Above Ground Gasoline Tank-Classified Area Question

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sumptester
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Above Ground Gasoline Tank-Classified Area Question

Post by sumptester » Sun Jan 12, 2020 11:30 am

I have an inspector who is saying we cannot mount S1’s on our Convault tanks because the head of the S1 is not XP and the tank exterior is a classified area.

I cannot get a definitive answer via the internet.

Here is the question: How far from the ends of the tank does an electronic dispenser need to be on a gasoline AST?

I have always thought that areas around the tank itself are not classified.

I know the classified area is from the 18” out top gasoline all the way to the ground and then 18” and below within 20 ‘ of the dispenser.

Once a seal is installed above the 18”, you could run non xp electrical fittings, if you wanted to.

I have an NEC cut cut sheet but it is showing an AST with a dispenser mounted on top so the "area" is referring to the dispenser

Can some on point me to something that shows me the extent of the classified area on a gasoline ast. Including the fill, STP, vent and a dispenser.

Tx

ZMiller
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Re: Above Ground Gasoline Tank-Classified Area Question

Post by ZMiller » Sun Jan 12, 2020 1:07 pm

What did Con Vault say?
When you are dead it's likely you won't know it. It could be difficult for others. It's the same if you are stupid.
"Tact is the ability to tell someone to go to Hell in a way that they will begin looking forward to the trip"

sumptester
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Re: Above Ground Gasoline Tank-Classified Area Question

Post by sumptester » Sun Jan 12, 2020 3:17 pm

Asked them the same question today. Hopefully I'll get an answer tomorrow.

tankgenie
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Re: Above Ground Gasoline Tank-Classified Area Question

Post by tankgenie » Tue Jan 14, 2020 8:54 am

Chapter 8 of NFPA 30A is the guideline for this. It is confusing because Table 8.3.2 talks about dikes and tank shells which generally aren't terms used to describe the 6" reinforced concrete of a ConVault or the protection offered by other UL 2085 protected tanks.
NFPA 30A 8.3.3. helps clear this up a bit to me, some regulators don't agree, but some clearly see the point. It says "A designated classified area, as specified in Table 8.3.2, shall not extend beyond a floor, wall, roof, or other solid partition that has no openings." And in the handbook further advice is provided, such that "This requirement assumes that any penetrations of the assembly by pipes or conduit are tightly sealed to prevent the passage of vapors." So a 2-hour fire-rated, 6" reinforced concrete side wall on the ConVault (which has no penetrations) provides the wall protection to negate the classification found in table 8.3.2 for the "tank shell", however there is still the matter of the tank vent. This vent is open allowing passage of vapors, so you should still be minimum 5' away from the normal vent per Table 8.3.2. Emergency vents (especially the CARB EVR rated ones) are not designed to open unless an over-pressure "emergency" and are designed to keep vapors in. These opinions are my own, and I would appreciate any feedback on this and what others have experienced with regulators or designers regarding this issue.
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hardworking
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Re: Above Ground Gasoline Tank-Classified Area Question

Post by hardworking » Mon Feb 24, 2020 6:14 pm

You can also refer to Table 514.3 of the NEC.

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