Vintage cylinder questions

[oceancurrent]

I recently came across a vintage set that looks very cool. The cylinder appears to be steel from 1960 very well preserved. If I am reading the stamps right, the cylinder was manufactured January 1960 and is rated at 1800 psi working pressure. The valve appears to be manufactured May 1959 and it appears to have a 2500 psi burst disk. I wonder a couple things about this cylinder:

1. Am I reading the stamps correctly? I.e. is the cylinder 1800 psi working pressure? Seems a bit low by moderns standards.
2. Can this cylinder pass hydro with the ICC stamp on it alone (without a DOT stamp)?
3. How does the valve seal to the cylinder? There does not seem to be a groove for an o-ring, but there is some sort of white substance over the valve threads?
4. What is the proper way to remove the valve from the cylinder to take a look inside and then reinstall it? I tried to unscrew the valve, but it didn't budge. And I am a bit worried about getting it to seal again after.
5. Where can I find a schematic and some service notes for the valve (if at all such exit)? It appears to be standard post valve from the 60s, but I don't know much about these.
6. Would a current valve fit the cylinder threads? Would the O-ring need a groove to be machined?
7. What is the mechanism of the burst disk? Is it sealed with a lead capsule? Is it reliable and to what extend 50+ years later?
8. There is a second plug of sorts protruding perpendicular to the burst disk. What is its role?
9. What is the history of this cylinder/regulator set? Who was it marketed to at the time (does not seem to have much capacity for anything but shallow dives)?

Lots of questions, I know. I hope that some of you know something about this kind of cylinders/valves and what is possible in terms of DIY servicing today. Any information will be much appreciated. Let me know what you think about this find.

 

[2airishuman]

I have some older cylinders that are similar.

I recently came across a vintage set that looks very cool. The cylinder appears to be steel from 1960 very well preserved. If I am reading the stamps right, the cylinder was manufactured January 1960 and is rated at 1800 psi working pressure.

It appears to me that the 7-45 date is the manufacturing date, and the 1-60 date was a subsequent hydro test.

2. Can this cylinder pass hydro with the ICC stamp on it alone (without a DOT stamp)?

Yes, I have two ICC- cylinders that I have hydroed and filled routinely. The name of the responsible agency changed around 1970.

3. How does the valve seal to the cylinder? There does not seem to be a groove for an o-ring, but there is some sort of white substance over the valve threads?

It uses a tapered (NGT, similar to NPT but with an extra couple of threads) fitting, which is sealed with either tape (usually now), or clay-based pipe dope (past and sometimes present). The cylinder has 3/4" threads, and the valve is a 1/2" valve, so there's a bushing to make up the difference.

4. What is the proper way to remove the valve from the cylinder to take a look inside and then reinstall it? I tried to unscrew the valve, but it didn't budge. And I am a bit worried about getting it to seal again after.

Ideally with a cylinder vise and a suitable wrench. It will be easiest to remove the valve from the bushing first, because then you can use two wrenches and the torque for the 1/2" connection will be less (probably). Once the valve is out of the bushing you can put a six-point socket and breaker bar (or impact wrench) on the bushing, put the cylinder in the vise, and pull on the breaker bar until something gives. You'll end up with two pieces one way or another, and hopefully one will be the cylinder and the other will be the bushing

5. Where can I find a schematic and some service notes for the valve (if at all such exit)? It appears to be standard post valve from the 60s, but I don't know much about these.

I've been told they are called "I-valves," part of the I J K series of olden time. I have one, and I've had it apart. Nothing unusual there. Modern valve parts will fit except for the seat. I believe Vintage Double Hose has seats that will work, although you'll have to go by the photos and find one that matches, rather than by the valve make and model.

6. Would a current valve fit the cylinder threads? Would the O-ring need a groove to be machined?

XS Scuba makes a 1/2" NGT pro valve. Leisure Pro has them in stock, and no doubt there are other sources.

7. What is the mechanism of the burst disk? Is it sealed with a lead capsule? Is it reliable and to what extend 50+ years later?

That one's not original because the original ones used a slotted drive, not a hex drive. I would expect that it's an ordinary copper disk. Lead disks were/are only common on acetylene cylinders and some other similar gasses where temperature is more of a concern than pressure. Burst disks should be replaced at every hydro. A modern one-piece disk will fit, and that's what I use on my I-valve.

8. There is a second plug of sorts protruding perpendicular to the burst disk. What is its role?

It is a 1/4" NPT(probably) fitting for a pressure gauge. Regulators of that era didn't have a port for an SPG, so they put them on the cylinder valve. I can't remember if it's constantly pressurized or if it is downstream of the valve.

9. What is the history of this cylinder/regulator set? Who was it marketed to at the time (does not seem to have much capacity for anything but shallow dives)?

It is likely that this was originally a CO2 fire extinguisher cylinder. They were commonly repurposed as SCUBA cylinders in that era, and they had an 1800 PSI working pressure. Also of note, this is a 3A, rather than 3AA, specification cylinder. That means lower strength steel and therefore thicker walls.

If you want to use it, I would suggest you inspect it and determine the water capacity (by filling it using a graduated cylinder or measuring cup), and figure out the usable CF capacity from there. Then compare the weight and buoyancy characteristics (both of which you'll have to measure) to modern cylinders, and decide for yourself. If it passes hydro, it's safe to use, but you'll have to decide if it's practical.

You may want to replace the bushing with a stainless steel one rated for at least 1800 PSI. I believe McMaster-Carr has them.

A few dive shops won't fill cylinders with tapered threads. Some won't VIP them. The tapered threads are subject to a certain amount of wear each time the valve is removed, and are something of hassle to work with due to the higher torque and need for tape. That said, most industrial gas cylinders still use tapered threads. They are more of a problem with annual inspections than with the 5-10 year inspection cycle for industrial cylinders.

 

[herman]

That appears to be a USD "Vigo" tank. It came in 18 and 24 cf models (also 38 but with a different harness) I am guessing the second plug was the opening for a pin pressure gauge, the catalog says there was one.
Go to VDH, "Manuals and Catalog" section (way at the bottom of the page) go to the USD catalogs and look at the back cover of the 1959 catalog and page 9 (they are somewhat out of order) of the 1961 catalog. I don't see it in the 60 catalog and it may be in others. By all means do not scrap it, lots of the vintage guys would love to have it.

 

[oceancurrent]

It appears to me that the 7-45 date is the manufacturing date, and the 1-60 date was a subsequent hydro test.

XS Scuba makes a 1/2" NGT pro valve.

I would expect that it's an ordinary copper disk. A modern one-piece disk will fit, and that's what I use on my I-valve.

You may want to replace the bushing with a stainless steel one rated for at least 1800 PSI. I believe McMaster-Carr has them.

Thank you very much for the awesome info and pointers. Wow 1945 is the manufacture date on the cylinder? A bit hard to believe, but that could be consistent with the suggestion that AquaLung/USD may have re-purposed a batch of 15-year old fire extinguishers around 1960 for their Vigo product line.

The XS Scuba PRO 1/2" NPT Threads looks good - I may try it with this cylinder for fun. Would Thread seal tape - Wikipedia, the free encyclopedia work for sealing?

I am pretty sure the burst disk is lead shot type, which according to Luis (see Vintage Double Hose • View topic - Questions About Burst Disks) is a major hazard when it blows (practically a bullet). I'd love to replace it with a copper disk. Wonder if this PRD Safety Assembly (Burst Disk Kit) | Dive Gear Express® will work (sounds like it may).

Not sure what you mean by "bushing". Do you have the link to the approximate item at McMaster-Carr?

That appears to be a USD "Vigo" tank.

Nice catch! I checked the catalogs and indeed everything matches. It looks like they were marketing them for pool training of novice divers, boat owners, and lifeguards.

 

[2airishuman]

If you're replacing the valve, you'll be using a modern burst disk, since that's what they take. I get mine from Dive Gear Express, per your link. Technically you would want a 3000 PSI burst rating (5/3 * 1800), though, which they don't have. Some people might use a 3360 PSI one, but it's not officially allowed by USDOT.

Here's a link to a bushing. McMaster-Carr and other vendors have similar ones. Watch the PSI rating, many are not rated for tank pressure.

https://www.grainger.com/product/GRAINGER-APPROVED-Bushing-1MNJ9

I use ordinary teflon tape like in the Wikipedia article, for air. I have no idea what oxygen service would require.

 

[oceancurrent]

If you're replacing the valve, you'll be using a modern burst disk, since that's what they take.

Right, but I also want to change the burst disk on the original post valve. Do you think that the modern version will work there?

Here's a link to a bushing.

I see. This is the 3/4 in to 1/2 in adapter on the cylinder. But, why do you think that the original brass bushing is not strong enough and needs to be replaced?

 

[2airishuman]

Right, but I also want to change the burst disk on the original post valve. Do you think that the modern version will work there?

::shrug:: Maybe, depends on how the valve is threaded. There's somebody selling NOS valves that are essentially identical to that one, with modern burst discs, on ebay right now for like $20 each. If you take out the burst disk and see what kind of threads it has and how it seals to the valve, you'll be able to tell. If it has tapered threads then the modern ones won't work.

I see. This is the 3/4 in to 1/2 in adapter on the cylinder. But, why do you think that the original brass bushing is not strong enough and needs to be replaced?

Oh, it's probably strong enough now.

It may not be after you get it off the cylinder.[/QUOTE]

 

[captain]

The reducing bushing is not 3/4" to 1/2", it is 1" to 1/2". These tanks were military surplus co2 fire extinguishers or co2 life raft inflation cylinders. The burst disc is common 3/8 x 24 and readily available.
All this being said, realize that dive shops will probably not fill it even if it passes hydro for 2 reasons 1 because it is old, 2 they believe incorrectly that the reducing bushing is illegal. Other than having a compressor your best option to fill it would be to transfill from 3000 psi tanks.
In the long run it may not be worth the effort unless you have 2 that can be made into doubles

 

[John C. Ratliff]

Okay, a couple of other useful observations about this tank/valve combo are appropriate. First, the valve is 1/2 inch tapered threads. Normally these are now sealed with Teflon tape, and you need to putt the tape on in at least three tight wraps around the valve before putting it back on the cylinder's bushing. The Teflon tape wrap needs to be done against the direction of thread tightening ("counter-clockwise") instead of with the thread rotation, otherwise it will bunch up and come off during tightening.

Second, I don't know about the threads on the bushing, but suspect they are straight threads (not tapered). This is important as it determines how best to seal the bushing.

Third, this tank was manufactured before U.S. Divers Company existed. This means it probably started out either as or intended to be a CO2 fire extinguisher. The other possibility is this was originally a life raft bottle. Either way, this was converted for diving; hence the bushing so that a scuba valve could be used.

Yes, do use a vice, but not with metal grips like normal vices. It would be best to use a dive shop's strap vice, with padding so as not to scar the metal sides of the tank, which could disqualify it for a hydrostatic test.

Finally, take a very good look inside, as a steel tank that old could have significsnt corrosion from just a single misuse years ago.

But saying that, I feel it is well worth the restoration, and I think any dive shop could swap out the over pressure relief plug with a modern one, as I don't think this fitting has changed over the years. These tanks were used for stage safety bottles, alternate air supply bottles for ice diving (mounted onto twin 72s with a separate regulator, before the octopus regulator had been invented), and for teaching children to scuba dive. I started diving on a converted fire extinguisher 38 cubic foot tank and Healthways SCUBA double hose regulator in 1959 at age 13. I bought the scuba used (not new) with money I earned picking strawberries and beans in the fields around Salem, Oregon. Good luck.

SeaRat

 

[captain]

John the threads are 1" tapered pipe threads and you could use teflon tape. My preference is
Permatex® Thread Sealant with PTFE - Permatex