Calculating MOD with EANx

[dantfarley]

Maybe someone can help simplify MOD when using EANx up to 100%- I am not understanding what is written in my book

ie.- 40% MOD, 50%, 60%, etc.
my equations are not computing with a balanced PO2 somewhere in the range of 1.4-1.6


Thank you

 

[Searcaigh]

Use this site

Lloyd Borrett - Interests - Scuba Diving - Maximum Operating Depth (MOD) Calculator

MOD (m) = 10 x [(ppO2/FO2)-1]

In which ppO₂ is the desired partial pressure in oxygen and the FO₂ is the decimal value of the fraction of oxygen in the mixture. For example, if a gas contains 32% oxygen and the maximum ppO₂ is 1.4 bar, the MOD (m) is 10 metres x [(1.4 / 0.32) - 1] = 33.7 metres.

For EAN40 MOD = 10 x [(1.4/.40)-1] = 25 metres

For EAN50 MOD = 10 x [(1.4/.50)-1] = 18 metres

etc

Hope that helps

 

[JohnN]

Maybe someone can help simplify MOD when using EANx up to 100%- I am not understanding what is written in my book

ie.- 40% MOD, 50%, 60%, etc.
my equations are not computing with a balanced PO2 somewhere in the range of 1.4-1.6


Thank you

It's not quite clear from your notes where you're getting confused. . .

MOD = 33*(ppO2/EANmix -1) or if you're metric MOD = 10*(ppO2/EANmix-1)

for EAN40:
MOD = 33*(1.4/.4-1)
MOD = 33*(3.5-1)
MOD = 33*(2.5)
MOD = 82.5 feet


John N

 

[Searcaigh]

Use 33 instead of 10 in the formula for feet, just noticed that you are from across the pond

 

[kotik]

You first have to decide exactly what the maximum O2 partial pressure you're comfortable with. The fraction of O2 (FO2) is given to you, it's whatever is in the tank.

For salt water, with depth (MOD) in feet and O2 partial pressure (PO2) in atmospheres, this equation should work:
MOD=33fsw*(PO2/FO2-1)

So if you are comfortable diving at PO2=1.5 ATA (this is a little higher than is generally recommended), and you have a tank w/ 36% FO2, then the MOD would be 33*(1.5/.36-1)= 104 feet

---------- Post Merged at 12:32 PM ---------- Previous Post was at 12:30 PM ----------

Doh!! I knew better than to try to reply to this, somebody's always quicker on the draw with the math!

 

[levi]

%02 x ATM/BAR = p02
OR
p02 / %02 = ATM/BAR -1ATM = MOD

i.e. max p02 required is 1.4 divided by %02 (ex. 45%(.45)) = 3.11 ATM - 1ATM =2.11ATM = 21.1 meters MOD for 1.4 p02 max [or 21.1 x 3.3 = +/- 70ft MOD].

or did i misunderstand the question?

 

[Orlando Eric]

Hey -- the math portions are the hardest for me in dive theory. In case you were also a "C-" student in Algebra as I was...

If you are using 1.4 --- 1.4 / mix percentage (.36) x 33 - 33 = 95.33 Feet

This is what they were typing up there but at a highschool level which is beyond my immediate grasp I have to stare at it for like three or five minutes.

---------- Post Merged at 05:39 PM ---------- Previous Post was at 05:37 PM ----------

best mix is (depth) / 33 + 1 = X then divide 1.4 by X = best percentage mix these two you will use alot of times -- well you should unless you just jump in alot with trust me dives

 

[Insta-Gator]

It's not quite clear from your notes where you're getting confused. . .

MOD = 33*(ppO2/EANmix -1) or if you're metric MOD = 10*(ppO2/EANmix-1)

for EAN40:
MOD = 33*((1.4/.4)-1) parens to ensure operations done in proper sequence (yes I know there are rules for operational sequence but some may not know)
MOD = 33*(3.5-1)
MOD = 33*(2.5)
MOD = 82.5 feet


John N

Not criticizing, just clarifying for others.

 

[Orlando Eric]

instagator -- see I do not understand that. -- :x lucikly I do not have to do any real abstract math in my job. The back seat only holds four.. five if you stack em

 

[James R]

Here's a scan I made of the MOD tables for 1.4 and 1.6 in FSW.

Can't get any easier for you than this!