PSV Closed Discharge

[marchieV]

Do we have to consider the reaction force of PSV with Closed discharge system? I know it is considered for Open Discharge but for Closed Discharge system I don't know if it is required.

I need your expertise please. Thank you.

Regards,

Marco

 

[LittleInch]

Yes.

Those forces may be resisted by the closed drain or flare pipework but they are still there.

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

 

[marchieV]

Where do we impose the reaction force? How do we compute the reaction force since it has a leg or several elbows and the orientation at the discharge is different from the open discharge?

 

[The Obturator]

API-520 Part II does not really consider them provided the relief flow is steady. See attached extract.

Per ISO-4126, only the term Safety Valve is used regardless of application or design.

 

[marchieV]

Thank you for sharing. I read that also and they do not directly tell that it is not considered. Maybe because it is very rigorous to perform and I read also from other references that in order to get an accurate reaction force time-history is required.

It was also mentioned in ASME B31.1 Appendix II. They also consider that the closed discharge can be considered as steady-state.

 

[1503-44]

Put in a few clamps anyway. Its not like they won't move if they can find a way to.

 

[marchieV]

Actually it is a revamp pipeline and in the existing condition the line has spring support on both upstream and downstream of the PSV. I was wondering if in the previous analysis they considered the reaction force because how did they pass the stress analysis without using guide or clamp on the upstream and downstream?

 

[LittleInch]

Difficult to comment with a decent drawing.

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

 

[KernOily]

Yes it's required. No it's not difficult to calculate. It's just a basic fluid jet momentum transfer. i.e. rho * A * v2 calc type of thing. Look in any fluids text, look in the Crosby Technical Book, which is now Emerson

https://www.emerson.com/documents/a...-valve-engineering-handbook-en-us-3923290.pdf

or get CAESAR II to do it for you. The line of action of the fluid jet/force matters. Look in your fluids text.

 

[1503-44]

Yeah. We should remember that API 520 is not a design code for Pipe and that piping engineers are responsible for including all potential loads applied to the pipe even, or rather especially, when not specifically mentioned by name in any piping design code.

 

[KernOily]

^ this. Another one folks forget is maintenance loads and accidental loads e.g. someone bumping into the line with a forklift, or a couple dudes standing on a small-bore line at mid-span between supports. All that has to go in your Occasional load cases if it's reasonably foreseeable.

 

[gsakamoto]

Yes, always check any credible case and review the results. It's good engineering practice to check this.