N2 tanks in an unpresurized enviroment?

[SkElL~ObIsSiS]

What whould happen if u took a fully presurized nitrogen tank (3000psi) up in a hold of a plane (unpresurized atmosphere). Would the lower outside presure allow the tank to explode or what? Just wondering what the big deal was concerning having partially full tanks onboard airlines.
I dont know if the pressure difference is drastic enough to rupture a tank or not.....

[bjjb99]

The pressure difference between the inside of a full tank of the type you describe and normal outside air pressure is 3000 psi (psig). Normal air pressure is 14.7 psi (psia). If you take that tank all the way into orbit in the space shuttle and accidentally depressurize the ship, the tank would feel a pressure difference of 3014.7 psi (psia). Since the tank is most likely designed to handle overpressures of 4000+ psi, a mere fifteen psi of extra pressure over its normal fill level probably won't hurt it.

That being said, airlines require all tanks to be depressurized during flight. They're just one more thing that can go wrong, and the airline doesn't want to deal with protecting folks against a high pressure tank failure while at altitude.
BJJB

[Aranarth]

I was wondering the same thing today.

And I came up with the same conclusion (easy question for myself). Then I came up with this one, which may be just as easy, but I don't seem to recall if it works.
(does not apply to paintball, unless someone were to build a prototype tank for high pressures. . .)
If you have a tank thats pressurized to 3k, and place it inside a tank thats pressurized to 1k, the tank on the inside only has to hold 2k differential pressure before rupture, but does the tank on the outside have to hold 1k, or 3k? I am having scrambled logic on which way the mechanics work. . . Right now leaning toward the 3k, but if the inner tank doesn't flex at all, the outer tank seems like it only has 1k on it. . . arg. Too late in the morning for this.
-AranarthX

[bjjb99]

Assuming that both tanks are rigid, the outer tank would need to contain 1000 psi of pressure. In theory, you could contain a small volume of high pressure air by containing it in successively larger shells, each pressurized 1 psi lower than the one inside it. Things rapidly become impractical with this approach.

BJJB

[nutz]

hmm heres what i think...

the tank gets filled at normal ground level pressure or whatever, to 3000psi... the plane goes to 30000 feet and if the cargo chamber is unpressurized the outside of the tank would be a much lower pressure than it was filled at so my best guess is that the air in the fiber wraped tank would exsert more pressure on the bottle because of lower pressure on the out side causing the burst disk to blow or the bottle to expand, depending on how much the outside pressure actually affects it

[nutz]

also i figure that the pressure would not actually become much lower at 30,000 feet... if i remeber correctly from scuba classes, 1 atmosphere = like 16lbs per square foot

so take like 1/20th(30,000 feet) of the atmosphere and and multiply 1/20 times 16 = .8

so essentially the pressure on outside of the tank would be lifted .8 psi or so...

not very much at all, probably causing little or no change in tank pressure or size