Looking for a mathamatical explantion of why nitro tanks are safe

[jamesmbaldwin]

Well, Tom Kaye started the use of nitro in paintball, and since he is into that fancy engineer math stuff he obviously wouldn't use nitro himself if it could blow up and kill him. What I'm looking for is a mathematical reason why nitro tanks are so safe (E.G. pressure is 3000 psi but steel tank can hold 40000psi). I have no way to calculate this but I know it can be done. I think you may have to get the grade of steel and thickness of the wall, there may be other factors involved though, I have a pure energy 47/3000 we can use that as the test tank.

I just started using nitro and am a little worried, probally just being paranoid that's why I'm asking.

[nippinout]

It's all about a Factor of Safety, FS.

Say I have a steel tank that will ultimately fail at 12,000psi. I want a FS of 4, so I can have that tank at an operating pressure of 3,000psi.

Tanks have been over-pressurized and shot at. No real explosions. The real danger is the reg popping off, and the seperated tank and reg becoming high velocity projectiles.

I do not know the strength characteristics of fiber reinforcement. But you can look at the stresses of the metal tank. For thin-walled cylindrical pressure vessels, you look at the hoop stresses and the radial stresses.

Hoop stresses are the stresses in the walls running perpindicular to a lengthwise cut, and is
(pressure * radius ) / (thickness)

Radial stresses are the stresses perpindicular to a cut across the vessel (Like a circle) and is
(pressure * radius ) / (2 * thickness)

As we can see here, you will have the greatest stresses in the hoop. This disregards the stresses in the neck and hemispherical portions, which has some internal stress already due to manufacturing.

Ultimately, the tank manufacturers do not try to design tanks that will kill. Just use common sense. Use a tank cover and never fill beyond the tank's working pressure (Use the gauge on the fill station, it is more accurate than the one on your tank). Never put lube in the fill nipple. This will cause diesling in the tank.

In addition, you can use a marker to make a mark on the tank's neck and regulator. That way, you can tell if your regulator is unthreading from the tank. Always pay attention while removing the tank!

When any nicks in the fiber wrap are deep enough to expose the actual fiber, the tank is no longer safe.

Use your head, and you'll be alright.

[ThePixelGuru]

There's a lot more to it than the thickness of the tank walls... To explain all that, someone would have to post the majority of a materials class they took in college. Be assured, though, that your 3000psi tank has been tested to 5000psi without failure.

EDIT: Oh well, the guy above me posted a pretty good summary. Basically, unless you gouge the hell out of your carbon fiber wrap tank, it's not going to blow up. Just make a mark on the reg like he said so you know if it's coming out. That's pretty much the only place a tank might fail, and it's extremely unlikely to happen anyway.

[SGranier]

Yay for engineering. Reminds me of my statics class last semester. Hoop strength, thin-walled pressure vessels, and factor of safety!

Would most CO2 and HPA tanks be considered thin-walled pressure vessels? I forget what the ratio is 10-1? Diameter of tank to wall width? to be considered thin-walled.

I'd have to go check my notes. But great explanation!

[Dark Side]

"Tanks have been over-pressurized and shot at. No real explosions. The real danger is the reg popping off, and the seperated tank and reg becoming high velocity projectiles"


My dad saw an acetaline tank fall off a weld cart, break off its cap, the proceed to go through 7 brick walls. Damn tank was just fine save for a few small dents. If thats a testament for its durability....

[warpspyder]

My dad saw an acetaline tank fall off a weld cart, break off its cap, the proceed to go through 7 brick walls. Damn tank was just fine save for a few small dents. If thats a testament for its durability....

I would pay to see something like that. But really there's no danger. Look at SCUBA tanks. They're subject to all sorts of weird situations, and they hold don't they? (I know terrible example, but I gave it a shot).

[ScatterPlot]

"Tanks have been over-pressurized and shot at. No real explosions. The real danger is the reg popping off, and the seperated tank and reg becoming high velocity projectiles"


My dad saw an acetaline tank fall off a weld cart, break off its cap, the proceed to go through 7 brick walls. Damn tank was just fine save for a few small dents. If thats a testament for its durability....

Interesting tidbit to add here... I think acetylene tanks are only pressurized to around 300 psi or so IIRC, because acetylene is such an unstable gas. It's even dissolved in something, can't remember what though, cause if compressed over about 15psi or so regularly it will explode :)