According to HG-T20570.2-95 on the installation and selection of safety valves, there are some doubts regarding the design of safety valves
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According to clause 7.0.8 of HG-T20570.2-95 on the installation and selection of safety valves, regarding the requirement in case of rupture of the heat exchange tubes: if the design pressure on the low-pressure side of the heat exchanger is less than 2/3 of the design pressure on the high-pressure side, it should be considered as an emergency condition. A safety valve needs to be designed. So for example, if the outlet on the low-pressure side leads into a tank at atmospheric pressure, and the distance between them is very short, is it then necessary to install a safety valve? Even if the pipe ruptures, the fluid will be discharged directly into the atmospheric pressure pipe; theoretically, this process is faster than pressure release through a safety valve. Is this requirement mandatory?
My understanding is that this standard, marked with a T, is a recommended standard. The term “required” in the standard indicates something that depends on specific circumstances, and it is not a mandatory requirement.
If there is a valve separating it from the atmospheric pressure tank, a safety valve needs to be installed； If not, it is not necessary to install a safety valve.
First, you have only considered the outlet on the low-pressure side; what device is connected to the inlet on the low-pressure side? If the tube side of the heat exchange tube ruptures, the medium will also enter the upstream equipment from the low-pressure side inlet. Valves should be installed at both the inlet and outlet on the low-pressure side of this heat exchanger. If the design pressure on the low-pressure side is less than 2/3 of that on the high-pressure side (the Petrochemical Design Manual stipulates that a safety valve must be installed when the design pressure on the high-pressure side is more than 1.25 times that on the low-pressure side; in China, the test pressure for equipment is 125% of the design pressure), it is necessary to consider emergency scenarios and install a safety valve. If the low-pressure side is connected to the tower, that is, if the heat exchanger here is a reboiler, it is possible to install a safety valve at the top of the tower.