Dive Talk Go Rebreather

[InWay2Deep]

I don't think scrubber should be included in the rule of thirds regardless of the severity of the dive. You have bailout gas (or a bailout rebreather) to take care of loss of functionality of your rebreather.

I plan my dives to be 100% on the breather, not planning to bailout. Bailout is my safety margin, not a dive extender.

Rule of 1/3 for scrubber duration?!!!!! Really?!!!! Do you dive CCR?

Yes, Cave CCR.

1/3rds of a scrubber? I dont know anyone tossing 1/3rd of a scrubber. What unit are you diving? What temp, depth and duration do you consider the scrubber 100% spent and what's your 66% temp, depth, time?

So you do a 2hr dive and just put the unit away and not change the sorb? I account for it as a consumable during my dives just like everything else. 1/3 in, 1/3 out, 1/3 contingency and I use 6hrs as my duration limit. Unit is in my sig. I have done over 6 hrs on the scrubbers w/o issue and I have done just over 4hrs on it and got a hypercapnic hit and had to bailout. Water temps were about 10* difference. slightly more workload. If I do a 3hr dive and have another one planned for over an hour I will be changing the scrubber before the dive. I'm not saving sorb week to week or even day to day unless I only had an hour or 2 on the unit, even then if I have a down day I'm putting in new sorb. It's cheap, my life and my trips are not.

I'm kinna shocked that people here are not planning for scrubber duration for cave/tech dives and just using their bailout as part of the 'normal' dive plan. My dive plan is to stay on the loop for the entire dive unless there's an issue and not a 'planned' issue.

 

[LFMarm]

I plan my dives to be 100% on the breather, not planning to bailout. Bailout is my safety margin, not a dive extender.



Yes, Cave CCR.



So you do a 2hr dive and just put the unit away and not change the sorb? I account for it as a consumable during my dives just like everything else. 1/3 in, 1/3 out, 1/3 contingency and I use 6hrs as my duration limit. Unit is in my sig. I have done over 6 hrs on the scrubbers w/o issue and I have done just over 4hrs on it and got a hypercapnic hit and had to bailout. Water temps were about 10* difference. slightly more workload. If I do a 3hr dive and have another one planned for over an hour I will be changing the scrubber before the dive. I'm not saving sorb week to week or even day to day unless I only had an hour or 2 on the unit, even then if I have a down day I'm putting in new sorb. It's cheap, my life and my trips are not.

I'm kinna shocked that people here are not planning for scrubber duration for cave/tech dives and just using their bailout as part of the 'normal' dive plan. My dive plan is to stay on the loop for the entire dive unless there's an issue and not a 'planned' issue.

Got your point. My way of planning for cave CCR is to use 50% of the scrubber on entry, 50% on exit. How conservative is the estimation of 100% scrubber duration depends on diver choice based on water temperature, expected work of breathing, etc. In case of emergency, I have bailout gas. If I do not have an emergency, my dive plan is to be executed all on CCR (same as you).

 

[InWay2Deep]

Got your point. My way of planning for cave CCR is to use 50% of the scrubber on entry, 50% on exit. How conservative is the estimation of 100% scrubber duration depends on diver choice based on water temperature, expected work of breathing, etc. In case of emergency, I have bailout gas. If I do not have an emergency, my dive plan is to be executed all on CCR (same as you).

If I were more confident about the stated scrubber duration I might do 50% as well, but I'm not, so I don't push it, plus 4hrs is about my limit now anyway. I hate going off the loop so I try really hard not to do a dive where I will be on OC anymore.

 

[LFMarm]

If I were more confident about the stated scrubber duration I might do 50% as well, but I'm not, so I don't push it, plus 4hrs is about my limit now anyway. I hate going off the loop so I try really hard not to do a dive where I will be on OC anymore.

Very sensible approach. Scrubber duration is indeed a variable that is harder to predict compared to light or gas duration. I just got confused by the rule of thirds. Applying a conservative factor on scrubber is very sensible.

 

[rjack321]

I plan my dives to be 100% on the breather, not planning to bailout. Bailout is my safety margin, not a dive extender.



Yes, Cave CCR.



So you do a 2hr dive and just put the unit away and not change the sorb? I account for it as a consumable during my dives just like everything else. 1/3 in, 1/3 out, 1/3 contingency and I use 6hrs as my duration limit. Unit is in my sig. I have done over 6 hrs on the scrubbers w/o issue and I have done just over 4hrs on it and got a hypercapnic hit and had to bailout. Water temps were about 10* difference. slightly more workload. If I do a 3hr dive and have another one planned for over an hour I will be changing the scrubber before the dive. I'm not saving sorb week to week or even day to day unless I only had an hour or 2 on the unit, even then if I have a down day I'm putting in new sorb. It's cheap, my life and my trips are not.

I'm kinna shocked that people here are not planning for scrubber duration for cave/tech dives and just using their bailout as part of the 'normal' dive plan. My dive plan is to stay on the loop for the entire dive unless there's an issue and not a 'planned' issue.

What is a sig? Even the Meg 8lb scrubber isn't rated for 6hrs so you are already arm waving about your denominator.

Of course people are planning their scrubber usage - usually more thoughtfully than just tossing 1/3rd of it

 

[jale]

I'm kinna shocked that people here are not planning for scrubber duration for cave/tech dives and just using their bailout as part of the 'normal' dive plan. My dive plan is to stay on the loop for the entire dive unless there's an issue and not a 'planned' issue.

Of course that scrubber duration is planned and that BO is not used as the "normal" dive plan!!!
The problem is this 1/3 of your scrubber.
You state your scrubber is rated to 6h and that then you only do 4-hour dives.
First, how did you manage to rate your scrubber? Which unit?
Second, unlike OC, there are too many factors to affect the scrubber's time and to state a general specific rule like the rule of third gives a false sign of safety, a kind of "nothing can happen if I stay within the limit".

 

[rjack321]

Got your point. My way of planning for cave CCR is to use 50% of the scrubber on entry, 50% on exit. How conservative is the estimation of 100% scrubber duration depends on diver choice based on water temperature, expected work of breathing, etc. In case of emergency, I have bailout gas. If I do not have an emergency, my dive plan is to be executed all on CCR (same as you).

Same. I start with a relatively conservative estimate and then plan to use up to 100% of that. I don't inflate my potential time then divide it by thirds.

In the temps and workload I dive (we don't have little river or ginnie like flow), the 6.5lb meg axial is a 4 hour scrubber and the 5lb sidewinder is the same.

 

[InWay2Deep]

Of course that scrubber duration is planned and that BO is not used as the "normal" dive plan!!!
The problem is this 1/3 of your scrubber.
You state your scrubber is rated to 6h and that then you only do 4-hour dives.
First, how did you manage to rate your scrubber? Which unit?
Second, unlike OC, there are too many factors to affect the scrubber's time and to state a general specific rule like the rule of third gives a false sign of safety, a kind of "nothing can happen if I stay within the limit".

Guess I'm still confused why the 'outrage' at planning to use 1/3 scrubber duration for "IN" when others are suggesting 1/2? Or something else? I managed to 'rate' my scrubber based on claims by the manufacture and my own observations diving it and adjust accordingly based on new experiences and information since it's dependent on person-to-person, workload, temp, etc. I never said 'nothing can happen', I was simply pointing out, w/ the GO, that the claimed scrubber duration is short, therefore many are saying it's not suited for tech/cave dives which typically are longer than the GO scrubber can support with a built in safety margin and somehow this got turned into whatever this is saying 1/3, 1/2, blah whatever, is the wrong way to plan a dive w/o anyone offering other options than eh just bailout.

 

[rjack321]

Guess I'm still confused why the 'outrage' at planning to use 1/3 scrubber duration for "IN" when others are suggesting 1/2? Or something else? I managed to 'rate' my scrubber based on claims by the manufacture and my own observations diving it and adjust accordingly based on new experiences and information since it's dependent on person-to-person, workload, temp, etc. I never said 'nothing can happen', I was simply pointing out, w/ the GO, that the claimed scrubber duration is short, therefore many are saying it's not suited for tech/cave dives which typically are longer than the GO scrubber can support with a built in safety margin and somehow this got turned into whatever this is saying 1/3, 1/2, blah whatever, is the wrong way to plan a dive w/o anyone offering other options than eh just bailout.

Because saying you are diving 1/3rds is misleading. Saying you adjusted your manufacture speced 4hr scrubber to 6 hours based on your personal temps and workloads then dividing that 6hrs into thirds is the same as saying you are diving 100% of the rated specifications. Albit conservatively because nobody can sustain the CE workloads for 4 hours, and the temps used are frigid.

The Go is both short duration (scrubber mass) and has a shallow bed depth hence the depth wariness in the specifications.

 

[InWay2Deep]

Because saying you are diving 1/3rds is misleading.

Let's forget about the specific numbers in terms of hours. Use whatever numbers you want for your rebreather scrubber duration. Why is rule of 1/3 not applicable to CCR scrubber duration?