Why is CCR not DIR?

[Doc Intrepid]

Thank you for the informed response, Cameron. Good to hear from you here.

Also, thanks RTodd for your clarification.

(I'm aware of the difference between rebreathers. I've just been away from the scene for quite awhile. George makes no secret of his phone number, and if anyone is truly interested they can either call him or Casey and get most recent details.)

 

[Mike Edmonston]

At what point will SCRs reach the end of the line and CCRs then become the better solution? Can we expect to just throw bigger and more SCRs at the problem without increasing the risk? Are the scrubber limitations identical between SCR and CCR? I'm really asking, I don't know the details to come up with the answers.

What it really comes down to is : Needed equipment for the task at hand.

A SCR is nothing more than a gas extender. It allows you to use a bottom mix, and not have to worry about po2 tox issues UNLESS you exceed your MOD. With twin hp 120's on your back, you could actually run out of scrubber duration and have a co2 breakthrough before you run out of gas (depending on depth). The scruber Limitations are based on your metabolic rate, and how much co2 you produce. Some folks can push a scrubber far, some cannot. The only worry is having a hypoxic mix in your loop, due to not enough "clean gas" being inserted on the constant feed. That is for me, the main reason that an o2 sensor should be on the unit. You need to know your po2, even if you won't tox, you can still pass out.

So in answer to your questions:

1: NO, SCR's have not reached the end of the line, nor should they. They are great tools.

2: CCR's are MORE APPROPRIATE in certain situations where carrying huge tanks is not optimal. They also allow you to go deeper and run your deco straight off the loop. Yes, SCR's can do that too, but they need other gear (Tanks, travel gas, etc...)

3: Do CCR's have more failure points than SCR's... Yes. Does the task outweigh the risk? Depends on the task. In some explorations, CCR is the only way to go. Alot of sites do not have picnic tables, drive up lanes, a sandwich shop, and a compressor.

IMHO, SCR's and CCR's both have their place. Some archaeological sites that I have been to WILL NOT ALLOW bubbles below the anoxic halocline. If you need to do that job, you need a CCR. For long duration, task loaded big cave exploration, a SCR is perfect. When I want lobster, I use an AL80. Just match the equipment to the job at hand.

Cheers

 

[TSandM]

Hey, we have some great content in this thread! Thank you, Cameron and RTodd, and Mike, too; although Mike's answer isn't DIR, it's good additional information.

 

[rjack321]

When considering CCR as an exploration tool , the OW scenarios don't affect the decisions at the end of the line.

From your post, scrubbers and bailout seem even, so at what point does a cave dive become long enough and/or deep enough that taking enough drive gas is riskier and introduces more failure points than diving CCR? How much more efficient is CCR than SCR? 10x 1000X?? What order of magnitude are we talking about?

Basically the RB80 is currently being used out to the point where sleep deprivation is as much of an issue and gas/deco. So having an even greater CCR capability (cause you don't have to haul much drive gas) doesn't get you much - except a diver passed out in the habitat...

Although I don't know the exact scubber durations of all the possible units out there, I doubt there's something which solves the exhaustion problem

 

[Jimmer]

This has been a really informative thread for me, I just want to thank everyone who posted. I've got a very good understanding on the working of all the various types of rebreathers, and have had that understanding for a very long time, but it has been great to see other viewpoints on their use and applications.

Jim

 

[do it easy]

Although I don't know the exact scubber durations of all the possible units out there, I doubt there's something which solves the exhaustion problem

Yup, hadn't thought about that one! Now someone needs to do some studies about sleeping underwater and DCS

 

[amascuba]

You should have seen the discussion over the dinner table about what Venn diagrams are . . .

You're giving me nightmares about a math class I took this summer.

 

[RTodd]

Hey, we have some great content in this thread! Thank you, Cameron and RTodd, and Mike, too; although Mike's answer isn't DIR, it's good additional information.

TSM, I didn't gripe about Mike's post because it wasn't blatantly bashing. But, it is still a non-DIR answer and violates the little red cautions sign. It is totally inappropriate to have mods endorsing that behaviour in this forum.

 

[Sloth]

TSM, I didn't gripe about Mike's post because it wasn't blatantly bashing. But, it is still a non-DIR answer and violates the little red cautions sign. It is totally inappropriate to have mods endorsing that behaviour in this forum.

I was thinking the same thing but couldn't find a polite way to say it.

 

[limeyx]

I think I did, but as I mention, these posts seem plausible, but not definite....There is a NACD CCR in caves workshop later this year.... JJ will be there as a co-presenter I believe. Someone could just ask him.

If the only answers that will satisfy you are from Jarrod then either

1) Stop reading this forum
2) we should close the forum because Jarrod doesn't post here, so therefore there never can be an answer that satisfies you.

What if the posts "seemed definite" but were wrong?

I think good answers were given, and if you piece them together, the relevant points were covered.

I also think that answers from non-GUE founders/instructors while maybe not as thoroughly "correct" are useful and often all we have to go on here ...