Vintage steel 72 rescue center.

[RickI]

This is going back a long time, but as I recall the "+" signifies it is ok to have a 10% overfill in the first five years of the tank. It used to be hard to find a good, cool 2500 psi fill. Eventually it became fairly common place. Don't recall many shops refusing to provide 2500 psi fills in 2250 psi cylinders even after five years however.

In almost forty years, I've seen or heard about quite a number burst steel tanks. Fortunately, never first person however. Why did they fail? The reasons varied. How many fail per year, perhaps not that many. Aluminum tanks may be more prone to failure as others have said. It is personal choice but I would prefer to use newer pressure cylinders myself.

This is a forum for vintage diving, correct? Back in the day in the early 1970's, deep air bounce dives weren't that uncommon around SE Florida and in parts of the Caribbean. Accidents during them weren't that uncommon either. Fortunately, survived my deep, ill advised bounce dives before I turned 20, all on tables and air. Used O2 on rare occasion during shallow deco stops. Grew up some, got smarter and moved on after that, largely intact fortunately. Have a bit of old gear, may get rid of it one of these days. In no particular hurry at this point however.

 

[rx7diver]

Dumb question, why the interest in using old 72 cft. tanks these days?

RickI,

My interest in Steel 72's really has to do with assembling a set of small independent doubles to use when doing modest solo dives. I haven't done the type of technical Great Lakes diving I did in the mid-1990's through early 2000's in a long time, as where I live (MO) and my current life situation (3 primary school children) have reshaped my priorities. My manifolded PST HP 120's are *way* overkill for me now. And, besides, my middle-aged back groans these days whenever I even glance at my wreck doubles.

For solo diving, I've experimented with (1) using my HP 120's as independent doubles, (2) using a single OMS LP 126 with a slung Al 40 buddy bottle, and, most recently, (3) using independent double Luxfer Al 80's. I'm hopeful that independent double Steel 72's--when I finally locate a second 72--will finally satisfy.

As you're probably aware, the 1970's-era USD steel 72's are 3AA tanks and will last "indefinitely" if they have been properly cared for (and they pass hydro and VIP). They can be hydroed for a plus rating (= 2,475 psig = 2,250 + 10%) even if a previous hydro was only for a non-plus rating.

 

[captain]

Other than some of the pleasant characteristics mentioned my interest in 72s is partly economical. I have three Aluminum 80s made from the 6351-T6 alloy and there are a lot of problems with them. Most of the problems seem to be political or philosophical. Some dive shops won't fill them and many people think they are going to explode even though they passed VIP, Hydro, and Visual Eddy. I have one tank that is current but I'm not sure if the VE is required along with the Hydro test, or annually with the VIP. At $10 per VE test, in addition to $15 or so for a VIP, they may not be worth keeping. There seems to be a few places that won't fill old steel 72s (rumor has it Sport Chalet is one of them) and, for some reason, less fear of them blowing up. Back in the old days. before aluminum tanks became popular, it seemed like it was steel tanks that blew up. I recall seeing a ruptered steel tank on display at a dive shop. Perhaps they were tanks that were way beyond their hydro date but then I doubt that very many shops would have filled them, even back in the 60s. Meanwhile, my 1963 steel 72 still passes hydro and VIP so I check Craig's List every day to see if I can pick up a few more and give up on the 6351 tanks. I'd prefer to find some with J-Valves because they are easier to carry, even though I've never actually used a J-Valve because my scuba instructor said they were evil.

Can some tell me what the "+" on the 72s means? I realize it means that it can be filled an additional 10% but does it need a new "+" with every hydro test, or is that "+" good for it's life?

BTW I've only had a tank filled at Sport Chalet once because I had to carry it across the parking lot, through the store, and up the stairs to get it filled. Then it took a long time and cost more.[/QUOT

The main reason for steel tank failures years ago was rust under boots or inside from compressors pumping wet air and bad fill procedure and a lack of frequent (yearly) interior inspection. Since compressors are much better and we have learned to do yearly inspections catastrophic failures are non existent now, we find the problem before it is a problem.

The tank must qualify for the plus at every hydro, but most shops don't do the necessary math for a variety of reasons.

 

[Darol]

I just love diving the old gear, my Healthways horse collar, and my Hy's doublehose reg.
Seems the local shops are doing VE tests with every visual at no extra charge on Alum
tanks. The first reg I purchased, when I learned to dive was a Dacor R-4, followed by the
new Scuba Pro Mk-7 aka the honker....

 

[duckbill]

I don't know for sure, but have heard that many steel 72s rupture in Florida due to cave fill after cave fill after cave fill. RickI, if you are in Florida, it's no wonder you have seen a bunch of failed 72s. Caves fills do not constitute proper care for any cylinder, and dive shops who do the cave fills then display the blown old steel 72s as some type of message should be ashamed of themselves.

 

[halocline]

In almost forty years, I've seen or heard about quite a number burst steel tanks. Fortunately, never first person however.

So I guess you never really saw any steel tanks "ripped open", right? You're just saying they're dangerous based on hearsay and rumors?

 

[elmer fudd]

Dumb question, why the interest in using old 72 cft. tanks these days? I still have some, last used a pair as swing bottles for transit mix in the early 1990's. I still have one that I got the second year after I started diving in 1972, did a bounce dive to 300 ft. on air with it once too. Ah nostalgia, still would I want to use them today? Not so sure, given all the ripped open steel tanks I've seen over the years. So, it passes hydro, what if it fails before the next one, while in service? Three to four decades can bring latent weakening to a high pressure vessel subject to cyclical loading and fatigue. Just curious, thanks.

Two reasons. First off, this is the vintage forum and people that are drawn here generally just like old stuff to begin with. Second, LP72's are dirt cheap. If I keep an eye out on Craigslist, I can almost always find an LP72 for $50 and sometimes for as little as $25. Throw in a $25-$35 hydro and vis and I can have a diveable tank for between $50 and $85. Now if I could get HP80's for that same price, you can bet I'd forget all about LP72's.

 

[Eric Sedletzky]

It must be steel 72 heaven where I live.

I have been given 4 so far. The most I paid for one was $75 and that was from a dive shop down in San Luis Obispo. I bought two and they had fresh hydro's and VIP's.
I've never had one fail Hydro and the oldest operational one I have is from 1967. I just got the 1959and I need to bead blast the outside and zinc it then send it in for hydro.

There's a dive shop up in Fort Bragg that had a sh*t load of them. They were only $50 a piece, take your pick. Some in hydro some not, many had great looking J valves too. I was broke at the time I was in the store (damn it!) and they all looked so lonely.
If I had a wad of cash I would have made a deal on all of them.

 

[JamesBon92007]

[
The main reason for steel tank failures years ago was rust under boots or inside from compressors pumping wet air and bad fill procedure and a lack of frequent (yearly) interior inspection. Since compressors are much better and we have learned to do yearly inspections catastrophic failures are non existent now, we find the problem before it is a problem.

The tank must qualify for the plus at every hydro, but most shops don't do the necessary math for a variety of reasons.

I noticed many small rust spots when I remove the boot before I got my old 72 Hydroed. I now remove the boot and backpack after use and let it dry. Hopefully this will extend it's life. Now I'm only looking for galvanized 72s.

I guess doing the math is up there with asking to see a diver's C-Card I can't remember anyone ever asking to see it. Heck, I doubt if I paid for air half the times I got my tanks filled. I guess if you tell a good enough diving story it's "on the house."

 

[Akimbo]

If they're lined and nobody will hydro them then probably not for trying to restore for diving, but I'd want to at least look at it.
But I'm thinking about taking condemned tanks and cutting a few access holes around the tank with my plasma cutter (similar to how they cut holes in cleaned wrecks) and make octopuss condos out of them. I'd like to start a condemned steel cylinder artificial reef up in my area.

So either way, yes I'll take it. It will get a new life one way or the other.

Here is the best use I have found for cylinder that doesn't pass hydro:

Anyone have a LP air system in your shop? An old inverted cylinder at the end of the air line makes a great volume tank to help compensate for line loss. The 72s with ½" CGA taper threads are a little easier to adapt. You can hack saw off a straight thread Scuba valve, drill, and tap for ¼" NPT to make an adapter if you also have an extra valve. I have one that failed hydro and it works great and stays dry because the inlet and outlet are on the bottom.