• Welcome to ScubaBoard


  1. Welcome to ScubaBoard, the world's largest scuba diving community. Registration is not required to read the forums, but we encourage you to join. Joining has its benefits and enables you to participate in the discussions.

    Benefits of registering include

    • Ability to post and comment on topics and discussions.
    • A Free photo gallery to share your dive photos with the world.
    • You can make this box go away

    Joining is quick and easy. Login or Register now by clicking on the button

J-valve question

Discussion in 'Vintage Equipment Diving' started by broncobowsher, Jul 14, 2019.

  1. 2airishuman

    2airishuman Solo Diver

    # of Dives: 100 - 199
    Location: Greater Minnesota
    2,385
    1,593
    113
    Historically, they were used before there were reliable, affordable SPGs.

    To some degree, they are still used in blackwater diving where it is not possible to see an SPG.
     
    John C. Ratliff likes this.
  2. 2airishuman

    2airishuman Solo Diver

    # of Dives: 100 - 199
    Location: Greater Minnesota
    2,385
    1,593
    113
    I am going to answer your question from the standpoint of actually having put a pressure gauge on a J-valve cylinder, and from the standpoint of actually having had a number of J-valves disassembled on my bench.

    The answer is that it depends. Here we go:

    1) During the J-valve era, it was common for there to be an SPG port on the valve itself. Typically this was on the cylinder side of both the shut-off valve and the reserve mechanism, so that the SPG would display the actualcylinder pressure regardless of whether a reg was attached and regardless of the position of the reserve lever.

    2) If you use a modern regulator with an SPG on a J-valve, and the reserve lever is in "dive" position, typically, the pressure will fluctuate, going down when you inhale, and up when you stop. On the J-valves I had (two of them), it would typically stop about 300 PSI lower than the actual cylinder pressure and then possibly creep up a little since the reserve seat didn't completely seal all the time.

    The reserve mechanism on these two valves is not complex. It's just a spring-loaded seat that is fully retracted when you put the lever in "reserve." The mechanism is upstream (cylinder side) of the main valve and so is always pressurized. They are prone to stem leaks over the years and parts are unavailable, so I would end up with empty cylinders after a month, and quit using them. I have a Calypso "J" regulator that I use now if I really want to dive with a reserve mechanism. It works the same way, but I can put it on any cylinder I want, and any minor stem leaks that it may have aren't important since it isn't pressurized except when I'm using it.
     
    alpegmusic, Bob DBF and captain like this.
  3. John C. Ratliff

    John C. Ratliff Instructor, Scuba

    # of Dives: I'm a Fish!
    Location: Beaverton, Oregon
    2,688
    1,158
    113
    This discussion has assumed that the J-valve was on a single tank, and in the past that was a single steel 72 cubic foot tank. But as I was trained in the U.S. Naval School for Underwater Swimmers (USS), and later as I served as a USAF Pararescueman, we dove double tanks. In the USS, we dove twin 90 cubic foot tanks (see the photos below of the grey cylinders). In the USAF, it was twin steel 72s and twin 42s (old 20-person life raft CO2 bottles). In both these cases, the J-valve was over one cylinder, and affected only that cylinder. If using a SPG on the regulator, it would not fluxuate, even though 500 psig was being "saved" in one of the two cylinders. When the first cylinder was empty, the second one would have 500 psig. Pulling the reserve allowed the two cylinders to equalize noisily (the buddy could hear it), and it would equalize at 250 psig. That, on a double cylinder scuba, was enough to allow a no-decompression ascent to the surface.

    Now, if a diver used a J-valve reserve on a regulator, which is center-mounted on the twin cylinder rig, and without a J-valve on the manifold, it would be the equivalent of having a J-valve manifold with a 600 psig spring, and the center-mounted J-valve regulator would hold back 300 psig from both cylinders. In the USAF, up until the mid-1970s, we dove a single-hose regulator as a single hose regulator, no SPG, no octopus, no BCD inflator. We also jumped those smaller tanks parascuba, where we really did not want anything unnecessary to be hanging off the scuba as if we got twisted or tumbled by the air turbulance jumping out of a HC-130, for instance, it could tangle in the lines of the deploying parachute (see the photo of Pararescueman Rick Harder, below). Examples of these regulators were the Calypso-J, the Scubair-J, and the Sportsways Navy.

    Now, the J-valve was not the only reserve mechanism used in vintage diving. There was also something called the "restricted orifice" reserve, which made breathing harder at low tank pressures. My first regulator, a Healthways Scuba double hose regulator, had this feature. My second regulator, a Healthways Scuba Star single hose regulator, also had this restrictor orifice inserted behind the sintered filter to warn me of low tank pressures. Healthways made another regulator, the Scubair, with a knob which would allow the diver to select either a restricted reserve (Auto-Reserve), or a J-valve setting if the tank had a J-valve on it (no restrictor orifice reserve). Finally, both Healthways and Scubapro came out with "sonic reserves," in which at low tank pressures the regulator would "sing," or give an audio warning that the diver was low on air. The Scubapro Mk VII was an example of this regulator, which would vibrate into the mouthpiece when low on air.

    That's what we had in the early days of diving, and we did very well with those regulators. With both J-valves for single tanks, and my own J-valve for double hose regulators, we could mount the J-reserve on the opposite side so that it could not be knocked down if inadvertently hitting something too (see the photo of my twin 45s with a Sherwood manifold, reverse-mounted J-valve with a Scubapro Mk VII/Pilot regulator). With both the sonic reserve, and the J-valve manifold, there was some double security for diving. It was like having a 12.5 cubic foot pony bottle if the reserve was not pulled and the diver simply went by the sonic reserve.

    SeaRat
     

    Attached Files:

  4. Ghetto Diver

    Ghetto Diver Solo Diver

    # of Dives: I just don't log dives
    Location: Beerfield Beach, FL
    620
    294
    63
    ^ great post sir.
    I have a Healthways SCUBA and the restrictor works well. I like how simple a design it actually is (a washer basically)

    Is that the jetty west of Yaquina Bay? Spent a few summers there as a kid in the 70s commercial fishing.
    Need more pics of the car :wink:
     
  5. John C. Ratliff

    John C. Ratliff Instructor, Scuba

    # of Dives: I'm a Fish!
    Location: Beaverton, Oregon
    2,688
    1,158
    113
    Ghetto Diver,

    Yes, that was taken at Yaquina Bay, Oregon. We had a dive training weekend for the 304th Aerospace Rescue and Recevory Squadron's Pararescue Team. This was in 1975, I think.

    Concerning the car, I'll look to see whether I have any other photos of it.

    SeaRat
     
    Ghetto Diver likes this.
  6. 2airishuman

    2airishuman Solo Diver

    # of Dives: 100 - 199
    Location: Greater Minnesota
    2,385
    1,593
    113
    You do not mention the "bell" reserve.

    These involved a clapper suspended inside the cylinder, from the bottom of the valve. A mechanism caused the clapper to strike the side of the cylinder for every inhalation after the reserve pressure was reached. I've only run into one and it was missing parts of the mechanism.

    They never caught on.
     
    captain and John C. Ratliff like this.
  7. John C. Ratliff

    John C. Ratliff Instructor, Scuba

    # of Dives: I'm a Fish!
    Location: Beaverton, Oregon
    2,688
    1,158
    113
    That clapper reserve never caught on for a reason. First, it came out when the tanks were made of steel, and so the diver had a bell-like sound clanging with every breath; very disconcerting, but your buddy surely knew when you were on reserve. Second, if there was any rust on the inside of the cylinder, the clapper would knock it off, and that represented a hazard if the rust flakes got into the rod on the bottom of the valve.

    SeaRat
     
    Sam Miller III likes this.
  8. captain

    captain Captain

    8,983
    7,399
    113
    I have a Healthways Scubair Sonic 300 with a sonic reserve. At low pressure it makes a clicking sound on each inhalation.
     
    John C. Ratliff likes this.
  9. vjb.knife

    vjb.knife Angel Fish

    # of Dives: 5,000 - ∞
    Location: the Big Island of Hawaii
    57
    38
    18
    Where I currently work we generally use SCUBA which is the first mistake; they should be using surface supplied air. The second mistake is that OSHA requires us to use J-Valves or pony bottles when working with SCUBA so we have them on all of the tanks, however the pull rods are not attached and we simply have the handles in the down position from start to finish of the dive. My take is, even though I used them when I started diving, they are stupid and should not be relied on or used in any situation. Dive a K valve and monitor you tank pressure closely.
     

Share This Page