allowable overpressure for low pressure vessel
allowable overpressure for low pressure vessel
(OP)
We are doing relief valve sizing for a client who has numerous vessels, which have an MAWP of 0.6 psig. We realize these do not fall under ASME, but if we were to install an RV, RD or tank vent at a Pset of 0.6 psig, what would be an acceptable overpressure?
Utilzing 10% or 21% for fire would only yield 0.726 psig relieving pressure. If you refer to pressure vessels between 15-30 psig, you can utilize 3 psig overpressre, but seems quite excessive. I have also heard of a proposed ASME code which would allow 2 psig overpress for MAWP < 15 psig??
I am wondering if anyone has guidance on how ASME specifies the allowable overpressure and what ASME code would be for the MAWP of <15 psig?
Thanks
Utilzing 10% or 21% for fire would only yield 0.726 psig relieving pressure. If you refer to pressure vessels between 15-30 psig, you can utilize 3 psig overpressre, but seems quite excessive. I have also heard of a proposed ASME code which would allow 2 psig overpress for MAWP < 15 psig??
I am wondering if anyone has guidance on how ASME specifies the allowable overpressure and what ASME code would be for the MAWP of <15 psig?
Thanks





RE: allowable overpressure for low pressure vessel
David
RE: allowable overpressure for low pressure vessel
Good luck,
Latexman
RE: allowable overpressure for low pressure vessel
RE: allowable overpressure for low pressure vessel
if it has elliptical heads, it might be good for several psig. we have taken several vessels that were stamped for 35 psig and FV and had them rerated for +50 psig.
basically you need to find someone with a pressure vessel design program, have an inspection and do a hydro-test.
RE: allowable overpressure for low pressure vessel
If you can't do it with an Anardo Valve (tank specs) then I'm out of ideas.
David
RE: allowable overpressure for low pressure vessel
Little pressures require huge relief devices during 'Fire Case'.
RE: allowable overpressure for low pressure vessel
In my opinion, this discussion points toward a "minimum recommended design pressure" that should be part of ASME VIII, API-650 and similar codes. Some older in-house design standards by PENZOIL, EXXON and others used to have these
ASME and API are silent about this.
I suggest for example:
- Any metallic vessel with eliiptical heads and a diameter of less than 10 ft should have a MRDP of 5 psig and be tested to 7.5 psig
- Any flat bottomed tank of API-650/620 construction should have a MRDP of +10 IWG and -5 IWG
- FRP, plastic and vessels of any other construction should be bound by the limitations agreed upon by the purchaser and the fabricator.
RE: allowable overpressure for low pressure vessel