7 replies to this topic

[invssse]

Dear Experts,
 
I have a question regarding the location of PSV.
 
We have a project of natural gas sweetening and there is a MDEA regenerator column. I found PSV is located in the bottom (on the top of once-through reboiler shell, steam goes through reboiler tube). 
 
Since normally PSV is located in the overheat, I am wondering why this PSV is on the bottom. Thank you!
 
Regards,
INVSSSE

Attached Files

•  PSV_on_Bottom.xlsx   45.82KB   38 downloads

Edited by invssse, 05 May 2016 - 09:28 PM.

[Art Montemayor]

Your sketch shows a kettle type reboiler, not a once-through reboiler.  The PSV is shown located on the top of the kettle reboiler's vapor space - and that is the perfectly logical place to relieve the vapors generated there.

 

Your description of your sketch doesn't make sense or you are mis-interpreting the equipment and how it works.

[shvet]

If reboiler is the only sourse of pressure during all emergency contingencies then PSV located on kettle reboiler shell is the best choice. During emergency relief velocities can arise much higher then those normally expected. Emergency relief can cause  trays/packing damage or even PSV plugging by trays/packing pieces.

[Bobby Strain]

This is yet another case of too little information. The sketch is not a P&ID. So, no one knows what the installation is. We can only guess. But I, for one, am not going to guess. This is simply a riddle without a solution without full disclosure.

 

Bobby

[invssse]

Dear Shvet,

 

This would be a reasonable reason why PSV is located on the bottom.

While this is the sole case I have ever seen because in most cases PSV of distillation columns will be installed on the column overhead and/or the accumulator.

Thank you.

[fallah]

invssse, on 06 May 2016 - 02:36 AM, said:

We have a project of natural gas sweetening and there is a MDEA regenerator column. I found PSV is located in the bottom (on the top of once-through reboiler shell, steam goes through reboiler tube). 
 
Since normally PSV is located in the overheat, I am wondering why this PSV is on the bottom. Thank you!
 

 

invssse,

 

The top of column cannot be seen in the picture hence it can just be supposed there is no PSV installed on column overhead...

 

Then, if so the PSV on the reboiler shell is mostly installed there to handle the relief load of the tube rupture case (the tube rupture case is probably a credible scenario) and at the same time can handle the relief load of overpressure in the column itself.

If the PSV had been installed on the column overhead then handling the tube rupture case might be followed by the column flooding due to passing high pressure/flowrate steam through it...

 

Please let's know your viewpoint on above mentioned assumptions and subsequent results...
 

[shvet]

invssse, on 07 May 2016 - 09:18 AM, said:

 

While this is the sole case I have ever seen because in most cases PSV of distillation columns will be installed on the column overhead and/or the accumulator.

 

Hi, invssse

 

PSV on distillation column bottom (not on kettle reboiler) is recommended way by some local codes and many design companies's recommended practicies in post-USSR countries.

[invssse]

Dear Fallah and shvet,

 

thank you very much for your valuable information!

 

Invssse