2airishuman
Contributor
Can I take the tank somewhere to get certified, they can't test it and certify it? that seems pretty ridiculous.
No, they have to be certified at the time of manufacture, because many of the things that the cylinder must comply with cannot be verified except at the time of manufacture. For example, in the USA, an aluminum cylinder must be made from a single block of cast aluminum, and that block must have a specific composition of metals in its alloy, and must have a tensile strength within a specific narrow range. And a six sister cylinders made by the same process must be pressure tested, three to at least 10,000 times, and three to the point where they are destroyed. At least one out of every lot of 200 cylinders has to be destructively tested in various ways.
Cylinders are arguably more complicated to make than any other piece of dive gear.