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[ManuDR]

Hello,

My first question in this forum refers to Anex F of the API2000 standard (sixth ed. november 2009).
I'm reviewing some low pressure storage tanks which contain flammable components. According to paragraph 4.5.3 and 4.5.4 of the API2000 standard, a conservation vent is insufficient for flashback protection and they refer to Anex F for more detailed discussion on flash back protection. I see there are 3 levels of inert blanketing, each providing comparable flashback protection.

When I look at the formulas for required nitrogen flow rate in the three cases, only the effect of thermal inbreathing changes. What is the fundamental difference between these three levels? Does a level 1 protection still allows "some" oxygen to breath into the tank and level 3 none? I thought level 1 protection would be sufficient to keep all oxygen out of the tank.

"For level 1 protection you shall measure tank pressure AND oxygen concentration." Does this mean that every low pressure storage tank containing a flammable (which is above the lightning critical volume), needs to be fit with an oxygen analyser?

Many thanks in advance for your opinion on this.