Quiz - Equipment - J-Valve

[Scuba-74]

Don't forget the lowly P-valve.

P-valve is not something you mount on a tank, but rather a drysuit I assume?

That would make a good quiz question. Which of these you DON'T want to attach your regulator to?

 

[tursiops]

This was a problem with American J-valves. The Technisub J-valve, which was the most widely used here in Italy, had a spring-loaded mechanism, which avoids the lever can be pulled down accidentally, until the pressure drops below the activation point.
Here you see it on the Aralu twin set (we own two, one is mine and one is my wife's):
View attachment 579989

So how did you fill the cylinders if they were only partly empty?

 

[Doc]

I have a bunch of tanks with J Valves

Maybe you, too?

None of them still have the wire pull-down activation rod thingy.

I believe that my wife uses them to retrieve cat toys from under the refrigerator.

 

[emoreira]

US Divers catalog in the 1950s had the valve with the reserve labeled J and the valve without the reserve labeled K, still called the K valve.

Having dived a J valve for 10 years from 1970-80, this was an easy question for today's quiz

 

[tursiops]

View attachment 579995

Cool. Thank you for this. The pix goes into my teaching bag....

 

[Angelo Farina]

So how did you fill the cylinders if they were only partly empty?

If the pressure is above the set point for the spring, the valve is open, so the air will flow in. So when you fill the cylinder, you first try pulling the rod down. If it comes back up, driven by the spring, there is no problem, it means that the internal pressure is above 50 bars, the valve is open and you can charge.
If the lever stays down, it means that the pressure is below 50 bars, so you must leave the lever down for filling, as usual. When the pressure reaches 50 bars, the valve pops up with a loud "click", driven by the spring. And charging continues without problems.
Last point: if the pressure is below 50 bars, and you push the rod down, there is a retention mechanism, which impedes (or makes very hard) to bring it up by hand. It will come up only automatically, by charging the cylinder with more than 50 bars.
This valve was a masterpiece of engineering, as many things manufactured by Technisub.

 

[tursiops]

If the pressure is above the set point for the spring, the valve is open, so the air will flow in. So when you fill the cylinder, you first try pulling the rod down. If it comes back up, driven by the spring, there is no problem, it means that the internal pressure is above 50 bars, the valve is open and you can charge.
If the lever stays down, it means that the pressure is below 50 bars, so you must leave the lever down for filling, as usual. When the pressure reaches 50 bars, the valve with pop up with a loud "click", driven by the spring. And charging continues without problems.
Last point: if the pressure is below 50 bars, and you push the rod down, there is a retention mechanism, which impedes to bring it up by by hand. It will come up only automatically, by charging the cylinder with more than 50 bars.
This valve was a masterpiece of engineering, as many things manufactured by Technisub.

Fascinating. Our J-valves HAD to be down to fill them....and the most common problem was forgetting to put it back up before diving. When the breathing got hard, and you reached back to pull the rod, it was not a good feeling to find that the rod was already down, having been left there by mistake after filling.

 

[TMHeimer]

Another PADI "trick" question. I put A, because that is what it was intended for. But "both A & C are correct" could also be marked right. Why must they do this?
I got 98% on the OW exam. The one I missed was--
Cause of DCS is:
A) too deep, too long.
B) hung over
C) exercised beforhand (not sure, could've been something else like not enough sleep, etc.)
D)all of the above

A was the correct answer. D could be correct beacuse B & C can contribute to DCS (Perhaps not much if the diver is well within limits, but....). My instructor said she would have also marked D correct & I should have gotten 100%.
No need to be cute with these. Plenty of ways to spell it out so there is no confusion. Maybe they just don't check thoroughly what they write at times?

 

[Scuba-74]

Another PADI "trick" question. I put A, because that is what it was intended for. But "both A & C are correct" could also be marked right. Why must they do this?
I got 98% on the OW exam. The one I missed was--
Cause of DCS is:
A) too deep, too long.
B) hung over
C) exercised beforhand (not sure, could've been something else like not enough sleep, etc.)
D)all of the above

A was the correct answer. D could be correct beacuse B & C can contribute to DCS (Perhaps not much if the diver is well within limits, but....). My instructor said she would have also marked D correct & I should have gotten 100%.
No need to be cute with these. Plenty of ways to spell it out so there is no confusion. Maybe they just don't check thoroughly what they write at times?

D makes sense. But this exam is one of those exams where you supposed to just blindly plug in answers from the book you just read, and won't remember tomorrow.

 

[scubadada]

Hi @Pedro Burrito

I have found the discussions around your quiz questions quite interesting, and a nice diversion. Thanks