Is there still a place for the J valve?

[fisherdvm]

Isn't your tank and valves fairly reliable. More so than your regulator. Don't you save more weight by packing all your air into one tank? Don't they make a valve that actually have 2 valves on it.

So, instead of carrying a pony, wouldn't there still be a place for simply a J valve, and two firststage/reg mounted on two valves? If you ignored your SPG, hopefully your J valve is in the up position?

Is this a stupid question? Of course, you can answer it by voting one star.

 

[300bar]

Ok I gave you the 1 * i've seen to many J valves fail,due to age, bad maintenance and user error.
Don't know if you even can get a new one,have not seen a new one for years.
Only divers I know still use them are navy and fire dept. but they work in a NO viz. situation and can't see a SPG.
For rec.diving better to stear clear of them.

just my 0.02 cts

 

[SDAnderson]

The J-valve is a dangerous anachronism and should be disabled or, better yet, replaced. They never were an effective solution to the problem of monitoring your air supply, which is why they were replaced by the spg.

 

[spectrum]

fisherdvm

You really pretzeled two concepts in your question.

For redundancy you can put an H valve on your cylinder and have 2 independent air delivery systems working from one supply. Assuming it contains enough air, you monitor your supply and can shut down a failed subsystem quick enough it is fairly redundant.

The J valve as a gas management tool is past it's day. It was better than nothng i it's heyday. As gas management goes it's a step below "get back on the boat with 500 PSI".

Pete

 

[fisherdvm]

Thanks, you guys. That is kinda neet to understand who still would use them - I mean folks who work in limitted vis. And I guess the H valve has value in redundancy. I imagine, if your reg had a free flow problem than you can reach back, turn the air off. Turn the other valve on, and use the back up regulator.

The only situation where the H valve might not do is probably in a high pressure hose break, or a first stage blow out, right? Where even 30 seconds would drain your tank.

 

[spectrum]

The only situation where the H valve might not do is probably in a high pressure hose break, or a first stage blow out, right? Where even 30 seconds would drain your tank.

A HP hose failure is the least of your concerns. It is fed by a very small hole since it only presents cylinder pressure to the SPG.

A stage blowout or LP full failure your require immediate intervention.

The H Valve would be normally left all on. You would shut a side down in the event of a failure.

 

[fisherdvm]

How fast would your tank drain in case of a stage blowout or LP full failure? Probably as fast as if you fully opened your scuba tank, right?

3 minutes maybe? And if you reached back and turned that off, you should have enough gas on your back up, right?

Of course, it might be hard to decipher which valve to turn off if it were a first stage failure, unless your buddy saw it for you.

 

[spectrum]

80 CF can be lost in several minutes with an open LP line. If you search enough someone actually collected data on this a year or 2 back. As I recall 3 minutes was in the ballpark. Question 1 is how much gas do you have at the moment of failure?.

I have no experience in deciding which to shut off. I suspect it would be very scenario dependent but if your primary starts working hard that might be a clue but not 100% definitive. A buddy would be handy!

Pete

 

[Buoyant1]

Thanks, you guys. That is kinda neet to understand who still would use them - I mean folks who work in limitted vis. And I guess the H valve has value in redundancy. I imagine, if your reg had a free flow problem than you can reach back, turn the air off. Turn the other valve on, and use the back up regulator.

The only situation where the H valve might not do is probably in a high pressure hose break, or a first stage blow out, right? Where even 30 seconds would drain your tank.

I'm working on getting that set up (my cylinders have modular valves, just need the second 1st & 2nd stage set up for it) I like that configuration for cold water diving although (knock on wood) I haven't had a free flow issue it seems like a viable solution on a single tank dive!

J valves? hmmm do they still make them?

 

[johnny_bravo]

Yes. In a dive museum

Cheers.

-J.-