[Discussion Post 48] What are the pressures and stresses on heat exchange tubes?

Let me start with the beginning: heat exchange tubes are the main pressure components, defined in TSG 21 1.6.1 The main pressure components in the pressure vessel body include barrel sections (including reducing sections), spherical shell plates, non-circular vessel shells, heads, flat covers, expansion joints, equipment flanges, heat exchanger tube sheets and heat exchange tubes, M36 or above (including M36) studs, and nozzles and pipe flanges with a nominal diameter of 250mm or more.

1. The heat exchange tube is the main pressure component, please refer to the solid capacity regulations. 2. The thickness of the heat exchange tube is generally calculated based on the internal pressure (generally, high pressure will travel along the tube side), but the calculated thickness is generally thin. When selecting the thickness, commonly used specifications are generally selected. 3. The calculation is based on internal pressure and the stability of external pressure is checked. 4. A large thickness affects the heat transfer effect and the price is high. If the thickness is too thin, it may be corroded (abraded) and perforated. 5. Heat exchange tube: Internal pressure, external pressure, temperature difference thermal stress (fixed tube sheet) Tube sheet: It is related to the tube plate type and connection form. . .

1. The heat exchange tube is a pressure component or the main pressure component. A.TSG 21 1.6.1 The main pressure components in the pressure vessel body include barrel sections (including reducing sections), spherical shell plates, non-circular vessel shells, heads, flat covers, expansion joints, equipment flanges, tube sheets and heat exchange tubes of heat exchangers, M36 or above (including M36) studs, and nozzles and pipe flanges with a nominal diameter of 250mm or more. 2. Is the wall thickness of the heat exchange tube selected according to standards or calculated, and how to determine the pressure during calculation. A. Generally, the thickness is calculated based on the internal pressure (generally high pressure will go through the pipe), but the calculated thickness is generally thin. When selecting the thickness, commonly used specifications can be selected. 3. The heat exchange tube is subject to internal pressure, external pressure, or internal and external pressure. If there is a need to calculate the pressure, how should it be calculated? A. The calculation is based on internal pressure and the stability of external pressure is checked (generally there is no problem). 4. What will be the impact of the wall thickness of the heat exchange tube? A. A large thickness affects the heat transfer effect and the price is high. If the thickness is too thin, it may be corroded (abraded) and perforated. 5. What are the stresses on the heat exchange tubes and tube sheets, and what are the combined stresses. A. The radial stress of the tube sheet, the shear stress around the tube sheet layout area, the stress of the shell flange (also used as an extension), the pull-out stress of the connection between the heat exchange tube and the tube sheet... There may be differences among different types. 6. What are the main differences in the influence of tube sheet heat exchangers, U-shaped heat exchangers and floating head heat exchangers on heat exchange tubes. A. For fixed tube sheet heat exchangers, whether the connection between the heat exchange tube and the tube sheet has greater pull-off stress, and the latter two involve less stress. U-tube bend sections require special considerations. 7. If the shell is connected to the atmosphere at normal pressure, what should you pay attention to in the heat exchange tube? 8. If only the tube side is at normal pressure, what should you pay attention to in the heat exchange tube? A.2/3 principle, or other special places?

Does item 7.8 above have anything to do with this?: https://bbs.hcbbs.com/thread-1032463-1-1.html

The heat exchange tube is the main pressure component. Although the diameter is small, the stress characteristics are good, and the general strength is sufficient, the strength will still be insufficient for thin-walled, high-pressure, and heavy corrosion applications. The surface still needs to be calculated. The thickness of the heat exchange tube directly affects the heat exchange effect. For fixed tube plate heat exchangers, when the temperature difference between the tube and shell is large, the temperature difference stress between the heat exchange tube and the shell is still very large if there is no expansion joint. When the heat exchange tube is working, the pressure on the shell side of the tube will cause the heat exchange tube to be subject to internal pressure and external pressure. Especially when one side is positive pressure and the other side is negative pressure, the pressure the heat exchange tube bears is the sum of the pressures on both sides.