Scrubber Duration

Drmike

A little trick we sometimes use when wishing to do multi deep dives off same fill is to go onto OC Oxygen during the 6m stop.



In this way when Im diving the Repulse (55m) for eg. I can do;

Dive 1 , 55m for 35mins - total time on scrubber up to 6m stop = 66mins
Then OC for 6m stop.


Dive 2, 55m for 35mins - total time on scrubber up to 50m level = 100mins

(Total scrubber usage for both dives = 150mins)


So in some cases like this, going to OC at 6m can give me say an extra 35mins of scrubber time that will enable me to do another deep dive off the same fill.



Going to surface supplied (or staged) OC at 6m also saves having to mess around with O2 flushes and reduces need to refill on-board O2 so often.

Mdemon

That sounds like an interesting trick... Not having a booster I'm always sending back half-full J's of O2. Maybe I could be sticking the rest in a 15 and breathing it off - saving slime and halving my O2-costs...

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schford

Guys,

I know people that have died pushing the scrubber - please don't you're life is worth more than a few pounds / dollars.

Stuart

Pierre Farrugia

100% agree but I am curious how certaine dives are done! Altough Deco diver gave an explaination about very deep dives, I tought that if you can do a 120m+ dive then 2 dives to 60m could be ok, just curiousity nothing else, not interested to become a crash test dummy

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Mdemon

Very wise!

Stuart, I don't think the theme of the thread was really pushing scrubbers, more a query on how the deep stuff works duration-wise and there have been some good answers and tips.

I'm interested to hear of what people have pushed their scrubbers to, on the other hand, not to copy them, but to get a better idea of what might be achievable in a worst-case situation. Deeper/longer than intended etc. People are very shy of posting their experiences for many reasons and it's refreshing to read Decodiver's post on this. If it's just a matter of economics then I agree with you...

__________________
www.southwestmafia.com

"small minds talk about people, Average Minds Talk About Events, GREAT MINDS TALK ABOUT IDEAS!"

The WRONG Attitude will get you killed.

"Once the agenda-monkeys and perfect-worlders have moved on, perhaps we can do some diving?"

Drmike

You can do as many deep dives as you want on the same (YBOD) scrubber provided you dont go below 50m after you have total usage of 100mins (120?) on the scrubber. I cant explain it any simpler than that.


The critical thing with scrubbers is not during deco its during the bottom time at depth when a breakthrough is far more likely on a part used scrubber - hence the 100min rule. Scrubber life is a function of the depth that you are at at that moment in time. A scrubber that may still be good for another 2hours on a 10m dive or deco might be useless at 100m.

caveseeker7

Mike, I don't quite agree with that statement. Scrubber duration at shallows depth is quite critical, as it will make the difference wether you can finish the dive on the loop or not. The Inspo's rating allows for 82 min at 100m, most divers won't stay that long at that depth. But getting past the 180 minutes during the entire dive isn't exactly unheard of.

I do agree though that breakthrough is more likely at the deep part of the dive due to ambient pressure, workload (compared to hanging on the line) and maybe temps.

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Drmike

So in fact you do agree with my statement.

Im confused - what part of my statement dont you agree with?


A used scrubber can sustain you a heck of a lot longer during deco than it can at depth - especially if, as in here, we are talking about deep dives.

So in my book that makes scrubber remaining time a far more critical concern during the deep part of the dive - hence my statement.


I have no problem running a YBOD scrubber for significantly longer than recommended on deep dives - when practically all that time is spent on deco when you are not producing much CO2. But Im not recommending that of course.

Remember the scrubber lifetime is based on the assumption that the diver isnt sat on deco doing nothing for hours at a time.

However I wouldnt ever exceed the rating for the bottom part of the dive (single or repeat dives) because you just dont have as much to play with there.

I hope that clarifies my meaning.

Mdemon

So would 6 or 7 hours be feasible during "normal" diving conditions then?

Again, I'm asking as a comfort blanket in case I outstay my plan/go deeper than planned in an emergency...

__________________
www.southwestmafia.com

"small minds talk about people, Average Minds Talk About Events, GREAT MINDS TALK ABOUT IDEAS!"

The WRONG Attitude will get you killed.

"Once the agenda-monkeys and perfect-worlders have moved on, perhaps we can do some diving?"

Drmike

No. That's not what I wrote an I don't see how that can be inferred from what I wrote. I was talking about the difference between scrubber usage at depth and that during deco.

I personally would never do 6 or 7 hours off a YBOD scrubber - unless it was on one deep dive and 95% of that time was spent on deco. - But if I was going to be doing a dive like that I wouldn't be using a YBOD anyway.

Now if your YBOD had a scrubber monitor then maybe thats a different story as it wouldnt be 'guess work'