questions about old 72's for the experts

[goatboy_k]

i bought what im pretty sure are some old 72's from a friend of mine. the are a hair under 7 inches in diameter and a bit over 25 inches long not including the valve or boot. They have the PST stamp so i know they are Pressed Steel, and the have some old AMF swimmaster stickers on them. First hydro stamps are from 76 on both. The guy i bought them from paid for the hydo and they came back good, so i bought them and they worked great last weekend.

now the questions

he has 2 more for sale, but they are not marked PST.
they have

DOT-3AA2250
HJ 391488
10 75+ 9

DOT-3AA2250
HJ 135393
11 66+

I belive they had some kinda FD or an F and a D together about 180 degrees from all this other stuff and they are about the same size as the above tanks

are they Fabers?

they are also pretty old from the hydro stamps, but they both just came back as well, passing the test.

I am thinking about buying them . im pretty sure they are 72's but i was just wondering if you experts could tell me a little more abou these 4 tanks. Who made them, etc..

I am also considering turning these into doubles. Do any of you dive double 72's. Is it a good setup as far as balance and all that good stuff. Who makes good bands and manifolds for these smaller tanks, i am running a FredT plate if it makes a difference?

thanks in advance for anything you can tell me about these tanks

kurt

 

[DA Aquamaster]

It was common for steel 72's to be manufactured for a specific company and be marked as such. I have steel 72's marked "DACOR" and "USD" and "HJ" as well as PST. I suspect the HJ may have went on tanks made by healthways, but it really does not matter as there is no difference in the tank.

A steel 72 will last for decades if properly maintained and routinely inspected. I would not worry about using or buying one with a current hydro and VIP. I can't say that about an AL 80. There are still 1/2" valved steel 72's in service from the 50's and the problem is nearly always the valve, never the tank. It is almost unheard of for a steel 72 to fail a hydro unless it has been badly and repeatedly overfilled.

Rust is responsible for most steel 72's being condemned and that is not a problem with a regular VIP, reasonable care to keep the tank dry inside and possibly a tumbling every 10 years or so as needed to remove any rust that may start to develop.

Steel 72's work well with any band and manifold designed to accomodate similar sized tanks (approx 6 3/4" diameter). Just be sure to check that the burst disc is correct for the service pressure.

Bouyancy is very similar to an AL 80 at about -2.0 lbs full and 3.5 lbs empty. They work well for doubles and normally allow more ditchable weight than higher capacity steel tanks which can run 7 to 13 lbs negative when full depending on the specific tank.

Balance in the water is great as their bouyancy traits do not require you to try to balance 15-20 lbs of negative bouyancy above your center of gravity. They are long enough to work well with backplates with standard 11 inch centers and still have ample room to be moved for or aft for trim. They are shorter than an AL80 and in my opinion more comfortable to dive with.

Capacity of a steel 72 at 2250 psi is around 65 cu ft and you need to overfill 10% to 2475 to get an honest 72 cu ft from it. But at 29 lbs they are (relatively speaking) lightweight and only very slightly heavier than a single 120 and are lighter than a single 140.

 

[quimby]

the DOT 3AA means the units are chromium-molibdenum steel and the 66 bottle just missed being marked ICC which was the Interstate commerce commision which changed to the dept of Transportation around that time. I have a whole bunch of em and been divin em since before your tanks were made
I believe most of the steel from that time came out from a outfit called Norris Thermador down in Pa. which has become a victim of absorption, and you can find old double manifolds and bands on Ebay pretty cheap and are very comfortable.......:doctor:

 

[Rick Murchison]

DA Aquamaster once bubbled...
Bouyancy is very similar to an AL 80 at about -2.0 lbs full and 3.5 lbs empty.

Not mine.
My steel 72's are nearly 6 pounds more negative than AL80's at any given pressure. This is measured on a balance, not taken out of a book. (AL80 + 6 pound weight balances with steel 72 at 500 psi). This is also confirmed by diving - I take six pounds off when going from AL80 to Steel 72.
Rick

 

[Genesis]

3/4" NPSM (straight thread) necks then they're good to go with any of the current manifolds and valves.

If they have NPT threads - and some do - then you're going to have trouble doubling them, as manifolds to fit are antique pieces and essentially all of them are just crossbar designs with questionable sealing, no isolator, and only one outlet.

I would not buy the NPT tanks, but anyone who has older steel 72s with NPSM threads I'd buy in a heartbeat and turn into "light doubles". As has been noted, they will typically last for decades.

The O2 cylinder I have in my garage right now (from my gas supplier) has a first hydro date on it in the 1950s! And that tank has been in COMMERICAL service, not occasional recreational service....

Keep the rust off the outside, and don't let moisture get inside it. That's basically it.

 

[Don Burke]

Rick Murchison once bubbled... Not mine.
My steel 72's are nearly 6 pounds more negative than AL80's at any given pressure. This is measured on a balance, not taken out of a book. (AL80 + 6 pound weight balances with steel 72 at 500 psi). This is also confirmed by diving - I take six pounds off when going from AL80 to Steel 72.
Rick

This is my experience as well. There is 12 pounds difference between my double 80s and my double 72s.

Roman (whose last name escapes me) can set you up with custom bands at a really good price.

Here is his email:
mrdeco@aol.com

There are still half-inch 72s and tapered thread 72s out there, so be careful.

I really like how much lighter the 72s are on the surface.

 

[O-ring]

I also have a set of Roman's bands on my steel 72s and I love them.

 

[goatboy_k]

yes all the tanks in question have the "modern style" 3/4 threads so i think i will buy for a set of doubles.

can anyone tell me about the AMF swimmaster stickers on the 2 tanks i already own. Did they build scuba stuff for awhile kinda like harley's. Kinda showing my younger age here but just wondering

kurt

 

[Rick Murchison]

AMF Voit marketed a complete line of scuba gear.
I still use a Voit mask occasionally... and a Healthways snorkel.
Rick

 

[pescador775]

In 1956, Swimmaster, a fledgling skin diving products co, bought the patents and molds for Art Brown's Duckfin. Subsequently, they also bought rights to produce a gun designed by Jack Prodanovich (remains in production under the JBL name) In the 60's, Swimmaster was merged into American Machine and Foundry (AMF) along with Voit Rubber co. to produce/market a diversified line of diving gear, including your tanks. "HJ" is the symbol for Norris Industries.