| Offboard connection setup - Thoughts please?
For a while now I have been thinking about plumbing in a system which will allow me to:
1) use a redundant o2 source
2) isolate the solenoid
3) allow access to onboard and offboard diluents through the ADV
4) allow access to onboard and offboard gasses throught the BOV
Currently I have been using a gas switch block (from M&J) just to select which gas goes to the BOV - onboard or offboard with good results. Yes, it does make breathing through a 2nd stage with high flow rates harder, but only slightly so. So low flow rates, like that on a Rebreather on the loop should be no problem.
Encouraged by this, I have drawn up a schematic diagram of how things would work. I know it looks rather untidy, but with careful hose routing I think it should be fairly neat.
The M&J switch blocks are pivotal to this design, as they allow isolation of one or both sources of gas plumbed into them.
On the diagram, should you have a catastrophic BOOM on the O2 side, you would turn off the O2 cylinder, check handsets/gauges, dil flush etc etc to manage the immediate problem, then open the redundant O2 cylinder, flip the GSB and away you go. You have access to redundant O2 through the solenoid.
If the failure is further upstream, e.g within the GSB or stuck open/closed solenoid, the redundant O2 can be unplugged from the GSB and either sources of O2 can be used to fly the unit manually through the manual add valve and standard LP inflators on both O2 sources.
Similarly on the dil side, you can put both your onboard and offboard dils through the ADV, giving a very quick way of flushing the loop. Also, you know that whatever you have in the loop is what will pass through the BOV, so no need to switch gasses on your VR3, just switch to OC - only 2 switch presses.
Catastrophic loss of onboard dil, turn off the cylinder, check handsets / gauges etc etc. Just flip the GSB to offboard and open the cylinder valve.
Failure of the GSB, unplug the offboard and just add manually through the manual add valve using the standard LP inflator on the offboard / deep bailout. This would also mean loss of use of the BOV, but you have standard 2nd stages on the offboard, so this would mean a standard OC bailout.
Leaking ADV? you can still isolate the ADV as normal, but you can also isolate from the GSB as well.
I think that is everything. I am aware this would open up a load more potential failure points, but the degree of flexibility this would offer I think outweighs this.
I am very keen to hear your thoughts, feel free to criticise as I may have missed something glaringly obvious!
Thanks for reading this!!
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