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

[slackercruster]

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

 

[Rainer]

Is the car on fire? If not, you're good.

 

[Slamfire]

Refer to Gay-Lussac: P₁/T₁ = P₂/T₂

So if a tank with 1600 psi at 289 K (60 F) ambient temp is left in a car and the temperature rises to 578 K (581 F)then the pressure of the tank will rise to 3200 psi.

p.s. the formula will work with degrees K only

 

[eponym]

The problem with the post immediately above* is that absolute temperature (Kelvin) has to be used, not Fahrenheit. The actual increase in pressure from 60F to 120F is quite small, on the order of ten percent.

Read this thread http://www.scubaboard.com/forums/basic-scuba-discussions/335436-scuba-tanks-my-car-trunk.html for more than you ever wanted to know . . .

-Bryan

* (which has since been edited)

 

[slackercruster]

Thanks for the info!

BTW, at what psi does the disc burst?

 

[Rainer]

Depends on the burst disk.

Thanks for the info!

BTW, at what psi does the disc burst?

 

[eponym]

I have been told 140% of rated fill is common. At least that's the design goal. I could be wrong.
As Rainer says, it would depend on both the design and the particular disk in question.

-Bryan

 

[Dr Wu]

Depends on the burst disk.

Depends on how hot the car is.

 

[tr3a]

A full tank will probably be save in the car (from experience). Burst disk depending on tank will probably be good for 500psi over rated fill pressure.

 

[Rainer]

Not sure where you got the 500psi number.

Taking this from a post Joel (JS1scuba) made elsewhere:

"Safety Assemblies (burst disc) are designed to fail when they reach a certain rated pressure with a 5% tolerance on either side. The specified burst disc for a cylinder is based on what it's hydrostatic test pressure is. Most cylinders test pressure is 5/3rds working pressure some cylinders are 3 halfs working pressure.

Some standards:

3000 psi aluminum cylinder will have a 5000 psi safety
2400 psi steel cylinder will have a 4000 psi safety
3180 psi steel will have a 5300 psi safety
3442 psi steel will have a 5160 (5250) psi safety
3500 psi steel will have a 5250 psi safety
4350 hoop wrap aluminum will have a 7250 psi safety"

A full tank will probably be save in the car (from experience). Burst disk depending on tank will probably be good for 500psi over rated fill pressure.