes within the heat exchanger is constrained, no instability-related failure occurs under normal operating conditions (negative values from SW6 calculations are not acceptable). Addition: The GB/T 151-98 standard provides a detailed explanation for this, but the GB/T 151-2014 standard omits such an explanation. 7. The thickness of the tube sheet shall be not less than 0.6 times the effective thickness of the equipment flange (as required for flange stiffness). 8. Calculation conditions for fixed double-tube-sheet heat exchangers: The outer tube sheet is used as a flange for calculation purposes ； The inner tube sheet is not considered for flange calculations; the isolation chamber (of the outer tube sheet) serves as the design pressure for the shell side ； (The inner tube sheet) The isolation chamber is designed for a pressure corresponding to the tube side pressure. 9. Under high-temperature and high-pressure conditions, a calculation report is generated when using SW6 to verify the tube sheet, in order to check whether the pressures inside and outside the heat exchange tubes are within acceptable limits. If you only look at the calculation results, you won’t even notice the problem. 10. Design of the reboiler dummy tube structure: Several rows of dummy tubes are installed, with the floating ends sealed off ； A row of round steel tubes (for corrosion protection and foam removal) is installed at the inlet; the higher up the tube bundle, the greater the degree of corrosion. 11. Notes for the design of vertical heat exchangers: Avoid interference between the inlet and outlet tubes and the bolts ； Is the distance between the ear holes standard? 12. Floating head heat exchanger: The expansion and contraction length at the rear end of the floating section shall be ≥ 60 mm (2M + 10) min. 13. The BJS heat exchanger does not have any tube retaining structures or baffles; the number of slides or bypass baffles at the tube inlets has been reduced from 2 to 1. When the baffle is cut transversely, bypass baffles need to be installed on both sides. 14. When the baffle is arranged transversely, the number of baffles at the inlet and outlet of the shell side is generally even. If, due to an excessive span, only an odd number of baffles can be used, one of them can be designed as a support plate (with its upper and lower surfaces leveled) due to gravity considerations. 15. When the diameter of the openings in the equipment is small, it is necessary to carefully calculate the flow area taking the anti-scour plates into account ； If this condition is not met, punching holes in the flood plate can be done. 16. Gap between partition grooves and R value for cross-piped U-tube heat exchangers: φ25 heat exchange tubes: 90.5/50.6 ； φ19 heat exchange tubes: 75/43.3 17. Seamless steel tubes used for containers (φ426x12, φ325x10) must meet the requirements of 6.3.9 in HG/T20584; re-inspection upon return to the factory is required for tensile strength, impact resistance, and water pressure tests. 18. Vacuum container ； >300℃ containers ； Media that are extremely or highly hazardous shall not use a lining structure. 19. Reinforcement rings shall be installed at intervals of 1 to 2 meters in externally pressurized vessels ； Moment of inertia: T-shaped steel > inverted angle steel > flat steel. 20. Calculation method for reinforcement with combined openings: First, calculate the reinforcement for a single opening, using at least a 50% increase, and then proceed with the reinforcement for two openings together. 21. The longitudinal circumferential welds of thicker high-pressure equipment can be inspected using TOFD in accordance with NB/T47013.10-II Class B (recordable UT inspection is also possible). MT/PT testing is performed on the sealed welds of fixed-tube-sheet heat exchangers; when special requirements exist, the tube ends at the sealed end can be removed for radiographic testing using a gamma source. 22. If the pre-tightening force of the stainless steel bolts at the floating head flange of the stainless steel floating head heat exchanger does not meet the requirements, high-strength stainless steel bolts as specified by ASME can be used. 23. When there are attached devices on the tower, be sure to take into account the eccentric load ； When there are equipment flanges in the tower, the height of the flange sealing surface above the ground level must be entered in SW6. 24. The heat transfer area of a half-tube jacket should be understood as the contact area between the half-coil and the equipment. 25. Pay attention to the usage conditions of the reinforcement ring ； Enter the value of B for the reinforcement area of the access opening; if it is insufficient, enter the actual B value.