Rigging for slinging a stage bottle

[mathauck0814]

A 100m+ head down scooter descent is a weird position that can leave the second stage upright and burping gas. I'm happy to learn if you've got a solution to that, but managing a 30m+/min descent speed, equalizing, keeping the suit/wing inflated and managing loop volume is enough to worry about. If you've got practical advice for how to rig my bailout so that I don't need the inline valve I'm all ears, otherwise I feel like undoing a slide valve is fairly low effort when/if you need it.

Of course, I'm referring to a solution that's not a BOV as I'm quite fond of the WOB of the stock DSV at those depths ;-)

 

[PfcAJ]

BOV buddy

 

[kwinter]

How common is it to use an inline shut off valve for a stage bottle, or for independent doubles, or even sidemount?

I understand the reasoning (preventing loss of air if the 2nd stage leaks or freeflows), but just wonder about the wisdom of placing a restriction / possible failure point between the 1st and 2nd stage, which also eliminates the downstream "over-pressure valve" function of a 2nd stage in the event of IP creep or HP seat failure in the 1st stage?

Just curious what others think.

Best wishes.

I have shutoffs on the second stage of all my bailout regs because I also have inflator hoses on all those regs to be able to plug in that gas to my rebreather or wing or drysuit or donate to my buddy. A second stage free flow would either lose all my gas or force me to shut down the valve, making that gas unavailable through the inflation hoses as well. The elimination of the over pressure function is the reason I said that you must put an OPV into the first stage if you put a shutoff on the second.

 

[dreamdive]

If only there was some way to rig your bailout so it wouldn't free flow and you didn't need those shutoffs...

There is nothing wrong with shut-offs! Free-flow is not the only problem we worry about!
Case in point, I was the 300 ft safety diver on a deep dive drill. Turned out that the practice bail-out at 375ft turned into a real one. When the diver went to his bail-out, his second stage started to free flow. When he reached me and I handed off my bail-out, upon opening the valve, I had a first stage failure. After analysis, both of these could have been prevented with shut-offs. After this, the team elected to put shut-offs on all of our bail-outs.

BTW, these shut-offs have been to >650ft without incidence and there is NO OPV on any of them.

---------- Post added August 1st, 2014 at 09:54 AM ----------

I have shutoffs on the second stage of all my bailout regs because I also have inflator hoses on all those regs to be able to plug in that gas to my rebreather or wing or drysuit or donate to my buddy. A second stage free flow would either lose all my gas or force me to shut down the valve, making that gas unavailable through the inflation hoses as well. The elimination of the over pressure function is the reason I said that you must put an OPV into the first stage if you put a shutoff on the second.

Ken, non of us have OPVs on our shut-offs.

 

[tbone1004]

you should really put OPV's on the first stage, it can save a lot of damage. OPV's will relieve the pressure without losing a terrible amount of gas, but a blown LP hose can run a tank dry in a matter of minutes. This is why the Poseidon first stages have them built into the first stage as well as built into the special hoses at the top. The OPV is only a concern if the HP seat is failing and there is IP creep, a blown hose is a huge problem, a leaking OPV will still allow you time to get things situated.

 

[PfcAJ]

How does a shut off prevent a 1st stage failure?

and of course you need an opv if you have a shut off. There's no where for any over pressure to blow off to.

 

[dreamdive]

How does a shut off prevent a 1st stage failure?

and of course you need an opv if you have a shut off. There's no where for any over pressure to blow off to.

NO, I dont need an OPV. But, if any of our shut off valves cause a hose rupture, I will sure to post it here.

regarding the first stage: the bottle was charged at the surface, checked and then shut off to prevent gas loss. At 300 ft, there was enough pressure loss in the first stage (din valve), the seat loosened and when turned back on, the o-ring dislodged leading to a failure. What we do now is turn the bottles on, check the system, turn the shut off to off and dive. If we need to bail during any part of the dive, all is required is to turn the shut-off to on.

We cannot afford to have an unrecognized bail-out gas loss. If you need to bail because of high CO2 for example, you cannot simply swim over to another diver and ask for theirs. When you are having a bad day, you don't want to make it any worse.
If (even though we have never heard or seen this) I were to have a hose rupture, that would most likely happen BEFORE I encounter a bail-out situation and I can turn the dive.

 

[PfcAJ]

So you're saying the gas in the reg drained and the reg was no longer seated to the valve?

and the solution to that is to add another part to your rig instead of simply reseating the reg?

okidokie...

 

[tbone1004]

go have a bad HP seat and watch the hoses burst, they can come at the strangest times without warning. This is why I have BC hoses on all of my regs spare O2 and do IP checks before I get in the water.

Not having an OPV on the first stage is just stupid, I'm sorry, but it really is. They're $3, and at best can save a $20 hose, at worst can save your butt if you don't run out of gas. The failure point there is controlled by a spring and an O-ring. The O-ring is no different than with the port plug, and the spring is a spring, they don't usually fail.

 

[Ayisha]

when you install a shutoff valve you are supposed to put an OPV on the first stage in one of the LP ports which will blow upon reaching whatever PSI it is designed for. Poseidon incorporates these into the bottom of the 3960 and Xstream first stages, and some divers will replace them with the port design if the spring breaks or whatever.
It isn't a restriction, the design allows for the same volumetric flow rate as normal, which is well above what a diver can realistically use anyway. Failure point, there's not a lot inside of them and I believe they fail open. I haven't pulled all of them apart, but most of them function the same way as the QD's on the inflator hoses, they're just enclosed into one unit.

I could be wrong, but I've heard that some Poseidon's fail closed? The high pressure seating mechanism is upstream of the orifice, causing it to be pushed closed if the seat fails. They apparently need an over pressure valve on a special hose to protect from ip creep and hose failure. Most other types of regs on the market though, fail open.

So all this talk about possibly needing a shut-off valve and opv, is it dependent on the type of regs you have and the diving you plan to do? I have Sherwood regs and I don't have a shut-off valve or opv on my stage bottle or other regs.