Dear All,
I need to perform stress analysis of piping plant where there are some PSV; Vendor give me the reaction forces of each PSV but I don't know how to apply this forces in Caesar, In which direction I must apply these forces? Someone can help me, thank you to all.

U have to apply these forces in PSV outlet line.
Downstream of PSV whereever bends/elbow comes. U need to apply this kind of forces.
But forces values is depend on the piping leg in particular direction.

One is Static Equivalence method, to apply force as concentrate force and apply DLF of 1.5-2,
second is dynamic method ( Spectrum and Time History), you have to develop your spectrum curve based on information you have, tutorial has very good example,
you should know what kind of condition of downstream of PSV before PSV openning,
If PSV downstream pipe is empty, the speed of pressure is flow velocity,
if PSV downstrean pipe is fully filled, the speed of pressure is sound velocity (about 1200m/s),
if PSV downstream pipe is partially filled, this will become slug flow, you have to use your engineering judgement to calculate reaction force + slug force,

Hope this will help you,

Ok, thank you for your reply; then I will perform a static equivalence method, therefore I need to apply concentrate force in correspondence of my PSV. For Example, if Vendor give me a reaction force of 400 N, I will aplly this force in both direction(inlet and outlet) of my PSV. Is it right?
I'd like to attach a sketch of my PSV in order to make easier the explanation but i don't know how to attach file to this post.

In PSV's the first step is to define the forces first at the PSV nozzle and then at each bend. Process Engineering can define the value of the forces as it changes with change in diameter on the outlet side (Bernoulli's Equation). The forces are applied tangentially to each elbow’s as two components. On an open system you may provide just one reaction force, unless the opening has a 45 deg. slot cut then resolve it into components. Process can go further and provide you the exact forces at each location.

You may like to refer ASME B31.1 Appendix-II.