Thanks for all the info Guys. I definitely hope these check out OK. They look good, and have been stored with around 300-500 PSI in them. I haven't emptied one yet to check inside. New question, along with the tanks I was given two three piece US diver dual tank J valve manifolds. Does anyone know if these could be made safe, or are they a real deal "Kill ya right now" item. I know these are properly a vintage item, but I would like to use them if possible.
Opinion on steel 72's
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I have 10 steel 72's currently with 4 of them set up as doubles (the rest will hopefully get traded 3 for 1 for LP95's) They are great tanks that make lightweight doubles with decent capacity if you push the fill pressure to the 2600-2800 psi range.
At 2250 psi double 72's only hold 130 cu ft total. They hold 142 cu ft at 2475psi, 150 cu ft at 2600psi, 161 cu ft at 2800 psi and 172 cu ft at 3000 psi. You have to fill them all the way to 3500 psi to get 200 cu ft and that is beyond what I would call prudent. But at about 2700 psi they are equivalent to double AL 80's and that is not an unreasonable overfill and it tends to be about where I fill them with my compressor. With a decent SAC that is enough gas for about 20-25 minutes at 150 ft using thirds - although in a technical diving situation you want an isolator manifold. That same volume also works great when using one set for two "single tank" boat dives.
I plan to keep 1 set of the doubles with an isolator manifold as they are great quarry/shallow water doubles and the other set will end up with one of the two new old stock USD manifold that I came up with at an estate sale a few years ago and will be used with my double hose regs.
A vintage manifold is safe if it has newer style burst discs and as long as it still functions. Just treat it like a big single tank in terms of gas management though rather than thinking it has anything in common with an isolator manifold from a redundancy perspective.
It is fairly easy to disable the J-valve internally so that it will not function, or you can just zip tie the lever in the down position to disable it.
At 2250 psi double 72's only hold 130 cu ft total. They hold 142 cu ft at 2475psi, 150 cu ft at 2600psi, 161 cu ft at 2800 psi and 172 cu ft at 3000 psi. You have to fill them all the way to 3500 psi to get 200 cu ft and that is beyond what I would call prudent. But at about 2700 psi they are equivalent to double AL 80's and that is not an unreasonable overfill and it tends to be about where I fill them with my compressor. With a decent SAC that is enough gas for about 20-25 minutes at 150 ft using thirds - although in a technical diving situation you want an isolator manifold. That same volume also works great when using one set for two "single tank" boat dives.
I plan to keep 1 set of the doubles with an isolator manifold as they are great quarry/shallow water doubles and the other set will end up with one of the two new old stock USD manifold that I came up with at an estate sale a few years ago and will be used with my double hose regs.
A vintage manifold is safe if it has newer style burst discs and as long as it still functions. Just treat it like a big single tank in terms of gas management though rather than thinking it has anything in common with an isolator manifold from a redundancy perspective.
It is fairly easy to disable the J-valve internally so that it will not function, or you can just zip tie the lever in the down position to disable it.
marchand
Contributor
they are all crap!!
Send me a pm and I'll tell you the best way to get rid of them
Send me a pm and I'll tell you the best way to get rid of them
Steel lp72's are a great tank.....I own one and it is in service as a deco bottle----love it. Would love to get 2 more for another set of small doubles in the future.
72/2250=.032
.032(3000)=96
96(2)=192
Even if you used 71.2cuft as the real volume, you'd still get way more than 172. Did I do something wrong?
Jimmer
Contributor
Steel 72's only held 71.2 cu ft at the 10% overfill pressure of 2475 psi.
71.2 cu ft at 2475, so 71.2/2475=.029
But...100 cu ft at 3442 psi is 100/3442=.029
So you are correct in that both the steel 72 and X or E series 100 are 12 liter tanks that hold the same volume at the same pressure.
The LP 85 is very similar in volume but not exactly the same and has a slightly larger internal volume and tank factor: 85/2640=.032
71.2 cu ft at 2475, so 71.2/2475=.029
But...100 cu ft at 3442 psi is 100/3442=.029
So you are correct in that both the steel 72 and X or E series 100 are 12 liter tanks that hold the same volume at the same pressure.
The LP 85 is very similar in volume but not exactly the same and has a slightly larger internal volume and tank factor: 85/2640=.032
DoubleHoseDiver
Contributor
I really don't know why they do not make these anymore? Great tanks with so many uses and time proven. Tim
The Faber 75.8 was the last tank of that general volume and dimensions that I have seen. It had very slightly thicker walls to provide the 2400 psi service pressure but was otherwise very similar. I thought they were great but I suspect Faber stopped making them as it would have been hard to sell a "new" 72 for around $200-$250 with thousands of nearly identical steel 72's floating around on the used market in excellent condition for $100 or less.
Now however, with older 72's getting a bit harder to find in excellent condition and with some shops doing overfills on 3AA steel LP tanks and n shops willing to do the same on the slightly older steel 72's (even though there are designed to the same 3AA standard) there might be more of a market.
It is common in north florida to fill a 2400 psi steel tank to 3600 psi. 3375 psi in a steel 72 would give you the same 50% overfill, but no one will do it on a tank that "old". If they did, it would give you 97 cu ft in a tank that trims better on many people than the short LP 85's and HP 100's.
Similarly, a 3600 psi fill in a 2400 psi 75.8 would give you 103 cu ft. in the same basic package, making it an attractive option for some divers wanting a smaller but longer tank in the 100 cu ft capacity range.
For everywhere else where overfills are not an option, the 75.8 cu ft capacity at 2640 psi would offer a slimmer and slightly shorter alternative to the AL 80 that would also have much better buoyancy traits and only 1.2 cu ft less capacity. Maybe with enough interest Faber woudl start punching them out again.
Now however, with older 72's getting a bit harder to find in excellent condition and with some shops doing overfills on 3AA steel LP tanks and n shops willing to do the same on the slightly older steel 72's (even though there are designed to the same 3AA standard) there might be more of a market.
It is common in north florida to fill a 2400 psi steel tank to 3600 psi. 3375 psi in a steel 72 would give you the same 50% overfill, but no one will do it on a tank that "old". If they did, it would give you 97 cu ft in a tank that trims better on many people than the short LP 85's and HP 100's.
Similarly, a 3600 psi fill in a 2400 psi 75.8 would give you 103 cu ft. in the same basic package, making it an attractive option for some divers wanting a smaller but longer tank in the 100 cu ft capacity range.
For everywhere else where overfills are not an option, the 75.8 cu ft capacity at 2640 psi would offer a slimmer and slightly shorter alternative to the AL 80 that would also have much better buoyancy traits and only 1.2 cu ft less capacity. Maybe with enough interest Faber woudl start punching them out again.
mwilding
Contributor
I bet if they called them steel 80's, they would sell.
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