BOV on-board or off-board what do U do?

cardysnr

cardysnr

Member
I've just completed my IANTD Normoxic course on the MEG in the Red Sea with PURE.

On air I plumbed my GG BOV via a 'Lancer' manifold through the DIL 1st stage with plug in from off-board from single stage.

Now using multiple stage gases it becomes less clear, BOV connected to bottom bailout tin only? then use O/C reg from stages ?

Use BOV via off-board manifolded connection for access to DIL & stage gases, possible water ingress with every disconnect & connect U/W.

Any practical advise to save re-inventing the wheel etc....

David.
 
I use a JJ, but:

My BOV is connected to my inboard dil, although I use common QDs and whips on my bailout regs, so have the option to attach offboard gas should I wish.
 
A half emty 3l is nothing in deep water and can not see ant reason to connect it to onboard diluent at any depth! In my world, the only right thing to do is to connect the BOV directly to the deep bailout with a simple quick connection without using any gas blocks or other things that make it unnecessarily complicated.

If you dive with a hypoxic bailout you have to consider switching the gas that is connected to the BOV when you get shallow. Swaglock QC6 is a nice QC. :luke:
 
offpro said:
A half emty 3l is nothing in deep water and can not see ant reason to connect it to onboard diluent at any depth! In my world, the only right thing to do is to connect the BOV directly to the deep bailout with a simple quick connection without using any gas blocks or other things that make it unnecessarily complicated.

If you dive with a hypoxic bailout you have to consider switching the gas that is connected to the BOV when you get shallow. Swaglock QC6 is a nice QC. :luke:
Click to expand...

I was considering plumbing bov to onboard dil with quick disconnect and option to connect it to an offboard dil. But:
A/ the bov are not as good as "normal" 2nd stages therefore why bothe over complicating and adding failure points where you most probably have one on your bail out.
B/ there was a good report on a caustic coctail incident. This is when your bov is becoming useless.
 
If you already have one of Lance's manifolds, you can make it very easy. Both onboard and offboard gasses feed into the manifold (more about that in a minute). Wing, ADV, MAV, BOV all feed off the manifold. Whatever gas (onboard or offboard) is "active" to the manifold is driving everything including your BOV.

How to determine which gas is actively feeding the manifold is up to you. Some do it with a whip hose to a QD and slide shutoff for the offboard gas. All offboard cylinders have a mating QD hose. To switch to offboard gas you slide the offboard shutoff open and then close the valve on your onboard cylinder.

Others use a 3-way ball valve that has inputs from both offboard (via QD) and onboard cylinders and the output goes to the manifold.

The use of a manifold like this provides a simple way to always have a breathable gas to your BOV no matter what depth. IMHO it is criminal to have hypoxic gas connected to your BOV while shallow, or rich gas connected to your BOV while deep. And connecting and disconnecting QDs attached directly to the BOV is not very easy underwater.

As far as a BOV not being as good as a "normal" second stage, I think the difference in WOB is only the small additional amount of dead space and is insignificant in most cases. My Golem Shrimp uses an Apeks second. My Divematics BOV has a Poseidon Xtream second. They both breathe just fine.

Just one man's opinion. YMMV.
 
humpbackdiving said:
I was considering plumbing bov to onboard dil with quick disconnect and option to connect it to an offboard dil. But:
A/ the bov are not as good as "normal" 2nd stages therefore why bothe over complicating and adding failure points where you most probably have one on your bail out.
B/ there was a good report on a caustic coctail incident. This is when your bov is becoming useless.
Click to expand...

I've just made my bov able to access offboard, so if the worst hit the whatsit, i can bail to my bov, which will burn my 5L inboard, then my 11L off board DILL, via a qc6, all via the built in manifold on the KISS.
I've also got the quick disconnects (miiflex) to get the O2 if i need it.
but every bottle also has a trusted reg on it as i've had a caustic on the unit ( it may have been my post but yep, you cant use that air source anymore if yu get a caustic)

regards
B
 
kwinter said:
If you already have one of Lance's manifolds, you can make it very easy. Both onboard and offboard gasses feed into the manifold (more about that in a minute). Wing, ADV, MAV, BOV all feed off the manifold. Whatever gas (onboard or offboard) is "active" to the manifold is driving everything including your BOV.

How to determine which gas is actively feeding the manifold is up to you. Some do it with a whip hose to a QD and slide shutoff for the offboard gas. All offboard cylinders have a mating QD hose. To switch to offboard gas you slide the offboard shutoff open and then close the valve on your onboard cylinder.

Others use a 3-way ball valve that has inputs from both offboard (via QD) and onboard cylinders and the output goes to the manifold.

The use of a manifold like this provides a simple way to always have a breathable gas to your BOV no matter what depth. IMHO it is criminal to have hypoxic gas connected to your BOV while shallow, or rich gas connected to your BOV while deep. And connecting and disconnecting QDs attached directly to the BOV is not very easy underwater.

As far as a BOV not being as good as a "normal" second stage, I think the difference in WOB is only the small additional amount of dead space and is insignificant in most cases. My Golem Shrimp uses an Apeks second. My Divematics BOV has a Poseidon Xtream second. They both breathe just fine.

Just one man's opinion. YMMV.
Click to expand...


Almost the same set up minus the online shutoff I just use the tank valve as on and off switch. Plus all bail cylinders have a normal second stage as a backup to the BOV and for the possible event of having to pass the stage to a buddy.
Gabe
 
divingabe said:
Almost the same set up minus the online shutoff I just use the tank valve as on and off switch. Plus all bail cylinders have a normal second stage as a backup to the BOV and for the possible event of having to pass the stage to a buddy.
Gabe
Click to expand...

Yup, all bailouts have a second stage with slide shutoff in case of free flow. Which means adding an OPV to the first stage. They also have a standard BCD hose in addition to the high flow QD in case someone else needs to use them or for emergency drysuit inflation. Yes, it all means more o-rings and potential failure points. But I think the flexibility is worth it.

Lance's old post on RBW has some good photos, but I'll try to remember to post some here.
 
I've missed something regarding a BOV & a caustic cocktail......why does the BOV become useless?

My stage tins have as minimum a 2nd stage & LPH...

David.

humpbackdiving said:
I was considering plumbing bov to onboard dil with quick disconnect and option to connect it to an offboard dil. But:
A/ the bov are not as good as "normal" 2nd stages therefore why bothe over complicating and adding failure points where you most probably have one on your bail out.
B/ there was a good report on a caustic coctail incident. This is when your bov is becoming useless.
Click to expand...
 
kwinter said:
Yup, all bailouts have a second stage with slide shutoff in case of free flow. Which means adding an OPV to the first stage. They also have a standard BCD hose in addition to the high flow QD in case someone else needs to use them or for emergency drysuit inflation. Yes, it all means more o-rings and potential failure points. But I think the flexibility is worth it.

Lance's old post on RBW has some good photos, but I'll try to remember to post some here.
Click to expand...

I can do a search on RBW later today. Thanks.


Sent from my Shearwater Predator...
 
I run all of my DIL off-board, since I use dual on-board O2. That way I always have plenty of gas plugged into my BOV. Also it gives me the option to ditch my unit and continue out on sidemount OC in the event of a catastrophic failure. Since all I have to do is unplug my bailout/DIL from the unit and unclip the unit from my sidemount harness.

The amount of gas you get from a normal DIL tank is negligible, it is not even worth it in my opinion to plug a BOV into it.

I have isolation sliders on my BOV and ADV, incase one free-flows/minimum loop volume.

Sorry that the pictures kinda suck.
 

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cardysnr said:
Bump..
Click to expand...

Because your BOV itself may be fully loaded with a caustic liquid that will spray into your throat when you try to breath open circuit.

BOV's are, in my opinion, a "transition" tool, allowing a more orderly transition to an open circuit regulator on a stage bottle. I would never stay on one for more than the length of time needed to get onto a "real" regulator.

If you watch my presentation on bailout plumbing that I gave at the URI Oceans of Opportunity Symposium, you'll hear me discussing the genesis of the BOV, which was NOT for the purpose of bailout, but was for the purpose of a Cis Lunar diver to transition to open circuit *at low workload* while his partner opened up his rig, extracted a spent scrubber, replaced it with another fresh (waterproof) scrubber, and then allowed the diver to rejoin the loop after clearing the rig of water.

The cheapest open circuit second stage likely breathes better than the best BOV. With WOB driving C02 retention, switching to the lowest WOB system as soon as possible under the most critical bailiout imaginable (hypercapnia) seems the conservative approach.


Here's the link to my little talk:

2010 Workshop | Dave Sutton - YouTube


Dave


.
 
Fantastic...thanks Dave just what I was after :big:

Dave Sutton said:
Because your BOV itself may be fully loaded with a caustic liquid that will spray into your throat when you try to breath open circuit.

BOV's are, in my opinion, a "transition" tool, allowing a more orderly transition to an open circuit regulator on a stage bottle. I would never stay on one for more than the length of time needed to get onto a "real" regulator.

If you watch my presentation on bailout plumbing that I gave at the URI Oceans of Opportunity Symposium, you'll hear me discussing the genesis of the BOV, which was NOT for the purpose of bailout, but was for the purpose of a Cis Lunar diver to transition to open circuit *at low workload* while his partner opened up his rig, extracted a spent scrubber, replaced it with another fresh (waterproof) scrubber, and then allowed the diver to rejoin the loop after clearing the rig of water.

The cheapest open circuit second stage likely breathes better than the best BOV. With WOB driving C02 retention, switching to the lowest WOB system as soon as possible under the most critical bailiout imaginable (hypercapnia) seems the conservative approach.


Here's the link to my little talk:

2010 Workshop | Dave Sutton - YouTube


Dave


.
Click to expand...
 
I have my BOV plumbed into my off board DIL. On board gases are O2 and inflation although I can access inflation as a DIL gas if I need to. And access Off board DIL as an inflation gas if I need to ( Via a ball valve).
 
cardysnr said:
I've missed something regarding a BOV & a caustic cocktail......why does the BOV become useless?
Click to expand...

Get a little lime dust on your finger and lick it... I did it once by accident. I can't imagine it would take much contamination to make a mouthpiece unusable.

That said, I don't generally have another 2nd stage on my deep bailout, just the BOV connection.
 
Dave Sutton said:
BOV's are, in my opinion, a "transition" tool, allowing a more orderly transition to an open circuit regulator on a stage bottle. I would never stay on one for more than the length of time needed to get onto a "real" regulator.


Dave


.
Click to expand...

FFS, it's about time!
Preach it buddy. Common sense at last.
 
Im not sure that there would be many that would argue with that.

But how long can it take to get on to a regular 2nd stage worst case scenario.

Will a half full 3L dil tank last long enough at depth to do that?
 
Thanks guys for input here on BOV to manifold or Offboard.....

So the two main relevant CCR issues here are:

Hypercapnia:

BOV need to be connected to off-board gas due to elevated breathing rate compounded by depth, max bottom time & depth as the worst case failure; on board DIL (3ltr tin) at max depth won't last long.

BOV to be used as a transition tool to safely swap to 2nd stage on bailout tin, as soon as you can swap.

Flood/Caustic Cocktail:

BOV not an option, use bailout tin 2nd stage, off-board connection not relevant here.

A DSV would have a similar issue being not an option, i.e no sanity breaths from the Meg ADV.

Has anyone experience of this they can share?

Does your breathing rate go through the roof, is it prudent to place the bailout 2nd stage on a necklace round your neck?

Does anyone dive like this with a BOV?

Cheers,

David.
 
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