SCRs ...whats the point?

magentaseas

What i like about SCRs is their simplicity over CCRs. I like to keep things simple and enjoy the dive.
Im mainly after the extended dive time, and I think a SCR would be better than a twinset. They wouldnt be as bulky and heavy.
And of course theres the dosh side of it to consider!

But while Im looking into it I'll keep an open mind.

cheers

sharon

Pawel

Great take, Stefan

(two in the bunker)

caveseeker7

Simplicity (or lack of it) comes in two ways, the simplicty of the unit itself and its pre- and post dive maintainance, and the simplicity of diving it.

With regards to the the cmf-SCRs and the Sport Kiss, the simplicity of the unit and maintainance is about the same. If you add an O2 monitor to the SCR (I would not dive without it) you'll have to calibrate one or two cells, depending on the monitor, vs. the three cells on the SK. They all have a DSV, hoses, breathing bags and scrubber, two tanks with valves and 1st stages. The SK probably gets the nod for ease of (dis-) assembly.

The SCRs are a bit simpler to dive, as the use of premixed Nitrox almost eliminates the chance of hyperoxia and reduces the chance of hypoxia (can happen when you 'overbreath' the relatively high flow rates).

On the Sport Kiss you have to monitor and need to actively control the pO2, not much work but it's there. The resulting advantages have been pointed out.

Best way really is to do an intro and make sure you're around for the pre- and post dive as that will give you a very good idea of what's involved before and after your dive.

On a CCR gas consumption is incredible. The rebreathers are limited by the capacity of their scrubbers. The small 2 liter O2 tank on the SK easily supplies gas for 5 hours, twice its scrubber duration.

The cmf-SCR on the other hand are limited by gas supply (the Azi in shallow water using both tanks can probably outlast the scrubber), and gas consumption depends on flow rate which depends on the gas selected for the MOD.

I only have the numbers for the Dolphin and Azimuth.
The Dolphin offers 4 orifices as mentioned before:
Mix ....... Flow ....... Time ........ MOD
60% .... 5,8 lpm ... 124 min ... 17 msw
50% .... 7,3 lpm ..... 98 min ... 22 msw
40% .. 10,4 lpm ..... 69 min ... 30 msw
32% .. 15,6 lpm ..... 46 min ... 40 msw

Those times based on 4 ltr/200 bar gas supply and don't take into consideration prepping the unit or increasing gas consumption with yoyo profiles etc. If you open the valve on a full 4 ltr tank with the 60% orifice installed, it'll be empty in about 2 hrs, even just sitting there. You can install larger tanks, but loose some of the weight advantage.

You'll have to figure out if those savings make it worth to dive an SCR ...

Rather unfortunate, that.

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Cheers
Stefan



"Political Correctness is a doctrine, fostered by a delusional, illogical minority, and rabidly promoted by an unscrupulous mainstream media,
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nl_carey

An SCR equipped with appropriate bailout for a deco dive for example, will be of very very similar weight overall. Don't forget, particularly when compared to steel tanks, you will need considerably more weight due to the amount of air in your loop. For most diving, the Dolphin, which is the lightest SCR (aside from the Ray, which I don't rate simply because it isn't as flexible) was about the same weight as twin 10.5's. And as for bulk, when you compare twin 10.5's on a backplate to a Dolphin they are more streamlined, as well as less clunky (the mounting of the bailout/inflation on the dolphin for example is way clunky, and the Azimuth is honestly HUGE [nice streamlining and good comfort though]).
The simplicity of letting the unit do things itself is compared to actually KNOWING what is going on. I find diving with the KISS more relaxing than OC simply because I am not at all worried about duration - I just keep tabs on my displays for Po2, and top it up when it needs it.
And, compared to twin 12's for example, anything below ~25m or so (see times above) and because of your jetting the twins will actually get longer duration.
IMO SCR's are great for less bubbles and warm air. The duration aspect, as well as the Nitrox aspect are simply marketing gumph.

JonnyB

Guys (KISS owners), Stefan is out of the bunker again... let get him!

mixgas

SCR vs OC.
I'm considering to by a SCR, most likely a RB80, EDO04, Tuorill MK or similar.
Purpose, cave exploring and deep wreck diving. If you have experience on this field please enlighten me !

In wather advantages:
Breathing hot gas during cold wather diving
Less bubbels, less silt
Gas duration
Gas block, easy to switch gas when deep diving

In wather disadvantages:
More complicate during demanding situations
Breathing effort, Co2 hazzard
More complicate logistics regarding bailout in caves
Monitoring Po2, or hazzard if not monitoring
Hard to keep a simple configuration

On shore advantages:
Drive tanks will last a lot longer and require less frequent re-fills
Able to do several dives on same tanks without carry theme in and out from the cave

On shore disadvantages:
More weights to carry when diving remote caves
Hard to keep system clean while assambling the unit inside a drycave
Pre-post dive preparations
Maintenance


Regards, Jan Arild

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EBT

Gas logistics, drive tanks will last a lot longer and require less frequent re-fills. (be aware of the need to maintain a bailout volume).

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mixgas

Did a test dive today, nice but require alot different breathing technique.
Breathing warm gas was a big advatage fore divers far north.

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silent running

Hi everybody, as a former SCR diver, I can say safely that there is very little difference btw the work involved in setting up/maintaining an SCR vs. a CCR. So why would anyone prefer an SCR? I think the simplicity argument is totaly spurious, given the KISS. So the only thing I could see as a selling point is the protection against a CO2 hit that comes with a loop which vents every 4-5 breaths and will thus handle high workloads without having to worry about which is the most optimal scrubber design: it's a bit crude but still much more efficeint than OC. All this being said, RMV SCRs are very ingenious solutions to the constant PO2 problem, but simple they are not.
Anyway, I believe SCRs are certainly not any more simple than a manual MCCR, nor is trying to find Nitrox 'simple' in far away places, as it requires a lot of extra equipment. O2 is always easier to find because it is commonly used in Hospitals, other Med providers and welding. I don't think anybody really needs nitrox except divers.-Andy

esc

This is the question that I am currently pondering myself. What's the point?

While I personally prefer eCCR and the benefit it gives, there is indeed a point for SCR's one of them being much easier entrylevel.

Too many are touting the price difference between the actual rebreather and while SCR's are cheaper, the difference is not that huge. However the total cost including training is a huge difference.

SCR = AOWD or similar + Basic Nitrox + SCR training

All relatively cheap and something you can jump from your previous single tank setup.

CCR=AOWD or similar + Basic Nitrox + Advanced Nitrox + CCR training

Not to forget that to do Advanced Nitrox, you might need to do some sort of Technical diving course and use doubles. I know that it is now possible to do Advanced nitrox in conjuction with the CCR training now.

Also the course requirements for those are much higher in both skill requirements and learning material than the entry level training that the SCR requires as they are considered more technical diving than recreational diving, even if you plan to continue doing recreational type dives.

So I am still hovering between buying Dolphin with Oxygauge (2500 euros) and doing SCR course (450 euros) and see what I think of the rebreather diving and the pre/post dive maintenance and if I think it is for me, buying eCCR later.

I think I could still sell the Dolphin for a reasonable price after a year or two use if I decide to do so...

If I go eCCR route, it will be most likely Prism, Ouroboros or Meg and well... none of those are cheap with the unit cost + training included. Atleast nowhere near the 3000 euros I would need to dive Dolphin.

So is this a point enough or utter nonsense?

/esc

- Newbie asking questions