need some help

[deepdiver4]

can someone explain the pressure tee in english ihave the technical encyclopedia.. pg=fgxp fg=pg /p p=PG/FG
THANKS

[CaloosaCaver]

Pressure of the gas equals fraction of the gas mutiplied by pressure

Fraction of the gas equals partial pressure of the gas divided by total pressure

pressure equals pressure(partial) of the gas divided by the fraction of the gas

remember to always calculate percentage of gas and fraction of gas in decimal form.

I did not recheck these formulas, I assumed they were inputted correctly.

Hope this helps.

[Jim Wyatt]

http://cavediveflorida.com/Dalton.htm

Perhaps this link will assist you.

Jim

[skip]

I love that formula and the three-piece pie - the pyramid is nice too, but I like the circle - looks more like a happy face!

PP
________
ATA l FG

Imagine a circel drawn round. This thing does it all...once you get the basics use it for END and EAD and then add helium. With just a little thought and a basic calculator you will never need to know any other formula.

best mix for a dive to 132 feet in salt water? 132 feet is 5 ATA; you want to hold your PP at 1.4 (always) 1.4 / 5 = 2.8 (EAN28). If you drop your camera and chase it how deep before you reach 1.6PP (of O2)? That's 1.6 / .28 = 5.71ATA (5.71x33-33 = 156 feet). You asked your LDS for 36% EAN, but they mixed you 38% cause the fill station operator couldn't read your handwriting. How deep can you go now? 1.4 / .38 = 3.68 ATA (3.68x33-33 = 88 fsw. You say really need to go to 125 feet if only for a minute? hmmmm....125 feet is 125/33+1 = 4.79ATA. And now .38 x 4.79 = 1.82 PP!! Yikes, maybe you should drain off about 700 psi and top the tank (now at 2300 psi) with air (21% O2 will knock down that 38%). But would 700 psi of 21% reduce your mix to a safe mix for 125 fsw? Well, that's a whole other thing!

But let's see... .21 x 700 is 147 psi of O2 added to 874 psi of O2 (.38 x 2300 psi = 874psi of O2) gives you 1021 psi of O2 out of 3000 psi. Now you have a 34% mix (1021/3000 = .34033). And that 34% will let go to 102 fsw with PPO2 of 1.4 and to 122 feet with a PPO2 of 1.6. But 122 feet is not the 125 you really want. 125 fsw is 4.79 ATA (125x33+1 = 4.78787). And that means your PPO2 with 34% would be 1.63 at 125 fsw (4.79 x .34 = 1.6286). Ahh what the heck, you did say "just for a minute" didn't you?

And if you do dive that 34% to 125 feet what is the EAD? Some may prefer END, but that's a quibble for trimixer's. So what is the PPN2 for 34% nitrox at 125 feet? It's 3.16 (.66 x 4.79ATA = 3.1614). And at what depth would you find a PPN2 of 3.16 using air (79% N2)? Well, let's see...... 3.16 / .79 = 4 ATA, which is 99 fsw (4 x 33 -33). Diving down to 125 feet of salt water on 34% nitrox has the nitrogen effect of 99 feet on air. And my old NAUI air table (1985) says that my NDL at 100 feet is 25 minutes.

In summary then, if you dive down to 125 feet for a minute or two on 34% nitrox, you'll be pushing your PPO2 to 1.63, but the narcosis and nitrogen loading will be similar to an air dive to 100 feet.

How much gas will this dive take? Dang, do the questions never stop?

It's a bit cold and a bit of current may be running, so let's set your RMV at .95cf/min (SAC with workload added). At 4.79 ATA (125 feet deep) you will breath .95 x 4.79 = 4.55cf/min. Now you can't stay at 125 feet too long (pushing your PPO2), so a minute or two is about 9cf. Let's say 10cf. So you come up to 100 feet for most of the rest of the dive (100 fsw = 4 ATM, close enough). So .95 x 4 = 3.8cf/min. That AL80 with 3000 psi will last about 21 minutes, but you already used 10cf and a bit more getting down to depth, so it's more like 16-18 minutes.

I have no doubt that my math errors will be discovered and corrected with lots of hoots and hollers resulting in me slinking off in shame, to never post, nay, worse....to never dive again for fear of stoning while gearing up at Peacock. Ahhh, what the hell, it's really only my cyber neck that's stuck out!

-skip

[FW]

Hey Skip, he asked for it in *English*

[skip]

Hey Skip, he asked for it in *English*

Does that mean without numbers? Well then what good would the pressure T be? But let me see....

The pressure T tells us the Partial Pressure of any Gas in a mix of Gases given the Fraction of that gas in the mix and the Depth at which we breathe it.

The pressure T tells us the Best Mix for a planned depth.

The pressure T tells us the Maximum safe Operating Depth of any Gas.

The pressure T tells us the relative rate of on-gassing (and off-gassing) in living tissue of any Gas at any depth.

And so much more.....

I just can't get any more English than that!

-skip

[FW]

Much better

Hey deepdiver4, does Skip's explanation help, or was there something else you were looking for?

[deepdiver4]

i get it wish the ins went over it like that thanks all great help

[Mike]

Once a professor always a professor.
(I hope I spelled professor right)
Mike M

[OFG-1]

What are you guys talking about? Isn't this the pressure tee????