On 2021/11/15 00:07, Robert Helling via subsurface wrote:
Hi Poltsi,
On 14. Nov 2021, at 22:44, Paul-Erik Törrönen via subsurface
<[email protected]
<mailto:[email protected]>> wrote:
When CCR, you're mainly interested in the consumption of O2 as noted
previously. The diluent is not really telling since it is mainly a
function of your profile as you use diluent to equalize the pressure
in the loop. A serrated profile (lot's of ups and down) == large
volume of diluent used because of addition to loop when going down,
then dumping it when ascending.
I can see that the amount of O2 used divided by total dive time could
be of interest. But it’s definitely something else than SAC and thus
should not be mixed with it. For example, in any statistics when you
have both CCR and OC dives, it would make zero sense to combine the
two. So even if we computed this number, it should not be displayed as
SAC or stored as such. Let alone the number with an ambient pressure
correction like the SAC makes zero sense for a CCR.
Of course this also happens to O2 also, but what would be interesting
to see is how/when your consumption of O2 changes due to increased work.
I meant more the other way around: If you diluent also contains O2,
you underestimate the O2 consumption if you only use the pressure drop
in the O2 cylinder.
The O2 consumption under CCR is not a dive characteristic because the
diver can bail out to OC. So O2-consumption would be a cylinder-level
characteristic, associated with cylinder 0 ?? (i.e. the diluent cylinder
because as far as I can remember the O2 cylinder does not explicitly
exist in the Subsurface CCR dive log). In pSCR bailout is often part of
the normal dive procedure during deco.
So here is a question I have: For a typical CCR dive, what is the
ratio between used O2 and used diluent? I understand this depends on
how often descend and how often you flush but what is a ballpark type
figure?
As a ball park approximation, many CCR dives (up to 65m) are done using
air as a diluent, supplemented with oxygen from the O2 cylinder to make
up for oxygen consumed as well as for higher O2 levels during shallower
deco.
Kind regards,
Willem
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