General design question - flood recovery....

Genesis

As I close in on something actually divable for the K1, I'm looking at some final things I can add - or not - to the design.

One of the issues is "total" flood recovery.

I have an OPV (drysuit dump valve, really, Poesidon's "no backflow" design) on the exhale lung, down low, to clear water that gets into the loop via the mouthpiece or into the exhale side. Theoretically, water that gets into the scrubber may end up there / can be rolled to there.

But in a full-on flood, where the loop is badly compromised, you're unlikely to be able to drain it all that way. There is no provision to drain on the inhale lung as it stands, and none directly on the cannister. Of course if you get flooded THAT bad, you might also have a cocktail problem...... water traps or no!

How significant is this capability (e.g. a dump in the cannister) in the real world?

I know a number of units have no real capability to recover a full-on flood. I've mixed feelings on this - a flood that is caused by a severe loop compromise (e.g. torn hose) is not recoverable anyway, as you can't fix that problem underwater, so you're left iwth a bail irrespective of other considerations.

So..... draining water from the exhale lung, yes. Is more capability than that useful? It seems to me that there's a ying and a yang - the yang being that an OPV on the cannister bottom, for example, could stick open and cause a flood instead of curing one!

Anyway, thoughts of those with experience with "both worlds" would be helpful as I start buttoning things up and preparing to actually dive this beast.....

__________________
"A venturesome minority will always be eager to get off on their own, and no obstacles should be placed in their path; let them take risks for Godsake, let them get lost, sunburnt, stranded, drowned, eaten by bears, buried alive under avalanches - that is the right and privilege of any free American."
http://www.denninger.net
http://www.diversunion.org/liability.htm - Fix the Diving Cert racket

Marc T

I think its much more important not to have flood, so the less valve in your system, the less holes cutted in your counterlung, the lowest is the flood risk.
On several of my home made Rebreather I ( and first a friend on its own ) are now using a very simple ADV wich is a simple second stage reg with and added disc and spring to turn the exhaust valve into a OPV.

It can seem to be a radical choice but it works fine and its a simple and ( so ) finally secure way.

Mdemon

I disagree. Remember, your loop is likely to be at ambient. So, even the odd leak at the bottom of the lung shouldn't be disasterous. On my MOD 1 my dil inflator came undone (bad technique taken from the Internet - you have been warned! ) and although it was a damp, gurgly breathe, it was some minutes before I thought I ought to bailout, rather than actually needed to. The water entered only to the point where it was equalised, if that makes sense.

I've cleared water from counterlungs before by gripping onto a rock with my knees and adding dil to the CLs. I then unscrewed the injector and crushed the lungs until the water was all out and bubbles started to come out of the injector hole, then replaced the injector and carried on.

So, for Genesis; what might be useful is a dump valve or something easier to operate than unscrewing an injector, set low into the lungs. I suspect clearing them mid-water would be do-able as long as it was done slowly and carefully. To clear the scrubber you are going to need another dump valve in the bottom of it as some rebreathers do already. However, that might be a hole too far - if that's leaky then your risk of a cocktail massively exceeds the risk of needing to empty a flooded loop and also requires you to bailout. I think even those who have been diving for decades have only experienced a couple of floods, and IIRC, the worst part was the cocktail that came with it. So for my money, I'd want to be able to empty counterlungs if necessary but wouldn't want any extra compromising of the scrubber. You can always roll and move water from scrubber/hoses into the counterlung should you need to.

HTH

__________________
www.southwestmafia.com

Lake_Tahoe_Diver

Have you thought of the style of drains found on the counter lungs of the prizm?

__________________
Scuba Diving,the only sport where it is good to be in over your head....

Marc T

Well perhaps you think my first response to be a little bit provocative and it was even if the system is fully operative and safe.
If you really worry about recovering the loop and want a dump vavle the question is how many and where.
At the bottom of the scrubber seem to be quite dangerous, so on the bottom of the counterlung is a better place.
One on the exhale CL cannot dump cocktail coming from scrubber except on a boris design.
One on the inhale CL cannot dump water coming from mouthpiece and dont prevent later caustic cocktail
So if only one I prefer on the Inhale CL because give you a backup solution for a leak anywhere in your Rebreather.
Two on each CL is better.
Two loops seems to me to be the future of the Rebreather, so need simpliest design of the loop and so dont worry too much about loop recovery.
Just my two cents as some say

Marc

michael hearn

i agree ,i wouldnt want to cut holes in the scrubber. i have just converted my inspo to bmcl, ox and dil inflaters are compact bcd inflaters conected to the bottom of lungs and mounted on each side at hip level. since the inflaters have exaust valves i can eject water from each lung. i have tested this out of the water works fine, am a bit reluctent to try underwater since it would mean deliberatly flooding a lung,wouldnt want to tempt fate.as someone pointed out floods dont happen very often, putting more holes in your Rebreather can surely only increase the chance of a flood.
mike