Old steel tanks?
- Thread starter KGNickl
- Start date
Please register or login
Welcome to ScubaBoard, the world's largest scuba diving community. Registration is not required to read the forums, but we encourage you to join. Joining has its benefits and enables you to participate in the discussions.
Benefits of registering include
- Ability to post and comment on topics and discussions.
- A Free photo gallery to share your dive photos with the world.
- You can make this box go away
It's true they are thinner than a 3000 psi medium pressure 3AA steel tank and even a bit thinner than a low pressure 2400 psi 3AA steel tank.These are great tanks! I have a set with original hydros of '60 and '66. DO NOT OVERFILL THESE!!! They are thinner than new tanks and will not do well with overfilling. Enjoy them!
But that is only becuase they are designed for a 2250 psi service pressure. All of the above mentioned tanks are designed to the same 3AA engineering standard and all of them have the same test pressure of 5/3rds of their service pressures and have the same safety margin.
To put this in perspective the common "cave fill" of 3500 psi on a 3AA LP 95 with a 2400 psi service pressure is 146% of the rated servcie pressure. In comparision that same overfill on a steel 72 overfilled to the same 146% would be 3285 psi. So 3000 psi in a steel 72 is "conservative" compared to the north florida LP 95 or LP 108 cave fill standards for 3AA steel tanks.
There are LOTS of very valid arguments against overfilling tanks beyond the 10% plus rated steel tanks are approved for, but the wall thickness of the steel 72 is not one of them. They are just as strong in terms of safety margin as any other 3AA steel tank.
Age also does not fly as a reason to discriminate against them as a steel tank has an extremely long life. I haver seen pre-WW1 3AA welding tanks that have been in constant use and still pass hydro test and even do it with a plus rating. As long as it is properly cared for and is tumbled every 5-10 years or so as needed to remove any accumulated flash rust that would otherwise attract moisture to one spot and promote pitting, a steel tank will out last the divers that own it.
This is not a recommendation to overfill steel 72's, it is just a clarification to point out there is no need to fear a fill in a steel 72 anymore than any other tank.
skdvr
Contributor
Is there any clarification on what kind of threads these have?
Phil
Edit: I see that DA already answered that they have the same threads as an AL 80
Phil
Edit: I see that DA already answered that they have the same threads as an AL 80
Jimmer
Contributor
Man those tanks looks fantastic, nice buy. I have a set of galvanized double 72's that are my personal favourite to dive, and the tanks happen to be nearly twice my age and still passing hydro with no problems. I'm sure you'll enjoy them.
captain
Contributor
skdvr
Contributor
OP
KGNickl
Contributor
They have 3/4 valves. I dropped off all 4 tanks today at the GADC to have them hydro test and visually inspect them.
OP
KGNickl
Contributor
All 4 tanks passed visual and hydro. One has slight rust on the inside and would be perfect if tumbled, but is good for normal air fills. The other three tanks have no rust and are perfect and would look no better if tumbled.:banana:
skdvr
Contributor
I have overfilled steel 72s and they are routinely overfilled in the day. I have two that I have had since a child (ofthe six I have) and they still pass hydro and are in excellent condition. I no longer fill them beyond 2,500 but these tanks are not weak or structuraly deficinent in any way. At 2250 psi they are about 68 cf and at 2,475 they are 72.4 cf. An aluminum 80 filled to 3,000 is only 77 cf.
N
N
Similar threads
