Erich S
Contributor
These UDS systems were really cool back in the day!
Check this vintage ad out...
- Thread starter Open Ocean Diver
- Start date
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Did you ever dive one of those ? I've always wondered if they were cumbersome (or not) once upon your back, and what about the drag underwater ?
I missed the opportunity to try one in Malta, some 20 years ago. Boy, was I disappointed...
It took a while for the air to get out of the cowling so it was not great when jumping off a boat and worse when jumping off a pier. I thought it was fine in the water.
A friend loaned his to me while traveling for work. I never tried it without the cowling but my friend removed it and preferred it that way.
Thank you. For a non US denizen, would you care to explain D.O.T ? I've never came across it before.
Unless I'm very much mistaken, those tanks were also in use in the French Navy during Cousteau's time. According to Frédéric Dumas (can't remember in which book though) they were the best tanks ever. More stable than the later iron twin sets and easier to adjust on the back as they were shorter. No idea if it's just an opinion or a fact.
Unless I'm very much mistaken, those tanks were also in use in the French Navy during Cousteau's time. According to Frédéric Dumas (can't remember in which book though) they were the best tanks ever. More stable than the later iron twin sets and easier to adjust on the back as they were shorter. No idea if it's just an opinion or a fact.
OP
OP
For some reason, pressed and spun metal cylinders are regulated in the US by the DOT and welded pressure vessels (boilers, volume tanks, decompression chambers, etc) are regulated by the ASME (American Society of Mechanical Engineers). I imagine it was a case of failures causing death and bureaucrats casting around for an agency to regulate it.
ASME is a non-governmental professional association organization that was formed in 1880 to set standards for boiler design. Boilers were blowing up and destroying trains, ships, and buildings (and anyone nearby). I am guessing that failures of HP pressed steel cylinders didn't become a political issue until being transported by motor vehicles getting into collision accidents.
DOT (Department of Transportation) cylinders are relatively light weight cylinders designed to be portable or at least intended to be transportable across state lines. And that is why they are regulated by the DOT.
The DOT agency was previously know as the ICC or Interstate Commerce Commission. Many older cylinders are stamped ICC instead of DOT. I own several ICC cylinders.
Because the cylinders are intended to be lighter (for transportation purpose) the fabrication method requires for them to be formed from uniform material and heat treated without the use of welding material.
Because these cylinders are designed and built with very minimal safety factor and basically zero corrosion allowance, they require periodic retesting and re-qualification. The typical 5 year hydro test (and VIP) for all 3AA or 3AL pressure vessels,
ASME cylinders or pressure vessels on the other hand are designed and normally intended for stationary installations. They are much heavier and they are designed with a larger safety factor in addition to the extra material consideration for corrosion allowance.
Because of the extra safety factors, ASME cylinders do not require periodic hydro testing.
I have designed and certified (with my engineering license) several ASME pressure vessels, but that was over 20 years ago. So, I really don't remember very much about the ASME codes. And no one ever tries to remember them, they are just too many details and they are relatively involved.
The codes have extensive details on welding procedures and fabrication detail. There is also testing and in process inspection procedures.
ASME cylinders are heavy and normally not intended to be moved once they are installed.
The DOT agency was previously know as the ICC or Interstate Commerce Commission. Many older cylinders are stamped ICC instead of DOT. I own several ICC cylinders.
Because the cylinders are intended to be lighter (for transportation purpose) the fabrication method requires for them to be formed from uniform material and heat treated without the use of welding material.
Because these cylinders are designed and built with very minimal safety factor and basically zero corrosion allowance, they require periodic retesting and re-qualification. The typical 5 year hydro test (and VIP) for all 3AA or 3AL pressure vessels,
ASME cylinders or pressure vessels on the other hand are designed and normally intended for stationary installations. They are much heavier and they are designed with a larger safety factor in addition to the extra material consideration for corrosion allowance.
Because of the extra safety factors, ASME cylinders do not require periodic hydro testing.
I have designed and certified (with my engineering license) several ASME pressure vessels, but that was over 20 years ago. So, I really don't remember very much about the ASME codes. And no one ever tries to remember them, they are just too many details and they are relatively involved.
The codes have extensive details on welding procedures and fabrication detail. There is also testing and in process inspection procedures.
ASME cylinders are heavy and normally not intended to be moved once they are installed.
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