Hi Guys,
I am dealing with PSV open discharge system. System is short horizontal pipe after discharge about .5 m horizontal pipe, then about 2 M vertical pipe with guide and +y restrain at node 840 after 1 M and the remaining 1 M to atmosphere with last node 850.
I put the reaction force of safety valve at node 850 in -Y direction.
Reaction force from vendor data sheet is 8666 N acc. to API 520.
I add force in load case like that:
W+P1+T1+F1 (OPE)
W+P2+T2+F1 (OPE)
when I run the system I load at node 840 +y restrain is maximum about -1600 N in Y direction.
Which mean the force at restrain is less the reaction constant force I input in the system.
I think force at restrain should be at least -8666 N in y direction but it is more less than value.
can any one explain how it is done ?

You should post a screenshot of your CAESAR model. I'll step out on that ledge and guess you modeled the vessel the PSV is attached to, and it is growing upwards, lifting off the support at 840, and the force you place at 850 causes 840 to warp the pipe, but then set back down onto the support.

To that end, the force is being absorbed into piping with the left over force transmitted into the support.

Hi Michael
PSV connected on Pipe Header not on Vessel and tomorrow I try to upload some screenshots
Thanks for help

SCREENSHOT
SCREENSHOT
these are screenshots

The links you posted give me the message "this album is empty".
I think you have two "subsystems" giving the restraint force there. Is the restraint at 840 loaded having no F1 force?

yes the restrain hasn't have F1 force

In fact the question is that 840 restrain shows forces when element 840-850 has no external forces (those described in F1)? If yes, you may analyse how the restrain acts on piping and confirm that indeed "the force at restrain should be at least -8666 N" when you apply F1 forces.
It is in fact what Michael Fletcher suggested (you answered "PSV connected on Pipe Header not on Vessel" but this aspect is not really relevant).

I review the result again and I notice node 850 move upward (+Y) by 9.125 mm so I guess the expansion force is bigger than reaction force so support lift up in Ope and design cases.
But I also think that doesn't present the actual case when safety valve open suddenly which effect in directly on restrain at node 840. so i think should calculate the force on support manually or by any other method.
is that right??

You can post images directly to the forum by clicking the "switch to full reply" button at the bottom of any thread.

As Richard mentioned in the other thread, the system must be in equilibrium, no matter what. If you absolutely want the most conservative combination of values, you have to analyze the full gamut of possibilities.

In this case, you have lift-off competing with the force to result in decreased piping loads on supports. It would then follow that you could simply run a case without temperature to get dead weight combined with relief loads.

Whether or not that's a credible design scenario is something that we cannot answer in this forum. That's something you must answer, and something you should clear with your process engineer.

These are the screenshots. real nodes number in my system 10060 for restrain and 10070 for reaction force

Some comments:

1) You're missing some load cases. You need to calculate W+T1+P1 by itself, and you need to subtract it from W+T1+P1+F1 as an OCC case, and then you need to add W+P1 to it also as an OCC case. This is obligatory.
2) If you then run a restraint summary extended, you'll see displacements for this node in both cases. Your pipe is too rigid to set back down onto its support after it's thermally grown upwards, even with your thermal growth applied. The proximity of the closest upstream support is the culprit, here, and you'll find that in your current model, that's likely where all your relief loads are being transmitted to.
3) For a conservative restraint load, you can also run W+P1+F1, which will be roughly the same as W+P1, with F1 applied to it. The numbers may vary based on how the various centers of gravity allow the pipe to warp.
4) You can also apply a stiffness factor for all supports, which will allow them to all sag, but possibly maintain contact with all supports. However, this can be a tedious process to input manually. It could also be done by adding structural elements to your model. It all boils down to time versus money versus expectation of realism.

Thank you Michael for your help