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Master Diver
Posts: 1233
Joined: Sat Jan 01, 2011 2:03 pm
First Name: Eben
Location: Alexandria, MN
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Twin 48s

Wed Jan 11, 2017 12:50 pm

Are These Twin 48s?
- I've been figuring they are 50cf tanks based on calculations I did from the tank volume stenciled on the outside of a military surplus oxygen tank I converted to Scuba last year. But I figured it to be filled 10% over the working pressure of 1800 psi.
- Recently I was reading my Basic Scuba book and saw the Scott Hydropak tank listed at 48 cf and 1800 psi working pressure. I found a picture of that tank and it is identical to my surplus oxygen tank...
- I saw a photo of a Scott Hydropak advertisement that listed a tank looking like this as 50.3 cf at 1980 psi... Which is 10% over 1800 psi.
- It seems like a piddling distinction to call them Twin 48s but when you say Twin 50s, I always picture the 50cf aluminum tanks at 3000 psi. I refer to my Twin 38s and you know I'm talking about the 1800 psi short tanks. I say Twin 42s and you know I'm talking about the Sportsways 1880 psi short tanks. I think I'm going to call this new set Twin 48s at 1800 psi... You can see they are significantly smaller than an Aluminum 80 (top photo) as well as Steel 72s... They are quite different looking than aluminum 50s... And they are lighter weight than 50s, 72s, and 80s.
- Above is the military surplus oxygen tank I converted... It has been Hydro tested and visual inspected (insides are pristine). The rings you see on top and bottom have anti-shatter wire wrapping the entire length of the tank. This was to protect from shrapnel. I read last night in Basic Scuba that its actually a law that you're supposed to remove the wrapping before hydro testing and conversion to Scuba. I kind of like it the way it is with the marking and stenciling but I probably will have to comply with the law.
- The surplus 48 is a great tank for no BCD diving by the way... A single 48 lasts about an hour in 16-25 ft lake diving and requires wearing a weight belt even when diving without a wet suit. :)
The Freedom and Simplicity of Vintage Equipment and
Vintage Diving Technique are Why I Got Back Into Diving.

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