Question Older steel 72 Pitt Depth

[Luis H]

I had a scuba shop in Cape Cod Mass take a pair of steel 50s that I dropped off for hydro. He gave me back my valves & other hardware but kept my tanks, saying that it was illegal for him to return them to me. He said that they failed due to having NPT threads & they didn't even need to get pressure tested. He had failed them visually. I was very angry that he took my property & would not return it, but I was young at the time & didn't understand my legal options. I never shopped there again. I doubt that he is still in business. It was a long time ago.

Yes, what he did is totally illegal. He stole your property and he might have destroyed it...

It is hard to know if he was really that ignorant. There is nothing wrong with NPT (tapered) threads. If he had storage cylinder with his air system they would be that style of threads even with new cylinders.

I am fairly certain that they are the most common threads for pressure vessels. Most industrial pressure vessel use tapered threads.

 

[Clashswims]

I would add, have you tumbled and/or cleaned prior to examining these pits?

I have had tanks that looked ok, with pits, then cleaned and the pits were wtf? Non intrusive, phosphoric cleaning.

I just got my hands on “ Inspecting Cylinders “. looks surprisingly good. But found a pin hole pit. its Deeper than it is wide. Good news is I can cut it up and physically examine it.

 

[Tracy]

I just got my hands on “ Inspecting Cylinders “. looks surprisingly good. But found a pin hole pit. its Deeper than it is wide. Good news is I can cut it up and physically examine it.

While that method works well to examine the pits, you will find it is a pain to put back together if you determine they are fine.

 

[lowviz]

Good news is I can cut it up and physically examine it.

Jeez. Maybe be a bit more kind to our history?

 

[Gone for diving]

You can always weld history back together

 

[Clashswims]

While that method works well to examine the pits, you will find it is a pain to put back together if you determine they are fine

While that method works well to examine the pits, you will find it is a pain to put back together if you determine they are fine.

I have a construction background, I’ll caulk it.

 

[Clashswims]

It has more issues than one pit. Not worth it.

 

[tmassey]

I thought I would leverage this thread again instead of starting a new one for another LP72 identification question. Who made these tanks? And how would I tell if it has a liner inside?

I can't tell what the hydro mark is. Is it a circle with something inside of it (a D maybe?), or is it an outline of a C? In any case, the rest of the marks are:

ICC 3AA 2250
K64433
USD
9C67+

They are indeed US Divers tanks: I got a pair of them that were still attached to the "aqua-lung-pac" (why did USD put everything in quotes?!?) with J-valves and the pull levers still in place.

According to @captain it seems that the hydro mark might be a C over an L which would make it a PST? Ref: 1970 US Diver's LP72 - Lined or not?

The tanks are seemingly in nice condition. They seem to be vinyl-wrapped on the outside? I don't think it's paint, but it is quite intact. I'm guessing that it's the "Tuff Koate" that @Akimbo refers to in a 1970 catalog a couple of posts later in the above link.

One thing that is different from the 1970 description is that I'm pretty certain that these are *not* galvanized under the Tuff Koate. The couple of places that the outer liner is damaged shows brown-black metal, not galvanized metal. So they're probably not the exact same tanks as were sold in 1970.

I'm more worried about whether they have the epoxy liner or not. It seems that 1967 is right on the border of internal liner or not. The inside looks like a uniform brown-orange coating. I've seen tanks that looked like that when they were consistently exposed to wet fills; but I've never seen an epoxy liner before, and I understand that they're brown, too. I've got the tanks soaking with phosphoric acid right now, so we'll see what happens.

However, if it is liner, it seems intact. If they pass hydro, I'm using them as-is, and I get to keep the original stickers this time!


Thank you very much for any help you might be able to provide. I appreciate it.

 

[James79]

Don't know if it helps, but I have one lined tank and it is the dark brown epoxy liner... Still going strong. It's a later tank than yours (don't remember the date off hand, but it's DOT not ICC).

Respectfully,

James

 

[Jimchris]

ICC is Interstate Commerce Commission(think pre-DOT). The CL hydro is for Cochran Labs, who is/was an independent inspector who conducted the original pressure test. I have two of these cylinders, neither one has an internal lining. However they are not galvanized, rather they have a vinyl exterior coating.

I'm clueless as to who actually built the cylinders as these don't have any of the usual/easily recognizable MFG stamps/markings, though other threads mention that Cochran Labs was the tester chosen by Pressed Steel (PST).