Is a 1/2 full tank safe in a hot car?

[TMHeimer]

I never take chances. Even in NS with cooler air temps. If you are down South beware. You don't want to blow a burst
disc. Even in NY or more North than that in the summer I store it under the car. Out of site-especially near NYC! Cracking car windows may help if you leave it in there. And keeping it covered or out of the sun. Why take chances? Good question.

 

[captain]

Burst disk will go long before test pressure. Al 80, 3000 psi, 5000 psi test, burst disk will go well before 4000 psi (3500 - 3700). Steel 2475psi will go about 2700 psi. This is assuming proper disks are installed. If you do not believe this take a cylinder and pump it till the disk fails (note the fail pressure)

No way a good correct bust disc will burst at that low pressures. I have often filled 2250 psi tanks with the correct disc to 2800 and never blew a disc. The disc is designed to blow about 3500 -3600 psi . In the case of a 3000 psi tank it would be between 4700 - 4900 psi. Any disc that burst much lower was either bad or wrong for the application.

 

[DivemasterDennis]

So the answer to the question posed is "Yes, the tank is safe." I have had a single bust disc go. It went on an older steel cylinder rated to 2500 psi, and the inattentive tank filler (not me) had it to almost 3500 psi when the burst disc went. Tanks filled to rated levels will not burst if in a hot car or in direct sunlight. That is, if the tank in properly maintained, and inspected, including the burst disc.
DivemasterDennis

 

[JB]

I have thought about this, since the temperature in my home town can reach 40 degrees celsius in the shade. The clue is the gas laws work from absolute zero so a temperature rise from 20 degrees C to 60 degrees C is not a tripling of pressure but a mear 13.65 % increase in pressure (40/293 x 100). So if my tank is full (220 bar), in a hot car with internal temp of 60 degrees C the resultant pressure in the tank would be 250 bar. I once had my tanks filled i winter and stored them until sumer, when I connected up my gear the pressure was 260 bar, and burst disc held!! These pressures are well within test pressure which for my Fabers is over 300 bar, so there should be absolutely no concerns for a half full tank at all. I suspect the real concern is in a fire where the temperatures will way exceed this and the heat may affect the metal.
ps. I don't know how you guys work in Fahrenheit, and psi, it's just so hard to figure simple things out.

 

[TMHeimer]

JB, I'm Canadian & American. Know Celsius & Fahrenheit back & forth--don't care. I ALWAYS get the heebee-jeebees thinking about at tank (regardless of pressure) in a car. Cracked windows can help, of course.

 

[mattoau]

At little over 180F/80C aluminium tanks can start to degrade, and it is possible to reach these temperatures in a car in direct sunlight.

 

[Bob DBF]

In order to account for cooling it is perfectly acceptable to exceed working pressure 10% when filling . Actually I think it's 11% with a temp limit of something like 132F. The key is to not exceed the working pressure at 70F.

With all of that in mind hot storage essentially recreates the hot fill condition. If the burst disc has not been abused you should be fine.

So the key is to change your burst disk on a regular basis so you won't have the crap scared out of you when the burst disk fails at a lower pressure than expected. I change mine at hydro or when I service the valve (the disk is very cheap), never had a problem.


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

 

[String]

If a tank is at 1600 psi or less. Is it pretty safe from having the burst disc popping in a hot car?

Yes. Its fine.

 

[Gilldiver]

At little over 180F/80C aluminium tanks can start to degrade, and it is possible to reach these temperatures in a car in direct sunlight.

More like 230-250F depending on the aluminum alloy per AMS 2770.

Think about this,

1) Pure O2 is delivered in aluminum cylinders to many elderly or people who need supplemental O2, how many oxygen delivery trucks or gandmas have you seen being blown up? Especially in the Sun states like Arizona and Florida in the summer.
2) Diving is done in the tropics, its the major diving industry, so how many SCUBA tanks are being blown up sitting on the boat or dock in direct sunlight?
3) Airplanes are made out of aluminum, how hot do you think the wings and fuselage of the plane get in direct sunlight during your 2 hour flight delay sitting on the flight line.

In other words, fears of SCUBA tanks and aluminum degradation from ambient heat effects expected on the surface of the earth are the fears of ignorant and uneducated non-engineers.

 

[captain]

More like 230-250F depending on the aluminum alloy per AMS 2770.

Think about this,

1) Pure O2 is delivered in aluminum cylinders to many elderly or people who need supplemental O2, how many oxygen delivery trucks or gandmas have you seen being blown up? Especially in the Sun states like Arizona and Florida in the summer.
2) Diving is done in the tropics, its the major diving industry, so how many SCUBA tanks are being blown up sitting on the boat or dock in direct sunlight?
3) Airplanes are made out of aluminum, how hot do you think the wings and fuselage of the plane get in direct sunlight during your 2 hour flight delay sitting on the flight line.

In other words, fears of SCUBA tanks and aluminum degradation from ambient heat effects expected on the surface of the earth are the fears of ignorant and uneducated non-engineers.

All good points. When I was in the Navy working on aircraft in the tropics the wings would get so hot it would be uncomfortable to walk on them in leather sole shoes, definitely couldn't touch them bare handed.