K valve vs J valve

[Walter]

The J & K getting their names from the US Divers Catalog (1953?) is true, although I'm pretty sure the H got its name (as did the Y) from its shape.

Sounds like you have a J valve. Does the extra knob have a tab on it? Does this knob only turn about 45 - 50°?

I've never seen a J valve with the knob on the top, all of those I've seen were K valves.

As long as your J valve is in good condition there's no reason to replace it.

DSSW,

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[TwoBitTxn]

Thanks everyone.

Yes the knob has a little tab on it with a hole and it doesn't turn very far. The shop where I took it to get hydro'ed confirmed it was a J valve. I really don't see any reason to replace it. It just looks different from all the other valves and it will make it easier to find in a cluster of tanks. It all looks in really good condition.

Thanks again.

Tom

 

[Ontario Diver]

Tom;

Most of the J's that I see have been changed to Ks by having the second valve removed and plugged. Might be worthwhile to have the shop do it at some point so you don't "lose" 300 PSI while diving some day.

 

[The Chairman]

With OD! Thats why they always give me the heebie jeebies when I see one. All you need is some kid playing with it with out your knowledge. Walter, I have one that I took out of service and the valve is on top with the switch a lot lower and on the side.

 

[Walter]

Pete, thanks. I've never seen one, but there's lots of gear I've never seen being a relative new comer to the sport.

DSSW,

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[The Chairman]

Sarcasm does not become you. Should I take a picture of it for you??? I am sure that I can get hold of a digital camera to do that. It is an "AMF" valve and has a tiny little "T" on the top for the valve, and the switch is a stubby lever with a hole drilled in it about 2" or so below the valve. It came off of a steel 72, that I don't own anymore.

 

[Walter]

Pete, I was serious - no sarcasm. There is lots of gear I haven't seen. I enjoy learning about other things. I mean it - Thank you.

DSSW,

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[TwoBitTxn]

All the valve does is cut off access to the last 300-500psi correct? I check it the same as I check to make sure my air is on and all is ok. I don't understand how replacing it would be a priority.

Tom

 

[Ontario Diver]

Tom;

The problem is that some of the older valves can stick or slide.

The way that the J valve works is at the beginning of the dive the reserve valve is closed but it is on a spring set to about 300-500 PSI (I know PSI isn't the right measurement but it it simpler this way and I'll just pretend that every thing is perfect and it is a perfect spring set exactly at 500) so as long as there is more that 500 PSI in the tank the spring is pushed back and air flows. When the tank pressure drops below the spring threshold pressure- the spring has more power than the air pressure and it closes. As the diver, you would pull on the rod (Which you don't have on and reaching behind your back is dificult) to release the last 500 psi by opening the reserve valve.

The problem is that your SPG will read the tank pressure quite well. It doesn't know about the 500 PSI thing. So if the reserve valve is mistakenly turned on or slips on or whatever, you'll find out only when your SPG goes from 501 to 0 in one breath. If you get the spring and valve seat/pin removed - the problem goes away.

If the valve is old it may slip and do you know which way is opened and closed? I remeber that up was off and down was on but I wouldn't bet on my recollection.

I hope that this helps. If I didn't make it clear enough just pop a message to me and I'll try again or I'll give you my AIM handle.

Matt

 

[Walter]

J valves are fine as long as they are serviced and in good working order. Leave the J down and it works exactly like a K valve. I've heard of them getting knocked down when they should have been up, but never the other way around. If it were mine, I'd have it serviced, but as long as it's in good condition, I wouldn't replace it.

DSSW,

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