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Originally Posted by kmacdonald
The places that swap tanks for full ones don't seem to test the tanks.
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I would be extremely surprised if you could find a place that swaps tanks that gives out cylinders that were filled after the hydro test expired.
Typically the hydro test is good for 10 years for natural gas cylinders. The shorter five-year cycle applies to aluiminum cylinders, cylinders taken under
water, cylinders containing corrosive gases (including CO2), and a variety of other oddball situations like cylinders permanently mounted in a bank. Propane cylinders follow a different set of rules with expiration times that vary depending on how they are tested.
Once a cylinder is filled, it can continue to be transported and used until it needs to be filled again even if the test has expired.
Quote:
I haven't heard of SCUBA tanks exploding except for a 50+ year old expired tank in Australia a few years ago. The tank doesn't care if it has CNG or air in it. It's not rocket science to put together a safe CNG system.
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Worldwide, it happens every year. The accidents with air are usually in countries with weak regulatory oversight. There was one on some
remote island this year involving a fellow who salvaged an aluminum cylinder from a recycling pile. It had been discarded because it failed
inspection. He filled it and it ruptured while he was carrying it to the
boat.
There are fires and explosions with oxygen and nitrox cylinders most years in the
USA, usually with aluminum cylinders, always as a result of contamination with combustible material. This goes on in
medical settings also.
Anyway, as I posted upthread, the problem you're going to have is finding a CNG cylinder valve that will fit the cylinder neck threads of a SCUBA cylinder. There aren't any, and there aren't any adapters.