Gas blender Toolkit, wrong calculation?

Please register or login

Welcome to ScubaBoard, the world's largest scuba diving community. Registration is not required to read the forums, but we encourage you to join. Joining has its benefits and enables you to participate in the discussions.

Benefits of registering include

  • Ability to post and comment on topics and discussions.
  • A Free photo gallery to share your dive photos with the world.
  • You can make this box go away

Joining is quick and easy. Log in or Register now!

Agro

Contributor
Messages
106
Reaction score
32
Location
Zurich, Switzerland
IMG_6268.PNG
IMG_6269.PNG

I have EAN29 in my cylinder at 150 bar.
I have a cylinder of EAN34 and I have a compressor.
Result should be:
1. Add x bar EAN34
2. Add y bar air
3. Result: 270 bar EAN29

But the tool sais: can not be calculated.
a) Tool is wrong
b) Tool believes, I have EAN34 only, no air. But doesn't tool take air as always available?

Thanks for help.
 

lermontov

Contributor
Messages
1,180
Reaction score
721
Location
christchurch
# of dives
500 - 999
View attachment 689570 View attachment 689571
I have EAN29 in my cylinder at 150 bar.
I have a cylinder of EAN36 and I have a compressor.
Result should be:
1. Add x bar EAN36
2. Add y bar air
3. Result: 270 bar EAN29

But the tool sais: can not be calculated.
a) Tool is wrong
b) Tool believes, I have EAN36 only, no air. But doesn't tool take air as always available?

Thanks for help
you could bleed down your 36 % to 144 Bar then top up to 270 with air - then you had have 29% in both cylinders
 

Agro

Contributor
Messages
106
Reaction score
32
Location
Zurich, Switzerland
Sorry type mismatch, it's EAN34, not 36, I corrected.

Lermontov, that's not what I want. The 34 cylinder shall stay 34. I want to use some 34 to make 29. So no use of oxygen but 34+air.
 

lermontov

Contributor
Messages
1,180
Reaction score
721
Location
christchurch
# of dives
500 - 999
Sorry type mismatch, it's EAN34, not 36, I corrected.

Lermontov, that's not what I want. The 34 cylinder shall stay 34. I want to use some 34 to make 29. So no use of oxygen but 34+air.
either way i dont believe it can be done
 

Agro

Contributor
Messages
106
Reaction score
32
Location
Zurich, Switzerland
Of course it can be done, no doubt about that. Pocket calculater sais for ideal gas:
74 bar of EAN 34, top off by air.
 

lermontov

Contributor
Messages
1,180
Reaction score
721
Location
christchurch
# of dives
500 - 999
Of course it can be done, no doubt about that. Pocket calculater sais for ideal gas:
74 bar of EAN 34, top off by air.
maybe post a pic when you find a software that can do it
 

Agro

Contributor
Messages
106
Reaction score
32
Location
Zurich, Switzerland
I hope Gasblender Toolkit can hadle it. I hope I am to stupid to know how to do it......
 

inquisit

ScubaBoard Supporter
ScubaBoard Supporter
Messages
389
Reaction score
221
Location
Boulder, CO
# of dives
1000 - 2499
The toolkit doesn't handle the addition of two gasses, but you could always go back to first principles. You have two unknowns: x=amount of EAN 34 to add and y=amount of air. You have two equations: 1) the amount of O2 and 2) the total pressure. Either do the math on a calculator or the easiest approach is to type this expression into Wolfram Alpha:
  • 150*0.29 + x*0.34 + y*0.209 = 270*0.29, 150+x+y=270
As @Agro said, "74 bar of EAN 34, top off by air." 👍

1635948921277.png
 

Agro

Contributor
Messages
106
Reaction score
32
Location
Zurich, Switzerland
Is there a software which can handle this?

Inquisit's calculation is working with ideal gases. As we all know EAN at 270 bar is far from beeing ideal, we do need Van der Waals calculation. I hope there is a software for that.
 

DiveClimbRide

Contributor
Messages
212
Reaction score
127
Location
New Zealand, South Island
# of dives
200 - 499
The reason the app cannot handle it is because it assumes you ALWAYS top off with 100%O2. The top off gas that you changed is what it wants you to top off with AFTER O2. So it's says that it is impossible to get your mix (29%) by useing 100% and 34% when the cylinder has 29% in it already. Hope that helps. It's my only annoyance with the app it doesn't support weak nitrox top off. What I do is see how many bar of O2 I need to add then divide by the percentage of gas I have to get the amount I need to add. An example. I want to mix up 210bar 32%. My tank is empty. I would need to add ~32bar of O2 and top off with air. 32/0.50 or 32/50% = 64bar of 50% that needs to be added. That's how you do it, obviously works best at low pressures not high pressures.
 
https://www.shearwater.com/products/perdix-ai/
http://cavediveflorida.com/Rum_House.htm

Top Bottom