Crossbar and isolator valve: do they help?

[Akimbo]

The interesting thing about valve checks and breathing both regs is that it won't catch a closed isolator if you're convinced you're turning the isolator in the correct direction.

I normally operate with the isolation valve shut for Progressive Equalization. The concern there is to check that your iso valve is fully shut and not leaking, but you can do that by comparing gauges. It is easy to do with a valve-down rig and the protector keeps any valves from being accidentally changed.

 

[tbone1004]

I normally operate with the isolation valve shut for Progressive Equalization. The concern there is to check that your iso valve is fully shut and not leaking, but you can do that by comparing gauges. It is easy to do with a valve-down rig and the protector keeps any valves from being accidentally changed.

to do that effectively you have to get a bit weird in the pressure gauge side of things with a gauge on the primary regulator side. Just means either 2spg's, moving the spg to the right post, or moving the primary to the left post. Not really something I'm interesting in futzing with and I'll keep my indy's...

 

[2airishuman]

to do that effectively you have to get a bit weird in the pressure gauge side of things with a gauge on the primary regulator side. Just means either 2spg's, moving the spg to the right post, or moving the primary to the left post. Not really something I'm interesting in futzing with and I'll keep my indy's...

Not necessarily. You can equalize before you check the SPG.

 

[tbone1004]

Not necessarily. You can equalize before you check the SPG.

yes, but then you are guessing on when to equalize. If you have known "milestones" that require you to equalize, you can just equalize and go from there or do it on a time interval vs doing them in predetermined pressure intervals

 

[2airishuman]

yes, but then you are guessing on when to equalize. If you have known "milestones" that require you to equalize, you can just equalize and go from there or do it on a time interval vs doing them in predetermined pressure intervals

I don't get it. There's never a reason to refrain from equalizing unless you've blown a burst disc. Progressive equalization isn't a technique I use routinely, but if I did, I would have no hesitation about reaching back to open the isolator every time I wondered how much gas I had.

 

[Akimbo]

to do that effectively you have to get a bit weird in the pressure gauge side of things with a gauge on the primary regulator side.

I use a Cobalt on the primary and an SPG on the backup side for long decompression dives. I just use the Cobalt most of the time since the original purpose of Progressive Equalization was there was no SPG or you couldn't see it.

 

[tbone1004]

@2airishuman it's not about when you're curious about how much gas you have, it's about strategically keeping gas in reserve.

From what I understand and @Akimbo can correct me, the initial process went something like this
Start full and isolate
Breathe until you felt resistance which meant that tank was empty
Open isolator until it equalized and close
Breathe until you felt resistance
Open and ascent.
That meant that you consumed 3/4 of your gas supply on the bottom and had a quarter to get to the surface. Great for working dives when you don't always know if you can read the SPG if you had one *which back then they probably were only diving with J valves.

You can't use this for penetration dives since your interval goes in halves not thirds.

In a more modern sense, you could use that for strategic gas reserves if you had the ability to monitor your SPG and do something like this.
Isolate and breathe until you hit 2/3's of one tank. I.e. 800, 1000 or 1200psi depending on the fill
Open and turn the dive
Close and breathe until some arbitrary number. For me that would be about 500psi
Open and close

Assuming a normal cave dive and true equal penetrations it'd look like this
Start at 3600, turn at 1200.
1200 becomes 2400 at the turn with 2400psi in the bank on the left
Come out until 600psi, open and it becomes 1500psi
Exit cave with 900psi in one tank, 1500psi in the other
Open isolator and end up with 1200psi.

In any event, when you had to air share, you would always have more gas in your tank than the guy breathing the primary which would give a better chance at getting out. If I'm diving in manifolded doubles and have a real OOA incident, the isolator gets closed as soon as the situation mostly resolves and we start moving. I don't want a panicked diver sucking down my gas to get out and causing a double fatality. *obviously in a cave that's resolved in sidemount or independent doubles and with more conservative gas planning in the real world, but I do isolate in a real or simulated OOA scenario for that reason

 

[Patoux01]

I don't want a panicked diver sucking down my gas to get out and causing a double fatality.

What do you think happens when he's out of air and he sees you bubbling around?

 

[tbone1004]

What do you think happens when he's out of air and he sees you bubbling around?

with proper gas planning it shouldn't come to that and you can always open it strategically on the way out. OOA diver is also in front on the exit

 

[PfcAJ]

If I'm diving in manifolded doubles and have a real OOA incident, the isolator gets closed as soon as the situation mostly resolves and we start moving. I don't want a panicked diver sucking down my gas to get out and causing a double fatality.

And what if you're the one with the increased consumption rate? Furthermore, wtf do you think is going to happen if your oog buddy's tank runs out and he looks over at you breathing? You're gunna get straight up mugged for that 2nd stage. Then you're both FOR SURE going to drown.

Bad approach all around. You should stick to solo diving.