Increasing PPO2 wet?

[Akimbo]

Let me suggest you learn how a rebreather actually works and get some experience on one before you start using it in peculiar ways

Actually, I have been trained on eCCRs starting with the GE Mark 10 in the early 1970s and helped evaluate prototypes for clients through the early 90s. I also was trained on a couple semi-closed rigs, pure O2 rebreathers, helped design, build, and operate commercial push-pull systems (surface based closed circuit gas reprocessing systems used on saturation complexes). I have had no need to investigate rebreathers in the last 15-20 years. Some interest yes, but not enough to dig this deep or make a serious investment with other people’s money.

 

[DwayneJ]

We considered switching to an umbilical for the pure O2 stops but logistics makes it hard to get the divers on a hose for deep stops, let alone dealing with several premix banks on deck.

Wow - There is a difference between toxing while lying on a bench or while wearing a hard hat vs toxing while biting down on a loop? Throwing around hard hat and chamber numbers is completely meaningless.

Also, since when is NOAA a recreational agency concerned about liability?

Dwayne

 

[Mr.X]

Perhaps I should have been more specific in my original post to indicate that this project, which is currently in the proposal & budget development stage, would be conducted by experienced mixed gas commercial divers. Several have been trained in the military with O2CCRs and eCCRs, but all would go through training on the specific eCCR selected. The project would not actually fall under the constraints imposed by regulators on commercial diving operations, so eCCRs could have saved a lot of money if we could find one to fit the required profile.

I only asked this question here to see if actual users could provide some quick guidance before wasting a lot of time and effort with sales weenies. Unfortunately, after talking with two instructors who are certified to teach virtually all of the eCCRs available (meaning between the two of them), it looks like this project will have to done mostly with ROVs and some limited surface supplied operations if it gets funded at all.

I do feel that recreational CCR divers might gain useful information from commercial operations, as we can from you. Perhaps these comments will be interesting.

I imagine that tweaking software so that it allows higher-end PP in ECCR automatic control wouldn't be all that difficult given that the designer, or manf. is freed from all liability. There would be a few manufacturers out there doing gov./rec. market work who could probably fit that bill? If you need some current manf. / designers you can PM me and I can send a few links in that direction.

As per ROV's - I like em'. These days just sitting and watching a monitor is more fun. I like how the bot doesn't feel pain, gets tired, or gets bent. At the end of the day - cheaper for some types of jobs.

X

 

[Akimbo]

I imagine that tweaking software so that it allows higher-end PP in ECCR automatic control wouldn't be all that difficult given that the designer, or manf. is freed from all liability. There would be a few manufacturers out there doing gov./rec. market work who could probably fit that bill? If you need some current manf. / designers you can PM me and I can send a few links in that direction…

I appreciate the offer, thanks. I considered that they could “up the limits” pretty easily, but I am reluctant to be the Ginny-pig on a new PPO2 switching hack/pre-release feature. We want to run a 1.2 on the bottom, let alone 1.8 or 2.0 decompression mix.

The instructors I spoke with weren’t too optimistic any of them could pull it off before a decision had to be made on which way to go. The idea of having to manually purge down the bags mid-water in a current to increase PPO2 sort'a sucks too.

This is one of those deals where all the triggers have to get pulled as soon as funding hits so R&D has to be very limited.

…As per ROV's - I like em'. These days just sitting and watching a monitor is more fun. I like how the bot doesn't feel pain, gets tired, or gets bent. At the end of the day - cheaper for some types of jobs.

X

Yeah, me too, even though they have put a lot of divers out of work. I haven’t met one yet who was a prima donna, an alcoholic, or hits on the client’s wife.

 

[Akimbo]

Wow - There is a difference between toxing while lying on a bench or while wearing a hard hat vs toxing while biting down on a loop? Throwing around hard hat and chamber numbers is completely meaningless…

That is one of the reasons we would be using a hat that supports CCR. There are several on the market here and in Europe.

…Also, since when is NOAA a recreational agency concerned about liability?

Dwayne

There is legal liability and career liability, which is probably far worse. NOAA is a government agency concerned with scientific diving. Careers don’t end and contracts are not lost because a science mission doesn’t get done due to safety concerns.

More importantly, there is a huge difference in training and support between recreational, scientific, military divers, military swimmers, and commercial diving operations.

There is no doubt that some individuals have higher oxygen toxicity tolerance than others. It is expensive and borderline unethical to perform large scale human testing for such a medically unimportant malady. Where the issue matters a lot, like military O2CCr swimmers, they do a lot more testing than on commercial or military salvage divers. All three are trained much more aggressively to monitor for O2 symptoms.

One of the guys I was offshore with was an ex-Seal. He said they were on an operation where they had to kiss the bottom at 85’ on an O2CCR and swim for 20 minutes… it appears they were less concerned with O2 toxicity than getting shot. I don’t think he was embellishing the story, it just was not his nature. I can’t help but think that physical conditioning is also a factor in tolerance based on this story. I would have barfed in my sorb or worse... to say nothing of what would be coming out the other end.

 

[Mr.X]

I appreciate the offer, thanks. I considered that they could “up the limits” pretty easily, but I am reluctant to be the Ginny-pig on a new PPO2 switching hack/pre-release feature. We want to run a 1.2 on the bottom, let alone 1.8 or 2.0 decompression mix.

The instructors I spoke with weren’t too optimistic any of them could pull it off before a decision had to be made on which way to go. The idea of having to manually purge down the bags mid-water in a current to increase PPO2 sort'a sucks too.

This is one of those deals where all the triggers have to get pulled as soon as funding hits so R&D has to be very limited.

Yeah, me too, even though they have put a lot of divers out of work. I haven’t met one yet who was a prima donna, an alcoholic, or hits on the client’s wife.

the above!!!!



Cheers. I certainly understand. Getting software written and getting past liabilities would involve time, lawyers and other crap which doesn't help in time-dependent proposals.

As per the ROV's - they are also getting unemployed. Those AUV's are kicking their metal butts lately. The ROV's are going to have to take up drinking some WD-40.

Cheers and best with your projects.

X

 

[rjack321]

Since you're not being shot at, what's the big rush to get out of the water here?

While you seem to think your CNS limits can be ignored...

I think if you actually sat down and planned your bottom phase at 1.4, your deep deco at 1.8-2.0 and then your chamber ride afterwards you are going to see pulmonary limits blown away too. To the point of permanent damage. You'll be out of the hot water suit faster and into a different hot water.

 

[Akimbo]

Since you're not being shot at, what's the big rush to get out of the water here? ...

Exposure and logistics. The cost escalates too much to have two chambers along with 2x compressors and support crew. All that takes a much bigger $boat$. It is way too risky to plan overlapping dives — splashing the second team before the first team completes Sur-D-O2. Running a constant in-water PPO2 at 1.2 (the max deep mix) drops production to one team a day and would be a deal killer due to daily operating cost and a short weather window. Secondarily, if things turn to crap, keeping warm enough in drysuits is a concern on Trimix, yeah we know about Argon. Keep in mind that around 50% of heat loss is through respiration, though rebreathers help out a little in that area.

The different sensibilities here are interesting. None the guys on this project would dream of diving mixed gas (HeO2 or Trimix) without a deck chamber and qualified diving supervisor on deck. A lot of recreational rebreather divers do it all the time, but freak over moderately high PPO2s. We all have to make value judgments when our butts are the ones on the line.

… I think if you actually sat down and planned your bottom phase at 1.4, your deep deco at 1.8-2.0 and then your chamber ride afterwards you are going to see pulmonary limits blown away too. To the point of permanent damage. You'll be out of the hot water suit faster and into a different hot water.

None of us are willing to do 1.4 at the bottom due to anticipated work load, especially untethered. 1.8 at deep stops is also more conservative that we normally run due to environmental variables. We have run a lot of different profiles, all of which are more conservative regarding oxygen exposure than is everyday practice around the world (for surface supplied divers). None of us have permanent damage from thousands of decompression hours and hundreds of mixed gas surface dives. All of this would be academic if we were in hot water suits, because there would also be gas, comms, and a pneumo hose in the umbilical.

 

[rjack321]

I don't know if you are bidding on this job or already have it.

But clearly there's a substantial budget already and getting 2 smaller chambers or a bigger boat that can carry 2 chambers and diving the CCRs as the manufacturer has agreed is "ok" would be how I would approach this problem.

vs. getting new CCR compatible helmets, somehow getting software written for a CCR so you can dive ppO2s which nobody dives on the available recreational units (for whatever reason), validating the linearity of the cells across the range of ppO2 which you wish to expose them to, all to shorten up the deco, so you can free up the chamber, so you can splash more people per day.

The former seems more plausible. The job costs what it costs.

 

[Akimbo]

I don't know if you are bidding on this job or already have it…

It is a non-commercial (as in not offshore oil) proposal that would depend on grant and documentary funding. I came into the project through a friend, who is friends with the non-diving guy trying to put the project together. We are all working on the come until/unless we find a plan that sells.

…But clearly there's a substantial budget already and getting 2 smaller chambers or a bigger boat that can carry 2 chambers and diving the CCRs as the manufacturer has agreed is "ok" would be how I would approach this problem.

vs. getting new CCR compatible helmets, somehow getting software written for a CCR so you can dive ppO2s which nobody dives on the available recreational units (for whatever reason), validating the linearity of the cells across the range of ppO2 which you wish to expose them to, all to shorten up the deco, so you can free up the chamber, so you can splash more people per day.

The former seems more plausible. The job costs what it costs.

Well, rebreathers (and maybe all untethered dives) was killed on a conference call this morning. Thanks all for the conversation, which is interesting.

One of the other guys in the project was in charge of thermal dynamics calcs and found data that we could see 38° F temperatures top-bottom, down from 42°. Between reduced absorbent capacity and hypothermia risks, it is all just too close to the edge.

Unfortunately, this dictates a much more expensive boat for surface supplied operations because of either multi-point mooring or dynamic positioning (DP) capability. I don’t know of DP capability on any boats under 200', which is getting into the saturation complex cost range.

One of the guys on the project even suggested refurbishing a wet submersible or a non-US swimmer delivery vehicle to carry the gas for open circuit, power for lighting, and maybe even electric heating. Those weight numbers start getting big really fast and handling something like that over the side/stern at sea is not too thrilling. It seems like the key to keeping costs low enough to be practical is being able to live boat or single point moor. Divers don’t have a lot of area to cover around a well-placed down-line, so maybe we can find a solution there.