Location of Pressure Relief Valve in ASME VIII-1 Vessel 2

[IdanPV]

Hello All,

I would like to know if there are any special requirements regarding the location of the pressure relief valve which is to be installed in a ASME VIII-1 vessel.
This is a rectangular vessel which designed to contain steam, due to design considerations, I would like to install the relief valve on one of the vessel walls (left side or right side) and not on the top of the vessel.
Is there any requirement in the Code which prevent me to do so?

Thank you all

 

[The Obturator]

ASME VIII (2019) UG-135 provides guidance on this including cautions on any vessel liquid level relative to the PRV. For a more comprehensive guide I suggest you also consult the relative content in API-Standard-520 Part II (2020).

What is important, is that the PRV is installed in a vertical position (spindle above disc). Non-mandatory Appendix M Section M-11 reinforces that in ASME VIII though exceptions are allowed.


*** Per ISO-4126, the generic term 'Safety Valve' is used regardless of application or design ***

*** 'Pressure-relief Valve' is the equivalent ASME/API term ***

 

[IdanPV]

Thank you for your comment

 

[don1980]

Installation location constraints exist, and they're based on the relief fluid phase. ASME VIII (and other codes/standards) say that a PSV which is designed to relieve vapor must be mounted on a nozzle in the vapor section of the vessel. The reason for that is obvious when you think about it. Say you have a PSV orifice that's sized to relieve one cubic meter of gas per second at the relieving pressure. And someone mistakenly mounts that PSV on a nozzle in the liquid section of the vessel. Now, because of this error, the PSV has to relieve a cubic meter of liquid per second. Obviously, that's not going to happen.

Regarding the orientation of the installed PSV, it has to be consistent with what the manufacturer has tested and approved. Obviously, the vertical upward orientation is approved by all manufacturers for all PSVs. If a horizontal orientation is needed for whatever reason, say for example because of limited physical space, then you'll need to choose a PSV that is approved (by the manufacturer) for horizontal installation. Leser has the greatest number of PSVs that permits horizontal installation - the majority of their PSVs can be installed horizontally, but check the catalog to verify that you haven't selected one that's not approved for that.

 

[KevinNZ]

Don1980

Good points about discharge from the below the liquid level. I have had to explain this to a number of clients who were expecting burst disks to be installed at a steam pipeline a low point rather the high point near the source.