Roll Off!

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12-18-2008 02:16 PM
OWSI176288

Quote:

Originally Posted by cavemark

Wow!! Are complete roll-offs really that common? I mean, it takes a lot of contact with the ceiling to completely roll a valve shut. I will admit to making contact with the ceiling and I mentally smack myself on the back of the head every time. The only area I can think of that is tight enough for intro divers to completely roll off a valve is the Lips and coming out of the Eye. I have experienced about a quarter to half of a turn once during a dive and I believe it was after going through the Lips.

I think that all instructors teach about and drill on roll-offs. I think that everyone should be able to reach their valves even if there is pain involved, 'cause nothing hurts worse than death. But, if I had significant pain doing a valve check then I would incorporate a period check by my partner into the dive plan.

But one thing is for sure, the valves don't roll-off without contact.

Mark

I don’t think complete left post roll-offs are all that common outside of OOG training situations. I hope most cave divers have enough sense to know if they can’t get through a certain passage without hitting the ceiling they shouldn’t be in there in the first place.

I’ve never been in a true OOG sharing situation in a cave, let alone one in low vis. All I know is that’s not the time I want to find out I can’t reach my valves. Plus it sure is nice to know I am able to reach the correct valve during other situations such as a first-stage freeflow, a ruptured hose, a blown rupture disk, etc.

Valve drills seem to be a nice way to practice quickly opening and closing all three valves. But it would seems that there also has to be an emphasis on knowing why and when to quickly isolate a specific valve as Elisha previously stated.

For example, I’ve heard different arguments on what to do if one hears a sudden air loss behind them. Some say to try and figure out which post to close and then close it, potentially saving as much air as possible in both tanks. Other say pick a post and close it, if there’s still air loss, then open it back up and close the other post. Again, trying to save as much air as possible. Me…..I am closing the isolator ASAP and saving at least half my air and working things out from there. I don’t know if this is wrong, correct, or whether one is preferred over the other. All I do know is to breathe off the leaking side reg as long as possible if I can't isolate the air loss.
12-18-2008 02:20 PM
chimie007

Quote:

Originally Posted by OWSI176288

For example, I’ve heard different arguments on what to do if one hears a sudden air loss behind them. Some say to try and figure out which post to close and then close it, potentially saving as much air as possible in both tanks. Other say pick a post and close it, if there’s still air loss, then open it back up and close the other post. Again, trying to save as much air as possible. Me…..I am closing the isolator ASAP and saving at least half my air and working things out from there. I don’t know if this is wrong, correct, or whether one is preferred over the other. All I do know is to breathe off the leaking side reg as long as possible if I can't isolate the air loss.

Same for me if I dive backmount. I recall seeing data on TDS about how fast it takes to empty a tank for different scenarios... if I recall the fastest by far was a burst disk... Make sense to isolate, unless it's an obvious free flowing second stage.
12-18-2008 02:27 PM
Serota

Reaching valves

I used to have considerable discomfort reaching my valves and found this set of exercises which helped: http://www.divefitness.com/html/arti...ld_stretch.pdf

Since then, I only dive SM and the problem is fully resolved.
12-18-2008 02:42 PM
WEPIV

Quote:

Originally Posted by Serota

I used to considerable discomfort reaching my valves and found this set of exercises which helped: http://www.divefitness.com/html/arti...ld_stretch.pdf

Since then, I only dive SM and the problem is fully resolved.

Thanks for posting this info. I've already saved it to my computer for reference.
12-18-2008 05:28 PM
stairman

I had a complete rolloff once at little River.In the cavern zone is an air pocket and I popped up in it and dropped back down.A couple,who is O.W divers were on the bottom and I pointed to it and popped in it again.This time when I dropped back down my reg went dead.Coming down twice was enough to roll off my right post.I just switched regs but surfaced before realizing what happened.I never realized the valve had touched either time.If that happened to an O.W diver on a single valve it could be a scary situation.Luckily its near the entrance.
12-18-2008 06:54 PM
BabyDuck

mike o teaches to check your left valve every time you check your spg. i'm not that good about it, but i mostly dive peacock where hitting the ceiling is less of an issue since it's mostly so big. anyway, i need to get back in that mode for class next month, so timely post, elisha.

in intro, we were a class of 3. one of the others was being donating diver to the other other in the peanut tunnel, then came me, then mike. donating diver stopped about halfway through the tunnel and skipped me & went to mike & told him 'air low'. (still donating.) very calm. anyway, mike put him on *his* long hose and very quickly sorted out that he had rolled off. it's the only 'for-real' one i've seen that i know of.
12-18-2008 07:40 PM
john

Quote:

Originally Posted by cavemark

Wow!! Are complete roll-offs really that common?

Werent the Sea Elite manifolds popular because they didnt require many turns on or off?
12-18-2008 07:53 PM
diveconjeff

FWIW, my first exposure to a roll off came not in doubles, but with a single tank. As I was completing my DM training, I was to drop into the pool with some OW students and lead them through some drills. My instructor had rolled my valve off all but 1/4 turn. I could breath fine at first, but after descendng ten feet I was over breathing the available supply from the first stage. A quick check of the guage showed that the pressure was rising and falling as I breathed. I simply reached behind my head and while the students thought I was scratching my neck, I was turning the valve back on. Of coarse while I was truning it back on my middle finger remained extended in clear sight of the guilty party. He was still laughing when we came back to the surface.
He mentioned rolloffs to me later in the evening, but it has always been a priority since that day to understand how the gas got from the tank to my mouth and what I could do to manage such an issue. I never would have dreamed of going beyond my pool with doubles if I was not certain of the function of the valves or manifiold configuration.
I am pretty certain that there will continue to be rolloffs, not much can be done about that. BUT, if you are diving with some you are not familiar with, do you do a bubble check? an S Drill?
In some cases would it be out of line to observe each other do a shut down sequence?
12-18-2008 08:07 PM
Bob Cree

Thoughtfully consider diving with your inflator off the left post. You will quickly know if you have an issue with the backup reg gas supply (rolloff) when your inflator stops working, likely long before you need it as a breathing supply.

With left post inflator...the pressure gauge not dropping will now directly indicate the crossover is shut...you now have clear and separate indications for both, and you are still in you streamlined BM outfit.

Some people don't do this...can't figure that one out.
12-18-2008 08:26 PM
TonyDCaver

Quote:

Originally Posted by addexdiver

Thoughtfully consider diving with your inflator off the left post. You will quickly know if you have an issue with the backup reg gas supply (rolloff) when your inflator stops working, likely long before you need it as a breathing supply.

With left post inflator...the pressure gauge not dropping will now directly indicate the crossover is shut...you now have clear and separate indications for both, and you are still in you streamlined BM outfit.

Some people don't do this...can't figure that one out.

I have been diving with my inflator on my left post for a long time, but I am considering switching. I heard the first "logical" explanation, not the it will most likely happen but it could very well happen. If one routes the inflator off the right post it can be used as a third reg essentially. For example if I was going through a real tight nasty area and I had already donated my long house and I have a roll off in which I cannot get to my left post, I can use the inflator hose to breathe off of until I'm on the other side.

Just my .02 that I have been considering. Not that I will be going through any restrictions like that until after apprentice/full.

-Tony DC

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