The Isolation Manifold, lessons not learned and a small defence of the IUCRR

[Gone for diving]

What about fully open vs 1/4 open?

I tend to run mine about 1/3- 1/2 open
I don't buy, argument that it should be fully open,
So that there is only on way to turn it,

Plus back seating a scuba valve doesn't work any more, it's a different design

If the isolator is closed during the diving.
You are effectively running independent doubles with one pressure gauge,
Or sidemount with one pressure gauge.

 

[p_kos]

What should be and what is are often not the same. If a solution to an extremely rare problem causes more problems, then there is a problem. You can't ignore human factors in process.

Yes, kind of sad that we’re debating getting rid of isolators because people don’t bother with the very basic habit of looking at their SPG every now and then.

 

[Akimbo]

If a solution to an extremely rare problem causes more problems, then there is a problem. You can't ignore human factors in process.

This is the engineering conundrum with every "safety feature", even something as simple as an isolation valve. They add complexity and complicate rapid failure diagnosis. Add sub-optimal human factors to the mix and more people get hurt than helped.

What about fully open vs 1/4 open?

I dive with the isolation valve fully closed, unless I'm packing a third bailout cylinder. I breathe one tank down, open the isolation to equalize cylinders (a clearly audible process), close it, and continue the dive until the next "equalization event". The dive plan uses equalization events to trigger actions, like turn around and head back to the boat or leave bottom.

The technique is called progressive equalization and was developed by Royal Navy divers working in zero visibility. It provides a "hard" reserve throughout the dive but provides more options during a failure than independent doubles.

 

[rob.mwpropane]

Your post was the first time I have heard of this partially-open method.

It's not something that I came up with. Maybe a NJ thing? To me it makes sense, I don't really see a need to fully open?.. but I'm 100% aware that I don't know **** when it comes to diving. So I'm always interested to see what other people do.

I dive with the isolation valve fully closed, unless I'm packing a third bailout cylinder. I breathe one tank down, open the isolation to equalize cylinders (a clearly audible process), close it, and continue the dive until the next "equalization event". The dive plan uses equalization events to trigger actions, like turn around and head back to the boat or leave bottom.

The technique is called progressive equalization and was developed by Royal Navy divers working in zero visibility. It provides a "hard" reserve throughout the dive but provides more options during a failure than independent doubles.

That's really interesting. I believe I saw you post that before but I had forgotten. Do you notice a change in buoyancy on your back throughout the dive?

 

[Vicko]

Something that people here are ignoring.
Most of divers don't fill their own tanks, and my guess that a good deal don't even own their own tanks. So imagine a situation that I personally don't have to imagine, just remember.
You are on a nice relaxed Mediterranean island, diving once a day. You go out for the morning, dive, leave your twins on board and tomorrow morning they are magically filled without you having to do anything. And the last dive of the trip is coming, a beautiful wreck almost 3 hours boat ride away. You check your gear, check the spg, tanks are full. All your friends are splashing, you make one last check of the valves.... and there goes the hissing noise that makes your dive, and the 50 euros of helium in your tanks totally useless. Now you get to sit in the sun on a pitching boat for 3 hours while everyone else (including me) are down there having fun. Trough no fault of your own.
Now sure, that would never happen to super squad on this forum but I personally saw it dozens of times in different, reputable dive operations. Funny thing is I never saw a neck oring or valve stem blow underwater. Neither has anyone I ever talked to about it. And as long as we are worried about a failure that never happens, that isolator adds 3 more points where the said exotic failure can occur, along with the mentioned human error.

 

[Akimbo]

Do you notice a change in buoyancy on your back throughout the dive?

Not that I have ever noticed. It might be more noticeable on a triples rig, which is what Cousteau's divers used on the Calypso (they also use 4-cylinder sets). One cylinder valve was left shut as a hard reserve and equalized into the other bottles when opened. They were single-regulator rigs.

 

[p_kos]

Something that people here are ignoring.
Most of divers don't fill their own tanks, and my guess that a good deal don't even own their own tanks. So imagine a situation that I personally don't have to imagine, just remember.
You are on a nice relaxed Mediterranean island, diving once a day. You go out for the morning, dive, leave your twins on board and tomorrow morning they are magically filled without you having to do anything. And the last dive of the trip is coming, a beautiful wreck almost 3 hours boat ride away. You check your gear, check the spg, tanks are full. All your friends are splashing, you make one last check of the valves.... and there goes the hissing noise that makes your dive, and the 50 euros of helium in your tanks totally useless. Now you get to sit in the sun on a pitching boat for 3 hours while everyone else (including me) are down there having fun. Trough no fault of your own.
Now sure, that would never happen to super squad on this forum but I personally saw it dozens of times in different, reputable dive operations. Funny thing is I never saw a neck oring or valve stem blow underwater. Neither has anyone I ever talked to about it. And as long as we are worried about a failure that never happens, that isolator adds 3 more points where the said exotic failure can occur, along with the mentioned human error.

Sure, the point is you didn’t die because you actually checked the valve before you splashed. Missed a dive because the operation made a filling error. You’re alive and they owe you. Refund or better. Where’s the problem? Same outcome if they forget to do a fill at all, sucks but no emergency. If you didn’t check your valve, you splash and should notice the problem if you look at the SPG at some point within the next half hour. Again, you catch the problem, open the valve if you think of it, or cut dive short. Operator has to answer for a sh@t fill job. If you dive doubles and don’t regularity check valves and monitor the SPG perhaps Darwin is at it again. Diving requiring doubles carries inherently greater risk and isn’t for everyone.

 

[rob.mwpropane]

Something that people here are ignoring.
Most of divers don't fill their own tanks, and my guess that a good deal don't even own their own tanks. So imagine a situation that I personally don't have to imagine, just remember.
You are on a nice relaxed Mediterranean island, diving once a day. You go out for the morning, dive, leave your twins on board and tomorrow morning they are magically filled without you having to do anything. And the last dive of the trip is coming, a beautiful wreck almost 3 hours boat ride away. You check your gear, check the spg, tanks are full. All your friends are splashing, you make one last check of the valves.... and there goes the hissing noise that makes your dive, and the 50 euros of helium in your tanks totally useless. Now you get to sit in the sun on a pitching boat for 3 hours while everyone else (including me) are down there having fun. Trough no fault of your own.
Now sure, that would never happen to super squad on this forum but I personally saw it dozens of times in different, reputable dive operations. Funny thing is I never saw a neck oring or valve stem blow underwater. Neither has anyone I ever talked to about it. And as long as we are worried about a failure that never happens, that isolator adds 3 more points where the said exotic failure can occur, along with the mentioned human error.

Just playing devils advocate... on a dive that cost $1000's to get there you're going to let the crew who makes minimum wage take care of all your gear needs? I've honestly never been on a boat where they do that, so I don't know..

A the end of the day that's still a human factor error rectified by a pre dive check list.

 

[PfcAJ]

Ok.. for all you tech certified folks.. do you dive with the isolator all the way open, or just 1/4-1/2 open.. a few turns? In the event of catastrophic hell fire wouldn't it be easier to turn it 2 or 3 times to closed flow as opposed to ALLLL the way off?

The way I do it now is fully open when filling, fully open for travel and at the site, but closed all the way and then opened 2-3 good turns right before I get the doubles on my back.

Also, if I plan to whip from tanks at the SI for another dive I try to remember to close the isolator ~ 15 min or so before the dive is over so it's more gas for the next dive. (All OW stuff, no tech).

None of these were my ideas, just stuff I picked up from better divers (or maybe worse, Idk) along the way. Thoughts?

And @cerich I think you had mentioned pilots and their errors in a post due to the layout of the panel. It's also true that a lot of pilots have made mistakes not following a check list. I know CCR guys use them, or at least are supposed to. Gareth Locke supports them. Why not instill checklists more so than doing away with something "could" become beneficial 1% of the time? Honest question... not at all trying to criticize your post.. here to learn. Wouldn't a good predive checklist eliminate any issues with the isolator?

I was at the airfield a day after there was an accident. The pilot who had owned the plane for more than 20 years forgot to turn on the fuel pump. It's plain as day in the checklist, he just forgot to do it... after 20 years of doing it all the time. Thankfully he landed in an open field without injury and the plane only had minor damage. I think about that all the time.

All the way open.

Valves are either open or closed. Anything else leads to ambiguity, and ambiguity + stress + limited time isn’t a great combo.

 

[p_kos]

Just playing devils advocate... on a dive that cost $1000's to get there you're going to let the crew who makes minimum wage take care of all your gear needs? I've honestly never been on a boat where they do that, so I don't know..

A the end of the day that's still a human factor error rectified by a pre dive check list.

Which in his example was rectified/mitigated by a pre-dive check. Not sure if the point was we should worry about isolators, or perhaps even avoid them, because a fill station operator may be incompetent/complacent? If you partake in valet diving you risk the odd issue anyway, and if you partake in valet diving without double checking your gear your risk is compounded greatly.