Tank Moist Air Intrusion during venting

[syntaxerrorsix]

banked 32%, partial pressure blending for trimix (don't dive air)

Doesn't change the premise or make bouldejohn or myself incorrect. To make Nitrox using partial pressure you decant gas down from the source bottle, if the target bottle is equal to or greater you will have to boost the source or drain the target.

To stick blend you continuously add whatever gas you like.

 

[nimoh]

I'm glad someone pointed this out. If you are partial pressure blending without a booster, you really need to drain the tanks. You will only be able to add the correct amount of O2 if the tanks to be filled are considerably lower in PSI than the source tanks.

Doesn't change the premise or make bouldejohn or myself incorrect. To make Nitrox using partial pressure you decant gas down from the source bottle, if the target bottle is equal to or greater you will have to boost the source or drain the target.

To stick blend you continuously add whatever gas you like.

I am only pointing out that the highlighted text is incorrect. If you keep the higher pressures in the O2 source tank, you can partial pressure blend without draining the tanks. When the source pressure gets lower, use it to bank nitrox.

The banked nitrox will cause less pure O2 to be used when partial pressure blending (a mix other than what is in the bank).

My point is only that draining the tanks is unnecessary

 

[syntaxerrorsix]

My point is only that draining the tanks is unnecessary

Maybe with a brand new bottle of O2. Not everyone uses stick blending.

They aren't going to throw away a partially depleted bottle.

 

[corvettejoe]

I'm with the others on finding a new shop. That's rediculous. The few that insist we do that when we go down to south FL we end up talking to a manager to tell them we DO NOT WANT them to do this. They usually give in. That's what an o2 analyzer is for, and if they're selling Nitrox, they better have an analyzer sitting around to test it with after.

I recall one chain shop down south that particularly likes to do this, and we always have the same conversation "Fill it with what I ask please and do not empty the gas out of my tank".

They REALLY freak out if you have left over trimix in there.

 

[nimoh]

Maybe with a brand new bottle of O2. Not everyone uses stick blending.

They aren't going to throw away a partially depleted bottle.

they should...cheap to make, and a big time saver.

 

[syntaxerrorsix]

they should...cheap to make, and a big time saver.

The stick is cheap to make. Not everyone wants to convert to an O2 compatible compressor however. That's not so cheap.

 

[nimoh]

The stick is cheap to make. Not everyone wants to convert to an O2 compatible compressor however. That's not so cheap.

don't need an O2 compatible compressor unless banking >ean40

 

[syntaxerrorsix]

don't need an O2 compatible compressor unless banking >ean40

Best of luck with that

 

[nimoh]

Best of luck with that

thanks

 

[boulderjohn]

I am only pointing out that the highlighted text is incorrect. If you keep the higher pressures in the O2 source tank, you can partial pressure blend without draining the tanks. When the source pressure gets lower, use it to bank nitrox.

The banked nitrox will cause less pure O2 to be used when partial pressure blending (a mix other than what is in the bank).

My point is only that draining the tanks is unnecessary

It all depends upon your situation.

Here in Colorado, there is so little demand for nitrox that most shops won't even make it. For most shops, even 98% of their air fills are for OW classes--there is very little local diving. For those that do, banking nitrox would be a ridiculously uneconomical waste of space. I don't know every shop in the state's situation, but every one I know that provides nitrox does it by partial pressure blending in the tank.

For those who say the blender is lazy for doing this, you cannot be more wrong. Partial pressure blending in the tank without a booster is extremely labor intensive. Everyone who does it that way made the decision to do so because it was uneconomical to do it any other way.