GUE Fundamentals

[BlueTrin]

So, for the 15°C factor, I computed the density using the formula pV=nRT. Since p is constant, the volume is proportional to the temperature (in Kelvin, that is 15°C=388K, 0°C=373K), and the density is inversely proportional to it. Therefore, it is sufficient to divide the density by a factor =373/388.

Anyway, it doesn't matter what temperature you use for the calculation since the reference is the air at 30m. The important thing is that you compare densities relative to the same temperature.

So it's ok to use 5.2308, but you need to compare it with other densities calculated at the same temperature (0°C). I believe that the 5.2 that @Heat Miser mentioned comes exactly from here (nx32 density at 0°C and 30m deep), and nx32 is always higher than the other GUE CCR standard gases at their MOD (see my table). This is why I believe that @Heat Miser made a mistake, but maybe I am missing something or I myself made some mistakes in my calculation.

OC gases are a bit different; I did the calculation during the tec1, but I don't really remember it (shame on me!), and I am too lazy to do it again now

EDIT: I modified the post, you calculated it at 0°C, not at 20°C... at higher degree, the densities are even lower (compare it with my table)

I put the temperature because I wanted to give the details of the figure I computed.

Just realised MultiDeco can compute gas density.

On my phone, for EAN32:
- 4.84 at 20C
- 5.20 at 0C

They use 4.02 ATA at 30m

 

[ginti]

I put the temperature because I wanted to give the details of the figure I computed.

Just realised MultiDeco can compute gas density.

On my phone, for EAN32:
- 4.84 at 20C
- 5.20 at 0C

They use 4.02 ATA at 30m

These numbers are slightly lower than ours, but I made some approximation in excel (I rounded the densities to the first two digits), and I guess you also used numbers a bit different from the one of MultiDeco. So, overall, it seems we are getting it right

 

[ginti]

I put the temperature because I wanted to give the details of the figure I computed.

Just realised MultiDeco can compute gas density.

On my phone, for EAN32:
- 4.84 at 20C
- 5.20 at 0C

They use 4.02 ATA at 30m

out of curiosity, could you calculate with MultiDeco the densities of the other mixes that I put in my table? Many thanks!

 

[BlueTrin]

 

[BlueTrin]

Also when I said they use 4.02 ATA for 30m I was wrong: the bottom figure ATA of air is the comparative equivalent pressure of air to obtain the same density.

I.e. we want to compare this against 4ATA for 30m air equivalent.

 

[Wibble]

The setpoint is always at 1.2. Only during deco I use my mav to add more oxygen. I know it’s also possible to change the setpoint in the controller during the dive, because I did try to change it during a deco stop at 6 meter.

I always use 1.2 during the dive, other teammembers are also using 1.2. Are your teammembers using always 1.3 or does it depends on the dive?

I dive whatever is appropriate and is available. My setpoint is 1.2 but is manually controlled at 1.3 or even 1.4 depending upon the dive profile.

For years we’ve dived with the bottom phase PPO2 at 1.4 and deco at 1.6. Suddenly on rebreathers we’re choosing to increase decompression with a lower PPO2. No, I’m not talking about extreme 90m/300ft dives where CNS limits and team bailout comes into play, just the run of the mill normal dives.

Although I sometimes dive with others they’re not in any way team members, just people I may dive with. This is good for flexibility, if there’s something really interesting then we go our separate ways and meet back on the boat. Similarly if anyone wants to cut their dive short, a wave goodbye suffices.

No buddies, no problems, just go diving. Whilst not the GUE way, it’s the way an awful lot of divers enjoy their diving.

 

[grantctobin]

Extreme 90m/300ft dives where CNS limits and team bailout comes into play, just the run of the mill normal dives.

You keep saying this “team bailout” stuff and someone that isn’t familiar with your background or inexperience in hypoxic dives is going to think it’s normal. Team bailout is unnecessary and fairly uncommon and frankly fairly dumb.

 

[Wibble]

You keep saying this “team bailout” stuff and someone that isn’t familiar with your background or inexperience in hypoxic dives is going to think it’s normal. Team bailout is unnecessary and fairly uncommon and frankly fairly dumb.

Simply that one would struggle to carry sufficient bailout for circa 100m/330ft dives without the assistance of others, thus becoming more team oriented.

 

[grantctobin]

Simply that one would struggle to carry sufficient bailout for circa 100m/330ft dives without the assistance of others

Which also isn’t true…

 

[Wibble]

Which also isn’t true…

Of course everyone carries four or more bailout stages with them. Or... they resort to team-based bailout and even safety divers, etc.


In any case this is precisely the type of diving I explicitly said I wasn't referring to:

I’m not talking about extreme 90m/300ft dives where CNS limits and team bailout comes into play, just the run of the mill normal dives.