Vintage Double Hose

Picked up a set from a local shop who had them sitting in the back. Owner said clean em up and give them a visual (I am a PSI inspector) and bring them back for a fill (vintage and DIY friendly shop).

Pulled the valves and insides look good (one has a bit of surface rust but no pitting). Will drop them off for a hydro at a local hydro facility on Monday.

I have a quick question about the valve. One thread on one side is a little messed up. Nothing major and I am assuming it is from years of torquing these things down. It is the topmost thread when seated. This side also seats much lower in the tank than the other.

Are there any CGA standards regarding these threads etc? Would you guys just leave it or run it through a 1/2 NPT die or anything of the like?

They were born in 1962.

Thanks,

Hydronaut

Kind of looks like a crack but it just may be the photograph. Looking at the assembled tanks it appears it is at the depth the valve is screwed in the tanks. If it isn't an actual crack I wouldn't worry about it. You could try running it in a die and see if it cleans up.

captain wrote:Kind of looks like a crack but it just may be the photograph. Looking at the assembled tanks it appears it is at the depth the valve is screwed in the tanks. If it isn't an actual crack I wouldn't worry about it. You could try running it in a die and see if it cleans up.

No crack. Just the way the photo was taken. Will probably just leave it. You are correct, it is right at the top.

Thanks.

Looks like it could be galling from overtightening, maybe compounded by lack of enough Teflon tape for lubrication between the tank neck steel and the valve brass.

If you have the proper NPT tap, you might lightly dress the tank threads, but don't go beyond what is just needed to make those look clean and sharp. Same for a die on the valve, just smooth it up without taking off much brass or the valve may seat too deeply compared to the other side.

I would use 6 or 8 wraps of Teflon tape on that valve (or both valves) and not overtighten. It's hard to describe the torque on tapered pipe threads, as there aren't really any specs for that, and so much variation in the size and fit. It's kind of a "feel" thing. I have had valves damaged like that that sealed up ok with lots of Teflon. Good luck.

antique diver wrote:Looks like it could be galling from overtightening, maybe compounded by lack of enough Teflon tape for lubrication between the tank neck steel and the valve brass.

If you have the proper NPT tap, you might lightly dress the tank threads, but don't go beyond what is just needed to make those look clean and sharp. Same for a die on the valve, just smooth it up without taking off much brass or the valve may seat too deeply compared to the other side.

I would use 6 or 8 wraps of Teflon tape on that valve (or both valves) and not overtighten. It's hard to describe the torque on tapered pipe threads, as there aren't really any specs for that, and so much variation in the size and fit. It's kind of a "feel" thing. I have had valves damaged like that that sealed up ok with lots of Teflon. Good luck.

Thanks for the replies. Figure it sealed before so will just leave it. Threads on thebtanknare nice and sharp. Just some wear on the valves from over the years.

The not die I have is not deep enough and stops midnway through. I don't want to risk messing them up. Might just try running a steel pipe coupler over it or cut it in half and make a clamshell type tool I can gently clean up the threads with.

Do you mean 6-8 layers of tape or 6-8 turns? What do you guys normally use. Plain old plumbing teflon tape or the thicker gas line stuff.

When tightening the valves I read tighten them hand tight and mark. Then put on the tape, tighten to the mark and go 1.5 more turns. Is this a good starting point or too tight. Or should it be finger tight with tape on then 1-2 turns?

What torque specs are normly used on the bonnet nuts when sealing with a brass washer? I have no experience with the old healthways valves. On any service manuals exist?

Thanks...

Been using this for years on my 1/2" NPT tanks. Not suitable for nitrox.

http://www.permatex.com/products-2/prod ... tfe-detail

captain wrote:Been using this for years on my 1/2" NPT tanks. Not suitable for nitrox.

http://www.permatex.com/products-2/prod ... tfe-detail

I have the tub of that stuff. When it actually said with Teflon not PTFE. I am assuming some trademark issue.

How much life should I expect to get from these valves. I read that every time you pull them off expect to loose a thread. That would mean after 4 visuals they would bottom out?

Has anybody ever taken a modern valve and machined it down to a 1/2 NGT thread?

Thanks.

Correction needed on my incomplete statement that I should have proof-read:
I meant to say "Tape it with 6 to 8 turns of Teflon, hand tighten, and then use a wrench to tighten between 1.5 and 2 turns..."

I left out some key words in this earlier message:

Antique Diver wrote:



Tape it and then hand tighten somewhere between 1 and 2 turns... you can always snug it a little more at a time if you have a leak.

hydronaut wrote:

captain wrote:Been using this for years on my 1/2" NPT tanks. Not suitable for nitrox.

http://www.permatex.com/products-2/prod ... tfe-detail

I have the tub of that stuff. When it actually said with Teflon not PTFE. I am assuming some trademark issue.

How much life should I expect to get from these valves. I read that every time you pull them off expect to loose a thread. That would mean after 4 visuals they would bottom out?

Has anybody ever taken a modern valve and machined it down to a 1/2 NGT thread?

Thanks.

Don't over-tighten and there is no damage done. I have a couple of 1/2" neck cylinders that I have inspected every year for well over 20 years with no damage. I must repeat... don't over-tighten. Teflon tape with Teflon thread dope will act as a lubricant and let the valves turn in more threads with less external torque applied, and save your threads for many years. I don't use the whole combination very often on Scuba valves, but often on 6000 psi pipe thread fittings. Especially helpful on Stainless fittings to prevent damage.

About cutting down the threads on modern valves, Sherwood did that back in the 70's with some of the new 3/4" straight pipe oring sealed valves, leaving the 1/2" tapered thread showing in bare brass where the original chrome plated material had been removed. I still have a couple of these. A good machinist(such as might be found on this forum) should be able to accomplish that for you.

Thanks. Any advice on how many turns. With the tape removed and the treads cleaned they seat right about to where they were originally tightened (to where the chrome is worn off). Previous people were pretty hard on the threads. Should it seat to where it was hand tight before tape with tape or deeper? How many layers (not turns) should I use?

I actually have a nice small lathe and am pretty good at cutting threads an tapers. Might try an old valve for fun one day.

hydronaut wrote:Thanks. Any advice on how many turns. With the tape removed and the treads cleaned they seat right about to where they were originally tightened (to where the chrome is worn off). Previous people were pretty hard on the threads. Should it seat to where it was hand tight before tape with tape or deeper? How many layers (not turns) should I use?

I actually have a nice small lathe and am pretty good at cutting threads an tapers. Might try an old valve for fun one day.

Correction needed on my incomplete statement that I should have proof-read:
I meant to say "Tape it with 6 to 8 turns of Teflon, hand tighten, and then use a wrench to tighten between 1.5 and 2 turns..."

I left out some key words in this earlier message:

Antique Diver wrote:

Tape it and then hand tighten somewhere between 1 and 2 turns... you can always snug it a little more at a time if you have a leak.

Thanks for all the advice and replies. Will update one hydroed. Hopefully everything works out nice as they will make a nice set of tanks.

Looks like these are actually twin 42s.

Passed hydro no problem. The guy said they were nice tanks. He was telling me about a tank (not sure what type) from 1902 that came in once and passed. One has a bit of rust inside but nothing that prevented a visual inspection. They will only do a + hydro if the REE is stamped on the tank (by the manufacturer) or can be provided by the manufacturer.

He was kind enough to install the valves for me. Done by machine. Still 3 threads on one and 4 on the other left.

It was funny, they do a lot of tanks for dive shops and mumbled something about most of them having no idea what they are talking about. Especially the 1/2 tapered thread as the NGT thread is used all over the compressed gas industry and SCUBA is a very small percentage of that industry.

He was a bit confused as to why I would want to pull them apart each year to look inside. Little unknown unrelated fact, unlike the CFR in the US Canada has the Transportation of Dangerous Goods Act. The current one in force does require a visually eddy during hydro or even at all on 6351 aluminum tanks. I also confirmed this via e-mail with transport Canada.

Now just to finish the valve rebuild and dive them.

A few questions. This valve is a little bit different that others I have worked on. On the stem of the J and shutoff valve, how does a single teflon washer prevent leaking? I find the stem can be moved up and down when the bonnet is screwed down.

Can I get away with reusing this washer? Should I flip it over as it has a groove worn in it from pushing on the cone on the bonnet.

Does anybody have a Healthways valve the can look at. There is a little spring with a pin on it which holds the J lever up/down. Can someone measure or take a picture so I know what it looks like? Is the end round or flat? I will make on on my lathe as mine is missing. Probably use brass. Not sure where to find a spring that small.

Has anybody tried paintball burst disks in scuba valves? They make single piece that will let go at 3000 PSI. Just wondering if they are long enough.

Does anybody have any recommendations on what to use between the bands and the tank that would look half decent. Without them the bands seem a bit loose when tightened. The original plastic liners is starting to crack probably not original to the tank). The had a bit of a lip that came over the edges of the band.

You can replace it with a new one but do not flip the teflon washer over once it has the groove impressed in it. It is a face seal and pressure forces the stem against the bonnet nut with the washer in between. They work quite well. There should also be a spring under the nut that retains the on/off knob to keep pressure on the seal inside
The stem will not move up and down once everything is assembled. There has to be space for the seat to move up and down when opening and closing the valve because the on/off knob doesn't move up and down because the stem is not threaded like the seat.