New question about tanks and heat

[mike_s]

I'm sure this has been covered before somewhere on this board, so sorry if I'm asking a repeat question here.....

I just bought a couple AL 80's (Luxfer). They had a nice little warning
label on them that said that full/pressurized tanks did not need to be
stored above 125f degrees.

Now typically I wouldn't store them this warm for any reason but the
only time they might get this hot is from sitting in a parked car all day.


I'm assuming that a parked car can get pretty hot during the day
and I'm curious about what other people do in a situation like this?

Example 1:
I'm going to dive after work and it's a nice hot day of 95f and could
easily get to 125f in the car during the day?

Example 2:
I'm on vacation in south Florida for a week long trip and we stop
at a tourist attraction for a day long event and leave the tanks in
the car.

Both are very similar with both having the tanks in the car for most
of the day in the hot sun.


So what should I do?


-mike

 

[MikeC]

Mike, when I worked a "normal" job and did evening dives I brought my tanks into the office. My immediate boss was cool about it, he did draw the line at firearms.. drat. The tanks and usually my regulator bag and mask fit inside the cubicle or maintenance room.

Regarding example #2, drain the tank to 200lbs and then fill it the next day. Or, make sure you can check into a hotel early and store the tanks there. Option 3, if tourist attraction is near dive shop you are using, ask shop owner if you can leave tanks at shop. Explain situation and offer to pay owner with a six pack of adult beverage.

 

[hdtran]

I'm sure this has been covered before somewhere on this board, so sorry if I'm asking a repeat question here.....

I just bought a couple AL 80's (Luxfer). They had a nice little warning
label on them that said that full/pressurized tanks did not need to be
stored above 125f degrees.

Now typically I wouldn't store them this warm for any reason but the
only time they might get this hot is from sitting in a parked car all day.


I'm assuming that a parked car can get pretty hot during the day
and I'm curious about what other people do in a situation like this?

Example 1:
I'm going to dive after work and it's a nice hot day of 95f and could
easily get to 125f in the car during the day?

Example 2:
I'm on vacation in south Florida for a week long trip and we stop
at a tourist attraction for a day long event and leave the tanks in
the car.

Both are very similar with both having the tanks in the car for most
of the day in the hot sun.


So what should I do?


-mike

First, understand that your tank is hydrostatically tested to approx. 160% of the maximum working pressure (MWP) of the tank (let's say MWP is 3000 psi). Second, the failure point of the tank is typically greater than 300% of the MWP. Scuba tanks have a burst disk so that failure, while catastrophic, is not, umm, spectacular.

So, just for argument's sake, suppose you didn't feel comfortable with a tank pressure greater than 3400 psi (approx. 13% overpressure). Well, we've got to do a little math. (PV/T)=constant, where P is the pressure, V is the volume, and T is the absolute temperature (e.g. Kelvin or Rankine, depending on your preference). Let's say 70 F is about 530 R, and 140 F is about 600 R. If your tank has approx. 3000 psi at (70 F) 530 R, at 140 F, because the volume is constant, the pressure will have gone up by (600/530), or your new pressure will be about 3400 psi (3396 if you use a calculator, but I'm only working to 2 digits here).

That said, I wouldn't be concerned. I might not leave the tank in the hot sun day after day after day because the heat might affect the valve packing, but I would not at all be concerned about the heat affecting either the aluminum temper, or causing overpressure in the tank.

 

[Hoosier]

I used to overfill my tanks up to 3200 psi and leave at the trunk (black color) all day long for a night dive after the work. I don't have any problems so far. It used to get hot, but it isn't hotter than when it gets a quick air refill. If your car is SUV or truck, it is helpful to use a "sun shield" to cover up the tank from a direct sun light. I always cover the tank with it when I use a SUV having a big rear window.

 

[Wayward Son]

I would not store them at temps above 125f for long periods of time, but a day, or even a week in your car, is not going to cause any problems.

 

[Leadking]

125 F is not going to hurt your tanks UNLESS they are at full pressure. You may blow a burst disc (and maybe the windows in your car)

 

[CD_in_Chitown]

125 F is not going to hurt your tanks UNLESS they are at full pressure. You may blow a burst disc (and maybe the windows in your car)

You ever seen a burst disc go? It won't blow the windows out of your car. 125 wouldn't blow it either, its common to leave a full tank in a trunk in the summer.

 

[Leadking]

Yes, I have seen a burst disc go-and it sent the tank spinning!

 

[mike_s]

If I left them sit in the car during the work day, it would be in the back of a SUV with tinted windows and also would leave all the windows cracked about 1" to let out heat.

How would this work?

-mike

 

[CD_in_Chitown]

Yes, I have seen a burst disc go-and it sent the tank spinning!

IMHO a tank in a vehicle should be secured in some manner to prevent movement while in motion. A bursting disc is pretty anti-climatic though, even if it were to fail inside the vehicle its not going to blow the windows out.