CCR SAC for Diluent /oxygen calkulation

[Remus Brukker]

  I was looking for the SAC setting for CCR, but I couldn't find it. Can Subsurface also calculate the gas consumption for Oxygen and Diluent during planning? In the dive graph, it shows the same pressure throughout the entire dive.  

Thank You

Remus

[Michael Keller]

Hi Remus.

On Wed, 18 Sept 2024 at 04:53, Remus Brukker <rbru...@gmail.com> wrote:

  I was looking for the SAC setting for CCR, but I couldn't find it. Can Subsurface also calculate the gas consumption for Oxygen and Diluent during planning? In the dive graph, it shows the same pressure throughout the entire dive.  

Unfortunately there is no good way to estimate the gas consumption for a CCR dive. Yes, there is a minimum consumption of O2 that is metabolised by the diver - but even this is highly variable based on the diver's physiology and the workload. But a lot of the O2, and all of the diluent, is actually used to regulate the loop volume and ppO2 during descent and ascent. And here a lot of factors like the unit type, dead air space, diver's lung volume, and how well the diver manages to stay at minimum loop come into play. And then you get your 'fixed cost' consumption for things like the O2 used for the sensor check at the start of a dive that will vary from dive to dive.

So any estimate will really only be a 'wild guess', and nothing of this sort has been implemented in Subsurface.

Cheers

  Michael Keller

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W++ N o? K? w O(++) M-- V+ PS+ PE+ Y? PGP+ t
5? X R tv b++ DI++ D++ G e+++ h---- r+++ y+++

[Remus Brukker]

  Hi Michael, thank you. I understand what you wrote. Yes, it's a variable that changes. I have calculated long-term average gas consumption for myself and my partner. We have Liberty and pressure transmitters, so we know exactly what the consumption was for each dive. When I'm planning a weekend trip, I have a rough idea of how much gas (cylinders) each person will need. It's just a suggestion to make it possible to enter the SAC, just like with OC, and calculate the consumption. Essentially, just like it is with OC. 

  Subsurface is amazing, and I use it very often, especially for complicated dives. These are just ideas that would make planning easier for me. :-)  

Thank you.  

Remus

ut 17. 9. 2024 o 23:43 Michael Keller <m...@042.ch> napísal(a):

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[Michael Keller]

Hi Remus.

On 18/09/24 20:36, Remus Brukker wrote:
> I have calculated long-term average gas consumption for myself and my
> partner.

What are you basing your average on? Is it liters per minute, or liters
per minute times average depth, or what?


Cheers

  Michael Keller

[Remus Brukker]

  I calculate the consumed pressure (bar) based on the dive time. It's pretty cold at depth here, so dives are 60-90 minutes long. Up to 50 meters, the consumption is more or less the same, but it increases significantly afterward, as both the diluent and oxygen are used more to fill the loop. For dives of 80+  meters, we always go with full tanks. Of course, this assumes we’re not doing any work during the dive and that the dive goes according to plan without any incidents. So, from long-term averages and dive plans, I know how many tanks and how much diluent and oxygen I’ll need to prepare for a trip.  

st 18. 9. 2024 o 15:17 Michael Keller <mike...@042.ch> napísal(a):

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[Michael Keller]

Hi Remus.

On 19/09/24 18:51, Remus Brukker wrote:
>   I calculate the consumed pressure (bar) based on the dive time. It's
> pretty cold at depth here, so dives are 60-90 minutes long. Up to 50
> meters, the consumption is more or less the same, but it increases
> significantly afterward, as both the diluent and oxygen are used more
> to fill the loop. For dives of 80+ meters, we always go with full tanks.

So we already have two different use cases for an estimation, which
require different consumption rates. And that's for one variable
(depth), with the rest of them being relatively constant.

This doesn't bode well for being able to use one fixed 'volume per
minute of the dive' value for a consumption estimate that is more than a
wild guess...


Cheers

  Michael Keller

[Gachoud Philippe]

I personally keep a record into the comments of consumed O2/DIL but it would be nice to be able to keep track of that another way even if that's not a very precise thing. I'd appreciate having a way of keeping track of that, even with a reduced complexity model. Am I the only one with that desire? or you all dream about it and just let it go because of its complexity to achieve the exact consumption rate :)

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[Michael Keller]

Hi Philippe.

On 26/09/24 22:05, Gachoud Philippe wrote:

I personally keep a record into the comments of consumed O2/DIL but it would be nice to be able to keep track of that another way even if that's not a very precise thing. I'd appreciate having a way of keeping track of that, even with a reduced complexity model. Am I the only one with that desire? or you all dream about it and just let it go because of its complexity to achieve the exact consumption rate :)

No need to dream - keeping track of gas consumption is really simple in Subsurface - just go to the 'Equipment' tab, and add and edit the gases you have used, and their cylinder sizes and start and end times:

Cheers

  Michael Keller