Thermal Expansion Psv Leakage

There is potential for one ammonia pipe to take a thermal expansion scenario. The psv is employed to protect against the scenario. But it is known that psv has allowable leakage. So my question is whether a rupture disk is needed at the inlet of psv to avoid the ammonia leakage.
Thank you for your comments in advance.

Where does the PSV discharge to? Can you discharge into another ammonia pipe or the ammonia tank?

Hi latexman
The discharge is to flare system.

Thank you ,latexman.

There is potential for one ammonia pipe to take a thermal expansion scenario. The psv is employed to protect against the scenario. But it is known that psv has allowable leakage. So my question is whether a rupture disk is needed at the inlet of psv to avoid the ammonia leakage.
Thank you for your comments in advance.

 

Hi,

 

Please specify the TSV set pressure and relevant line operating pressure. It might the leakage is due to small difference between such two pressures.

Thank you, fallah. Maybe it is the related point.

Is TRV set pressure as high as Code allows?  Look at your pipe spec. and adjust set pressure = MAWP.

 

For metal-to-metal seat, PSV will start leaking at about 90% of set pressure.

For soft seat, PSV will start leaking at about 95% of set pressure.

For PSV that will start leaking at about 98% of set pressure, look at pilot operated PSV..

TRV set pressure is the same as protected piping design pressure. Maybe it is preferable to use soft seat against the leak.

TRV set pressure is the same as protected piping design pressure. Maybe it is preferable to use soft seat against the leak.

 

Hi,

 

If there is no concern about high temperature to make damage on soft seat, you can use...

Yes,latexman. It should evaluate the temperature impact on the soft seat performance.thank you.