Graeme Tolton
Contributor
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?
2nd stage shutdown valves.
- Thread starter Graeme Tolton
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sambolino44
Contributor
I'll bet they probably work as intended, but are actually an equipment solution to a training problem.
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.
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
Contributor
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.
Haven't actually tried one myself.
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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:
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..
like this thing:
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
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I always dive with one. It looks like this and works like a charm.
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They work exactly as intended, although that isn't saying much.
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
Contributor
If the OP is talking about one of the shut-offs like Diver0001 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.
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.
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.
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.
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