Proposed new gas routing: opinions please....

PCDiver

You also have to think about gas donated from a buddy (team bailout). If all bailout bottles had a GCS connector, the procedure could be:

- take stage from buddy
- switch to off-board regulator
- disconnect empty bottle from GCS
- connect full tank to GCS
- open new tank
- switch to BOV

Padowan

Problem I have with using the GCS in a "connect it if you need it" fasion, is that they are a bitch to connect - I'd rather have it connected and disconnect if I don't want it, and by that nature, I limit myself to one source connectable.

I agree on PCDivers comments about analysing all the possible failure points, and what the implications would be - I'll have a think about that, and post something summarising what I think, and how I think I can mitigate anything catastrophic..... For example - out of the 2 o2 routes I propose there are more failure points in the line that uses the manifold, so perhaps one improvement would be to feed the manual injector direct from the first stage, and then have the solenoid connected to the manifold with the Whitey valve on the feed to that - then any failure on the most o-ring dependant line can be isolated.

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Padowan

You could do this transition by switching on the onboard gas and breathing that for the time it takes to hook up the new offboard, saves deploying the stowed reg! Although the male end of the GCS (connected to the manifold) would be pressurised (or perhaps not if the one way valves are used) the female end would not be, and that's the one that needs to be depressurised to allow easy connection...

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PCDiver

You could also put a compatible hose on the rich off-board and connect that to the manual injector.

If you are using BMCLs, you need to add another GCS on the O2 side, since you can't reach the manual injector easily enough to connect a new O2 rich supply. A second GCS on the O2 side wouldn't be a bad idea. It would create the same system for O2 supply. And if you were to add an O2 regulator on your manifold, you would have access to all your gasses.

Peter

PCDiver

I don't think that the one-way valves will make dis-reconnecting easier. About the on-board gas. That is probably your leanest (hypoxic?) mix. So usability could be limited.

Padowan

True.

I'm not sure I like the idea of an OC reg on the O2 side - I had that once before, then removed it when I started thinking "the Rebreather is just for RB-ing...". I know that I am relaxing that perspective on the diluent side, I still think that it should apply to the O2. If you lose that, you really are in the sh!t from an options perspective....

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diverklondike

Simon,

Great diagrams and thanks for the nice comments...

Here are some additional thoughts and responses to the points raised.

1) Flow of off board gas back into Dil Bot. - I am in total agreement that this could happen but it's something that I accept. From my perspective I wanted the capability to either feed the offboard only to the BOV or to the Dil manifold as a whole. This gives you choices. If you were so inclinded you could add a check valve to prevent the potential back flow. I did not since I was not sure of the effect that it would have on out bound gas flow.

2) Turning off flow to O2 solenoid - The bottle that I carry behind my head contains O2. In the case of my solenoid sticking open I can shut off the O2 in the case and plug my off board O2 into the manual O2 feed. For what it's worth I can also plug it into my BOV

3) Connecting/disconnecting GCS at depth. - Couple things here... a) I choose going with Swagelok connnector since I find them easier to plug and unplug at depth. b) This is part of the reason that I have an elbow on the Off-board connection since it's easier to hold onto.

4) Is the Whitey worth the effort?? - "Yes" Here are a couple reasons why.. a) It allows me to have my BOV fully isolated yet protect the integrity of the Dil in the case. b) With a flip of the whitey valve I can use all of my off board gases in an SCR mode via ADV if needed.

5) I also carry a small adaptor in the water that allows me to plug all of my Swagelok connections into the traditional AP manual adds. This allows me to support my dive buddies and ensures that I can still get gas where I want it in the case of a failure in the primary Dil manifold/hoses.

Great conversation...

Dive Safe...

Mark

PCDiver

But wouldn't you kick yourself if you run out of bailout gas with still half an hour (at 6 meters) of the best deco gass on your back that you can't get to?

And if you would loose your onboard o-supply ( or start with the wrong gas in it), you could connect an off-board O2 tank via the GCS. And you could still use the computer controlled solenoid what would reduce task loading.

Padowan

I guess so.

The other thought process that I go through to evaluate this stuff is to think about why I would be using the bailout in the first place - IMHO the only real reason that I will be off the loop and on OC for the WHOLE of the rest of the ascent portion of the dive would be a loop flood. In the event of a CO2 hit at depth, I'd certainly consider trying the scrubber out again in the shallows as an O2 Rebreather or in SCR mode with my richest bailout...

So at the end of the day, not only does it need to be a total loop flood, but I would have to not have enough rich OC gas AND not have anybody around me with some more OC gas AND have no gas staged on a station AND be diving off a boat with no drop gas procedures - how many failures in equipment or procedures is a reasonable level of cover?

Once at 6m, yes there is still danger, but you're a lot closer to help/boat/helicopter, than at the bottom, and if push comes to shove, you pop up and get bent (considering how many failures I'd need to have to make this the last resort, I'd be thinking I was pretty lucky to get out of it at all!) - so I consider the options available at depth, considerably more useful than the options available once I get to 6m so that's certainly my modularity focus...

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PCDiver

There are a couple of scenarios where an O2 reg could be useful:
1. (Solo) dive where you want to limit bailout gases - typical holiday reef dive e.g. 30 meter, no deco

2. wreck dive - You encounter a catastrophic loop failure. You try to fix the problem, but because of the extra task loading and bouyancy problems, the current gets hold of you and you end up off the wreck without buddy. In this scenario you probably loose extra gas compensating for the bouyancy difference.

3. To donate O2 to buddy CCR diver that ran out of O2 - He could use your O2 reg and blow it into his loop. An extra hose on your O2 would of course be easier.

I know, these are not very common situations. But I'd rather have more options to fix a problem. I have learned the hard way that Murphy, most of the time, does not come alone, but brings his entire problem family.

Peter