Tanks Left in Sun

[mccabejc]

The math sure seems to point to about 5psi increase per degree, as scubatoys Larry mentioned. Which means the temp of the tank would have to increase to around 350-400 degrees F to jack the pressure up from 3000-5000psi and blow the burst disk. Since that ain't gonna happen, it must be either burst disks that are going at much less than 5000psi (which wouldn't surprise me; I doubt you can manufacture them with any accuracy), or heating of the tank by direct sunlight.

Or maybe it's just one of those things...

 

[SouthFLdiver]

I had a burst disk blow on me one time. It was in a lp steel cranked-up, but it had to be at quite a high psi before it burst since i have 5000 psi burst disks in my lp steel tanks. Just dont leave them sitting in the sun

 

[SouthFLdiver]

In response to Jims comment, youre probably right about the burst disks blowing early. But i know my 5000 psi disks dont blow at 4000 ever?? So i wonder how hot the tanks actually get?

 

[whitedragon13]

You also have to worry about some jerk who rented the tank before you and dropped it, or the VIP that didn't get done correctly...

and consider that often you fill a tank in a nice cold bath of water, or inside a nice air conditioned room...say 65 degrees. Can the temperature in the trunk get up to 140 or more? Probably...so if you started with a tank pressure of 3300 psi (tell me ya don't overfill) and your old, never been changed burst disk will actually fail around 4000 or a little less, I'd say it's possible.

 

[Albion]

Living in an area where no one owns their own tanks i am not troubled by the temp in the trunk argument. However, tanks and other large heavy equipemtn in cars trunks, ooooh dear. I hope you have reinforced bulkheads between the trunk and passenger compartment. cold day or hot, if you are hit a staionary car or suchlike that tank is coming through through the back seat at a fair speed.

 

[RichLockyer]

This leads to a natural hijack about tank storage for aluminum tanks.

Store them either full, or very low (500psi or less).

At 3000, in the event of a fire, the burst disk is going to do it's job and go before the tank ruptures.

At 500psi, the tank is going to melt before the pressure increases enough to turn the tank into a frag grenade.... it'll just kinda "lay open" (I've seen the results)

At 1500-2000, the story is very different. 6061 heat treating fails at somewhere below 400 degrees. Problem is, that temperature won't be high enough to cause the pressure to increase enough to blow the burst disk. So now you have a tank with a very high level of pressure, where the burst strength of the tank is being lowered by the second. At the point where they cross, boom... and aluminum tanks do tend to fragment, even after heat damage.

Steel tanks CAN fragment, but are generally known to "peel" open.

 

[RiverRat]

This leads to a natural hijack about tank storage for aluminum tanks.

Store them either full, or very low (500psi or less).

At 3000, in the event of a fire, the burst disk is going to do it's job and go before the tank ruptures.

At 500psi, the tank is going to melt before the pressure increases enough to turn the tank into a frag grenade.... it'll just kinda "lay open" (I've seen the results)

At 1500-2000, the story is very different. 6061 heat treating fails at somewhere below 400 degrees. Problem is, that temperature won't be high enough to cause the pressure to increase enough to blow the burst disk. So now you have a tank with a very high level of pressure, where the burst strength of the tank is being lowered by the second. At the point where they cross, boom... and aluminum tanks do tend to fragment, even after heat damage.

Steel tanks CAN fragment, but are generally known to "peel" open.

Interesting......If my car ever crashes and burns I'm gonna run like hell. Probably would be nice to give the fire dept. a heads up too

 

[Lemonade]

At 1500-2000, the story is very different. 6061 heat treating fails at somewhere below 400 degrees. Problem is, that temperature won't be high enough to cause the pressure to increase enough to blow the burst disk. So now you have a tank with a very high level of pressure, where the burst strength of the tank is being lowered by the second. At the point where they cross, boom... and aluminum tanks do tend to fragment, even after heat damage.

I would imagine the burst pressure of the disk will decrease with temperature rise… Copper should melt before steel does.

 

[RichLockyer]

I would imagine the burst pressure of the disk will decrease with temperature rise… Copper should melt before steel does.

But again, steel is not the problem, as it doesn't tend to fragment.
Aluminum is the killer, and like I said, the heat treating is GONE by the time you get to 400 degrees, leaving your 6061 tanks back at basic T6.
Copper does not melt at 400 degrees.

 

[padiscubapro]

The math sure seems to point to about 5psi increase per degree, as scubatoys Larry mentioned. Which means the temp of the tank would have to increase to around 350-400 degrees F to jack the pressure up from 3000-5000psi and blow the burst disk. Since that ain't gonna happen, it must be either burst disks that are going at much less than 5000psi (which wouldn't surprise me; I doubt you can manufacture them with any accuracy), or heating of the tank by direct sunlight.

Or maybe it's just one of those things...

I have a chart somewhere for the normal burst disk pressures for specific types of tanks.. they are recommended to be the test pressure less 10% (but can be less in practice) so an al 80 would be 3000 x 5/3 less 10% or 4500 psi..

* the 5/3 is for not valid for all tyes of tanks... most hp tanks have alternate test pressures..