SCBA CGA 347 VALVE ADAPTER

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Ssgmac

Ssgmac

Member
May 19, 2018
23
3
California
Hi nube to the forum, 46 years exp with airguns . However, nube to the SCBA tank. I had been using high pressure SCUBA tanks til I bought my own high pressure air compressor. So far it's been one problem after another. Rolled the dice on one of those MIC $300 compressors and crapped out bad. Got it from an Amazon vendor. They sent me one that apparently had been burned and returned, there was scorched hydrolic oil leaking out of it by the time it had made the long journey to my house. The silver lining is that I got to keep it and got a full refund. If I can't find a rebuild kit for it, at least I'll have a good supply of spare parts and fittings. But that's all a different problem I'm sure I'll post later.

The problem I'm having now is strange. I bought a couple of carbon fiber SCBA 30 min air tanks on eBay. I'm trying to equalize all my SCUBA tanks into the SCBA tanks. I've got all the correct adaptors ..or at least my whip that I put together worked once when I got the first SCBA tank. The dude ended up cutting me a deal on a second SCBA tank. It has the exact same valve on it as the first one does but now, the CGA 347 valve adaptor isn't sealing to the valve. It won't seal up to either of them but nothing appears to be missing . But I don't remember if there was an o-ring or any other kind of soft seal where the rounded over mating survive mates inside the valve. I looked at images of other CGA 347 nipples and they're all without any seal also. When I make up the adaptor(er?) Screws all the way on to both bottles with ease. But when all the threads are buried and it's all snugged up, there's still at least 1/16" ~ 3/32" of free slop in the nipple. Theres nothing left to push that grounded face into the matching profile in the valve. I'm really hoping at least one of the people reading this now is shaking his/her head and face palming and chuckling at what an enormous idiot I am for overlooking something obvious.. meanwhile I'll go through all my welding regulator junk to see if I've got something that I can use to tide me over ... thanks for reading

aim small miss small

MODEDIT moved to Air Tanks & Compressors
 
Thanks for the reply. I checked my regulators parts. I have a bunch of CGA 346 nut n nipple. The nut works but the shaped end of the nipples aren't deep enough to seat at the bottom of the valve. I need to heat up the nipple on the adapter to be able to unscrew it from the rest of the assembly it's got that red thread locking compound on stainless. When I get it off, I was going to swap nuts but I think I just need to get a washer between the nut and nipple. It must have had one in it when I used on the first tank. ..or maybe there was a Teflon bushing that friction fit inside the tip of the nipple. 

Thanks again for the reply
 
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Hi and thanks. 
yea, I havent crossed anything yet. What appears to be different is the nipple only. The CGA 346 nut threads on perfectly to the CGA 347 valve. But what I did was make a round split washer out of a 3/32"Ø brass rod and put it between the back shoulder of the nipple and the nut so now it's like the nut is pushing the nipple into the valve seat from that much farther back, which is about how much more threaded surface I was needing to seat the nipple. I havent tried it out yet. Im still very curious why the adapter worked on the first tank and now it doesn't work on any of them. Im thinking there must have been something like that washer I just made on there before .. Maybe a teflon one and it broke without me noticing . ..but none of the ones I looked at online had anything like that. There are those that have a retaining clip behind the nut to limit it from sliding past it and there were some with o-ring at mating surface of nipple. But mine doesn't have a slot for an o-ring... 
 
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Cool. Thanks for that info on pressure ratings between the 2. I was curious but the places I checked didn't list that info. When I compare the 2 nuts, they're almost identical.. Almost. The 346, however is about .25" less deep than the 347. I was able to fix the problem on the 347 tho so I won't be using the 346 nut on the 347 nipple as I thought I was going to do. But really, a nut that's rated at 3,000 PSI was likely tested at 9,000PSI.
 
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The 347 nut is longer and after screwed on covers all the threads basically. The 346 nut is a lot shorter and on a 4500# SCBA valve leaves a lot of male threads unused. The nipple’s sealing end is also longer on the 347 than the 346’s. I’ve bought the 347 fittings at welding supply shops but they are are some sort of brass alloy and not the stainless which I prefer. Be sure and always use the proper fitting around this high pressure sport. 
Jimmy
 
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Thanks, I drew that same conclusion and decided to make a round brass washer out of a 3/32"Ø brazing rod. That 3/32" of space is just enough to set the nut far enough behind the nipple that now it seats the face of the nipple into the valve seat on the tank. But im still very curuous about what changed between the first time I used it (and it worked) and now. Now the nut makes all the way up on the threads on the valve. Causing the nut to tighten up while the nipple is still a good 1/16" away from seating. Anyway, thanks again for your comment
 
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