The Tank Valve Feathering/Modulation Technique

[Kevrumbo]

First read about it in some of the old Rec Scuba & Yahoo newsgroups; and AG mentioning it as a last resort contingency for overhead egress during my advanced wreck class in 2005 (but not actually performing the skill during training). The first time I actually did it was for real on single tank in Cozumel 2006 --and now occasionally practice it although I mostly dive backmount double manifolded AL80's here in SoCal homewaters.

Anyway, IIRC one post was in reply to George Irvine's suggestion of "pinching the hose" as an option to stop a non-fixable free-flow; the better solution came from a European DIR diver (Peter Steinhoff??) who recommended that on a reg-freeze free-flow to just shut-down the malfunctioning post (double manifolded cylinders). The main point is that gas is still accessible from that post, but you or a buddy would have to manually feather & manipulate the valve in order to control gas flow from it.

This is the reason why this skill should be taught at the beginning BOW/AOW level: If a novice diver on single tank at basic OW depth 18m/60' --with no buddy in sight-- has the option & ability and can successfully make the effort to conserve as much free-flowing gas by the valve modulation/feathering breathing technique, what he gains is time --time for the Buddy to find him and gas share. If not, then perform a "modified" Controlled Emergency Swimming Ascent (CESA) while taking breaths as needed by the valve modulation technique as described above. If possible & skilled enough to hold depth, do a safety stop. At the very least, the main objective is to safely reach the surface without suffering an AGE and with some tank pressure left to adequately inflate your BCD and Drysuit. You don't want an "out-of-the-frying-pan-into-the fire" SoCal worst case scenario of surfacing with an empty tank; getting tangled in kelp; inability to orally inflate the BCD because you're out-of-breath having just performed a conventional CESA; shrink-wrapped drysuit hampering mobility; and working hard treading water to maintain positive buoyancy in a typical prevailing 2' to 4' afternoon swell & wind chop --you had better at least be able to drop your weights!

To recap on an Uncontrolled/Unfixable Free-Flow:
Shut your tank valve down. When you need to take a breath, crack open the tank valve and shut it down again. Repeat as needed, switch to your back-up reg/octopus as well if the unregulated flow of gas from the malfunctioning primary reg is too much to handle. Perform this tank valve "feathering/modulation" technique while doing a CESA (if your buddy is nowhere to be seen and you're essentially solo). . .With your left hand, slow your CESA rate via BCD/wing hose deflator dump button . . .with your right hand reach back, feather/modulate your tank valve and take breaths as needed.

All it takes is practice (and IMHO --should be a mandatory skill taught in basic open water courses. . .)

The motivation after realizing that you can breath off a catastrophic non-fixable free-flowing 2nd stage reg, is to shut down the tank valve to stop further hemorrhaging of precious breathing gas. If you have a pre-dive Rock Bottom Gas Plan and you know how much pressure your tank has during all phases of the dive --you lose or become separated from your Buddy for an instant-- then why would you let vital breathing gas bubble away because of an unfixable free-flow on an emergency surface ascent? Especially if you have the ability to reach and manipulate your tank valve on & off to take breaths while not panicking, maintaining buoyancy at depth, spending a moment on the chance that your buddy will find you again? And if not, then how about a nominal ascent with a safety stop while still modulating your tank valve as needed for breaths?

The actual incident that happened:
Cozumel 2006, my adjustment knob on the second stage blew-out resulting in a catastrophic nonfixable free-flow, on a single-tank dive in 6m of depth, during a weightbelt lead check. I actually could see the gauge pointer/indicator hand on the SPG sweeping from 200 through 150 bar literally in an instant before reaching back to shut-off the cylinder valve. Switched to my bungied back-up reg around my neck and then modulated/feathered the tank valve behind my head while doing a CESA. (Again, this should be a skill regularly practiced starting in basic open water).

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A ScubaBoard Staff Message...

Thread Closed!!!

Unsafe Diving Practice advocated!

From our ToS

ScubaBoard Moderators may at their discretion, remove any post which advocates unsafe diving practices as defined by the major certification agencies of the scuba diving world. While ScubaBoard does not take an official position on these matters, ScubaBoard does encourage users to maintain safe diving practices. You and you alone are responsible for your diving safety.

As of this point in time, no known agency currently teaches or advocates this practice and for many good reasons. Fortunately, many have already debunked this solution looking for a problem as being dangerous and overly taxing of a new diver's skill level so we'll be closing it and not simply deleting it. If at such time an agency includes it in their syllabus, we will reopen the thread.

Again:

This technique is not currently taught or advocated by any agency. Trying to make it work can cause injury and even worse: death. Please dive safely and take the advice of real instructors and not someone trying to prove something.

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[Redshift]

At OW level I don't see that as necessary or even as an advantage. There was an experiment https://www.advanceddivermagazine.com/articles/lifeendingseconds/lifeendingseconds.html and discussed on this board http://www.scubaboard.com/forums/ba...-drain-80-cubic-foot-cylinder-4-failures.html where they showed that a free flow would drain an 80 cuft cylinder. At the surface it took 255s, at 99ft 155s. An OW diver will be limited to 60ft. Let's assume he has half a tank when the problem happens (when closer to the end of the dive and approaching the agreed pressure to go up, the divers will be together...) and, since we don't know the exact time it would take to drain the tank at that depth, let's say 200s for full, 100s for half. Takes 120s to get to the surface (although PADI even allows for a maximum ascent rate of 60 feet per minute http://www.scubaboard.com/forums/advanced-scuba-discussions/481272-ascent-rate-ssi-vs-padi.html which means 60s to get to surface). I think a diver in that situation will have time to go up and trying to do that procedure while going up in the blue would be more dangerous for an OW diver.

And you talk about saving air, but in your situation you changed to your octopus, therefore wasting the air coming out of your primary every time you opened the cylinder. Not hard to breathe from a free flowing reg.

 

[Ste Wart]

Mods; can we move this to a more visible part of the board? Advanced Scuba discussions?

 

[Kevrumbo]

At OW level I don't see that as necessary or even as an advantage. There was an experiment https://www.advanceddivermagazine.com/articles/lifeendingseconds/lifeendingseconds.html and discussed on this board http://www.scubaboard.com/forums/ba...-drain-80-cubic-foot-cylinder-4-failures.html where they showed that a free flow would drain an 80 cuft cylinder. At the surface it took 255s, at 99ft 155s. An OW diver will be limited to 60ft. Let's assume he has half a tank when the problem happens (when closer to the end of the dive and approaching the agreed pressure to go up, the divers will be together...) and, since we don't know the exact time it would take to drain the tank at that depth, let's say 200s for full, 100s for half. Takes 120s to get to the surface (although PADI even allows for a maximum ascent rate of 60 feet per minute http://www.scubaboard.com/forums/advanced-scuba-discussions/481272-ascent-rate-ssi-vs-padi.html which means 60s to get to surface). I think a diver in that situation will have time to go up and trying to do that procedure while going up in the blue would be more dangerous for an OW diver.

And you talk about saving air, but in your situation you changed to your octopus, therefore wasting the air coming out of your primary every time you opened the cylinder. Not hard to breathe from a free flowing reg.

To use an analogy: Why would you attempt to sip water from a full blasting fire hose if you have the ability to control the flow via a hydrant valve?

On the contrary, Curt Bowen's Advance Diver article is precisely why this technique is more vital to perform. Together with the air siphon technique for a controlled ascent, a single tank novice diver from the BOW limit of 18m/60' should be able to reach the surface, or at least approach near surface before exhausting the tank & having to "blow-and-go" the remaining but shorter vertical distance.

Difficult skill to coordinate and takes lots of practice . . .but better than letting your gas bleed away.

 

[Dsix36]

I think it might very well be a bit too much for BOW to grasp, learn, and actually master. Perhaps at the AOW level the student may have enough experience, comfort, and confidence to be more able to accomplish this task.

I could be all wrong. There is a first time for everything.

 

[Kevrumbo]

I think it might very well be a bit too much for BOW to grasp, learn, and actually master. Perhaps at the AOW level the student may have enough experience, comfort, and confidence to be more able to accomplish this task.

I could be all wrong. There is a first time for everything.

Perhaps for now . . .but like any new skill it takes time to practice it in order to use it effectively. But that should not be an excuse not to even try learning it and adding it to your basic knowledge & skill set.

Another analogy, the "Escape Fire" technique invented on-the-spot by Smokejumper US Forest Service Firefighter Wag Dodge, in the 1949 Mann Gulch Wildfire Disaster (now incorporated as contingency standard procedure):

escape fire noun, \is-’kāp\’fī(-&#601r\

1. a swath of grassland or forest intentionally ignited in order to provide shelter from an oncoming blaze.
2. an improvised, effective solution to a crisis that cannot be solved using traditional approaches

Escape Fire Defined » Escape Fire

 

[DevonDiver]

I'm not sure I agree it's necessary at OW/AOW level. There are plenty of practicable options already taught: free-flow breathing ascent, buddy air-share and, last ditch, CESA. All of which make a free-flow quite survivable. If the bottom depth exceeds the ascent capabilities of those methods, then suitable redundancy is the best option.

It's good for sidemounters, as the valves are so accessible.... and it does away with the need for pointless and expensive gimmick manifolds...

 

[scubadada]

And this is a useful skill for most single tank, recreational divers? I have 850 dives and am not at all sure I could reliably reach my valve repetetively. Sorry, but I will have a couple minutes to reach the surface with a free-flowing 2nd and will take advantage of that time. I'll be fine, thanks

 

[T.C.]

This is the reason why this skill should be taught at the beginning BOW/AOW level: If a novice diver on single tank at basic OW depth 18m/60' --with no buddy in sight-- has the option & ability and can successfully make the effort to conserve as much free-flowing gas by the valve modulation/feathering breathing technique, what he gains is time --time for the Buddy to find him and gas share.

That is not what OW divers are trained to do. They are trained to ascend immediately. Furthermore, they are trained in the technique of breathing from a free-flowing regulator. A diver at 60 feet has enough air and time to ascend to the surface with a free-flow. He does not, and should not, attempt to linger underwater with a serious gear malfunction waiting on a buddy that probably won't show up. He should ascend immediately.

You don't want an "out-of-the-frying-pan-into-the fire" SoCal worst case scenario of surfacing with an empty tank; getting tangled in kelp...and working hard treading water to maintain positive buoyancy in a typical prevailing 2' to 4' afternoon swell & wind chop

So teach this "technique" to SoCal divers. These sort of conditions are not universal or typical. How will it benefit a Florida OW diver who just wants to dive in warm water?

inability to orally inflate the BCD because you're out-of-breath having just performed a conventional CESA

So if the diver doesn't have the skill to orally inflate a BCD, a skill that is taught in OW class, How do you expect them to manage the much more complicated and intensive skill of

shrink-wrapped drysuit hampering mobility

Uhhh....Dry Suits, and the air trapped inside, expands as you ascend. It won't shrink-wrap you so you can't move.

If possible & skilled enough to hold depth, do a safety stop.

That is NOT necessary. No recreational dive requires a safety stop. They are recommended, but not required. What is more dangerous, a OW diver trying to hold at 15 feet while simultaneously feathering his tank valve, or an OW diver surfacing without their recommended safety stop? The important thing in any emergency is to safely reach the source of free, unlimited gas supplies. Tech Divers can't do this, because they are under a "ceiling" of deco obligations. While this skill may benefit them, Rec. divers are under no such limit, and should ascend directly to the surface.

 

[Kevrumbo]

I'm not sure I agree it's necessary at OW/AOW level. There are plenty of practicable options already taught: free-flow breathing ascent, buddy air-share and, last ditch, CESA. All of which make a free-flow quite survivable. If the bottom depth exceeds the ascent capabilities of those methods, then suitable redundancy is the best option.

It's good for sidemounters, as the valves are so accessible.... and it does away with the need for pointless and expensive gimmick manifolds...

And this is a useful skill for most single tank, recreational divers? I have 850 dives and am not at all sure I could reliably reach my valve repetetively. Sorry, but I will have a couple minutes to reach the surface with a free-flowing 2nd and will take advantage of that time. I'll be fine, thanks

That is not what OW divers are trained to do. They are trained to ascend immediately. Furthermore, they are trained in the technique of breathing from a free-flowing regulator. A diver at 60 feet has enough air and time to ascend to the surface with a free-flow. He does not, and should not, attempt to linger underwater with a serious gear malfunction waiting on a buddy that probably won't show up. He should ascend immediately.So teach this "technique" to SoCal divers. These sort of conditions are not universal or typical. How will it benefit a Florida OW diver who just wants to dive in warm water?So if the diver doesn't have the skill to orally inflate a BCD, a skill that is taught in OW class, How do you expect them to manage the much more complicated and intensive skill of Uhhh....Dry Suits, and the air trapped inside, expands as you ascend. It won't shrink-wrap you so you can't move.That is NOT necessary. No recreational dive requires a safety stop. They are recommended, but not required. What is more dangerous, a OW diver trying to hold at 15 feet while simultaneously feathering his tank valve, or an OW diver surfacing without their recommended safety stop? The important thing in any emergency is to safely reach the source of free, unlimited gas supplies. Tech Divers can't do this, because they are under a "ceiling" of deco obligations. While this skill may benefit them, Rec. divers are under no such limit, and should ascend directly to the surface.

Argue & whine for your own limitations ---they are alll just yours.

Those who have rhe ability, dexterity and coordination should not be discouraged from practicing it - in a pool for starters with a buddy at depth. . .