Help me read my steel tank, is it still good?

[captain]

In a dry Texas attic I don't think the busted burst disc is a big issue, or you can send it to me to keep my 6 72's company.

 

[weaserm99]

Steel 72's are 72 cubic feet within the first 5 years of existence. The tank is rated with the 10 percent overfill, but since it is so cost innefective to get the plus stamping on tanks that most people wont spend the money. Steel 72's after their first hydro are actually about 64 cubic feet. So there is a big difference between that tank and an AL 80. This doesnt mean that the tank is bad though, i will occasionally use a steel 72 on a shallow quarry dive or a niagara river drift dive. Just realize that these tanks are really not good for deep dives. I would not reccomend putting a different burst disc other than the one that is rated for the tank, overfilling tanks is bad for the tank and can also be bad for the person filling the tank.

 

[Don Wray]

I would say make a mail box out of it or give it away , cause a 72 as you guessed has less air in it than an 80 so the dive buudy of yours if hes got a 72 wondeful if he has an 80 hes going to pissed at you calling the dive cause your always short on air, also the bc strap will always have to be changed from the 72 from an 80....and the cost will be the same as an 80 fill, so now you have 3 negatives on keeping the 72......enjoy

Sorry Rob, not true.....The capacity of a steel 72 (71.2 cu.ft) at 2250 + 10% = 2475 psi. An al80 (77 cu. ft.) but it's late so let's say it's 80 at 3000 psi. In the steel tank each psi accounts for .0287 cu. ft. (71.2/2475=.0287 cu.ft. per psi) The al80 (80/3000=.0266 cu.ft. per psi) Now use these numbers and calculate the psi per cu.ft. at say 500 psi. Steel 72: .0287 x 500 = 14.35 cu. ft Al80: .0266 x 500 = 13.3 cu. ft. Well can't sleep anyway so I redid the al80 for 77 cu. ft and it would have 12.83

So if you using a steel 72 and your buddy using an al80 end the dive with 500 psi, you actually have more air left than your buddy does.

 

[captain]

Steel 72's are 72 cubic feet within the first 5 years of existence. The tank is rated with the 10 percent overfill, but since it is so cost innefective to get the plus stamping on tanks that most people wont spend the money. Steel 72's after their first hydro are actually about 64 cubic feet. So there is a big difference between that tank and an AL 80. This doesnt mean that the tank is bad though, i will occasionally use a steel 72 on a shallow quarry dive or a niagara river drift dive. Just realize that these tanks are really not good for deep dives. I would not reccomend putting a different burst disc other than the one that is rated for the tank, overfilling tanks is bad for the tank and can also be bad for the person filling the tank.

Getting the + is not a cost issue, all it amounts to is simple math. The problem is finding a hydro shop that has still knows the REE value needed to do it since the 72 has been out of production so long.
With the results of the hydro test and the REE value I can determine if the tank can be + rated I just can not legally stamp a + on it myself, but using my own compressor I can fill it +10% knowing it is safe to do so.

 

[pescador775]

Many good comments. About the S80 aluminum, Don is correct, the Alu tank is 11 liter and the steel tank is 12 liter. As mentioned, the capacity of the steel tank at 2250 psi is about 65 cf. Getting an overfill could be done privately but dive shops sometimes "diss" the old 72 and I doubt they would overfill by even 10%. Getting the tank plus rated would be difficult. However, it is what it is and many successful dives were accomplished with these tanks. The "72" was very well received at a time when the average diver probably weighed 150-160 pounds, air fills were hard to find and air management was practiced. The design is a stretched version of the aviator's breathing oxygen cylinder which was a surplus item in plentiful supply after WWII and Korea. A double set of these had about the same capacity as the commercially produced 72, eg 69 cf @ 1800 psi. Some divers liked them for light weight and buoyancy on the surface. However, since the 72 was specifically produced for divers, buoyancy characteristic was better for purposes of maintaining trim underwater.

 

[RonMurray]

David,

You've gotten some good feedback on your question. Let me just add my experience to help reassure you. I purchased a Steel 72 back in 1976. Dove with it for a year and put it away until this year. (31 years). I took it to my LDS who had it hydrostatic tested, tumbled, and Visual. Tank checked out fine. (Same for my ScubaPro regulator, had it serviced and the 32 year old S-190 second stages are back in service - warranty restored I might add).

So - what you have there is an oldie but a goodie - enjoy.

 

[northcoastdiver]

As most everyone has already stated, the "72" is a great tank. The first tank I bought was an old (1959) ICC stamped 72 with a 1/2" pipe thread j valve. It was well cared for and is still one of the cleanest tanks I own. I'll never part with it. If you have decent air consumption it will be adequate for the majority of rec dives out there. One of the best things about them IMO is that they will last dang near forever if you take care of them and are willing to clean them up now and then. Not to mention they have pretty good buoyancy characteristics. You won't regret the $30