Nitrox mixing at home...

[DudleyNMU]

PP02 Diver thank you very much...That i what i was looking for.

 

[300bar]

Don't know how things work at your place but for me the local fire Dept.
will have a say in this and in my case that a big NO NO :shakehead
Not even in my dive shop.

 

[Rick Inman]

You can figure this out with some basic math and a little logic.

Say, 80cf tank and you want 40% O2 (empty). Remembering that air is already 21% O2 (the free part), you'll need to know how many CF of O2 you need to hit 40%, less the CF you get for free in air.

O2 to add= (FO2-.21)/.79

That gives you the percentage, which you multiply times the CF of the cylinder. Divide that by your 250cf tank, and you get the answer.

But yes, take a blending class, buy the airspeed book. My instructor and I mixed our doubles and 4 stages in his garage the other day, for a 230' dive. As soon as we finished mixing, I said, "Well, the most dangerous part of the dive is over."

 

[DudleyNMU]

next question: If i have only one 250cuft bottle is there enough pressure to fill several tanks or should you bank them. I know banking them would be better but if you had only one would it work out ok?

 

[ClayJar]

Okay, just using ideal gas laws (no Van der Waals corrections or anything), and taking the units to be "volumes of gas at STP" (standard temperature and pressure) it works out to a simple set of equations you can easily figure it out:

V_tank * f_atank = V₁ * f_a1 + V₂ * f_a2 + ... + V_n * f_an
V_tank * f_btank = V₁ * f_b1 + V₂ * f_b2 + ... + V_n * f_bn
.
.
.
V_tank * f_xtank = V₁ * f_x1 + V₂ * f_x2 + ... + V_n * f_xn

V_tank = V₁ + V₂ + ... + V_n

1 = f_a1 + f_b1 + ... + f_x1
1 = f_a2 + f_b2 + ... + f_x2
.
.
.
1 = f_an + f_bn + ... + f_xn

1 = f_atank + f_btank + ... + f_xtank

Of course, if you want to include the VdW corrections or what-have-you, it becomes more complicated, as it does if you're working in something more easily measurable than "volumes of gas at STP". I think most people measure pressures when blending.

If you solve this for 250cf of pure O2 and an arbitrary amount of air, you get, simply: V_tanks = V_O2 / (f_O2 - 0.21)

Of course, this is assuming you can get all the O2 out of the 250cf cylinder and into your AL80s, which isn't the case. Still assuming that, and assuming you want EAN32, you could get a bit more than 29 hypothetical AL80s out of your 250cf of O2. Now, as to why you will not get 30 tanks of Nitrox I, at least several reasons should be quite plainly obvious.

 

[Rick Inman]

next question: If i have only one 250cuft bottle is there enough pressure to fill several tanks or should you bank them. I know banking them would be better but if you had only one would it work out ok?

How many PSI do you need to put in your scuba tank to get your desired percentage? That is the lowest percentage your O2 cylinder can drain before you need a booster, or a new bottle of O2. Figure out how much that bottle will cost you per square foot and you'll know. Of course, the more bottles you cascade into the more economical.

Look, this is interesting to talk about, but dangerous to actually try to learn on the internet. You think an O2 fire causes flames, just keep asking questions on this thread and see what happens.

Notice: If you take anything you get on this thread and attempt to put it into practice without taking a blending class (or the airspeed book and a mentor) you are asking for an O2 fire, or worse.

 

[wedivebc]

All this information is covered in a basic nitrox blenders class which the OP obviously does not have. Trying to PP blend nitrox can have its pitfalls especially to the untrained. Case in point:

...And i do know it is dangerous but not that dangerous...

This material should not be taught on the internet.

 

[Thalassamania]

Here ... I'll help you along. You want to raise the O2 from 21% to say 36%. That's 15%. Your using an Aluminum 80, so that 15% of 80 cubic feet or 12 cubic feet each time. Your oxygen supply is 250 cubic feet and each fill will need 12 cubic feet so the best you could do theoretically is about 21 fills, in reality it’ll be more like 15. last time I checked a cylinder of oxygen was about $15.00 with a $130 deposit and a $3.00/month rental, so costs were a buck and change per fill.

 

[The Horn]

my tourch kit cost way more than that to fill.....hmmmmm will have to check some things out on the ol' Praxair local store...........

 

[Thalassamania]

That's not delivered, and it's a few years back.