PSV/Pressure Vessel - Air Surge Tanks 2

[Johngoog]

Hey All,

I've got 6.5 gallon air surge tanks and i have no idea if that is technically considered a pressure vessel. Air with a 90psi feed regulated down to 40 psi before the tank. Tanks MAWP is 200 psi. In the state of Illinois.

So my questions are: (1) Is this technically a pressure vessel? (2) Does this need a pressure safety device? Regulator up-stream is relieving type, seems unnecessary.

Per ASME code:

"
(-f) a vessel for containing water1 under pressure, including those containing air the compression of which serves only as a cushion, when none of the following limitations
are exceeded:
(-1) a design pressure of 300 psi (2 MPa);
(-2) a design temperature of 210°F (99°C);
"

Would seem to me that is exempt, but want to make sure

Thanks

 

[RVAmeche]

States normally have their own list of exemptions that you may want to investigate. If the only connection is an air line that is capable of a maximum 90 psig and the MAWP is 200 psig, then you may be able to claim the system is safe by design (if it turns out the tank is considered a pressure vessel).

 

[mk3223]

IMO, the requirement of the PSV of the Air Tank may be depended on the process PHA/HAZOP review.

 

[don1980]

Here's a very useful reference document, published by the National Board. For each US state and Canadian province, it identifies whether the state has a boiler and a pressure vessel law, or just a boiler law.

[URL unfurl="true"]http://www.nationalboard.org/PrintAllSynopsis.aspx?Jurisdiction=Select[/url]

Illinois has a boiler and a pressure vessel law, so the answer to your question is that the vessel you mention is legally required to comply with ASME Sec VIII, if in fact it's an ASME Sec VIII vessel, and it's not otherwise exempted by one of the qualified exemption in ASME Sec VIII U1(c)2. That paragraph in the code list 10 qualified exemptions. In your message, you mentioned one of them (the one for vessels containing water and designed for P<300 psig and T<210F). But you said this is an air surge vessel, so it doesn't qualify for that exemption. Possibly it will qualify for the exemption for vessels with a diameter (ID) of 6" or less. If not, then you're legally obligated to protect it from overpressure, per the requirements in construction code, which I assume is ASME Sec VIII.