Diluent selection and the great alpinist v siege debate

Dave Sutton

And at 100 meters that would be INAPPROPRIATE, just as inappropriate as diving 10% at 30 meters.....

If you mean 100 feet, 21% dil there would be a perfect choice.

All I am drawing attention to is the unwarranted use of GROSSLY LEAN diluents in rigs when there is no reason to do so and to suggest that PROPER mixes be used and that *WEAKLY RICH* mixes can be tolerated if used *correctly* to provide far better SCC and OC Bailout capability in addition to being able to be used safely shallower. I do not advocate *deliberately* mixing hot dil but simply state that we can use normoxic dils deeper than one might think *if we pay attention* and use all of their advantages thoughtfully.


Dave

Dutchy

That will take another two minutes or so... I have an inline valve (positioned after the KISS valve) It works immediately. (part numbers are in steevke's blog) For those that will argue that's yet another failure point... sure but I'm no alpinist. For those that think it's an additional risk. When it closes you can't press the KISS valve button. You'll know the very first time you try to manually add oxygen.

__________________
= This post is environmentally friendly. It is composed of 100% recycled electrons only. = SK #007

Dave Sutton

What may not be obvious from this post is that the residual trapped 02 in the regulator, lines, and especially in the the HP gauge hose, will continue to allow 02 to feed into the loop for a while after the cylinder valve is closed. The ball-valve right against the KISS valve allows instant shut-off of 02 flow and is exactly how my own KISS rigs are all set up. It's a good method. My only change is to have the valve ahead (upstream) of the KISS valve so I can shut off all flow in event of a broken line at the KISS valve or an unthreaded part, etc. Better to isolate gas in front of any subsystem rather than behind. This produces two advantages with one part. Typical alpine mindset.


Dave

SteveL

Hi guys - just read my drunken post - sorry 'bout that

Anyway happy New Year again

Siting here now with VERY sore head coffee and greasy bacon sandwich -

I am a big advocate of gas that you can breathe on the surface panting like a steamtrain in a big current -

Back in my OC days I regularly dived with a mix that optimised deco - so it was always planned at close to 1.6 for every dive - did loads of dives like this - amazingly still here to tell the tale. So why is it so different with the breather.

I check my cells in a pot - to make sure they will produce the goods -

Most of us flush the loop with 02 around 6m anyway - which is where most of the dive time is anyway - if you are running SCR nice to have those extra molecules in there to leverage that gas as long as possible.

Gotta go need more grease.....

Steve

Dutchy

My mindset is to 'rely' on the Rebreather breaking down (allthough it hardly ever goes wrong) and have a BOV on diluent with FO2>=21% + a stage so for now I'll leave it in the current position. I agree with what you say but would hate to loose the stuck_kiss_valve_when_ball_valve_is_closed safety net allready. The design principle itself I'll try to engrain in my mind.

__________________
= This post is environmentally friendly. It is composed of 100% recycled electrons only. = SK #007

Sutty

Can't find the blog, interesting idea, do you have a link to find the part number?

Thanks,
Neil

__________________
Never forget that life is a finite resource.

Dutchy

It looks like his blog has vanished into thin air but I remember referring to it on an earlier occasion so a search on this forum revealed my old post hence the old thread

http://www.rebreatherworld.com/kiss-...arts#post68139

__________________
= This post is environmentally friendly. It is composed of 100% recycled electrons only. = SK #007

Dave Sutton

I put a very complete KISS Valve assembly sequence with isolation valve up on the web someplace a few years back. Tubby has taken his site down but the cache still resides here and the assembly is detailed:

DSkissvalve.html

I had a hard time gettign photos out of the cache (and what happened to Tubby anyhow?). In any event, here is the final photo from the series, showing all of the parts laid out in order. The valve is a chrome plated brass one that I buy for less than US$10.00. Works great. I shorten the handle with a saw to make it more compact. I also use custom made soft hoses, but with the correct fitting into the ball-valve, the original SS KISS hoses can also be used (in fact that is how my Spot KISS is set up)


The bottom line is that an isolation ball valve can be placed UPSTREAM of the KISS valve for about US$15.00. Please, guys, put the valve on the inlet side of the KISS valve. This way if the valve itself fails to leakage to the sea, the 02 can be turned off to conserve, the re-opened, a manual bolus injected, and then re-closed. And another note: Either make sure you have a second stage on the 02 side OR add an overpressure valve to the first stage. Otherwise a HP seat failed to creep will blow the hoses if the ball valve is closed.



Dave

Attached Images

KISS.jpg (24.6 KB, 284 views)

Dave Sutton

And fellow Alpinists, please remember the following:

We're betting our lives that we will not make mistakes. This is no place for the inexpert.


Dave

Attached Images

Warning.jpg (130.3 KB, 282 views)

Sutty

Thanks for the valve info Dave/Dutchy.

To get back on topic again..

I can see the benefit of rich-ish dil in terms of SCR mode deco benefit, and in the avoidance of hypoxic incidents near the surface (though you can drop a fair bit below 0.2 without problems - think what your PO2 is at altitude eg skiing at 3500m).
I can also see that in most circumstances having your PO2 at 1.6-1.8 for a couple of minutes while you drop the PO2 by metabolism is unlikely to cause problems.
However I can see the benefit in having a mix lean enough to lower PO2 quickly if you think you are at risk of imminent CNS O2 toxicity (susceptibility does vary from person to person and day to day). This makes me wonder whether it would be feasible to have a very small cylinder (eg as used for SMB inflation or on Buddy BCDs) filled with lean gas, as an emergency PO2-dropping feed to the loop, while having a fairly rich dil for normal use.

Neil

__________________
Never forget that life is a finite resource.