2nd stage shutdown valves.

[Graeme Tolton]

Does anyone have any experience with these 2nd stage shutdown valves that are widely available? I have never seen anyone using one, but have always seen them in stores... Do they work as intended or are they problematic?

[sambolino44]

I'll bet they probably work as intended, but are actually an equipment solution to a training problem.

[DA Aquamaster]

I'm not 100% sure what the valve in question is intended to fix, but I do know the above "an equipment solution to a training problem" answer is too cryptic to be of much use to many divers.

If you are diving in old water and the second stage freezes (either octo or primary) you screwed up on good cold water technique.

If on the other hand, the freeflow is the result of a first stage failure - either a freeze flow or a leak in the high pressure seat - the other second stage will have to leak to vent the excess pressure once you shut one of them off. For a single tank diver that is problematic and with both second stages shut off you would have to be on a buddies air supply or on a pony.

In the event of freeze flows, if you shut off the tank valve supplying your freeflowing reg for a couple minutes (while sharing gas with your buddy), the reg will thaw and you can go back on it. In a situation where you have redundant doubles or a pony, you can shut the offending reg off and switch to your own backup gas source.

So in short, knowing good cold water technique, knowing how to share gas and knowing how to shut off the valve(s) on your tank(s) are a far better set of solutions than a valve that at best treats a symptom but ignores the major problem.

[it_mike]

My impression was these second stage shutoff valves were aimed at the pony market to avoid inadvertent gas loss.

Haven't actually tried one myself.

[NWGratefulDiver]

Are you talking about these (http://www.scubatoys.com/store/detail.asp?PRODUCT_ID=OMS_Remote_Valve_Knob_Assemb ly)?

If so, then I can't think of any practical reason to use them ... which is probably why they're not particularly popular.

... Bob (Grateful Diver)

[roturner]

I think he's talking about one of those inline shutoff gizmos that you can attach between the LP hose and the body of the 2nd stage. In the case that it freeflows you can turn or slide it (not sure which) to cut off the air flow so the freeflow stops.

like this thing:

http://www.xsscuba.com/graphics/highland/large/hl404.jpg

and I agree with the second post. These kinds of devices are generally gizmos that make you feel better but have limited value if you follow your training.

R..

[Blackwood]

I always dive with one. It looks like this and works like a charm.

http://www.thermovalves.com/images/5251-Exploded-View.jpg

[Web Monkey]

Does anyone have any experience with these 2nd stage shutdown valves that are widely available? I have never seen anyone using one, but have always seen them in stores... Do they work as intended or are they problematic?

They work exactly as intended, although that isn't saying much. 8-)

As DA Aquamaster mentioned, in a situation where you might actually want one (where your first stage freezes open), it won't help.

OTOH, I can easily see a situation where you hand your octo to an OOA buddy only to have him find that there's no air in it because there's a secret valve that's turned off. Even after having seen the picture in the post above, if someone handed me a reg with one of those on it and I was OOA, I'd have no idea how to make it work or even know what it was.

It's much safer to use a regulator that isn't prone to freeflows, and if it does, just follow training.

Terry

[sunkmail]

If the OP is talking about one of the shut-offs like roturner shows, it is widely used in some tech applications, usually on Deco/Stage bottles.

In particular, I've heard them praised by people with scooters, as sometimes the flow past a 2nd stage will cause the reg to purge. Beyond the annoyance, it's possible that you may not notice the gas venting and lose a noticable amount. (I don't scooter myself, but I have heard that first hand from scooter pilots.)

There are a few other areas where they can come in handy, but again, it's in the tech area of things.

One thing to remember by anyone that is ever considering one of these - you MUST have an Over Pressure Relief Valve (OPV) to prevent damage to your first stage incase of failure. (As mentioned above, you need some way of getting the extra pressure safely out and your 2nd is the usual way.

Hope that helps.

[muddiver]

I agree with Web Monkey and sambolino44, I presume it is an anti-freeflow device. The problem being is the only regulator that would free flow without being a failure is the safe second. Installing one on your safe second (i.e. Octo) negates the safety of having the aditional second stage because you now have an extra valve to open to make the safe second usable.

There are simpler ways to prevent free flow. I have a clip for my safe second that has a little plug that presses part way into the opening of the mouth piece. It keeps the regulator from free flowing and also keeps sand a stuff out of the regulator. Those rubber ball looking octo holders probably do the same thing. So, why add an additional valve that no one else uses, that might cause the LP hose to rupture if the first stage leaks?

Solution looking for a problem.

[Michael_Lambert]

If the OP is talking about one of the shut-offs like roturner shows, it is widely used in some tech applications, usually on Deco/Stage bottles.




I can not say i have ever seen them used in any applications around here. I could see how a new diver could see the value of it however it is nothing but yet another failure point on you gear.

Especially on a Stage/deco bottle which would be primed at the start of your dive and shut down again once the dive has started unless you are breathing off it.

If you are diving a single tank setup and have a need for a device like this i would suggest you are going beyond the intended use of your single tank rig, you should be able to manage a free flowing second stage or at least breath off it while you do your accent.

[sambolino44]

I always dive with one. It looks like this and works like a charm.

http://www.thermovalves.com/images/5251-Exploded-View.jpg

I have one that looks just like this and it doesn't work at all!

Oh, wait, was I supposed to put it together first?:eyebrow:

[sunkmail]

I can not say i have ever seen them used in any applications around here. I could see how a new diver could see the value of it however it is nothing but yet another failure point on you gear.

Especially on a Stage/deco bottle which would be primed at the start of your dive and shut down again once the dive has started unless you are breathing off it.

If you are diving a single tank setup and have a need for a device like this i would suggest you are going beyond the intended use of your single tank rig, you should be able to manage a free flowing second stage or at least breath off it while you do your accent.

Some of the uses I eluded to are for rebreathers and a little beyond the scope of this conversation. As for many pieces of gear, there are some situations where these are handy, and many where they can be a liability.

It is not standard everywhere to prime a bottle and shut it down - some prefer to keep it on. I am not going too get into reasons for either method; it really isn't important or relevant for this thread. Just remember, different areas/environments/people/seasons/whatever sometimes necessitate different approaches.

For a typical recreational, single-tank diver, I agree - there is no real need for these.

[MichScubaMike]

I always dive with one. It looks like this and works like a charm.

http://www.thermovalves.com/images/5251-Exploded-View.jpg

In this configuration.... I have my doubts that it "works like a charm." My advice would be to put all the parts back together (in the correct order) and it will start to "work like a charm"! :rofl3::rofl3::rofl3:

[Graeme Tolton]

I can not say i have ever seen them used in any applications around here. I could see how a new diver could see the value of it however it is nothing but yet another failure point on you gear.

Especially on a Stage/deco bottle which would be primed at the start of your dive and shut down again once the dive has started unless you are breathing off it.

If you are diving a single tank setup and have a need for a device like this i would suggest you are going beyond the intended use of your single tank rig, you should be able to manage a free flowing second stage or at least breath off it while you do your accent.

I was simply curious about this product. I am not a new diver. My open water card was issued in 1997. I can manage a freeflow, however I would rather avoid the inconvenience of needing to end a dive over something that can be corrected.

[Cave Diver]

I was simply curious about this product. I am not a new diver. My open water card was issued in 1997. I can manage a freeflow, however I would rather avoid the inconvenience of needing to end a dive over something that can be corrected.

One thing to keep in mind with stuff like this, is will it introduce more problems than it solves? There are some applications for this type of valve, but I dont think normal OW diving is one of them.

[Graeme Tolton]

One thing to keep in mind with stuff like this, is will it introduce more problems than it solves? There are some applications for this type of valve, but I dont think normal OW diving is one of them.

One could also argue that manifolded double tanks with an isolation valve could be problematic. (not that I am). However, it comes down to being familiar with your equipment and practicing with it. As far as normal open water diving... we don't have a whole lot of that here. Most of my dives are in the 40 degree range, where freeflows are not an uncommon occurrence.

Diving with a sealed 1st stage, it is highly unlikely to have a 1st stage freezeup, but more likely a 2nd stage, thus reducing the risk of a burst lp hose signifigantly.

[Cave Diver]

One could also argue that manifolded double tanks with an isolation valve could be problematic. (not that I am). However, it comes down to being familiar with your equipment and practicing with it. As far as normal open water diving... we don't have a whole lot of that here. Most of my dives are in the 40 degree range, where freeflows are not an uncommon occurrence.

Diving with a sealed 1st stage, it is highly unlikely to have a 1st stage freezeup, but more likely a 2nd stage, thus reducing the risk of a burst lp hose signifigantly.

Totally agree on the practicing thing. I also agree that isolation valves could present a problem and I don't recommend using those when they aren't needed either.

Like I said, do they solve more problems than they introduce? In cold water where free flow is common, then they might have merit. In more "normal" diving, maybe not. Only you can decide where that balance is.

[rjack321]

Most of my dives are in the 40 degree range, where freeflows are not an uncommon occurrence.

Diving with a sealed 1st stage, it is highly unlikely to have a 1st stage freezeup, but more likely a 2nd stage, thus reducing the risk of a burst lp hose signifigantly.

Why are you having so many free flows in water that's "in the 40s"? (40+F presumably).

With good technique free flows should be quite rare even in the low 40sF and fresh water. They should not be happening in 40F sea water with its lower freezing point.

Relax, get your consumption down. Less gas and slower delivery = less adiabatic cooling and you won't form ice or free flow.

[Cave Diver]

Why are you having so many free flows in water that's "in the 40s"? (40+F presumably).

With good technique free flows should be quite rare even in the low 40sF and fresh water. They should not be happening in 40F sea water with its lower freezing point.

Relax, get your consumption down. Less gas and slower delivery = less adiabatic cooling and you won't form ice or free flow.

Pre-breathing in air temps below freezing?

[roturner]

I was simply curious about this product. I am not a new diver. My open water card was issued in 1997. I can manage a freeflow, however I would rather avoid the inconvenience of needing to end a dive over something that can be corrected.

Something to keep in mind is that once you turn off the free fllow that the regulator is no longer functioning and therefore can't be used as a secondary in the case that your buddy has a problem.

I suppose you could turn it off for a minute and see if it thaws out and then turn it back on but ordinarily any kind of equipment problem, especially a malfunctioning regulator is reason enough to cut the dive short.

R..

[muddiver]

Why are you having so many free flows in water that's "in the 40s"? (40+F presumably).

With good technique free flows should be quite rare even in the low 40sF and fresh water. They should not be happening in 40F sea water with its lower freezing point.

Relax, get your consumption down. Less gas and slower delivery = less adiabatic cooling and you won't form ice or free flow.

It is common for octos serviced at some of the "fast food" dive shops to be tuned to be to sesinative and they will free flow when the inexperienced diver using that rig enters the water.

There are many fixes for free flowing second stages from using a plug in the mouth piece to de-tuning them so they will not free flow when used as a safe second.

[Graeme Tolton]

It is being assumed that I have been having freeflows.. Not what I said. In fact, I have never had an uncontrollable free flow. Anyhow, i will not be buying one of these units... Just wanted others' opinions.

[mpetryk]

Couldn't such a valve result in the rupture of your line if the 1st stage free-flows? I am not sure, but you might be swapping a free-flowing 2nd stage for a firecracker near your neck and ear... :(

[sambolino44]

The Zeagle catalog has a relief valve right under the isolator valve.

Personally, the way I forget things, I'd rather not have one more thing to think about or possibly get knocked into the wrong position. I could see the logic of using one on a stage bottle, though, if you got into the habit of wiping the valve when you grab the reg. I wonder which way it goes: toward the reg for on?

[Mr Carcharodon]

I was simply curious about this product. I am not a new diver. My open water card was issued in 1997. I can manage a freeflow, however I would rather avoid the inconvenience of needing to end a dive over something that can be corrected.

But if it is a first stage failure then you close the second stage valve and your low pressure hose blows up. That seems like a more dangerous solution than closing your tank valve as Marc suggested. Oh and since you already have a tank valve simpler as well.