Why have a rebreather?

[silent running]

Thank you very much for fast answer, Silent Runner.
One more question, absorbant is cylinder too, right?
So, you have to check it in open, right?
How difficult it is to assemble it in let's say Mexico?
Does rebrether used regular cylinders, like aluminum 80's? Sorry if question is stupid, I'm starting on rebreathers, but have over 50 dives with regular cylinders under my belt.
Thanks again.

Hi Mike, I think you are asking what kind of container the absorbant comes in, right? Absorbant comes in sealed plastic containers some of which look like a joint compound bucket. They are sealed shut by the manufacurers to keep the moisture content steady. I have never had anybody ask to see inside my container. Sometimes they ask to see the material data saftey sheet, provided by the manufacturer, to see if it's safe for transport. This sheet basically says that there are no active chemicals or corrosive agents in the stuff. Your other question is about assembling cylinders, right? That's no big deal, just screw the valves back into the neck and put a big wrench on the valve and tap it with a hammer. This is something every dive shop does regularly. My unit, the Prism, will take any cylinders up to 40cuft., but it comes with 19cuft cylinders from the manufacturer. You don't need very much gas for a CCR as they recycle it. I could easily get 10hrs out of my19 cuft O2 gas supply and a full 19cuft cylinder of air for the diluent (which also functions as the open curcuit bailout supply) would be enough to get to the surface. The limiting factor for CCR bottom time is typically the scrubber duration.

 

[caveseeker7]

Apologize about the tone if it offended you, wasn't my intention.
Am off to a meeting, so I gotta be brief.

Dave Shaw used a MK15.5 CCR, one of the most capable ever units build.
But there were several factors, aside from the enormous depth far beyond the units design frame, that were contributing factors.

Unit specs call for 4-8 mesh size absorbant.
In order to get the duration needed, Dave opted for the smaller 8-12 size.
That increases WOB, and the additional physical labor/energy increases CO2 production.

He used a non-spec absorbant pad in the center section with a higher WOB.
The factory spec was unavailable to him at the time.

Said absorbant pad wasn't cut to fit properly, covering the exhalation gas path to the scrubber which increased WOB.

He assembled the unit incorrectly which inceases WOB when the pad is moist.

Four factors incresing WOB, four factors increasing CO2.

Add to that added WOB due to gas density at the enormous depth and the fact that rebreathers with backmounted counterlungs are much more susceptible to hydrostatic differences, and WOB must have been abysmal. The added workload of trying to bag the body and attempts of cutting himself out of the line certainly didn't help, either.

What you can't hear on that copy of the tape is that he hyperventilates and breathes very shallow.
Shallow breathing, like skip breathing, increases the CO2 that gets contained in the body.
And that's where it's dangerous. The best scrubber can't do its job when the diver doesn't vent his lungs.

Hypercapnia among OC isn't unknown. Skipbreathing, breath holding, poor performing regulators, high gas density all play into it. Even free divers have blacked out form it.

 

[jptrealty]

Failure modes. All your eggs are in one basket and some failures (whether diver error or apparatus error) will render you unconscious before you realize that there is a problem.... OC is much more forgiving in this respect.

R..

This is simply not true, in many ways RB divers have many more options than OC divers, for one they carry OC with them!! I don't have bottom time restrictions that I have with OC, I know many more divers that have been killed on OC in the Northeast. I can't think of one that I KNOW that has died on a RB in the Northeast, however I know of several people who would of died if they were on OC ( getting lost inside a wreck, hangups ect.)

I have a feeling these statements were made out of ignorance, not to worry, education can fix that, tal; to people like padiscubapro and caveseeker7 they have there **** together and from what I have seen they will point you in the proper direction.

Good Luck

 

[Diver0001]

I have a feeling these statements were made out of ignorance, not to worry, education can fix that, tal; to people like padiscubapro and caveseeker7 they have there **** together and from what I have seen they will point you in the proper direction.

I'm sure that's true. I didn't just write that to troll it though. In answering farrakhan's question about why one wouldn't want a rebreather I was pointing out--albeit clumsily--that more can go wrong than it might seem at first and that some of these things will get you before you have a chance to deal with them. Despite being out of my depth (so to speak) and despite starting with a bit of a troll I did find kicking this ball around a bit rather helpful.

Caveseeker7, thanks for your run-down of the Dave Shaw problem. I can place hypercapnia in that context much better now.

R..

 

[mattmexico]

Yo there

I have been recently traveling to Honduras with my Megadolon involving some driving, two international border crossings, three flights, three taxi rides and a little of walking. And that was just one way, same on the way back.

The Meg was taken apart and split into a pelican box and my check in gear, I was traveling with two 3 ltr steel tanks ( check in and Inspiration size ) since I knew my destination ( importand to check out before ) had oxygen but only up to around 2000 psi which is plenty for the little deco reef dives and some normoxic trimix dives I was planning to do. Larger tanks are better for not so high pressure without a booster. I did not take the valves out but emptied the tanks and left the valves open so they are ambient pressure inside.

I was traveling with my Inspiration before, same route to Honduras and left it complete, just drained the valves and left them open. I did the same with my Optima, shorter trip but harder security from Miami to Cancun Mexico.

I have never traveled with a lot of absorbent material since the destinations I dive at have to be rebreather friendly ( importand to check out before ) in order to support me and my bread box diving habit.

Matt
www.protecdiving.com

 

[gandhiReBreather]

decomprtion obligation very minial comparing to open at the same deep dive and time