Hey guys I’m looking for some advice on how you store your tanks. I recently bought 2 used tanks. No in the diving season I keep my gear in my garage which is not temperature controlled and out do the season I bring my kit and store it in the basement. Is there any concern storing my tanks in the garage year round? I live in the NYC area so normally we don’t have crazy winters or summers.
Tank Storage.
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Depending on how cold it gets, you might be better to store during the winter with a low pressure fill rather than full.
Even though cylinder compressors have moisture separators, there is still some moisture present in the cylinder air. The higher the pressure, the higher the dewpoint. This is clearly a problem for storing steel cylinders, but still undesirable for aluminum tanks. Here is a recent thread that touches on the subject:
Proper tank storage
I just checked my last test results for my 30+ year old compressor, and the moisture content was 3.7 ppmv which has a dewpoint of -90°F at ambient pressure, but that comes up to about -10°F at 3000 psi. That is important to know when storing a steel cylinder in an unheated garage during a Chicago winter. What I don't know is what that moisture content is in other filling stations, or if it would vary depending on the ambient humidity at the time of the fill. (I suspect it would)
Addendum: I just checked several test results from years past. Looks like anything lower than 3.4ppmv is not quantified, and just listed as <3.4ppmv, so that appears to be the low end of moisture content in compressor tests. It does look like that metric varies depending on when it is measured, and the highest I had was 13.1ppmv about 4 1/2 years ago, which has a dewpoint of +15°F at 3000 psi, and +18°F at 3500 psi. So yeah, don't store tanks 100% full in unheated areas in cold climates.
Even though cylinder compressors have moisture separators, there is still some moisture present in the cylinder air. The higher the pressure, the higher the dewpoint. This is clearly a problem for storing steel cylinders, but still undesirable for aluminum tanks. Here is a recent thread that touches on the subject:
Proper tank storage
I just checked my last test results for my 30+ year old compressor, and the moisture content was 3.7 ppmv which has a dewpoint of -90°F at ambient pressure, but that comes up to about -10°F at 3000 psi. That is important to know when storing a steel cylinder in an unheated garage during a Chicago winter. What I don't know is what that moisture content is in other filling stations, or if it would vary depending on the ambient humidity at the time of the fill. (I suspect it would)
Addendum: I just checked several test results from years past. Looks like anything lower than 3.4ppmv is not quantified, and just listed as <3.4ppmv, so that appears to be the low end of moisture content in compressor tests. It does look like that metric varies depending on when it is measured, and the highest I had was 13.1ppmv about 4 1/2 years ago, which has a dewpoint of +15°F at 3000 psi, and +18°F at 3500 psi. So yeah, don't store tanks 100% full in unheated areas in cold climates.
Thank you for all the info. Yea when I bought the the tanks they where completely rusted inside and I have spent a lot more money to fix them up. So I just want to make sure I care for them properly to last as long as they can. When you say low pressure are you talking about under 1000 psi or like. Under 500. I know pure oxygen takes have a safe residual pressure of about 500 psi so you should go under that. Is the same true for diving tanks?
Anything between 500 and 2000 will be fine.
scubafanatic
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I just store mine in my car garage, exposed to whatever the ambient temperatures may be here in north Texas. Normal temp range 100-ish mid summer down to mid/low 20's in mid winter. I store them full.
My tanks live in my car during the season from April to November in northern IL.
bamafan
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As stated just make sure they are pressurized and don't leave them where the sun can shine on them. I have seen tanks left in the sun and either the burst disk went or the o'ring under the valve extruded.
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