J valves - question

[NAM001]

Boy this goes way back. single j , doubles k and j , r and j. they all had j valves in the 60's and 70's. the j was the backup air. few had k valves and hp gage. the j was a valve that definately had its pro's and cons to it. i too have run short on air from my rod being pulled. not to worry we had our trusty co-2 horse collar to get us home. of course my first set of scuba was 200.00 health ways tank and reg 95.00 fins mask and snorkle 40.00 1/4" wet suit 50.00 weights and belt 15.00. cns was refered to as anoxia and that was at 297 feet.

boogey you talked about the reserve in the tank sounds like you are thinking that is a tank in a tank or something. its just one tank with a valve that is only open when the tank has 500 lbs or more in it. to hold the valve open below 500 lbs.. you had to pull the rod to override the valve. when you filled you pulled the rod and charged to 2250 and then raised the rod and you were sert to go. all that others have mentioned buddy breathing and the like is all in the past. ballasting was done right the first time as you did not have such things as bc's. suit squeeze was the ballast dragon to beat but that did not hit till 40 ft. the more i think about it i am not sure if things are simpler or more complex now??????? lots of thought replacing tech stuff.

 

[Hoyden]

Old school diving - early 70s - no certification required - basic dive training - don't hold your breath on the way up and when it starts getting really hard to breathe, pull the lever and it's time to come up. By the way, J-valves meet OSHA requirements for redundant breayhing supply and so are used in some circumstances for that purpose.

Jackie

 

[miketsp]

Old school diving - early 70s - no certification required - basic dive training - don't hold your breath on the way up and when it starts getting really hard to breathe, pull the lever and it's time to come up. By the way, J-valves meet OSHA requirements for redundant breayhing supply and so are used in some circumstances for that purpose.

Jackie

I find it very hard to accept that a single j-valve could be considered a REDUNDANT breathing supply under any circumstances.

It is however considered a RESERVE breathing supply.

There is a vast difference between the two.
*********************
(4) A diver-carried reserve breathing gas supply shall be provided for each diver
consisting of:
(i) A manual reserve (J valve); or
(ii) An independent reserve cylinder with a separate regulator or connected to
the underwater breathing apparatus.
(5) The valve of the reserve breathing gas supply shall be in the closed position
prior to the dive.

 

[Ber Rabbit]

We used J and K valves at the university until 5 years ago when we replaced our tanks. We never used the reserve feature and the students had no trouble remembering the J-valve needed to be in the down position. If they forgot it was no big deal because they were supposed to be standing on the shore at 500psi anyway. Recently we cleaned out our dive locker and threw away the old valves after selecting a couple of the nicer ones to keep for demonstration purposes. I even found 2 of the hooks they used to use to activate them when scuba first started at the university. I always like the J-valves because the two knobs were easier on your fingers than a single knob and a burst disk when carrying them by the valve.
Ber :lilbunny:

 

[Hoyden]

I find it very hard to accept that a single j-valve could be considered a REDUNDANT breathing supply under any circumstances.

It is however considered a RESERVE breathing supply.

There is a vast difference between the two.
*********************
(4) A diver-carried reserve breathing gas supply shall be provided for each diver
consisting of:
(i) A manual reserve (J valve); or
(ii) An independent reserve cylinder with a separate regulator or connected to
the underwater breathing apparatus.
(5) The valve of the reserve breathing gas supply shall be in the closed position
prior to the dive.

You are correct - the OSHA used term is "reserve" - at any rate, J-valves may be used to satisfy OSHA requirements - see CFR 1910.424(c)(4)(i) as quoted above.

Jackie

 

[Darnold9999]

Re depth guages - my first depth guage was a tiny capillary tube closed at one end mounted around a plastic disk with depth markings, worn like a watch. As you went down the water crept up the tube and the barrier line between water and air showed your depth. As long as you started with no water in the tube - it worked like a charm. Cost was minimal.

Re J valves - started diving with one, was part of the buddy check - lever up, and was something I checked as the pressure guage wound down. Didn't want to get to need the reserve and find the lever already down. Became a habit to reach back and check, something like checking the pressure guage is now.

Pressure guage was standard equipment, octo was not except for instructors - too expensive. Horsecoller BC which I don't miss. This was PNW in late 70's

 

[AndrewK2]

some of the rental cylinders at my dive shop still have j valves on them, but like others said, we just use them as if they were k valves.

In terms of K valves, I've never really understood why they (or other valves) need to be turned back half a turn when being used - can someone explain that?

 

[Walter]

They don't need to be turned back half a turn. Some folks turn them back, others don't. If you do turn it back, turn it back just a tad (that's a very precise measurement). The theory is a valve (any valve, not just a SCUBA valve) can get stuck in the open position.

 

[Darnold9999]

Had a valve that did exactly that. If you cranked it open too hard or left it in the full open position for a dive it required pliers to close it. If you were more gentle and backed it off a tad no problem.

 

[dherbman]

If you do turn it back, turn it back just a tad (that's a very precise measurement).

How many tads in a skosh? Come to think of it, I think a skosh is the metric equivalent of a tad.

The 'honking' Scubapro reg was a MKVII. You could feel the oscillation as well as hear it on every inhalation. J's were the valve of choice, but only in combination with a SPG during the mid-late 70's. I'll have to check my old Jeppesen manual tonight.