J-valve working pressure

[NAFOD]

I have a set of short-fat 80 cube Fabers painted white that would look pretty slick with Karl's Voit Lung decals and J-valves. The tanks hold 80 at 3440.

So, the question is whether a typical J-valve can handle that overpressure; is it simply a matter of installing the proper burst disc?

And I am assuming the high pressure seat in my Phoenix would be comfy at that pressure too.

[luis]

Most valves will have no problem with 3500 psi, but you may want to be more specific about which valve you are planning on using. Structurally they wouldn’t have an issue…and I can’t think that it would bother anything reserve chamber, like seals, etc.


As it has being mentioned before, the Phoenix first stage is the same as most of the new Aqua Lung regulators. It uses all the parts that Aqua Lung put in their Titan, Conshelf, etc. The seat is also the same as in the Legend.

In any case, it is a balanced first stage and the tank pressure doesn’t affect the seat motion. The sealing pressure on the seat against the volcano orifice is the same at any tank pressure. That is why the IP doesn’t change with tank pressure.

[NAFOD]

Right then . . . so at 3440, my Phoenix will not dribble and squeak at the overpressure. But my question was focused more on the burst disc in the J-valve.

For instance: I have a set of doubles with a solid bar manifold that has a little green sticker that says "2250 PSI Working Pressure" on the bar.

What is the limiting factor? From an engineering standpoint, what limits the "working pressure" of a J-valve?

[capn_tucker]

From what I'm led to understand, the only limiting factor is the burst disc. Put in discs suitable for 3442 psi and you should be good to go.
The aluminum 100s I once had were 3300 psi tanks, and I used old Dacor valves on them for years and years. These tanks would very often have 3500 psi in them, and it didn't faze the old valves..

[luis]

You do need to change the burst disc whenever you put a valve in a tank with a new working pressure, whether it is higher or lower.

Actually you really want to replace a burst disc every few years anyway to avoid premature disc blowout (during hydro is normally good enough).

A burst disc is design to let go at the hydro pressure (the tolerance is supposed to be +0% to -10% of the hydro test pressure). Therefore the disc on any valve is supposed to be replaced for a disc that is designed for a tank of that pressure (or at least close to it).


BTW, the 3442 psi is not an overpressure for the Phoenix anymore that it is an overpressure to any modern regulator.

The only thing that high pressures would have affected is the little O-ring in the balancing chamber, but that O-ring has had a back up ring starting in the late 60’s . The back up ring avoids O-ring extrusion at very high pressures. The newer back up rings are even better at avoiding O-ring extrusion than the early ones in the 60’s (but even those worked fine).

With a DIN fitting you could use the Phoenix to 4500 psi or 5000 psi (actually I don’t see much of a problem using the yoke at higher pressures, but now a day the yoke is not supposed to to be used at higher than 3500 psi).

[pescador775]

The USD solid bar manifold is tremendously strong. It has fewer joints which make it more reliable than some modern types. IOW, it can be carried by the valve with no worries about flexing an O ring joint. some modern manifolds now use three O rings per side which ought to tell you something about their issues.

Use a high quality face O ring, 90 duro nitrile or urethane. As above, install a 4900 or 5000 psi disc. Sherwood part nos are 14120-49 and 14120-50. Torque is 60 lb-ins.