Atmospheric discharge high backpressure 3

[RMWN10]

Hi all,

PSV discharge line is 6" diameter, several feet long, has one elbow, and discharges to atmosphere. The PSV outlet pressure is ~100 PSIG. The backpressure is ~70%.

What is a feasible method to reduce this backpressure to 30-50% where balanced bellows PSV can be used?

Thanks.

 

[Latexman]

Not enough info to get into details, but:
[ul]
[li]No discharge line.[/li]
[li]Bigger diameter discharge line.[/li]
[li]Shorter discharge line.[/li]
[li]Less fittings.[/li]
[li]If PSV is significantly too large, a restricted lift.[/li]
[/ul].

The PSV outlet pressure is ~100 PSIG.

You sure about that? At what point is this pressure? End of flow nozzle? PSV discharge flange? How was it calculated?

What’s the PSV set pressure and % over pressure?
Flow nozzle/“orifice” size?
Inlet and outlet flange size?
How many feet long is the outlet pipe sections?
Vessel MAWP?
What’s the fluid?

Good Luck,
Latexman

 

[LittleInch]

You forgot to mention that if it went off you could hear it in the next county....

Something sounds seriously wrong here.

More details.

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

 

[Snickster]

Is the 100 psig just due to frictional pressure loss? If so that is a lot for a short piece of piping. Is it because this is gas flow and sonic flow exists at the pipe exit and critical sonic flow pressure above atomospheric exists at the exit?

 

[MortenA]

I agree with the 3 first comments, either theres something wrong with your design or theres something wrong with your calculation.


--- Best regards, Morten Andersen

 

[pierreick]

Hi,
Discharge to atmosphere! How can you get a back pressure of 100 PSIg with a few feet long and an elbow?
You may want to perform a back calculation from the outlet of the pipe to the outlet of the PSV.
Definitely more info is needed.
Pierre

 

[MJCronin]

Wild, bizare GEEZER, suggestion here, RMWN10 (Petroleum) ...

Pehaps take three minutes to develop a sketch and a quick PID segment ?

Pehaps give us design pressures, temperatures and materials that you want to use ???

Perhaps identify the specific PSV, give us a catalog cut ?

Does your client have any preferred vendors ?

LittleInch, of course, is correct insofar as noise is ONE of the important design considerations

Does anyone else here get sick of these tedious guessing games ?

Why is it not brutally obvious that you must give ALL technical information to someone who is trying to help you ?

Bah !!! ... I grew up in another more respectful era ...

MJCronin
Sr. Process Engineer

 

[FacEngrPE]

Pressure drop of 100 psi(g?) is easily enough to suspect the flow is going sonic (choked flow) in the pipe, or perhaps you have 2 phase flow, see thread1203-488280.

Just guessing this might be useful.

 

[georgeverghese]

If you want, you could post the exit line isometric with line dia, lengths and fittings included, and vent stream details, and we could confirm this high backpressure of 100psig. So your PSV set pressure is about 140psig.

 

[Latexman]

RMWN10’s last login was 11 days ago on Friday, September 8, 2023.

Good Luck,
Latexman