3 replies to this topic

[marianine]

Hi everybody,

 

I have a doubt about change of the flange due to relief pressure. There is a PSV (sized to fire - overpressure 21%) located in a line of 600#. If you calculate the relief pressure, you will note that the flange of selected spec  does not support this value, but others components support. So I chose to stay with the same pressure classe for the line, however I specified the flange and PSV to 900#, adding the class break.

 

Nevertheless, I do not know regarding to the flange of block valve in the PSV inlet. Can I stay with 600# as it is an eventual situation (relief)? Or do I have change the pressure classe of line (full) to 900#?

 

Thanks,

 

Marianine

  

[Bobby Strain]

You select the system components, including the PSV, based on design pressure, not relieving pressure.

 

Bobby

[marianine]

Thanks Bobby!

 

I have to select the components based on design pressure, because the relief scenario is an eventual occasion, correct?

 

Do you know any standard about this? Because I have to justify for a client the reason why I do not change the pressure class of the line.

 

Once more, thank you!

[latexman]

It should be in the applicable piping Code.  Overpressure allowances are built into the Code.  If you design to the design pressure and are in compliance with the Code, you are fine.