Rebreather as bailout for sat divers

[Brad_Horn]

Hello Brad, This thread is a good example of what happens when a sat diving bailout rebreather is on the market, works, and has real world end-users. You can find a manufacturer website that advertises the product, and you can find abundant contemporary evidence of the product in actual use by clients who have purchased it. Simon M

Simon, The works part as a sat diving bailout rebreather might be debatable https://www.jfdglobal.com/files/5116/0579/4608/DB500-PCN-1_R0.pdf but yes I quite agree with you; noting I'm only aware of 1 primary saturation rebreather that has been awarded both CE and NORSOK certification and delivered to its client. OSEL never having offered a sat diving bailout rebreather!

 

[Dr Simon Mitchell]

Simon, The works part as a sat diving bailout rebreather might be debatable https://www.jfdglobal.com/files/5116/0579/4608/DB500-PCN-1_R0.pdf but yes I quite agree with you; noting I'm only aware of 1 primary saturation rebreather that has been awarded both CE and NORSOK certification and delivered to its client. OSEL never having offered a sat diving bailout rebreather!

You can call it whatever you like Brad, and hide behind procedural/administrative certifications; but you are dodging the important point which is that your saturation diving rebreather never made it to market, like your iCCR.

Actually, since you are running hot on technicalities, I must confess that the iCCR did make it to 'market'. Which is to say that you spruiked it and even took deposits in 2008. The only problem is that here we are 12 years later (and counting) and you have never delivered it. There are junior open water divers who weren't even born when you told customers that the iCCR was available and asked them for their money. Yet none of this has stopped you constantly spewing criticism of other rebreather manufacturers for failing (in your view) to meet a speculative ideal that you yourself have been unable to deliver on.

Simon M

 

[abnfrog]

simon he will never admit it

 

[Akimbo]

Indirectly related information that might be of interest:
A Failed Attempt to Introduce an Umbilical Supplied Electronic Rebreather to Saturation Diving

 

[Dr Simon Mitchell]

Indirectly related information that might be of interest:
A Failed Attempt to Introduce an Umbilical Supplied Electronic Rebreather to Saturation Diving

Thanks Akimbo, I had not seen that.

The key thing for people to ponder on is why a "commercial dispute brought production to a halt".

As the emergence of at least one other player with a successful functioning product has illustrated, there was space in the market.

Simon

 

[Akimbo]

The key thing for people to ponder on is why a "commercial dispute brought production to a halt".

Commercial disputes would be overcome or competitors would fill the gap if there was a market. My perception is that the reliability and simplicity of surface-based recirculating systems far outweighs any advantage of removing one hose from the umbilical bundle. They also allow all of the diver's back-mounted weight and bulk capacity to be used for bailout.

Overview:
The advantage of adding a demand exhaust regulator to the hat and an exhaust hose to the umbilical is all of the maintenance-intensive and critical systems are on deck where life support technicians can manage them. There is also a very long delay in recycled gas getting back to the diver, providing plenty of time to rectify a problem (like hours).

Surface-based recirculating systems aren't constrained by power, space, weight, or the necessity to go offline for repairs. Redundant compressors, water separation, scrubbers, analyzers, O2 makeup, and gas storage systems are in environmentally controlled spaces along with all the spare parts that decades of service have shown might be needed.

It is important to understand the demand for reliability beyond diver safety. The DSV (Diving Support Vessel) will lease for $100K to $500K/day. As far as the client is concerned, the entire value depends what a few divers can accomplish while locked out. They don't derive any value from the ship or crew beyond the necessity to support the divers. A failure of a back-mounted rebreather/recirc system would take at least an hour to turn the bell around to fix/replace the problem. That time would usually be charged back to the ship owner, down to the minute.

It is even worse when the work that divers are doing is time sensitive to the client, like production being offline, and/or other vessels are supporting the operation. These costs won't be changed back to the ship, but will make the client look for other contractors if downtime is more than with competing DSVs.

With all this in mind, it is easy to understand why rebreathers for normal operation aren't in demand. It doesn't matter how safe it could be made. It also wouldn't matter if it reduced the initial cost of equipment or the salary for a few technicians. That would be just a rounding error on a $50+ million dollar DSV.

 

[Pandora's Box]

Commercial disputes would be overcome or competitors would fill the gap if there was a market. My perception is that the reliability and simplicity of surface-based recirculating systems far outweighs any advantage of removing one hose from the umbilical bundle. They also allow all of the diver's back-mounted weight and bulk capacity to be used for bailout.

Exactly so. Having a sat diving rebreather that needs an umbilical supply is nonsense when systems like this exist:

JFD | Electric Gasmizer

Basically a giant rebreather but with most of the equipment on the surface. Offers all the benefit of reclaiming the expensive helium without the disadvantages of trying to scrub, analyse, and make-up O2 on the diver's back. Pays for itself in one or two trips.

Bailout is a different story of course and having a purely mechanical BO rebreather to give greatly extended duration when main umbilical supply has been lost is a huge advance in safety and has already been discussed on this thread so I won't go over old ground.

 

[Akimbo]

Bailout is a different story of course and having a purely mechanical BO rebreather to give greatly extended duration when main umbilical supply has been lost is a huge advance in safety and has already been discussed on this thread so I won't go over old ground.

That is an often cited theoretical benefit of sCCR bailouts but have not proven to be valid in depths shallower than 200M. They might work but the human doesn't. Extending bailout time is pointless without solving the hypothermia problem, as evidenced by the Bibby Topaz incident. I have never heard of an incident where gas was lost and the diver still had hot water (for more than a minute or two).

That is because there is backup gas on the bell to cover a hyper-rare surface gas supply failures. There are also multiple supply gas circuits the dive super can select to feed the bell umbilical so the diver rarely even notices a gas switch (due to the volume of gas in the hoses). Unlike gas loss, divers know instantly when hot water is interrupted because of the incompressibility of water. There are redundant hot water systems on the surface but are almost always manually switched.

All work on drysuits assisted by electric or hot water heating has been unsuccessful. Keeping them dry on working divers is impractical. Heck, divers are constantly wearing holes through coveralls and hot water suits, which is just another place for hot water to exit but they still stay warm. Leaks in a drysuit would be a far more frequent danger to a sat diver than gas loss.

 

[Pandora's Box]

That is an often cited theoretical benefit of sCCR bailouts but have not proven to be valid in depths shallower than 200M. They might work but the human doesn't. Extending bailout time is pointless without solving the hypothermia problem, as evidenced by the Bibby Topaz incident.

We've been through this already Akimbo (on this very thread) where I challenged the wisdom of your position that we should only give the diver a few minutes of gas because you thought he would be incapacitated by cold after that so why bother with more. I've also already debunked the myth you insist on promulgating (again on this very thread) about the Topaz incident where no-one (not even the diver himself) can say it was hypothermia that saved him. This was corroborated by someone I consider to be an expert in post 35 of this thread:

I believe this is the correct medical interpretation of that event.

Simon M

I'm not looking to start another spat here btw, just need to make sure facts and not personal opinion are kept to the fore.

As to whether those currently involved in sat diving are convinced of the benefits...

JFD | JFD produces and delivers 100th COBRA system

100 sold and counting, and a few industry safety awards to boot.

 

[Akimbo]

I've also already debunked the myth you insist on promulgating...

Nonsense. Nothing you have presented debunks the fact that sat divers are not capable of remaining conscious, or respiration, as long as typical OC bailout capacity in less than 200 meters in northern climates. Sixty meters in the tropics is a different matter, but that is a tiny percentage of sat diving operations. Therefore, increasing bailout capacity will not increase survivability. In fact, the substantial increase in WOB can inhibit involuntary respirations of an unconscious diver.

It's not accurate that Chris regained consciousness after 2 breaths from the bellman alone. They were also pouring hot water over him well before they got the hat off. There was gas left in his OC bailout so he didn't loose consciousness from lack gas.

Very deep (like 300M+) or shallow warm water makes a sCCR bailout more attractive. It is a question of balancing inherently lower reliability against longer bailout times and water that is warm enough for the diver to be able to use the added time.

There would be a lot more than 100 Cobras shipped if they were unquestionably superior to OC in all operations. I have yet to talk with any sat diver or diving super, out of dozens, who is remotely and as impressed with the Cobra or sCCR bailouts as you are. We are a very long way from an optimum solution to what is fortunately an extremely rare problem.