PSV Sizing Calculation (Swagelok Relief Valve)

[C26M13]

Hi All,

I am trying to size a PSV (PSV172) for a Nitrogen Supply Line to Well Control Panel as per attached file.

The PSV is installed on the N2 Supply Line with a set pressure of 1,380 kPag and Vent to Safe Location.

I have some information of the Nitrogen Regulator (BOC Regulator 8000) with it's specification and the type of installed PSV (Swagelok R4 Series).

My question is:
1. Is this PSV only protect the overpressure from Nitrogen Supply? or it protect also from Gas List Control Valve Failure Scenario? Which one is valid scenario?
2. How can calculate the rated flow of the PSV for a scenario of Nitrogen Regulator Failure (from BOC Regulator spec sheet, the flow rate at 21,000 kPag is 1,086 L/min)?

Please see the attached file of the schematic drawing with additional information of BOC Regulator and Swagelok PSV.





Much thanks

 

[LittleInch]

Depends how that three way valve works.

If there is no way to connect the two incoming gas supplies then no, it's just the n2 supply.

For flow rate you find out the max flow when regulator is wide open. That might be the 1086 figure,but double check.

 

[georgeverghese]

You've got critical flow across that BOC regulator with 21e3kPag upstream of the regulator and 1380kPag set pressure at PSV 172, so flow will remain at 1086litres/min and will be the sizing case relief load. However, this may not be with the regulator failed wide open, so in the absence of more info on this regulator, I'd add say 30-50% more flow as design case flow margin for this PSV. Temp drop will be based on isenthalpic path from 210e3kPag to 1380kPag - look up any thermo charts for N2 for this.