scuba tanks in my car trunk.

[Bob DBF]

Although burst disks are designed to fail at 40% over rated fill pressure, they will rupture at pressures between 125% and 166% assuming they are relatively new. If, however, you neglect to change them occasionally, like at hydro, the burst pressure may decrease further as the disk deteriorates.

If you keep your tanks packed well, it will just scare the crap out of you when it fails. Don't ask me how I know.

Bob
------------------------------------
You only need two tools in life – WD40 and Duct Tape. If it doesn’t move and should, use the WD40. If it shouldn’t move and does, use the Duct Tape

 

[craracer]

If a burst disk goes on a set of doubles, with the manifold open, could it break a window if your windows are closed (tanks not in the trunk)?

 

[iztok]

If a burst disk goes on a set of doubles, with the manifold open, could it break a window if your windows are closed (tanks not in the trunk)?

Doubles or singles it doesn't matter I seriously doubt it.

 

[Crush]

FWIW, within the ideal gas approximation, the increase in pressure (or volume) upon heating is:

Tf/Ti

where Tf is the final temperature and Ti is the initial temperature. All temperatures are in terms of Kelvin - for a Celsius version:

(TCf+273)/(TCi+273)

where TCf is the final temperature and TCi is the initial temperature, both in Celsius. I believe that the conversion from Celsius (TC) to Fahrenheit (TF) is:

(TF-32)*5/9 = TC (could be wrong).

If a tank is filled to 3000 psi at 25C (TCi=25) (77F?) and will burst at 5000 psi (I am just making this up), then

(TCf+273)/(TCi+273) = 5000/3000

TCf = 5/3 * (TCi+273) - 273
= 5/3 * (25+273) -273
= 224 C or 435 F

So, your tank will have to heat to 224C/435F for the tank to rupture at 5000 psi.

Caveat - real gases depart from ideal gas behaviour at high temperatures and pressures such that 224C/435F should be thought of as an extreme upper end temperature - the true pressure at 224C/435F will be higher than the ideal gas case of 5000psi. This corresponds to the bursting pressure being lower than the 5000psi ideal gas case. Just a guess, but I would allow up to a 20% departure from ideal gas behaviour (this is a bit extreme) at 5000psi leading to

TCf = (5-5*.2)/3 * (TCi+273) - 273
= 4/3 * (25+273) -273
= 124 C or 256 F

Now the tank bursts at 124C/256F rather than 224C/435F. 20% here and there goes a long way...

The true departure from ideal gas behaviour of dry air is quantified, but I don't have the number in front of me right now.

 

[elan]

If a burst disk goes on a set of doubles, with the manifold open, could it break a window if your windows are closed (tanks not in the trunk)?

Given your HVAC is able to pump air into the car the answer would be no....

 

[Garrobo]

If air tanks would explode in one's car trunk directly caused by overheating or just sitting in the sun, there would be thousands of exploding air tanks all up and down the east, west and Gulf coasts every day. DUH.

 

[Web Monkey]

In order for a tank filled at 3000 PSI (at 70F) to reach 3500 PSI the temperature would have to reach 154F.

How about 161F?

hot-in-the-car

Terry

 

[charlesml3]

Having seen the tank experiments on Mythbusters, the idea of a tank losing integrity is a very scary one indeed.

Well yea, but it took a shape charge of C4 to actually cause the tank to "lose it's integrity." They repeatedly shot full tanks with rifles and all they did was hiss around the inside of the shipping container until the air ran out.

Unless you're carrying shape charges attached to full tanks in your car, you really have nothing to worry about.

-Charles

 

[spectrum]

That actual cylinder won't loose integrity in a vehicle.

If you have a generous fill, a tired burst disk and a hot day disk failure is a possibility. In that case there will be a controlled release of the contents. Get the valve serviced along with the obligatory VIP inspection for a emptied cylinder and move on. No lives will be lost and no villages will be destroyed.

This issue is largely the complement to asking what will happen of my cylinder is "overfilled" such that it cooled to the correct pressure at 70F. I know of shops that routinely pump AL80s to 3300 PSI so they settle out just about right. Get that same perfectly filled cylinder back up to about 130F in the sun and you are back to about 3300PSI.

Pete

 

[Gilldiver]

I'll have to remember all of the BS when I go to the Red Sea and look at the tanks sitting out in the Sun.

Lake Mead would be just about the same.