Oxygen % in Tanks:73diver wrote:Hola Luis y gracias,
Soy buceador con escafandra autónoma clásica también.
It is possible that the 21% air in the tank was 'consumed' to oxidize the interior but I suspect the pressure loss was due to microscopic leaks in the valve or burst disk. BTW, not to shock you, I used the tank with the air in it from 1985 for 70 minutes. I think the oxygen was at the correct level.
I do have one question: This tank was manufactured for Dacor in 1973. The LDS says that the DOT exemption for the tank may have expired. I never heard of this. Could you or a fellow forum member enlighten me?
All of what Luis said is why I just said "find a new dive shop"!luis wrote:I am not aware of any DOT Exemption steel tanks back in 1973.
There were aluminum exemption tanks back then, but new high pressure exemption steel tanks did not show up until some decades later.
All the steel tanks that I am aware from the 70’s were DOT 3AA. The 3AA code refers to cylinders made out of chrome-molybdenum steel.
Dacor did sell some aluminum exemption tanks, but I don’t remember if it was as early as 1973 (it probably was). These were the early aluminum tanks made before the 3AL code had come out. I surely hope that your LDS can not tell the difference between a steel and aluminum tank…
If it is an aluminum tank from 1973, it would be made out of AL6351 aluminum alloy. The codes allow it to be hydroed, but it requires eddy current testing and INHO, they are not worth having them re-qualified… many dive shops will not fill them, etc…
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