FIRE CASE DESIGN STANDARD FOR VESSEL MOUNTED PVRV (PRESSURE AND VACUUM RELIEF VALVE)

[joengg]

I have a pressure vessel (design press: 3.5 barg) with a conventional PRV and a end of line PVRV mounted on top.

For PVRV I issued an inquiry to a vendor and asked them to size it as per API 2000 under fire case scenario. But PVRV vendor is regretting to quote as they claim that since PVRV is mounted on a pressure vessel, API 2000 cannot be used for sizing. I checked API 2000 and its pretty clear that its applicable for low pressure tanks of pressure upto 15 psig only. I am now wondering which standard can be used to size this PVRV since vendor is not aware of this as well. I dont want to use API 520 because I understand the size of this PSV will be very high and wont be in our budget.

Can anyone suggest a more economical way to size this PVRV?

PS: It might sound weird to have a PVRV and a PRV both on the tank at the same time. but this is client requirement so I need to supply this PRV even though its never going to be used as it is set at higher set pressure than PVRV.

https://files.engineering.com/getfile.aspx?folder=23c50ed2-0fa9-47fd-a4e4-044fc0b0a31e&file=PVRV.png

 

[mk3223]

It's interesting to see both PSV and PVRV on the pressure vessel protection. In addition, it looks that there is a purge line through PCV-001/002 on top of the vessel for the protection. It could be a "complete" safety design if the vessel was also designed under full vacuum condition.
As requested by the Client, it seems no actual economical justification needed to design with both PVRV and PSV as the cost might not be an issue without any engineering basis.

 

[georgeverghese]

If this vessel is in flammable fluids service, the vessel should have been mechanically designed to withstand full vacuum (without the need to admit free air through a VRV).
Agreed, at 3.5barg, relief requirements would be dictated by ASME / API520/521 and not by API2000.