Hydro data- steel 72 pressures and REE

[oldmossback]

Interesting reading this string......I have a question concerning the wall thickness of the older tanks.
I have two sets of what I presume are twin 38's......one Voit set and one USD. They both were first hydroed in 1961..the voits in march and the USD's in Sept.....the Voits are 1880 working pressure with 1/2 inch valves and the USD's are 1800 with 3/4 valves.......I routinely use them at 2050 or 2100, depending on the day temp during filling (I use my own compressor).........

My question is, why the difference of 80 psi working pressure?.....were the wall thickness that much different during manufacturing?.......I can find no manufactures stamp on either set.....one says Voit and the other USD........but I know these were made by a tank manufacturing outfit.......

Another point.......maybe this is because of my own body as I tend to sink without floatation aids, but I have never noticed these as bouyant as other fellows have stated.

Last point........I decided to purchase my own compressor when a young lady LDS operator filled my Voits to 3200 psi.........this scared the poo outta me as I was in the front of the shop waiting......I had new blowout disks installed the previous year by another dive shop and apparently they used the new disks for modern tanks.......ya gotta watch these people.......Not all are trained or experts..........

Anyway, my voits are due for a hydro this winter, I hope they pass.......

 

[duckbill]

Wow!!!


RIN D*** (********* Hydro) has expired. It expired October 31, 2008.


Linda Cooper
Transportation Specialist

U.S. Department of Transportation

Pipeline & Hazardous Materials Safety Administration
East Building , PHH-30
1200 New Jersey Avenue, SE
Washington , DC 20590
Telephone: (202) 366-4512
Fax: (202) 366-3753

 

[Scared Silly]

Okay, so now the rest of the story - did you report them???????

 

[duckbill]

It's in the works.

Hopefully it is just an error in the DOT's database

 

[captain]

Interesting reading this string......I have a question concerning the wall thickness of the older tanks.
I have two sets of what I presume are twin 38's......one Voit set and one USD. They both were first hydroed in 1961..the voits in march and the USD's in Sept.....the Voits are 1880 working pressure with 1/2 inch valves and the USD's are 1800 with 3/4 valves.......I routinely use them at 2050 or 2100, depending on the day temp during filling (I use my own compressor).........

My question is, why the difference of 80 psi working pressure?.....were the wall thickness that much different during manufacturing?.......I can find no manufactures stamp on either set.....one says Voit and the other USD........but I know these were made by a tank manufacturing outfit.......

Another point.......maybe this is because of my own body as I tend to sink without floatation aids, but I have never noticed these as bouyant as other fellows have stated.

Last point........I decided to purchase my own compressor when a young lady LDS operator filled my Voits to 3200 psi.........this scared the poo outta me as I was in the front of the shop waiting......I had new blowout disks installed the previous year by another dive shop and apparently they used the new disks for modern tanks.......ya gotta watch these people.......Not all are trained or experts..........

Anyway, my voits are due for a hydro this winter, I hope they pass.......

Most of the 38's people refer to as buoyant are the converted 3A military surplus oxygen cylinders.
I had a set of Voit twin 50's from 1961 that were way more negative than my twin 72's. I traded them for another set of twin 72's.

 

[duckbill]

Michael,
My twin 38s are 5-6 pounds buoyant at 300 psi reserve in salt water, and they are 1954 3AA1800 U.S.Divers tanks.

Right now my problem is that all three of my manifolds nearly bottom out in the threads. I don't know if I need to find another manifold, or if the threads on the tank have been swaged out through the years. I thought the steel of the tank would swage the brass valves, but now I'm wondering if the steel threads swage out as well and I may never find a manifold for it. Too bad. They are my favorite tanks and they are out of commission now:depressed:

 

[WD8CDH]

Try more wraps of heavy duty teflon tape. Not the thin stuff from the hardware store. That will give you a turn or two and still give you a safe seal.

 

[duckbill]

Thanks for the idea, but I've heard that can stress the thread tips. If that's not true, where do you get heavy duty tape?

I'm still curious to know if the threads of a steel cylinder can be swaged out to where no valves will work.

 

[captain]

All of my 1/2" pipe thread tanks have at most 1 thread showing and have been that way for years. Don't sweat it. I perfer to use Permatex thread sealent with teflon rather than teflon tape.
Leaks that I couldn't stop with teflon tape did stop with the sealent.

 

[oldmossback]

Terry,

Using either tape mentioned above will put your 38's back in business..........I doubt the steel is swaged.....just the valves.......

Note: I'm hitting my head against the wall now......just realized that y'all say your 38's float....in salt water..........well, mine don't....in fresh water, that is if you can call dirty, dark lake water fresh......anyway, they don't float......but I bet they do in the salty stuff.......ahhhh meeeeee.........I've never used them in salt water.....

I also have a set of sportways doubles 2250 working pressure, that weigh a ton......I thought they were 45's...but could they be 50's?.....not that ten cu inchs matters that much.........