Vapor Tight Tanks and ATG readings

[Fatmonk]

I hear those guys at the Cal Water Board are great to work with. Reasonable, charming and unlike Texas, don't have to wear drool bibs.

[CherokeeUST]

Not surprised to hear ZMiller is world famous.

I've been to the Texas Environmental Trade Fair and the CUPA conference. I learned much more at CUPA. I am looking forward to going back after California updates their UST regulations.

[ZMiller]

Yes they are. Nice people in California they are.

[Fatmonk]

California has a work shop on their federal regulations package on March 28th in Los Angeles (Region 4 HQ Building). They just had one in Sacramento earlier this week.

[CherokeeUST]

Article on Tank over-vacuumization: Unintended consequences of decommissioning Stage II vapor recovery systems

http://campaign.r20.constantcontact.com ... 0909b94762

[ZMiller]

Interesting that somebody important and in a positioned regulatory agency points at pressure and vacuum issues in fuel tanks.

Dramitic pressure fluctuations will cause stress and eventual containment boundry failure. Compounding issues caused by irregularities in actual fuel level measurement increase chances of over fill and spills.

When one for example has to pry a fill cap off with a crow bar to release vacuum a problem arrises where if the fill tube is missing the ullage atmosphere becomes explosive.

I'm told when conditions are just right and that happens it's painless and for a fraction of a second you sence weightlessness and hear a bird like buzz or churp in your ear(s).

So as Do You Feel Lucky Dirty Harry said. Is there a fill tube when I pry the cap off or could it be missing?

[ZMiller]

I might add that there might vary well be a flare flash if there is pressure in the tank. The ignition motivation being the quick release of kinetic energy caused by high velocity atmospheric differential pressure correction through a connecting conduit.

Ignition can and under ideal conditions will occure if a pressurized fuel tank containing highly saturated hydrocarbon vapor is vented to an oxidizing atmosphere.

[ZMiller]

It's refered to as flashing the tank. Back in the days for fun when excavating old tanks you pressured up the tank and popped the cap.

The visual 40 foot flare affect was better when done at night. Mostly the practice is harmless to canopies and surrounding structures as long as vapor ignition is outside the tank to atmosphere.

If the tank under extreme vacuum was all of a sudden to become oxidized with atmosphere (oxygen) for example the empty space atmosphere would be explosive. The ignition point being where the tank vent riser connects to the tank. Depending on exactly where you might be standing in proximity to a steel or glass tank exploding would determine how much fun you will have.

[CoseGurse]

This is a great article/study. Any way you could add where this was originally published?