API 2000 - API 650 Fire Venting

[Mondolfi]

For safety devices the overpressures indicated as 20% and 10% above maximum allowable working pressure apply to API 620 tanks only. As indicated in 4.5.1.1.4, these conditions do not apply to API 650 tanks where the internal design pressure should not be exceeded under any normal operating condition.

I understand that "Fire" wouldn't be a "normal operation condition". There for, if the tank is API650 can I assume an overpressure (let's say 10%) above the MAWP of the tank (in my case design pressure) or shall I fix the set point to a lower figure so I never pass the MAWP?

Best regards,

 

[JoeTank]

The MAWP deterimed per API-650, Appendix F may be limited by compressive hoop stresses in the shell-to-roof connection or by uplift of the tank bottom. When checking the emergency venting requirements of API-200 (a surrounding pool fire, not an internal fire), the MAWP should not be exceeded under any circumstances. API-650 is silent about overpressure; therfore, I would not assume that it's permissible.

Steve Braune
Tank Industry Consultants

http://www.tankindustry.com