rebreathers vs. regulators

[buff]

With the advent of the rebreather and it 's increased popularity and acceptance amoungst recreational divers, does it signal the end of the regulator?

I know nothing of diving rebreathers. Anesthesia machines are based on the same concept. Draeger makes most of the anesthesia machines-and they are very, very good with clever designs.


Mike

 

[Lost Yooper]

Not unless they can get the cost down for a reliable unit. As it is, they don't seem to have the best track record even at their current cost. I've pretty much ignored them because they are way out of my price range. I believe the SCR Halcyon Unit is over $8K and seems to have a great reputation among the WKPP.

Rebreathers are huge can of worms where there's a lot to learn. I don't know much about the guts of the subject, but I know who I would learn from if I had the moola .

Mike

 

[buff]

So is it safety or cost? Draeger's anesthesia machines seemed pretty safe to me.

 

[Zept]

Buff, you might like to take a look at this article.

It's safety and cost, as far as I can see. Rebreathers are more complicated than open-circuit systems (tank and regulator) and require daily maintenance. There is more to go wrong and thus more risk.

I'm not sure your anaesthesia analogy holds, because an anesthesia machine isn't operated by the patient! If there's a problem, the anesthesiologist can intervene.

On the cost front, I don't see diving schools replacing their open-circuit equipment with rebreathers any time soon, so people will learn with a regulator and tank, and mostly that's what they'll stick with.

That's my 0.02c worth, anyway.


Zept

 

[Lost Yooper]

If you think that the WKPP's OC protocols are stiff, you should see how they treat the rebreathers. Even though they basically designed their own RB, I get the feeling they are not 100% trustworthy of any rebreather (but I really don't know, I guess) -- especially CCR.
It just doesn't seem like the technology is quite there yet for everyday divers. Considering that there isn't too many rebreather divers really out there, there seems to be plenty of deaths, especially on CCR's, every year (human error or not). I don't have any stats or anything, but that's seems follow what I've read and heard.

Maybe another ten years or so.

Mike

 

[Green_Manelishi]

Correct me if I am wrong, but it seems to me that rebreathers
must also use a regulator (even if it is called by another name).
If there is no regulator would you not have a constant flow of gas? That would be even more *wasteful* than OC SCUBA.

 

[padiscubapro]

There are 2 main types of rebreathers SCR, and ccr
SCR rebreathers have several sub types, manual addition, constant mass flow, passive addition, and variable passive addition.
The draeger is a constant mass flow, it uses a special reg that drops tank pressure to a few hundred psi (I don't remember the actual pressure) but its higher than a standard scuba reg, the output of this goes to a demand flow valve (to add quickly if the bag bottoms out) and a constant injection port which bleads gas continualy into the loop(the rate depends on the gas used). PASV rebreathers dump/fill a fixed ammount of gas per breath, The halycon SCRs are variable addition, meaning they dump less gas as you go deeper but is still keyed to breathing cycle (same as passive addition). This is the most efficient type of SCR, but the square bellows used by them creates too many dead air spaces and a potential for CO2 buildup on High workload dives - This isn't a problem with wkpp beacuse they are usually on scooters (I haven't seen the latest units but I am told they are the same).

CCR units have 2 regulators (those that support multiple diluents have additional regs), 1 for diluent (the main volume of the breathing loop - only used during decents) and 1 for the o2 injection. on the ispiration both of these are APEKS first stages, the o2 side has the IP lowered. Since very little gas flow is needed (unless you are bailing to the onboard oc reg) you operate the unit with bothe valves just cracked open.. If you switch to OC bailout the you open the diluent valve fully..

Most people I know who dive CCRs myself included will never go back to OC.. Thats not the opinion of most SCR divers, they generally like their units but not enough to make a full switch.

Each type of RB has their pluses and minuses, I personally think the CCR is the best choice, most efficient gas usage and when a problem arises the unit can be used as a manual addition scr.

On my Inspiration my diluent cylinder (20 cf) lasts me about a week of diving everyday several dives a day, the oxygen cylinder (20 cf) gives me 10 hours underwater per fill, The scrubber is changed about every 4 hours..

There are plenty of articles on RB around, some of the best descriptions I have seen are from Richard Pyle.. DO a search using his name and youll find plenty of info..

Richard did a special on discovery (maybe national geographic) recently called "the twilight zone". He was doing 400-500ft fish collecting dives using his cis-lunar rebreather.

He has a full synopsis on his web site (sorry I don't have the link handy)