I am doing system in which 2 PSVs (open to ATM) are installed on header (6”) which is coming from 30m height reactor nozzle to scrubber which is installed @ 15 m level.
Psvs are installed directly above header on the reactor platform (independent, not supported from reactor)

1) In order to qualify nozzle loads of reactor I need to give spring to this header.
Is it right to give spring to the inlet psv header?
But I am not finding any other option to it.

2) Please confirm the forces and location of the forces, I have applied.
Set 1
Vertical upward force at psv:
F1 =W²RT/(gPsA)
Horizontal Force @ psv opposite to outlet
F2= DLF * W√ (kT/(k+1)M)/366

Set 2
Downward force @ elbow
F2=DLF*(Wsqrt(kT/(k+1)M)/366+(Pt-Pa)*At)

At : Flow area of tail pipe at tip
Pt :Pressure at Tip
Ps: Set Presuure
A: orifice area
Other terms are as in API520.

These two sets I have applied in two different cases .

3) Even I am not able to qualify nozzle loads at PSV pop up condition in set 1 forces as upward force at psv F1 is causing excessive moment @ reactor nozzle.
I can’t restrict this upward force by giving hold down support to psv inlet as support can’t take thermal upward force for 30m expansion, even it will fail in expansion.

I am thinking of relocating psv from the platform to far away from reactor so as it will not have any effect on nozzle loads.

4) Inlet temperature is 225 C. What should we consider outlet temp?
I have considered both, 225 C and 21 C. But this seems to be too conservative.

mmmm.

PSV should be close to the vessel (ASME?)
NEVER use springs on a PSV system
PSV/Relief header systems are the one thing people will disagree on but this is what i do..

Static
1.Calculate max force (ceasar tool etc)
2.Add DLF (2?)
3.Add out of balance forces to all elbows in all directions. (seperatly)


with regards temp, 225 looks like a design temp?

It can be argued that the temp is 21c at event, but we set fire to the building and use the boiling point of the vessel solvent to determine T

A very subjective subject. worthy of lots of discussion. but time is short.........

But as the psv is installed on top of reactor I can not give rigid support to the inlet line which is also on reactor top. I am not getting any other option but to give spring support as reactor displacement is about 60 mm .
And regarding Psv position near to nozzle, is it specified in B31.3 ?I didn’t get any reference though.

PSV location is stipulated in ASME and can be no more than 1.5D from the pipe centreline??????

but i'm no process engineer and it is they that will require this

With respect to PRV lift, is it not the case that the uplift force will be balance by the reaction force???

don't be scared of high (transient) vertical forces on the vessel nozzle, the vessel manufacture may well pass loads you may think ridiculous.


I would not wish to see springs on my PRV system.

You should ask for help and advice from a seasoned stress engineer within your company.