Quiz - Equipment - J-Valve

[TMHeimer]

I had a spiro 72 with reserve valve when I started diving but never thought of it as extra air or reserve ( which it wasn’t until the dive was over) when I pulled the bar I would move into shallow water and use it. I never dived without a snorkel for that reason.

That makes sense. Much like myself in 20-30' of water breathing my tank down to maybe 100-200 PSI on purpose on occasion, depending on circumstances. In the case of what you did with your 72 tank I agree that your J valve air was neither extra nor reserve. It was planned to be used in shallow water.

 

[TMHeimer]

No, it is not extra air. It is part of your basic air supply that you set aside as a reserve for your ascent. All the J-valve does is alert you that you now need your reserve, and (when pulled down) gives you access to that reserve.

No, I would not have gone to 100 ft with a J-valve unless it had been st to a higher break pressure.

FYI, here is how much gas you need to get to the surface, for an RMV of 0.7 cuft/min, from various depths, for yesterday (60 ft/min and no safety stop) vs today (30 ft/min with a 3 min safety stop). The 450 psi needed from 130 ft, and getting back with 500 pis still in the tank, is where the "leave the bottom at 1000 psi" comes from. All this presumes an AL 80, and no panic.
View attachment 581241

Understood.
Also agree that I may have gone to 100' back then with a J valve if it was set to a higher break value.
Thanks, now I know exactly where the " keep 100' PSI for every 10' you have to ascend" (ie. 1000 for 100') comes from.
So, if you are another who would plan to use the air the J Valve releases as part of your ascent plan (though not if it releases only 300 PSI), this leans me more toward not calling that gas "extra".
The Cousteau writing and the 1968 article explain what the valve is and does and how it works (we all know that). They don't explain if it was intended to be used on every dive or not.

 

[Celt]

That makes sense. Much like myself in 20-30' of water breathing my tank down to maybe 100-200 PSI on purpose on occasion, depending on circumstances. In the case of what you did with your 72 tank I agree that your J valve air was neither extra nor reserve. It was planned to be used in shallow water.

That’s it, compressors we’re scarce we got fills from the local fire station so we used every bit before bringing them for filling

 

[tursiops]

The Cousteau writing and the 1968 article explain what the valve is and does and how it works (we all know that). They don't explain if it was intended to be used on every dive or not.

From the same reference as before, page 143:
"Air Tank Valves
It is impossible for a diver to tell how much time or air he has left in his tank unless his breathing apparatus is equipped with an air-reserve device or a visible air-pressure gauge. The air-reserve mechanism warns you that the air is about exhausted and it is time to head for the surface."

 

[captain]

Cousteau’s group usually used triple 40 cu/ft cylinders. There was no J valve on them. The right side cylinder was the reserve. It had a manually operated shutoff valve on the bottom of the cylinder. When the 80 cu/ft was used up in the center and left cylinders the diver opened the valve and equalized the pressure.

 

[tursiops]

The 1963 book I quoted, twice, was not by Cousteau nor was it about Cousteau's equipment or diving. The guy who wrote it had been in Cousteau's group for a while, and JYC simply wrote the foreward to the book.

 

[CT-Rich]

I think there is applying modern standards to a premodern practice. Pre-cell phone, kids ran wild and if you came home 2 hours late you were yelled at. Today Billy is five minutes lates, he better f***ing answer the phone. Different time different standards.

How a dive went was filled with unknowable things How good was your fill? Much to our annoyance, we all know how variable that can with modern gauges. Unless you had a gauge, you may have barely an idea how bad of a hot fill you got on your tank. Capillary depth gauges get less accurate as you go deeper. A diver in the 1960s would not have known any other way of diving. The 60’ per minute rule was because that was about how fast the smallest bubbles would rise.

The tech today is infinitely better than it was in 1963, which is why we don’t use j-valves. We have SPG and computers that track all sorts of stufff. No one dives square profiles anymore because they don’t have to. Everyone used to carry a snorkel because they didn’t have a BCD and their tank was going to almost certainly be empty once they reach the surface. That was pretty normal. Everyone dove wet. Lights were super expensive and were utter crap by today’s standards

Saying you would have never dove like that assumes you knew any different.

 

[TMHeimer]

I think there is applying modern standards to a premodern practice. Pre-cell phone, kids ran wild and if you came home 2 hours late you were yelled at. Today Billy is five minutes lates, he better f***ing answer the phone. Different time different standards.

How a dive went was filled with unknowable things How good was your fill? Much to our annoyance, we all know how variable that can with modern gauges. Unless you had a gauge, you may have barely an idea how bad of a hot fill you got on your tank. Capillary depth gauges get less accurate as you go deeper. A diver in the 1960s would not have known any other way of diving. The 60’ per minute rule was because that was about how fast the smallest bubbles would rise.

The tech today is infinitely better than it was in 1963, which is why we don’t use j-valves. We have SPG and computers that track all sorts of stufff. No one dives square profiles anymore because they don’t have to. Everyone used to carry a snorkel because they didn’t have a BCD and their tank was going to almost certainly be empty once they reach the surface. That was pretty normal. Everyone dove wet. Lights were super expensive and were utter crap by today’s standards

Saying you would have never dove like that assumes you knew any different.

Agree with all, except I usually (not always) dive square profiles.

 

[CT-Rich]

Agree with all, except I usually (not always) dive square profiles.

Only because you choose to.

 

[captain]

Early J valve with metal ball seat. These would not completely shut off.