PP blending Nitrox Question

[willembad]

Could someone please explain why the O2 goes in the tank first? Wouldn't my shop be able to blend EAN with the air first as to avoid using a dedicated Nitrox tank?

Willem

 

[JeffG]

Because a shop would need a booster to get the O2 to a high enough pressure if they put it in last. (O2 tanks are around 2200 psi)

A shop could use continous blending (with the proper setup).

 

[Rick Inman]

Here is a quote from The Oxygen Hackers Companion:

"While the main reason for adding the O2 first is that it's easier and avoids having to boost it, it is also desirable to do so since it keeps the PO2 that the valve will see as low as possible. ...we are most concerned with adiabatic heating, and the valve will see a higher PO2 if the O2 is added after the air. "

 

[captain]

Because with the air first the pressure would be higher therefore you would need higher pressure in the O2 cylinder or a boosterpump. Say you put 2500 psi air in and now want to add O2, you would need an O2 cylinder with more than 2500 psi or a booster pump if you you only had 1000 psi in the O2 cylinder. If you start with only 500 psi air in the scuba cylinder and add the O2 first you get more useage from the O2 cylinder without needing a booster pump.

 

[willembad]

Thanks,

I knew they had a reason, I just wasn't sure. It does make sense.

Willem

 

[The_DivePirate]

My suggestion would be, take a blending class. It would do you good, and knowledge in blending as well as other things makes things safe. Just like in diving, knowledge is key.