15L steel tanks in Red Sea? Working pressure?

Going on a liveaboard on Red Sea in two weeks (Emperor) We have choice of 12L AL tanks or 15L Steel tanks. Can't seem to confirm what the working pressure of the steel tanks is.

My understanding is that if it's a low pressure tank it holds essentially same gas supply as a 12L tank at 3000psi.

Thoughts?

Most probably it's low pressure. In this case it'll be 15L @ 3000 PSI. The normal 12L tanks are also at 3000 PSI so the difference in supply is 15/12 = 1.25 (25% more supply).

Red Sea Shadow:

Most probably it's low pressure. In this case it'll be 15L @ 3000 PSI. The normal 12L tanks are also at 3000 PSI so the difference in supply is 15/12 = 1.25 (25% more supply).

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Thanks - so sounds like a 15L tank at 3000psi is essentially a 100ft steel tank. (107cf of gas)

Exactly. The 15L is 100 cf and the 12L is 80 cf.

Made more confusing that most places steel tanks are 232 bar so the "12s" here are usually 207 bar so hold less.

I HATE the aluminium tanks

From experience: all tanks (steel & Al) in RedSea (Egypt) 12L & 15L are filled with 200bars (country standard) unless you specifically ask for else.

Well, I don't see much difference between 207 or 200 Bars. Most places don't fill up the tanks so accurately anyway, so you may get anything between 180-220 Bars, depending on how fast the tanks were filled, whether they've been cooled during filling, if the guy operating the compressor was in a hurry etc.

Anyway, they tend to cool down considerably in the Red Sea which tends to be a little "air thief" (especially in the summer when air Temperature reaches ~40C and water is about 25C) and thus one experiences a drop of pressure of 10-20 bars immediately after entering the water

For me, it is easier to know how much air there really is in the tank, rather than knowing how much air (or gas) the tank may potentially contain.

Therefore, I just multiply the Tank volume by the actual pressure and get the real amount of air available for the dive. For a 15L tank pressurized to 2000 Bars it is 3000Liters, for 12L@200Bar it is 2400Liters to begin with.

Knowing one's air consumption may help determine for how long the tank may be used (at a certain depth of course).

To complicate matters, the commonly used aluminium '12 liter' tanks actually don't contain 12 liters, but only about 11.1 :

ArthurGerla:

To complicate matters, the commonly used aluminium '12 liter' tanks actually don't contain 12 liters, but only about 11.1 :

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Thieves are everywhere Finally you end up with a full functional equivalent of a pony bottle

AL80s passed off as 12 so you have bulky, physically heavy beasts of tanks that dont actually hold much gas at all and need lots of lead to sink. Worst of both worlds.