Rebreather as bailout for sat divers

[Fisheyelens]

You are very much on the right track Pandora.

Any diving contractor not completely phasing out the old bailouts that are no longer fit for purpose should not be taken seriously.
These contractors are cowboys. Any divers not wanting to move forward will soon be seeking work for said contractors.

 

[Brad_Horn]

A little, but not enough to make a meaningful difference. Keeping the absorbent warm enough to function at reasonable efficiency is challenging enough. There is a lot of surface area in the loop and the thermal conductivity of the mix is acting on lungs and the loop. The exothermic properties of the absorbent and heat conservation from the diver are pretty insignificant under these environmental conditions.

I did some consulting work in the 1990s looking at rebreather bailouts for deep (300-500M) applications in anticipation of potential regulatory requirements. We couldn't make the WOB, power, and thermal numbers work and the underlying technology has not changed except for batteries -- we had to use power-assist in the loop to meet the WOB requirements. Our parameters were -2°C water temperature because the client was investigating work in some more northern and deeper arctic fields. Granted that is much more severe than the Divex JFD Cobra is designed or certified for.

The scrubber solution for commercial rebreathers is MicroPore EACs which are remarkably flexible to the temperature environment and offer a very good duration for their 2.2kg size; which is why DL used them in their dual scrubber umbilical unit design, as do JFD with the Cobra.

The WOB issue for deep work has been resolved for a while now http://www.deeplife.co.uk/or_files/DV_OR_WOB_Respiratory_C1_101111.pdf
Onboard power and heating for the loop remains a consideration if the umbilical is cut.
Further details of the DL umbilical unit pg125 http://www.edtc.org/MINUTES/Minutes 2012 Oslo Members Meeting.pdf

 

[Fisheyelens]

Cobra, like SLS has no power requirement. No considerations required.

 

[JohnnyC]

Oh, are you guys supplying PDF's to the sat diving world now too?

 

[Fisheyelens]

The updated Cobra will have HUD, initially showing just if the set is flooded, is being discussed.

 

[Pandora's Box]

The updated Cobra will have HUD, initially showing just if the set is flooded, is being discussed.

You must be quite close to this?

as do JFD with the Cobra.

As far as I know it's a loose-fill system (Sofnolime 797).

 

[Brad_Horn]

As far as I know it's a loose-fill system (Sofnolime 797).

"The COBRA uses disposable cartridge-type CO2 removal scrubber canisters, so no requirement for sodalime granular filling."
https://www.jfdglobal.com/files/1414/6529/7789/DE-MDS-6609-R1.pdf

JFD also buy Micropore EACs from OSEL whom are Micropore's European distributor and use OSELs hyperbaric breathing simulator for their testing.

 

[Pandora's Box]

"The COBRA uses disposable cartridge-type CO2 removal scrubber canisters, so no requirement for sodalime granular filling."

Cobra does indeed have a ‘cartridge-type’ scrubber system, but it definitely does not use Micropore EAC. I’ve maybe been a little disingenuous when I said “as far as I know” in my earlier post ;-)

The PDF datasheet you have posted is out of date. You’ll see it’s labelled R1 (revision 1). The latest available on the company's website is R2 (revision 2) and the line you quoted (from rev 1) has been removed. It now states “The COBRA uses as (sic) easy fill scrubber system for fast, simple change out of sodalime.”. Here’s a link to the page on the company’s website where you can find the correct datasheet under the “related documents” tab about half-way down the page.: https://www.jfdglobal.com/products/commercial-divers-equipment/rebreathers/cobra-compact-bailout-rebreathing-apparatus/

It’s a cartridge that can be removed, re-filled (with sofnolime 797), then re-inserted. Or alternatively another pre-prepared cartridge can be inserted immediately and the “used” cartridge re-filled in slow time.

"JFD also buy Micropore EACs from OSEL"

Perhaps so, but these must be used in a different product (they have more than one type of rebreather). Have a look at https://www.jfdglobal.com/products/defence-divers-equipment/underwater-life-support-systems/enforcer/ where it clearly states use of ExtendAir cartidges.

BTW, I would also presume OSEL are only used for very small quantities at short notice when a quick delivery is required (both in Scotland after all), otherwise I’m sure they’d be buying direct and cutting out the middle man so to speak. OSEL are the distributor for Joe Bloggs to buy in Europe, but not for the big boys.

"and use OSELs hyperbaric breathing simulator for their testing.

Irrelevant to what we're discussing here (which is just as well!).

 

[iain/hsm]

These commercial units are not like recreational eCCR. They don’t require any additional task loading of the diver to keep them ‘ready for action

I'm not so sure about that looks to me like a cheaper copy of the YBOD Inspiration.

This new unit is entirely mechanical (and semi-closed). Also the WOB must have passed Norsok U-101 and/or (slightly more generous) BS EN 14143 requirements.

So was the old SLS one. Nothing wrong with that and it was much better looking.

How do you know the tech hasn’t changed? 20-30 years is a long time in the diving world.

I'm not sure about that you sure your not thinking of the computer world, diving world is still working fossel fuel

Ask yourself this; why would the diving company, and indeed the same vessel, bother with the new rebreather, after all they've been through, if they didn't think it was better than OC?? Bear in mind these people have the FACTS. Not half-truths and myths from internet forums.

I'm not so sure about that. You sure they did'nt get them for free to make a wee film with. LOL

 

[iain/hsm]

The updated Cobra will have HUD, initially showing just if the set is flooded, is being discussed.

I hear it's going to be be called the "Rotoflood"