mariog,

Thank you very much. You explanation was very clear.

Due relief is very slowly for liquid, I can't consider "pop condition" right? So, what is the direction of these forces? I understand should have a reaction force against pipe direction acting on valve and another in last elbow of the system. Please, look at draft attached.

At node 10 only F2 act (DLF x F1)

At node 20 all forces are balanced.

At node 30, vertical force is balanced and horizontal force act at the elbow.

Is my understand right?

Regards,

Miyamoto