Tank Valve Feathering in a Free-Flow

[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 Dec 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 message was in reply in a 2005 Yahoo Newsgroup to George Irvine's suggestion of "pinching the hose" as an option to stop a non-fixable free-flow. The better solution however came from a Scandanavian DIR Diver (Peter Steinhoff --see also attached image below) who recommended that on a reg-freeze free-flow to just shut-down the malfunctioning post (double manifolded cylinders as well as on single tank). 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.

[2005]
. . .Anyway, here in Sweden we dive under the ice in the winter and we have cold water year round.
. . .If it’s a freeflow it’s usually because you have ice in the second stage or wing inflator. If it continues without instant shutdown you will have your first stage packed in ice and it will freeze open. . .

All these problems can be resolved by shutting down the post immediately and you should be able to do that in about 5 seconds. And yes, I can do it on a single tank too. I can always feather the valve if I need to breathe, and I do that on doubles too. Otherwise sharing gas with a buddy would be nice.

So as you can see, we deal with this all the time. . . And even if most of the readers on this list dive other conditions I still think this is the best solution overall and it has proven itself again and again.

Peter Steinhoff (DIR-diver.com - Who am I?)

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).

 

[PfcAJ]

good grief.

 

[Redshift]

You've had a wealth or replies showing you why that technique is not necessary or even suitable for an OW diver. I thought you bringing up the same subject here on T2T would have been with a different focus, that of this being used in extreme circumstances in some technical scenarios. But it hasn't. Pointless thread.

 

[Kevrumbo]

You've had a wealth or replies showing you why that technique is not necessary or even suitable for an OW diver. I thought you bringing up the same subject here on T2T would have been with a different focus, that of this being used in extreme circumstances in some technical scenarios. But it hasn't. Pointless thread.

The point is that the Feathering/Modulation Technique seems to have been in use out there around the Scandanavian Peninsula (or Sweden at least) --for nearly ten years.

Pointless for you Redshift, ironically being from Finland --especially if you've never practiced it or even heard about it. . . maybe in that sense you should learn it and re-take BOW once again.

 

[Redshift]

Many things can have been in use, such as "when the air stops flowing, swim to the surface", buddy breathing from a single regulator, etc. It doesn't mean they are the best practices. And having the report of one person saying he is able to do something is not evidence of said something being common, taught or best practice. And that part of his comment came as an addendum to what is really important, closing the affected post. Then the ice melts and the regulator is useable again. And if in a recreational setting, that's why there's always a buddy and they are both tethered together and to a tender on the surface.

And you seem to assume a little bit too much...

 

[abnfrog]

this skill is NOT for ow /aow ascend on the primary or go to alt air source ,get out of the water ....we teach this skill on ccr rebreather for a 0 2 "freeflow "" situation ........

 

[PfcAJ]

I thought this was the technical sub forum for actual tech divers? Free flow= shut down reg switch to backup. If it's fixable cool, if not, go home. No need for monkey tricks.

 

[Kevrumbo]

I thought this was the technical sub forum for actual tech divers? Free flow= shut down reg switch to backup. If it's fixable cool, if not, go home. No need for monkey tricks.

Tell that to Peter Steinhoff, who's been practicing & performing the technique for real more years than you've been technical diving. . .

Speaking of monkey tricks, 'Orangutan Arms' AG can manipulate either doubles backmount valve post with the opposite hand & arm (i.g. Right post shutdown with his Left hand & arm) even in a dry suit.

 

[PfcAJ]

I'm not really concerned with what AG does (other than get booted out of a bunch of agencies) or what Peter does in a single tank. Sry Kev. I can't find a reason to do it in doubles even if Peter mentioned it once in some post on the Gavin list. A lot of thins can be done. That doesn't mean it's a good idea or practical or needed. Kinda like most of the things you post about.

 

[laurin]

Feathering the valve is one of those things that get way too much attention compared to their real world utility. A parlour trick really. A bit like buddy breathing today, SCR mode, open loop breathing on RB, breathing from a wing inflator, breathing from a tank valve etc. You could say "tools in the box" but they are generally of such limited use compared to better options that teaching or practising them might actually be counterproductive; students get a distorted view of their importance and give them too much priority in the problem solving tree.

About the only place where I'd see any utility to feathering the valve would be during long (why bother for short?) deco with a reg that's clearly starting to act up, and you want to give it a go. Never really for back gas - you'd have to come up with a rather convoluted scenario for that.

Deco stops on advanced tech course dives would be just about the only place to teach that too, if there's nothing else to cover and the situation is calm. On a deco/stage tank it's actually easy enough, but it does tie up one hand and takes a toll on awareness even when done by a competent diver, so it's not really a thing that will replace proper gas planning. I've had to do it on a few courses, and I've also used it for some lengths of O2 deco with a reg that started to be a bit too easy to breath for comfort. However, you do put yourself in a bit of problematic situation - any emergency requiring two hands will have you either breathing from a free-flowing reg or trying to breath from a closed tank...

//LN