Q) 1/2 valves?

[DA Aquamaster]

It goes without saying, but it needs to to be said anyway. Be sure the tank is empty before removing the valve and this needs to be said in triplicate if there is any potential for oxygen to be in the tank. Removing a pipe threaded valve from a full air tank has the potential to launch it through your roof. Removing one from a full O2 tank, has the potential for an explosion as the friction of the theads being turned will generate enough heat for ignition.

Some of the older 1/2" valves have been known to fail closed so that you cannot open the valve to release the contents. A tank in this condition, particularly an O2 tank, becomes a good candidate for the "I'd like to shoot a tank and see if it explodes" thread as I am aware of no safe way to remove the valve or release the contents.

 

[pescador775]

Hoosier, Luis is right about the technique. I see that you have already been hammering the valves but if visible damage has not been done don't worry about the rest. The brass threaded boss is quite strong and won't crack under ordinary forces. These short post valves are harder to remove than the longer valves because, as was stated, the only option is to tape the valve with one strip of masking tape and to place an 18 inch wrench across the valve face. The effort involved may be as high as 250 lb ft. Sometimes, depending on the type of dope and thus, the force required, some kind of fixture can be jury rigged, or a huge jawed vise can be used, but a chain vise is the way to go. If the valves are doped, a crescent wrench will probably damage the valve but not fatally. Personally, I use an antique monkey wrench which weighs about 12 pounds, or an enormous crescent wrench; it all depends on how the problem looks to me at the time. Once, I disassembled a brand new, vintage set of doubles made by Healthways. Before the valve started to turn, one end of my 400 lb workbench lifted an inch off the floor. Whe replacing the valve, use teflon tape or paste and there will be no problems next time.
Pesky

 

[Luis H]

Some of the older 1/2" valves have been known to fail closed so that you cannot open the valve to release the contents. A tank in this condition, particularly an O2 tank, becomes a good candidate for the "I'd like to shoot a tank and see if it explodes" thread as I am aware of no safe way to remove the valve or release the contents.

There are a couple of ways of dealing with that situation. I have resolved it successfully, but only dealing with air.

That type of valve (and many others) can be opened even if there is air pressure inside the tank. The valve seat seals the pressure on the face of the seat. I have encountered more than one of those valves with a broken stem or froze so hard it couldn’t be turned. As far as I can remember in most cases I was able to open the valve and carefully turned (unscrewed) the seat holder just enough to let the air out slowly.

The other technique works only with the old style safety disc screw retainers. Not the lead plug ones, but the type with a straight hole right in front of the burst disc. The idea is to use a very small nail, hold it tight with a pair of pliers and hit it with a hammer. With a very small hole there is not that much force. Warning: no one or nothing should be in front of the nail or air path. Hold the nail firmly with pliers, but move quickly out of the air path. Holding the nail prevents it from picking up speed and shooting across the room.

I think, I did this procedure once, but I can’t remember. I do remember at least seeing it done. I was standing behind the very well secured tank.

Did I mentioned I was a teenager at the time (and the owner of the shop was kind of nuts, actually he still is ). The firsts technique can be very safe if you are somewhat familiar with the valves and you are careful. The second technique…well it is not too…too bad if you are very careful.

A third technique that sometimes work is to just loosen up the burst disk just slightly and let it leak out. This works best with the newer burst disc plugs with the hex head (you can stand to the side wile you use a wrench). You don’t want to unscrew it completely or it will shoot out. The leak will be very slow, but sometimes it doesn’t seem to leak at all.


Any of the above procedures are done at your own risk, if you are comfortable working with high pressure air. This falls under the “don’t do this at home” recommendation.

Again it helps if you feel like you are bulletproof (as in a teenager).
“Sometimes you just have to live on the edge…if you are not living on the edge you are taking too much space.” (reference to another thread)

 

[Zieg]

Hoosier, Found those valves I mentioned earlier. They have never been used, as you can see from the original price tags where I paid $50 each for them over a dozen or so years ago. I'm willing to part with them for $75 each. PM me if you would like them, if not, no hurt feelings.

 

[Hoosier]

Of course, I opened the valve after emptying all air from the tank. I am wondering who is trying to open the valve without draining all air inside. And why? Thanks for a good discussion though.

Zieg, thanks for your offer. But, I should pass your offer this time.

 

[oxyhacker]

I'm confused. Everyone seems to be trying to find you 1/2" NGT scuba valves, but isn't that what you already have?

If you want medical O2 valves, that is to say, 1/2" taper thread 870 pin index yoke valves, you should have no trouble trading your 1/2" taper thread scuba valves for them - I got some O2 valves I'd trade. If you are looking for scuba valves, but newer ones, why not just rebuild the old ones?

 

[Hoosier]

First of all, I was NOT sure what kind of valves I have. So, that was my part of question on the initial post.

Second, yes, to build the existing valves is one option, As you see the link that I post above, NESS has a rebuild kit (one O-ring and two washers), but I am not sure if I can get all necessary parts I need to have from them. Because I don't want to end up these valve at the middle of rebuilding process. So, I thought if I can get the new one or 1/2 DIN valves somewhere (If this kind of valve is existed) at the reasonable price, it might be the better route.

Third, if it isn't a feasible or economical solution ($75 each) to rebuild these valves, buy the new ones, and there is no 1/2 DIN valves out there, I think that the medical valves will be another route that I can take if the medical valve can be swapped (That was one of my questions as well.).



In addition, one more newbie question.

Is this old 1/2 valve is durable enough for O2 bottle because this type of valve isn't manufactured anymore?

I have never rebuild 1/2 valves before and has no idea about its part availability and durability. So, my question might not be clear on the previous posts. This is a kind of cheapy DIY project to recycle old abandoned steel tanks.


Thanks in advance,

 

[oxyhacker]

When you consider that a scuba regulator HP seat must open and close 25 to 4 times a minute, and the seat on a valve only twice per dive, and that a regulator seat is held closed by a spring or air pressure, and a scuba valve seat by the considerable mechanical advantage of a screw thread, it is not surprising that valve seats last a LOT longer than regulator seats, often for the life of the valve or tank.

That being the case, valves, no matter how old, can often be revived simply by cleaning the part, replacing a couple O-rings with cheap generics, and lubricating (some valves use a crush seal, which must be replaced or annealed each time, but that's another story). The seat, which is the expensive and (for older valves) harder to find part usually won't need replacement. So if you want to use the tanks for scuba, the obvious first step is to try the valves and see if they are working, or give them a quick touch up overhaul as described above and see if they work. My guess is they will. If they do then you are all set - it's not worth replacing them, because anything you find to replace them with will in all liklihood be similar (unless you luck into some rare modern side-knob K valves in 1/2" NGT but they are very rare).

If you do a touch-up overhaul and they don't work, then you can start looking for a source of seats, or thinking about swapping for O2 valves.

First of all, I was NOT sure what kind of valves I have. So, that was my part of question on the initial post.

Second, yes, to build the existing valves is one option, As you see the link that I post above, NESS has a rebuild kit (one O-ring and two washers), but I am not sure if I can get all necessary parts I need to have from them. Because I don't want to end up these valve at the middle of rebuilding process. So, I thought if I can get the new one or 1/2 DIN valves somewhere (If this kind of valve is existed) at the reasonable price, it might be the better route.

Third, if it isn't a feasible or economical solution ($75 each) to rebuild these valves, buy the new ones, and there is no 1/2 DIN valves out there, I think that the medical valves will be another route that I can take if the medical valve can be swapped (That was one of my questions as well.).



In addition, one more newbie question.

Is this old 1/2 valve is durable enough for O2 bottle because this type of valve isn't manufactured anymore?

I have never rebuild 1/2 valves before and has no idea about its part availability and durability. So, my question might not be clear on the previous posts. This is a kind of cheapy DIY project to recycle old abandoned steel tanks.


Thanks in advance,

 

[dannobee]

Couldn't he take a modern DIN/yoke convertible valve to a machine shop and have them rethread the end to 1/2" NPT? I've seen valves like that on dive boats before. I've seen it at least a few times on different tanks, so somebody must be doing it.

 

[Hoosier]

When you consider that a scuba regulator HP seat must open and close 25 to 4 times a minute, and the seat on a valve only twice per dive, and that a regulator seat is held closed by a spring or air pressure, and a scuba valve seat by the considerable mechanical advantage of a screw thread, it is not surprising that valve seats last a LOT longer than regulator seats, often for the life of the valve or tank.

That being the case, valves, no matter how old, can often be revived simply by cleaning the part, replacing a couple O-rings with cheap generics, and lubricating (some valves use a crush seal, which must be replaced or annealed each time, but that's another story). The seat, which is the expensive and (for older valves) harder to find part usually won't need replacement. So if you want to use the tanks for scuba, the obvious first step is to try the valves and see if they are working, or give them a quick touch up overhaul as described above and see if they work. My guess is they will. If they do then you are all set - it's not worth replacing them, because anything you find to replace them with will in all liklihood be similar (unless you luck into some rare modern side-knob K valves in 1/2" NGT but they are very rare).

If you do a touch-up overhaul and they don't work, then you can start looking for a source of seats, or thinking about swapping for O2 valves.

Vance, thank you so much for your detail procedure. I have already learned a lot from your book (Scuba Regulator Maintenance and Repair) and your reply will be another great source of reference.

I will overhaul the valve first and let you know how it goes. If it doesn't work, I would like to get the medical valves from you.

As you guess, this DIY emergency oxygen system is pretty much from your book (OHC) as well. I will post the picture as soon as I have done it.


dannobee, it is possible option, but based on my local experience, it costs a lot to make a customized stuff.