Redundancy question

[Inspirationdiver]

The points that John is bringing up really emphasize the overall flexability of diving a CCR. You have a great range of depths you can efficiently dive to without having to make any changes to the unit or the gas you are using.

[Freedive WI]

Thanks John,

That really answers some questions. I did not realize that you could plug your bottle into someone else's rebreather as bailout- it makes a lot of sense.

How easy is it to "plug-in" and switch underwater with the Inspiration? I was looking at a Cis-Lunar a few years ago at DEMA to see how they mounted their main tanks and back-up bottles(on the outside of the shell) and how they could switch gases by the block built into the chest of the breathing bag. Is it that straight forward on the Inspiration?

What about redundant breathing loops? I see that the deep support divers for Tanya Streeter's 550' freedives all have two seperate breathing loops built into their rebreathers- that's two bags, two hoses, and I believe two scrubbers. I think that the RB80 was designed to be able to do that, but without the same effciency as a completely closed CCR. I haven't seen that around here, yet. I sthat something that your looking into?

What kind of OC gas rules do you follow in your bailout bottles- 1/3's, 1/2's ect?

For my gas planning, I dive as part of a DIR club who uses 1/3's as the MINNIMUM for our backgas and we always, at least, double our deco gas. I really don't want to turn this into ANY kind of a pro/con DIR discussion ( so please don't do that DRE) that's just happens to be what I do.

Over the years I have had so much gear fail on me that I don't trust any of it- maybe that's why I like freediving so much. ;D

Do you always dive in buddy teams? I would think that it would be mandatory since you could have a high/low 02 problem and not know it until it's too late. Always having a buddy would seem to be the easiest answer to that one. But, maybe you have another way that I don't know about.

Also, what kind of tank marking do you use?? I use 1.4 on my bottom mix and 1.6 on my deco gasses. When I have watched the RB guys up at Wazee I thought I saw all gasses marked at 1.6. Is that standard or not?

Thanks for all of the responses so far.

Jon

[john j]

The quick connect fittings on the whips are like the high flow drysuit inflation fittings. On the whip end, you pull back a collar and then push it on the male nipple and let the collar snap and the connection is secure. After some practise, you can do this without looking, just by feel, even with heavy dry gloves on.

The connections are on the chest about at the bottom of your rib cage, one on the left and one on the right. The one on the right is dedicated to the on-board oxygen whip but you could unplug it and plug something else in there if you needed to such as a second oxygen tank or whatever you wanted to.

I have seen pictures of Inspirations people have put together with redundant breathing loops. They call them "twinspirations". That would cost a bundle that's for sure and would get pretty complicated, but a few people are doing it I understand. I can't speak from experience but it looks like the RB-80 might be easier to rig up with redundant breathing loops than the Inspiration, but again you are doubling the cost of the system and that means some serious cash. I'm not doing long penetration cave or wreck dives so for me right now, I'm OK with just a single breathing loop. Besides, for me there would come a point where the gear set-up got so complicated and extended that it might not be fun anymore. We'll see what the future brings but I don't see a twinspiration on the horizon. Of course 10 years ago I was thinking that I'd never own a rebreather either.

I generally use rule of 1/3's for bailout planning with CCR just like I did with OC.

I do some solo dives, but maybe only 3% of them are solo. Usually I only solo dive when my buddies' wives won't let them go diving! I see the point about increased risk with solo diving but if it is a risk that I accept then, it's OK. Let's say I pass out and my buddy is around though, if I loose the mouthpiece will I still be alive when he brings me up? Maybe not, so how much actual added risk is a solo dive? Might be a good topic for us to debate. We are looking into full face masks right now for several reasons, and rescue from a pass-out or O2 tox situation is one strong point for using a full face mask. In that case, diving with a buddy would be way less risky than solo.

For tank marking, I write what gas it is, like TMIX 10/70, EAN 36, or AIR on the tank label and then also the MOD using 1.6 pO2 for all gases. I mark the tank neck with a label so whoever is wearing the tank can see the contents just by looking down at it and I also mark the side of the tank with large letters like most others do. I get a little more descriptive with the tank labels than most people do but then I dive with lots of different people and I want them to make sure they understand what is in each tank. My personal opinion is that many people are lazy about marking tanks. I like to make it very clear what is in there. Although I mark the tanks according to 1.6PO2 MOD, I apply 1.4 pO2 rule for actual use of bottom mixes and deco gases, except for O2 which I will use at 1.6.

If you ever see me at Wazee, stop by and ask all the questions you want. I think seeing how we use one of these things would answer lots of your questions. Maybe you would decide that rebreathers suck, but that's fine too.

[Freedive WI]

I could see a real benifit in using a full face mask for that kind of diving. You could pass out, have the unit reset itself on its own, and recover without a problem. The same could work for a tox hit.

Until that time I would think that a buddy could still get you to the surface to try and complete a rescue. We train all of the time to bring an unconcious freediver to the surface while maintaining a proper airway- although with freediving we keep it closed instead of open.

I mark all bottom mix tanks like they are 1.4 "to the mud". That means that even in the most dire emergancy I never plan on taking my bottom mix passed 1.4. If the bottom is deeper and there is even the slightest chance that I might have to go there, then I mix for it.

For deco tanks, and actually my doubles as well, I mark the sides with the max depth only. I might have a small tag by the neck with the gas markings inside, but the big numbers on the side are the maximum depths that I plan on using each bottle to. The only exception is my 02 bottle. It says "20 OXYGEN" on the side. The reason for this is because a "70 foot" bottle can look an aweful lot like a "20'" bottle if part of the number gets covered. By putting the word OXYGEN on there it makes sure that I can see the difference.

I don't know that I would say that rebreathers "suck". I find them to be facinating machines. Unfortunalty, I have dove with Murphy too many times and don't trust most of the dive gear out on the market right now. SO much of it is total crap in my humble opinion. I have had so many computers, BC's, drysuits, cameras, lights and regulators fail on me that I just can't commit to rebreathers.

I was trained on the Drager unit a while ago, before they had P02 gauges, and found it down right scary to not know exactly what I was breathing. I know all about the math formulas and knowing your breathing rate, but you can still make things fluctuate by working hard on something underwater- like with a hacksaw. not knowing excatly how that effected my deco obligation drove me nuts.

Maybe that's why I eventually found my way into a DIR crowd. I have had all kinds of gear fail and I really like the safety protocals and basic, standardized, gear set-ups that it entails.

Even more so, I like freedivng where there is even less gear than can break on you, but what little there is I have also manged to trash. : Like the time I broke one of my carbon fiber fins on a 60' dive and had to come up on one fin. Or, last month when both my Stinger and my D3 died on the same day! Keeping things simple has worked out much better for me.

Having said this, I want to return to the rebreather questions. I really don't want to turn this thread into a DIR thing- Lord knows that there is enough that has already been written on that.

I am more interested in what kind of extra steps rebreather divers take to meet the same safety standards of OC divers.

Let me ask about scrubber material for a minute. I know that the stuff has a much shorter life span in cold water than warm. Do you have a set protocol ot change it every day that you dive? or do people try and remember when to change it through some type of log book?

With the team that I dive with, we check all of our gases, and our buddies, everytime we make a dive. We don't rely on it being the same as the last time we checked. We check, and sign off on it, ever time we jump back in. Do you have something similar that you do with scrubber material?

Jon

[Freedive WI]

These are the units I was talking about.

Jon

[john j]

That's a cool picture. If I could get a gig like that, being a safety diver for free diving girls in bikinis, I'd gladly fork out the cash for a twinspiration. Something tells me though that nobody's gonna ask me to do that. :'(

John J

[john j]

Response to FREEDIVE WI regarding scrubber life in the Inspiration.

Scrubber is rated for 3 hours and they teach you to reduce the life in cold water. Below are the general rules for the scrubber which I lifted from Divermole's website. I know for a fact that many Inspiration divers run their scrubbers much longer than 3 hours. However, some of the deaths on the unit have potentially been linked to overuse of the scrubber.

As far as keeping track of the scrubber life, there is a timer built into the control computer that tracks total time that the system has been powered up. Some people use this to track scrubber time. Others write it down in a logbook or just remember it. I use the logbook method myself, unless it is obvious. For example, if I just did a 3 hour dive, I don't write it down anywhere, I just change the chemical.

If you run the scrubber for 3 hours, you are looking at cost of about $7 per hour of dive time for the scrubber chemical.

The Golden Scrubber Rules
1. Only use Sofnolime 797

2. Maximum scrubber time 180 minutes

3. Be shallower than 50m at all times after 100 minutes use

4. Be shallower than 20m at all times after 140 minutes use

5. If in doubt, tip it out

6. Always re-grease and check the fitting of the scrubber O ring and spacer

7. If you don't follow 1 - 6 fine, but don't moan if you get injured or die!

[Freedive WI]

I'm thinking that #5 sounds like a "golden rule". ;D

So, on a "normal" trimix, rebreather dive you have the following redundancies built in:

Predive-
positive/ negative pressure checks of the loop.
calibrate and check 02 sensors master and secondary control units- I don't know what they're called.
analize all bail out/ deco gases and have enough for planned dive.

Dive failure-
switch to semi-closed and continue to run the system.
switch to bailout bottles and run the system.(ccr or scr)
switch to buddies bail out bottles and run the system(ccr or scr)
switch to onboard tanks in opencircut more
switch to bailout bottles in oc mode
switch to buddies bailout bottles in oc mode

Computer crash-
switch to back up tables in thigh-pocket and run the worst case deco on bail out bottles ( tirmix/ air/ deco)
manual addition of dilulent and 02 by user

Hoses-
protected by covers, or switch to bailout(s)

hyperoxic/hypoxic-
buddy, full face mask, or meet your maker.


Did I leave anything out?

Jon

[john j]

Wow! There's a lot of stuff there and I don't think I will get it all with one reply so I'll break it down a bit...
This is what I do generally.

Pre dive checks:
Proper amount of gas and proper mix for dive. Analize gases after mix and in field before dive.
Check voltage of both batteries.
Scrubber chemical has sufficient life?
Scrubber packed properly?
Mouthpiece check valves working and installed properly?
Pos/neg leak check.
Calibrate and watch cell readings during calibration. Good way to see problems early.

Right before entering the water...
All gasses on?
Computers on?
Drysuit inflation working?
Counterlung dump valve set to low resistance setting?
Verify tank pressures and watch pressure gauges while pressing diluent and O2 add buttons. This tests the buttons and the first stage ability to deliver gas. Pressure should not drop during addition.
Begin breathing from system and watch cell response, listen for proper solenoid valve operation. System should maintain 0.7pO2.
Shut off master computer and verify slave takes over control of the system.
Turn master back on, shut off slave and verify master takes over. Turn slave back on.
Do a diluent flush and watch the cell readings. Buzzer should sound along with "low oxygen" text alarm. They should read the PPO2 for the diluent gas at 1ATM ambient. This verifies calibration with a seperate gas and is also a calibration linearity check.
Verify funtion and pressure of all bailout gases and regs.

In the water: visual bubble check. Bubbles mean there is a leak and the unit is quiet enough where you can even hear bubbles sometimes.
I also do a drill on the way down where I talk to myself and touch each cylinder and tell myself what it is and where each reg. is. Sometimes people see this and ask are you OK? Yep, just doing a drill.
Diluent flush to purge unwanted N2 out of system.

I typed this in kind of fast and it's harder to think through when I'm sitting at my computer rather than sitting with my rebreather. CCR folks, please add anything I've missed. This should at least get the conversation going. Then we can go to your other items later on...

[DRE]

Hey, I didn't say anything. To paraphrase a currently running ad: "I know where I stand."