Dear experts,
I have some concerns about the extreme low temperatures we can get in relief lines of steam exchanger in case of coil rupture.
I have the practical case where the effluent pressure and temperature at the entrance of the coil are 2100 psi and -16°C, respectively.
The relieving pressure of the PSV mounted on the steam vessel is 250 psi. To determine the PSV relieving temperature, I assume isenthalpic expansion from the coil pressure (~2100 psi) down to the PSV relieving pressure (250 psi). Note that I consider that the steam will be evacuated rapidly and finally it plays no role.
Applying isenthalpic expansion process, the calculated PSV relieving temperature is around -90°C (for coil temperature -16°C). The temperature becomes obviously lower downstream the PSV.
Our available piping for relief line is not rated for so low temperature ...
I'm wondering whether my reasoning is correct ? If yes, there is apparently no possible mitigation ?
Thanks for your support.
Regards
Dominique