Seeking advice on the installation of expansion joints in fixed-plate heat exchangers
Thread Content
1. Our company has a set of fixed-tube-sheet heat exchangers: the tube side contains aromatics and sulfolane, while the shell side is equipped with 2.2 Mpa steam； The calculated counterflow logarithmic temperature difference is around 58°C, but during previous maintenance operations, the heat exchange tubes and tube sheets were the most frequently damaged. The tubes are made of grade 20 steel, while the shell is made of Q345R steel. 2. Referring to the design of such heat exchangers in other aromatic hydrocarbon plants, most of them are equipped with expansion joints. Should our company’s heat exchangers also be fitted with expansion joints? 3. Is it the uneven pulling force or axial force between the heat exchange tubes and the shell that causes the joints between the tube bundle and the tube sheet to become detached? I would appreciate it if the teachers could provide some guidance. Thank you.
For counter-current shell-side steam, it is beneficial to use an external flow guide cylinder; this is not applicable to horizontal configurations.
Hello, what is an external flow guide cylinder? I’ve really never seen one before. Could you give me a brief explanation? Thank you
The structure in the poster by the original poster is exactly that
Is the heat exchanger mentioned by the poster the reboiler in the stripping tower or recovery tower of the aromatic extraction unit? In addition to distributing the shell-side steam, the outer draft tube also functions roughly as half of a wave-shaped expansion joint. Based on the described process conditions, it can be preliminarily concluded that there should be no issue of excessive thermal stress under normal operating conditions. It is likely that, during the initial stages of operation when the temperature of the material in the tower bottom was low, the opening degree of the reboiler steam control valve was too large, resulting in a large temperature difference; this led to the separation of some joints between the heat exchange tubes and the tube sheet.
Thank you for your reply. Could I ask you some specific questions? Would it be possible to add you on WeChat? My WeChat is 13252909539
On my diagram, it definitely isn’t a diversion cylinder
This post was last edited by wanlirn on 2023-9-29 at 13:43. The image shown by the original poster is the outer deflector tube. . . . If you don’t understand something, don’t speak in such absolute terms.
1. Our company has a set of fixed-tube-sheet heat exchangers: the tube side contains aromatics and sulfolane, while the shell side is equipped with 2.2 Mpa steam； The calculated counterflow logarithmic temperature difference is around 58°C, but during previous maintenance operations, the heat exchange tubes and tube sheets were the most frequently damaged. The tubes are made of grade 20 steel, while the shell is made of Q345R steel. Firstly, logically speaking, welding such materials poses no difficulty for most manufacturing companies; therefore, the welding issue can basically be ruled out. 2. Referring to the design of similar heat exchangers in other aromatic compound factories, most of them are equipped with expansion joints. Should our company’s heat exchanger also be fitted with expansion joints? This depends on the length of the heat exchange tubes, the average temperature thereof, as well as the average temperature along the length of the shell. 3. Is it an uneven pulling force or axial force between the heat exchange tubes and the shell that causes the joints between the tube bundle and the tube sheet to become detached? It refers to the comparison between the pulling force under the effect of temperature and that of the shell, with the average temperature difference along the length being the main factor
May I add you on WeChat? I’d like to ask you some questions. Thank you