Stage/deco/BO reg with inline shutoff

[tbone1004]

Good question. If you do the prescribed maintenance on one of the expensive XS Scuba/Highlands ones, like you do the maintenance on your deco regs (which you DO do, right?), what problems are you likely to have?

they leak all the time, even with rebuild. The only reliable ones I have ever seen are the ones integrated into Poseidon first stages.

I'm not for use of the shutoffs, just extra stuff to fail.

Skills solution to this equipment problem. Check pressure prior to opening valve. If gauge reads 0, verify the din screw is tight, pressurize and continue on with your dive.

 

[johndiver999]

You have to add an Op relief valve to each reg, if you go this route right? More $, more gear, more maintenance, more problems.

 

[tbone1004]

You have to add an Op relief valve to each reg, if you go this route right? More $, more gear, more maintenance, more problems.

the OPV's are basically free for the cheap ones, but it's much more that they fail all the time. Go to Ginnie and look at all of the CCR divers doing predive, odds are more than half of them have OPV's bubbling on their O2 first stages...

 

[Wstern5]

I searched on this subject and found a thread from 10 years ago. There, the consensus was that stage regs should not have an inline shutoff. But, nobody in that thread talked about the reason that I was given for why to use one. So, I'm resurrecting the discussion, but in its own thread, instead of continuing one from 10 years ago.

My tech instructor/mentor suggested to use an inline shutoff on my deco regs. I believe he was taught to do so by his tech instructor/mentor. His tech instructor is a very well-respected crusty old diver, expedition-level deep wreck diver, tech instructor, cave instructor, and CCR instructor. I'm not going to get into names because I think the practice should stand on its own merits, not the credentials of the person recommending it.

The recommendation to me was to add an OPV to the 1st stage and an inline shutoff to the 2nd stage on each of my deco/BO regs. Then dive with them all with the cylinder valve open and the inline shutoff turned off.

I'll explain the reason given by using an example. I was helping my tech instructor teach an AN/DP class and the reason he gave actually happened for real to one of the students. So, this reason is not just hypothetical.

The student did not have an inline shutoff setup. He started the dive with his deco reg charged and the valve off. During the dive, he must have occasionally bumped the purge on the 2nd stage of the deco reg. It wasn't leaking, but he bumped i enough to depressurize the line. Once the line was depressurized, the 1st stage turned in the valve a little.

When the student turned the deco cylinder valve on, as part of his normal gas switch, an explosion of bubbles came pouring out of the valve because the 1st stage had turned just enough to allow it to leak (a LOT) around the DIN O-ring.

In this case, the student was able to turn the valve off, tighten the DIN wheel on the 1st stage and re-open the valve. It did not extrude the O-ring and ruin its ability to seal. But, it certainly seems like on another occasion, that absolutely COULD happen.

My instructors point about using an inline shutoff was totally borne out by this incident in real life. If the student were diving with an inline shutoff (turned off) and the valve turned on the whole time, then accidentally bumping the purge on the 2nd could not have depressurized the line. Therefore, the 1st stage would not have had an opportunity to get loose.

There are some obvious cons to using the inline shutoff.

You can forget to turn your cylinder valve on and panic yourself when you open the inline shutoff, try to breathe, and get no gas.

You can forget to shut the inline valve and get none of the planned benefit (i.e. still bump the purge and accidentally depressurize the line).

You can forget the shutoff is there and panic yourself trying to breathe with it closed.

You can have debris that makes the inline shutoff become unable to open. The old thread had an example where the diver got a piece of shell stuck in just the right spot to block opening of the inline shutoff.

The inline shutoff adds 2 more O-rings to your LP gas supply to the 2nd stage, so 2 more opportunities for a failure.

Am I missing any of the cons?

Thoughts on the reason I was told for being in favor of using an inline shutoff?

I would think that shearing off the hand wheel on a closed valve, making the gas inaccessible could be a concern for some. Depending on their diving “style” of course.

No matter what happens there is lots of solutions- share deco gas with buddy, deco on back gas, unscrew regulator from back gas or stage and put it on the deco bottle, take the spare o ring from your wet notes and replace the extruded one...maybe more?

 

[rjack321]

I would think that shearing off the hand wheel on a closed valve, making the gas inaccessible could be a concern for some. Depending on their diving “style” of course.

Shearing off is rather rare IMO

The nut unscrewing and the knob falling off the valve stem is a very real thing however. If you're lucky, you still have the knob in hand to turn the stem and open the valve.

 

[rddvet]

My two cents is that you’re solving a problem that really isn’t a common problem you really have to worry about. Add to that you’re solving the problem by adding an OPV, the one piece of equipment you’re guaranteed to have fail at some point. I will say the highland rebuildable ones are much better, but will eventually fail too.
Lastly, I know you ended up limiting the discussion to be deco gass3s only, but I will add that the recent death at Ginnie was directly related to the diver either unknowingly turning off their oxygen’s shut off or knowingly turning it off but forgetting to turn it back on.

 

[Tracy]

Exactly!

Diver Daves Rebreather Site

Vehement distaste for Dave doesn't negate his contribution

What I have found, is that those that speak poorly of Sutton
are far more like him, than they would ever choose to think
or they are only following all the villagers up that steep hill


He tells me that link of yours was fashioned by a friend, that is difficult to believe

What contribution has he ever made?

As to being fashioned by a friend, easiest way to tell Dave is lying, he is talking.

 

[njdiverjoe]

I've been putting inline shut-offs and opvs on all my bailout tanks, simply because in the past I'd occasionally find my 2nd stage getting bumped resulting in either loss of gas(valve on) or flooding my 1st stage (valve-off).

 

[stuartv]

My two cents is that you’re solving a problem that really isn’t a common problem you really have to worry about. Add to that you’re solving the problem by adding an OPV, the one piece of equipment you’re guaranteed to have fail at some point. I will say the highland rebuildable ones are much better, but will eventually fail too.
Lastly, I know you ended up limiting the discussion to be deco gass3s only, but I will add that the recent death at Ginnie was directly related to the diver either unknowingly turning off their oxygen’s shut off or knowingly turning it off but forgetting to turn it back on.

I have not read about the death at Ginnie, but it sounds like you are talking about a shutoff on a CCR O2 supply?

I have definitely been swayed by the discussion and excellent points raised in this thread. Swayed against adding shutoffs to my deco regs. Now, I am looking forward to having an in-person discussion with my mentors about this subject. At this point, it certainly seems like the cons outweigh the pros by a large margin.

 

[jale]

Hi
It is good to have mentors but they should not become gurus