EKPP Ressel (August 2003)

[bang-on]

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Originally Posted by [b

Quote[/b] (adam @ May 02 2004,13:11)]Agreed Zak, but in Barrie's example?

adam,
the 1.3 setpoint that controls the solonoid is connected to the 02 onboard cylinder only and will only add 02 to the loop.
the dil is injected into the loop by the dv or manually normally on descent only,during ascents dil would not be added although 02 is to maintain the 1.3 pp02...

1.3 pp02 loop = 24.53% 02   43mtrs
1.3 pp02 loop = 29.55% 02   34mtrs
1.3 pp02 loop = 35.13% 02   27mtrs
1.3 pp02 loop = 46.42% 02   18mtrs
1.3 pp02 loop = 59.09% 02   12mtrs
1.3 pp02 loop = 68.42% 02    9mtrs
1.3 pp02 loop = 81.25% 02    6mtrs
1.3 pp02 loop = 92.85% 02    4.5mtrs
1.3 pp02 loop = 100% 02       3mtrs

the above is just an example but if you take the 1.3 pp02 setpoint and devide by the depth in bar that will be the % 02 in the loop at that depth and this % 02 reduces deco.    
when last stop '3mtrs' is cleared setpoint is lowered to 0.7 for ascent to prevent solonoid injecting constantly as 1.3 bar is no longer available.
handsets that control the setpoint are diver adjustable and 1.3 pp02 is my choice.
cheers
barrie

[Pierre Farrugia]

<font color='#0000FF'>Hello Barry,

Maybe off topic but I ask it here. When you dive a trimix diluent what happens to the mix at depth and your inspiration is set to 1.3 PpO2 eg:

If you dive a 17/50 trimix which has a MOD @ 1.4 of 75m what mix would you be brething at 50m ?
Oxygen: You would have 1.3ppO2 so an equivalent to open circuit of 21.6% O2, can you calculate what the other 2 mixes are?

[bang-on]

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Originally Posted by [b

Quote[/b] (Pierre Farrugia @ May 04 2004,09:31)]Maybe off topic but I ask it here. When you dive a trimix diluent what happens to the mix at depth and your inspiration is set to 1.3 PpO2 eg:

If you dive a 17/50 trimix which has a MOD @ 1.4 of 75m what mix would you be brething at 50m ?
Oxygen: You would have 1.3ppO2 so an equivalent to open circuit of 21.6% O2, can you calculate what the other 2 mixes are?

pierre,
the 'partial pressure' is the 'bar pressure' eg;
50 mtrs = 6 bar pressure
1.3 is the pp02 take 1.3 away from 6 = 4.7 pp of other gases.
this is the breathing loop as distinct from the diluent 17/50
if you wanted to know what % he or nitrogen is in the loop you would have to calculate it using the loop volume - the diference in pp between gas mix and the loop eg.
50 mtrs = 6 bar 17% 02 = 1.02 pp (1.3-1.02 = .28)
6 bar pp - .28 = 5.72 pp divide by 6 bar = .9533
.9533 divide by 100 x 50 = 47.67% he in loop
.9533 divide by 100 x 33 = 31.46% n2 in loop
.9533 divide by 100 x 17 = 16.21% 02 in loop
.28 pp x 6 bar =                4.67%  21.67%
                                    100% loop volume

cheers
barrie