1/2" to 3/4" Adapter Question's

[Paintballpsyco2369]

Hello, I know this is probably the stupidest thing to even ask and bring up in here, but I figured it was worth a shot, and might help satisfy my curiosity.


First off, I have seen these adapters on pictures tanks and such. And just today I bought a doubles manifold from a friend of mine. It is literally a brand new U.S. Diver's Co. double J valve. Literally NIB! I only paid $10 for it and a few other small items, so that is not a problem at all. I called the LDS that I go to, and I asked him his opinion. He laughed and said I'd like to see you try and get those filled. I agreed, and had not really been planning on using them anyways. I was just going to add them to my vintage stuff bag, and hold on to them. But then I found a picture of a set of double tanks using the same manifold I have with a set of tanks on it, using the 1/2" to 3/4" adapter.

So here are my questions. Would it be safe to use this adapter, or complete stupidity? Does such an adapter even exist anymore? If they do exist can they even be used still? I am just looking for some feedback on this subject, mainly just to satisfy my curiosity. Thanks again for all the help, and your input on this topic.

Paintball

 

[captain]

Adapters were used years ago to convert various oxygen and fire extingusher cylinders for diving. I have used them in the past. On those cylinders a 1 inch to 1/2 high pressure pipe bushing was used. I also have an old USD 1/2 twin manifold and made stainless steel bushings to adapt it to todays 3/4 inch O ring sealed dive tanks. A mechine shop can make them very easly from a high pressure 1 inch to 1/2 inch pipe bushing by machining the 1 inch end to 3/4 straight thread. All that being said I have a compressor and fill my own tanks so it is not an issue but you might have problems finding a shop that will fill them, not because they are dangerous but because they think they are.

 

[Luis H]

So here are my questions. Would it be safe to use this adapter, or complete stupidity? Does such an adapter even exist anymore? If they do exist can they even be used still? I am just looking for some feedback on this subject, mainly just to satisfy my curiosity. Thanks again for all the help, and your input on this topic.

Paintball

I agree with Captain.

If you have appropriately pressure rated bushing/ adapters, not only are they safe, they are totally acceptable per codes and regulations.
On the other hand many improperly informed (or totally uninformed) LDS will not want to deal with them, will incorrectly tell you they are illegal, and will try to sell you some new stuff.

 

[Paintballpsyco2369]

Where might I find these pressure rated adapters? Just curious, I need a doubles manifold with an isolator on it anyways. Might be good to know though for future reference, I do plan eventually to get a big set of doubles for use, and I might double up my old 72's for playing around and such. Thanks again for the help.

Paint

 

[oxyhacker]

You have to first get straight what threads your are talking about. It sounds like your manifold is ngt tapered gas thread. Most of the adaptors in the old days were 1/2' ngt to 3/4" ngt since there were many surplus tanks on the market then with 3/4 ngt threads. You are probably talking about an adaptor to go from 0.750-14 NPSM, the standard size on most tanks now, to 1/2 ngt. Not sure if these have ever even been made commercially, but they would be easy enough from a machine shop to make. If you did have any made, be sure to have them stamp them "5000 psi" or something similar, since of the few shops that will fill bushed tanks, some will insist that the bushing be rated for the pressure.

 

[Paintballpsyco2369]

Ok, bringing this back up because I still can not find the bushings. Any idea where I might find them? I forget at the moment what you mean by the ngt thing (VERY long day) but I would be going to a standard 3/4 valve to todays standards, so whatever that is, from what I guess would be the 1/2 ngt threds. If I go to a hardware store would they have a way to measure that at all? I do have a friend who owns a machine shop, so I might see if he could either make them for me, or if I get the 1/2" to 1" bushing, if he can re-thread it for me to the 3/4".

I have mentioned to a few people, friends mostly who are divers from the old days, and they all think I am nuts. LOL. If I did this, at this point it would most likely be for looks. The reason being, I will be making a doubles set soon, and need a complete isolator manifold for use with the team I am diving with, would rather have that anyways but would still be cool to have this manifold set up maybe for another set to play with or something. So if I can find the bushings, or have them made cheaply, I would still like to find them. So does anyone have any idea where I could find them? Thanks again for all our help.

Paint

 

[captain]

I don't think you will find any. The only option is to take the tank and manifold to a machine shop and show them what you want but it won't be cheap. Your best bet cost wise would be someone with a metal lathe at home who is a hobby machinest.

 

[pescador775]

Paintball, listen up. The modern tanks use a 3/4 straight pipe thread (O ring). The old, surplus, aviators oxygen tanks used a 3/4 tapered gas thread which is like a pipe thread. In fact, decades ago, we all thought they were pipe threaded and we used pipe thread bushings sometimes without problems. A tapered thread requires some kind of pipe dope or teflon tape to seal the connection. Lots of torque is required which means the tank should be fastened in a chain vise. A large wrench is needed and glomming on to the posts can be tricky. Tapered bushings can be purchased off the shelf from various sources. A special bushing to fit a modern Scuba tank can be fabricated for about $50 each depending on material. I recommend stainless steel but carbon steel is a lot easier to machine. Valves with 1/2 npt are best used on steel tanks which originally accepted this thread. This includes a variety of old Scuba tanks, CO2 tanks, steel oxygen tanks, etc.

 

[Paintballpsyco2369]

I somehow completely missed this last post here.

Anyways...

AS far as bushings go, I have a friend who works in a machine shop who could make me the adapters I need no problem as long as I get the metal. I also happen to know a lot of people who sell metal, or could get me the metal I need no problem, so the adapters are not too much of a problem. But I was recently asked my opinion about something else, to which all I could answer was ask a shop.

What the guy has is an older tank from his work that was used for compressed air but painted nitrogen use or something along those lines. He now has it (he owns the company so...) and wanted to use it for scuba. He got the valve off and tried to thread a scuba valve in to see if it would fit, but it was a 3/4 tapered thread, not a straight thread. His question to me was, if he has it re-threaded to accept 3/4 straight thread can he use it for scuba? I did not know so I said ask a shop or 2, but I do know that you would have to have it like oxygen cleaned before any use would be considered.

SO I guess my next question is then, would that be safe to do? having the tank re-threaded I mean for use with a scuba valve? Obviously a new hydro/vis would be in order as well as a cleaning.

Thanks again, hope to hear back soon.

Paint

 

[james croft]

It is easy to find 1/2" tapered thread steel tanks. Ebay is full of them as is Craigslist. I would think it would be easier to get other tanks than to make bushings unless you have a machinist buddy. I also have gotten the runaround with getting bushed tanks filled. I have some old US military non-shatterable aviation air tanks that I dive with. I remove the bushing when I send them out for hydro and fill them myself. I suspect the steel bushings are a lot less prone to failure than the brass valve that is screwed into it.