Expansion in a root valve

[Fran67]

Hello,

Here is my problem:

A root valve in my system let to isolate piping (process) to the tubing (instrumentation), in case of tubing breakage.
Process data: 70bars/-45°C
Root valve data: min operating T°: -50°C /design T°: -196°C

In case of tubing breakage, the process gas will undergo an expansion to the atmosphere through the root valve (70bars to 0 bars atm).
The temperature will therefore decrease in the valve (because of the expansion), certainly to a temperature below -50°C (min operating temperature of the root valve).
-> The root valve shall be closed in case of tubing breakage, but in this case the valve can be out of operating data -> I Wonder if the system is safe?

Would anyone have some answers for me?
Maybe a standard can speak about this point?
Or maybe the expansion occurs at the valve outlet and there is no impact on temperature in the valve?

Thank you for your answers
Fran67.

 

[LittleInch]

I don't think this is the right forum which is for hydraulic power systems.

At that sort of pressure and temperature, I can't see the root valve being closed manually if you get a full rupture of your tubing. You need other shutdown systems.

but you have half the answer - it's not likely to get that cold.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[mk3223]

It can be a process safety design issue. And, you may want to confirm actual types of instrument connection from your project for the cold stream process.
IMO, it can add a RO fitting after the root valve to minimize the process flow released in case the tube broken, or using the diaphragm type of instrument connection after the root valve.