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Chris
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US Divers J valve.

Sun Dec 16, 2018 4:43 am

Looking for some advise on my first tank valve repair. Knob was turning verry hard. Far as I can see, there is no copper gasket. Did someone leave it out, or is it smashed in so good I cant see the line? The oring looks square, but I asume thats from being in a square spot for 40 years. Am I close in thinking it looks like a #10 90 durom? Backup ring looks like it can be reused, didnt see them in the store. Rest of the parts are already measured and in my store shopping cart. The seat most likely the A192? Thanks for any tips.
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ScubaLawyer
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Re: US Divers J valve.

Sun Dec 16, 2018 10:42 am

I've rebuilt several. I've never been too scientific about that valve-stem o-ring.  I just dig around in my pile of miscellaneous o-rings until I find one that looks to fit. Never had a problem but I'm sure someone here has the exact size for you. You are correct, it is round, not the funky square set it takes over many decades.  The gasket can get ground in there so it is unrecognizable.  Can't tell from your photo for sure but I don't see it. Maybe ask someone with younger eyes. I usually take a plastic pik and see what I can pry up. I've been surprised before. Try running it through sn ultrasonic cleaner. I've done that before and suddenly the copper gasket has magically appeared. Of course it is also very possible it just got left out at some point. The teflon rings are nearly all reusable. Hope I haven't rambled on too much. I enjoy overhauling valves and manifolds. Don't forget the proper burst disc installed with the proper in/lb torque. Good luck.

Mark
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captain
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Re: US Divers J valve.

Sun Dec 16, 2018 11:16 am

Those valves do not use a copper gasket on the bonnet nut, it is a metal to metal seal. Sometimes you have to tighten and loosen the nut a few times to reform the metal to metal seal. If you find a copper gasket it's because someone thought there should to be one.
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ScubaLawyer
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Re: US Divers J valve.

Sun Dec 16, 2018 11:34 am

captain wrote:
Sun Dec 16, 2018 11:16 am
Those valves do not use a copper gasket on the bonnet nut, it is a metal to metal seal. Sometimes you have to tighten and loosen the nut a few times to reform the metal to metal seal. If you find a copper gasket it's because someone thought there should to be one.
Good to know. I have seen those gaskets in place more times than not (in my limited experience mind you). Just always assumed they belonged there. Guess I should look at manuals and diagrams more as opposed to just winging it. :D
"The diver who collects specimens of underwater life has fun and becomes a keen underwater observer. .. seek slow-moving or attached organisms such as corals, starfish, or shelled creatures." (Golden Guide to Scuba Diving, 1968) :D

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antique diver
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Re: US Divers J valve.

Sun Dec 16, 2018 1:46 pm

Careful about that valve seat. The proper seat for that J-valve has a small center hole all the way through the soft material to the brass carrier. The illustration for the A192 does not appear to have that hole, which would indicate it is for the K-valve. According to US Divers the hole is necessary, but only on the reserve (j-valve) to help prevent extrusion of the seat from air pressure getting behind it. I'll try to find the appropriate bulletin from USD on that subject and post it if I can.

Ironically, that same hole can actually can create a different problem when filling. Prior experience with those valves has shown that it is not completely foolproof, and on a worn valve that soft seat can be extruded from the brass carrier if the often neglected proper procedure for filling your tank through that valve is not followed. That would be first attaching the fill yoke, then next opening the tank valve, and finally opening the fill line valve. Note that opening the fill line valve first can cause the extrusion of the soft seat as your tank valve is opened, then causing a blockage of incoming air to your tank. This is due to the line air pressure entering the hole in the soft seat, which can on occasion cause it to be pushed out to some extent by the air pressure between the soft seat and the brass carrier as you open the tank valve. While it is true that closing the valve will push the seat back into place, once it has moved out and back it has loosened some, and becomes more likely to occur. This is more likely to happen on an older, well-worn valve seat, but it is a good practice to always open any tank valve first before opening the line valve. The tank valve is designed to hold back pressure from the tank, not the other way around. It may appear to operate just fine for many years before this happens, but why stress the seating system until it goes bad?

Virtually all line valves (but not tank valves) that operate with the unscrewing of the seat have a proper flow direction, many having an arrow to indicate the proper flow direction. Disregarding the proper flow direction on those line valves may eventually cause disruption of air flow in the backward direction in some cases... typically more likely on valves with heavy use.
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Chris
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Re: US Divers J valve.

Sun Dec 16, 2018 1:53 pm

Thanks Captain. Glad I was patient and didnt keep digging at it. Scuba Lawyer, Ive dug threw my tool box many times looking for orings. I looked for a schematic last night in the downloads section. I didnt see one, although I think I remember them being there, so I'm pretty sure I missed it. The one in Regulator Maintenance and Repair book was just a generic. Thanks for the info.

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Chris
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Re: US Divers J valve.

Sun Dec 16, 2018 2:00 pm

The seat was working, but with the sticky oring it was hard to shut off all the way. Wonder if the dive shop has the right one with the hole or if they just stick whatever in.

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Chris
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Re: US Divers J valve.

Sun Dec 16, 2018 2:02 pm

If the seat in the store does not have the hole, can it be center drilled? Carefully? I did happen to look at the hole when I removed the seat and thought it looked odd with no ballance chamber.

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antique diver
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Re: US Divers J valve.

Sun Dec 16, 2018 2:49 pm

tripplec wrote:
Sun Dec 16, 2018 2:02 pm
If the seat in the store does not have the hole, can it be center drilled? Carefully? I did happen to look at the hole when I removed the seat and thought it looked odd with no ballance chamber.

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I haven't tried drilling one, but I'll try to measure the hole with index drill stems and let you know what it is.

I could not find the bulletin pertaining to that seat issue. I do know there must have been a specific reason for the hole only being needed on the J-Valve and not the K. I never did figure out the physics of why, and it was not fully explained in the bulletin. Seems like I must have lost a whole notebook of extra info like that, but if it turns up I will post it.
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Chris
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Re: US Divers J valve.

Sun Dec 16, 2018 2:55 pm

Thanks.

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antique diver
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Re: US Divers J valve.

Sun Dec 16, 2018 3:13 pm

antique diver wrote:
Sun Dec 16, 2018 2:49 pm
tripplec wrote:
Sun Dec 16, 2018 2:02 pm
If the seat in the store does not have the hole, can it be center drilled? Carefully? I did happen to look at the hole when I removed the seat and thought it looked odd with no ballance chamber.

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I haven't tried drilling one, but I'll try to measure the hole with index drill stems and let you know what it is.

I could not find the bulletin pertaining to that seat issue. I do know there must have been a specific reason for the hole only being needed on the J-Valve and not the K. I never did figure out the physics of why, and it was not fully explained in the bulletin. Seems like I must have lost a whole notebook of extra info like that, but if it turns up I will post it.
The hole in a new unused seat is the size of a wire gauge drill #63, which is 0.037"
The hole is smaller in both used ones I tried, likely just due to distortion of the material.
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Chris
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Re: US Divers J valve.

Sun Dec 16, 2018 3:21 pm

Gotta alow some room for people to crank that knob down. Thanks.

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