scr deco

[max101]

i am aware with scrs that whats in your tank will not be what your breathing, so what do you set your computers to ??
on rb80 stlye units where decompression dives are ''allowed'' what do you use for the mix settings on a computer or when cutting tables, i know that drager dont recomend deco diving on their units because of this but i know people do so, what do you do ?????

thanks

max

[NotDeadYet]

There are different equations for different rebreathers depending on passive or active SCR, addition rate or dump rate, drive gas, depth etc., which will allow you to estimate what is in your loop.

Work out what you will be breathing at the dive depth and plug your figures into deco software, treating it as open circuit.

Alternatively, plumb a VR3 or Explorer into the loop with an O2 sensor.

[londonsean69]

Try this link, scr calcs it gives the calculations for working out what you are breathing on both passive scr (like the RB80 or my EDO) or active (Draeger etc.).

When I got my EDO there is also a chart giving expected drops.

I will be able to give real life examples as soon as I get my PPO2 monitors from Stuart

Cheers

[jknights]

If you have a Drager then you cn use and Alladin AIr Z O2 and an Oxy2 and this will provide you with pO2 readout and manage decompression.

Alternatively a VR3/2 with a P holder and an O2 cell will provide the same e.g. deco and pO2 readout.

Then there are the other home built units but theses dont provide both deco and pO2 management only pO2 readout.

[e-aquanauts]

Originally Posted by jknights

If you have a Drager then you cn use and Alladin AIr Z O2 and an Oxy2 and this will provide you with pO2 readout and manage decompression.

Alternatively a VR3/2 with a P holder and an O2 cell will provide the same e.g. deco and pO2 readout.

Then there are the other home built units but theses dont provide both deco and pO2 management only pO2 readout.

You could... but, you'd be as mad as a badger.

A single cell, in a RB enviroment should only be used as a crosscheck.

Two real obvious problems with deco tracking based on computers with PPO2 monitors;

1) Galvanic cells don't decay in a deterministic, predictable or constant way and are affected additionally and negitively by the enviroment inside the rebreather.

2) Computers remove all the additional safety fudge that used to occur with tables, PP02 tracking further removes more fudge. How close on any given day to the deco theories are our bodies?

For control logic either PPO2 or deco you need three cells, in a voting configuration (see reason 1), using the grey stuff between your ears to crosscheck that output and some of that uncommon sence, planning and some bailout strategies for when it all goes wrong.

Never ever let the technology dive for you, plan your dive, dive your plan.

For an SCR (mine's a Submatix);

I plan my tank mix, based on all the usual dive parameters, additionally I calculate my rebreather "bag" mix. The bag mix is the nitrox mix I'm actually rebreathing and this is based on nitrox mix from the tanks, flowrate and metabolism. I run a fixed nitrox mix deco plan based on my bag mix, a fixed depth based on the MOD PP02 in the bottles.

During the dive I have the EXT PPO2 on my VR3 turned off (thus it's not affecting my deco) and I can crosscheck with my PPO2 monitor on the VR3.
I dive to tables and use the computer as backup to my brain.

/F

[max101]

ok cheers, i am curently thinking about getting an edo4 thing

[e-aquanauts]

Cool. Why? and why not an RB80?

[max101]

no.1 rb80 = £££££££££££££
i prefer the ideas of the design over dragers etc

[e-aquanauts]

So how much is the EDO4? - I know last time I was at EE in Highsprings an RB80 and training was only US$ 7.5K nearly bought one then Not like it's real money....

[NotDeadYet]

When I was thinking about one, it was about £1100 but the price I think the price has rocketed recently.