Options for onboard gas access.

Gilles · 17th September 2007, 04:54

Quote: (Originally Posted by Drmike)

how does the check valve effect the wob?

When the check-valve was on the now redundant switch-block, I didn't notice any resistance.

In the one time I had the chance to test this setup (40m on air) so far, I tested but forgot to close the onboard tank valve

. The checkvalve has a stamp on it indicating 1 psi to open, but there'll surely be a greater P-drop with more flow.

I'll have to wait till next weekend (weather permitting) for a max 45m on air test.

G

**Dave Sutton** · 17th September 2007, 09:23

Quote: (Originally Posted by Gilles)

The checkvalve has a stamp on it indicating 1 psi to open,

Which says nothing about the flow available thru the thing.... just make sure.

Dave

Hanssing · 17th September 2007, 10:43

Quote: (Originally Posted by Dave Sutton)

Which says nothing about the flow available thru the thing.... just make sure.
Dave

Jakub would check this but has not returned with data, so perhaps M&J does not know? (See: http://www.rebreatherworld.com/rebre...low#post127815)

Nicolai

MarcLaukien · 19th September 2007, 20:54

After trying many different configurations, I have now chosen the simplest possible solution: The Optima hoses are all unmodified, and only the BOV connects to the off-board gas, using one long hose, routed from the right, behind my back under the Optima straps, down on my left side, to the bailout with a QD w/ check valve.

I didn't like the other configurations. Too many hoses! In particular, I want less stuff in the chest and counter-lung area, not more. With the simple setup, I have full access to my off-board with the turn of a switch, good head mobility (because of the rather long hose), and a simple setup.

The on-board dil tanks are too small for bailing out anyway, so all the extra hoses to be able to access another meager 5 cf of gas or so (if the dil tank is not full anymore) is not worth the added complexity of having the BOV access to both on-board and off-board.

Gilles · 12th November 2007, 12:49

Quote: (Originally Posted by Drmike)

how does the check valve effect the wob?

Finally after many weeks I tested using Nitrox 30 at 40m. I tested the Golem BOV fed by the offboard through the checkvalve, then the on board, then compared with a Poseidon extream 2nd stage directly off the 1st stage on the bailout.

Normal breathing, then breathing as hard as I could.

Very difficult to detect the difference between the on and offboard tanks (i.e. thru checkvalve and not thru) using the Golem 2nd stage Apeks clone of the Golem BOV.

I could notice a difference however, between this and the Poseidon 2nd stage (the latter breathing easier).

I believe I will continue with this set up. So easy to use with so much flexibility. It works really good.

Aknowledgements to Dave Sutton and DrMike for their respective influences generating this concept.

Lancer4545 · 13th November 2007, 05:09

These manifolds seem to make a lot more sense than a heap of Tee pieces and look a lot neater........With all the advantages

Lance

manifold 026s.jpg
manifold 027s.jpg
Manifold 029s.jpg

womble · 13th November 2007, 20:03

[quote=decoweenie;135503]When I first started diving Rebreather, I too wanted to add more complexity to the rig hoping to eliminate all possible failures.

IMHO, the more linkages between your options, the bigger chance that a single failure could take down all of the options. Or the bigger chance of selecting the wrong option.quote]

I have gone/am going through this at the moment. I tried rigging up what I thought was a great on/offboard connection system with redundant O2 etc, and found I would need extra hoses, lots of extra joins, each with extra o-rings, etc. . . . . So I scrapped that idea and have gone back to the Megs standard setup for the time being.

Quote: (Originally Posted by Drmike)

Why not get rid off all that hardware and utilize the LP port areas inside the onboard 1st stages as manifolds.

All you need is 2 QCs.

Is this manifold facility still useable in the event of a problem with the 1st stage?? E.g freeflow, freezing, IP creep, etc etc. Sorry, just a bit late to this thread.

FWIW, I have found that checkvalves do increase WOB by a little. I'm thinking about taking it off and just having a normal QC as I dont disconnect it (my offboard into my BOV) underwater anyway. The only time I can imagine water getting into the system would be when (sometimes) I disconnect the offboard at the surface to pass the cylinder up onto the boat. But, correct me if I'm wrong, the hoses leading upstream from the QC would still be pressurised so wouldnt this stop water from entering the hoses anyway??

Thanks in advance.

Gilles · 13th November 2007, 21:48

Quote: (Originally Posted by womble)

FWIW, I have found that checkvalves do increase WOB by a little. I'm thinking about taking it off and just having a normal QC as I dont disconnect it (my offboard into my BOV) underwater anyway. The only time I can imagine water getting into the system would be when (sometimes) I disconnect the offboard at the surface to pass the cylinder up onto the boat. But, correct me if I'm wrong, the hoses leading upstream from the QC would still be pressurised so wouldnt this stop water from entering the hoses anyway??

Thanks in advance.

The purpose of the checkvalve is to allow pressurization from the on-board tank. The QD on the Rebreather end is male and needs a checkvalve. The checkvalve allows even more simplicity than using a pair of QD's (as suggested by other contributors above). You can choose to connect the offboard or not.

Switching from on to offboard is done simply by opening/closing respectively of the onboard tank valve (assuming the manifold system above works the same way as my system using T junctions). If the onboard 1st stage has a problem, you close the valve and you thus have the offboard. Likewise if the offboard 1st has a problem (you dis-QD and close the tank valve).

What I consider disadvantageous of the basic set up (i.e. BOV to onboard) is the very few breaths available and the significant complication occuring (i.e. emptying the dil tank) just when sanity breaths are taking effect. In addition, for me personally, I like the comfort of being able to full flush my loop at will at any time, whether I imagine a problem or not, without worrying about my limited onboard dil supply.

Gilles · 7th February 2008, 06:15

I have made an important amendment to the design detailed in the above posts. This may serve some of you who have interest.

I have removed the in-line shut-off from the ADV (was serving insufficient purpose there) and installed it on the Y-block that joins the offboard and wing-inflator. The shut-off isolates the rest of the system from the offboard.

Why? well I see inadequate reason for shutting off the ADV on bottom. Additionally... should a leak spring from anywhere, the shut-off rapidly isolates my bailout (safeguarding it), and preserves wing inflation. If I want to shut-off ADV, I can shut-off offboard and drain the system pressure.

pic 1: photo of QD-wing inflator-shutoff
pic 2: revised schematic

note: this system provides OC access of both on and off board tanks.

View Poll Results: Which BOV plumbing concept (to include onboard gas) is preferred?
All QD's using no switchblocks	14	38.89%
1 Switch for off to onboard dil. QD at BOV for O2	5	13.89%
Like option2 but QD's at switchblock	2	5.56%
Two switchblocks.	1	2.78%
Use 2nd stages on each tank	17	47.22%
Multiple Choice Poll. Voters: 36. You may not vote on this poll

17th September 2007, 04:54	#51 (permalink)
Gilles Worship the feminine Current Rebreather/s: Megalodon Other Rebreather/s: Join Date: Sep 2005 Location: Den Haag (Netherlands) Posts: 761	Re: Options for onboard gas access. Quote: (Originally Posted by Drmike) how does the check valve effect the wob? When the check-valve was on the now redundant switch-block, I didn't notice any resistance. In the one time I had the chance to test this setup (40m on air) so far, I tested but forgot to close the onboard tank valve . The checkvalve has a stamp on it indicating 1 psi to open, but there'll surely be a greater P-drop with more flow. I'll have to wait till next weekend (weather permitting) for a max 45m on air test. G __________________ Gilles http://www.dirrebreather.com
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17th September 2007, 09:23	#52 (permalink)
Dave Sutton Living on Animal Farm Current Rebreather/s: Sport Kiss MK 15.X rEvo Other CCR Azimuth Home Build Other Rebreather/s: Classic Kiss rEvo Other CCR Azimuth Home Build Join Date: Jun 2006 Location: Narragansett, Rhode Island and Hackettstown, New Jersey Posts: 2,510	Re: Options for onboard gas access. Quote: (Originally Posted by Gilles) The checkvalve has a stamp on it indicating 1 psi to open, Which says nothing about the flow available thru the thing.... just make sure. Dave __________________ . "All animals are equal, but some animals are more equal than others" Professional Small Boy: Never Successfully Cubicled.
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17th September 2007, 10:43	#53 (permalink)
Hanssing flap-flop ..... flap-flop Current Rebreather/s: rEvo Other Rebreather/s: rEvo Join Date: Nov 2005 Location: Denmark Posts: 344	Re: Options for onboard gas access. Quote: (Originally Posted by Dave Sutton) Which says nothing about the flow available thru the thing.... just make sure. Dave Jakub would check this but has not returned with data, so perhaps M&J does not know? (See: http://www.rebreatherworld.com/rebre...low#post127815) Nicolai __________________ Woohooo - I can change my rEvo! Its going to be bitchin' tricked out piece of gear
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19th September 2007, 20:54	#54 (permalink)
MarcLaukien Custom Title Allowed! Current Rebreather/s: Other CCR Other Rebreather/s: Optima Other CCR Join Date: Dec 2006 Location: South East Florida Posts: 170	Re: Options for onboard gas access. After trying many different configurations, I have now chosen the simplest possible solution: The Optima hoses are all unmodified, and only the BOV connects to the off-board gas, using one long hose, routed from the right, behind my back under the Optima straps, down on my left side, to the bailout with a QD w/ check valve. I didn't like the other configurations. Too many hoses! In particular, I want less stuff in the chest and counter-lung area, not more. With the simple setup, I have full access to my off-board with the turn of a switch, good head mobility (because of the rather long hose), and a simple setup. The on-board dil tanks are too small for bailing out anyway, so all the extra hoses to be able to access another meager 5 cf of gas or so (if the dil tank is not full anymore) is not worth the added complexity of having the BOV access to both on-board and off-board.
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12th November 2007, 12:49	#55 (permalink)
Gilles Worship the feminine Current Rebreather/s: Megalodon Other Rebreather/s: Join Date: Sep 2005 Location: Den Haag (Netherlands) Posts: 761	Re: Options for onboard gas access. Quote: (Originally Posted by Drmike) how does the check valve effect the wob? Finally after many weeks I tested using Nitrox 30 at 40m. I tested the Golem BOV fed by the offboard through the checkvalve, then the on board, then compared with a Poseidon extream 2nd stage directly off the 1st stage on the bailout. Normal breathing, then breathing as hard as I could. Very difficult to detect the difference between the on and offboard tanks (i.e. thru checkvalve and not thru) using the Golem 2nd stage Apeks clone of the Golem BOV. I could notice a difference however, between this and the Poseidon 2nd stage (the latter breathing easier). I believe I will continue with this set up. So easy to use with so much flexibility. It works really good. Aknowledgements to Dave Sutton and DrMike for their respective influences generating this concept. __________________ Gilles http://www.dirrebreather.com
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13th November 2007, 05:09	#56 (permalink)
Lancer4545 Closed Circuit Divers Aus Current Rebreather/s: Megalodon Other Rebreather/s: Join Date: Jun 2007 Location: Cairns QLD Australia Posts: 573	Re: Options for onboard gas access. These manifolds seem to make a lot more sense than a heap of Tee pieces and look a lot neater........With all the advantages Lance manifold 026s.jpg manifold 027s.jpg Manifold 029s.jpg __________________ You can run but you can't hide! ISC Appointed Megalodon Dealer for East Australia http://www.closedcircuitdivers.com.au info@closedcircuitdivers.com.au
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13th November 2007, 20:03	#57 (permalink)
womble Custom Title Allowed! Current Rebreather/s: Megalodon Other Rebreather/s: Join Date: Aug 2006 Location: UK Posts: 188	Re: Options for onboard gas access. [quote=decoweenie;135503]When I first started diving Rebreather, I too wanted to add more complexity to the rig hoping to eliminate all possible failures. IMHO, the more linkages between your options, the bigger chance that a single failure could take down all of the options. Or the bigger chance of selecting the wrong option.quote] I have gone/am going through this at the moment. I tried rigging up what I thought was a great on/offboard connection system with redundant O2 etc, and found I would need extra hoses, lots of extra joins, each with extra o-rings, etc. . . . . So I scrapped that idea and have gone back to the Megs standard setup for the time being. Quote: (Originally Posted by Drmike) Why not get rid off all that hardware and utilize the LP port areas inside the onboard 1st stages as manifolds. All you need is 2 QCs. Is this manifold facility still useable in the event of a problem with the 1st stage?? E.g freeflow, freezing, IP creep, etc etc. Sorry, just a bit late to this thread. FWIW, I have found that checkvalves do increase WOB by a little. I'm thinking about taking it off and just having a normal QC as I dont disconnect it (my offboard into my BOV) underwater anyway. The only time I can imagine water getting into the system would be when (sometimes) I disconnect the offboard at the surface to pass the cylinder up onto the boat. But, correct me if I'm wrong, the hoses leading upstream from the QC would still be pressurised so wouldnt this stop water from entering the hoses anyway?? Thanks in advance. __________________ "What could possibly go wrong?? . . "
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13th November 2007, 21:48	#58 (permalink)
Gilles Worship the feminine Current Rebreather/s: Megalodon Other Rebreather/s: Join Date: Sep 2005 Location: Den Haag (Netherlands) Posts: 761	Re: Options for onboard gas access. Quote: (Originally Posted by womble) FWIW, I have found that checkvalves do increase WOB by a little. I'm thinking about taking it off and just having a normal QC as I dont disconnect it (my offboard into my BOV) underwater anyway. The only time I can imagine water getting into the system would be when (sometimes) I disconnect the offboard at the surface to pass the cylinder up onto the boat. But, correct me if I'm wrong, the hoses leading upstream from the QC would still be pressurised so wouldnt this stop water from entering the hoses anyway?? Thanks in advance. The purpose of the checkvalve is to allow pressurization from the on-board tank. The QD on the Rebreather end is male and needs a checkvalve. The checkvalve allows even more simplicity than using a pair of QD's (as suggested by other contributors above). You can choose to connect the offboard or not. Switching from on to offboard is done simply by opening/closing respectively of the onboard tank valve (assuming the manifold system above works the same way as my system using T junctions). If the onboard 1st stage has a problem, you close the valve and you thus have the offboard. Likewise if the offboard 1st has a problem (you dis-QD and close the tank valve). What I consider disadvantageous of the basic set up (i.e. BOV to onboard) is the very few breaths available and the significant complication occuring (i.e. emptying the dil tank) just when sanity breaths are taking effect. In addition, for me personally, I like the comfort of being able to full flush my loop at will at any time, whether I imagine a problem or not, without worrying about my limited onboard dil supply. __________________ Gilles http://www.dirrebreather.com Last edited by Gilles : 13th November 2007 at 22:00.
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