The working pressure of the pipeline system is 7.0 MPa, and the medium is an explosive gas

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Jiuquan Information Network has a fixed-tube-sheet heat exchanger with a nominal diameter of DN400; it belongs to Category II vessels. The working pressure in the tube side is 7.0 MPa, and the medium is an explosive gas; the material used for the tube side is S30408. The working pressure in the shell side is 0.4 MPa, and the medium is circulating water; the material used for the shell side is Q345R. Given the significant difference in pressures between the tube side and the shell side, are there any particular considerations when designing such heat exchangers? I have put forward the following requests; I’m not sure if they are reasonable. Everyone is welcome to discuss them and suggest additional requirements. 1. For the Jiayuguan Information Network, the welding joint coefficient for the shell side is taken as 1.0, while the welding coefficient for the tube side is 0.85. 2. The connection between the heat exchange tubes and the tube sheet uses strength welding + expansion bonding. 3. After the hydraulic test is successful, an ammonia leak test is conducted on the weld joints between the heat exchange tubes and the tube sheet. 4. To prevent high-pressure gas on the tube side of the Jiuquan News Network system from leaking to the shell side and causing safety accidents, a safety valve is installed on the shell side.