Tank Moist Air Intrusion during venting

[Steve_C]

In terms of the OP, I think the difference is that in his lab you are putting components in and out of things. If the pressurization is then done it will drive most of the air out but it is easy to see how some moisture could be left in the chamber. The tank is different. There is no sticking anything into the tank. There is no pressurizing from zero.

My LDS is happy to start with any tank pressure I give them especially if it was already filled by their banked 30% (30.5 actually).

 

[tplyons]

As a gas blender, I prefer to start with an empty tank as well. Not because I'm lazy, but because I use partial pressure blending and don't have a booster pump.

Filling to 494 psi is easier than filling to 594 without a booster. What kind of equipment does your shop use? Do they bank certain blends? Partial Pressure blending? Continuous blending?

I drain my tanks the same way, but they're only open for about 2-3 minutes after my tanks are "empty". Unless you leave them out like this for a few hours, I wouldn't worry about moisture getting in your tanks.

 

[kelemvor]

The shop I use for fills does partial pressure and dumps before filling if I haven't already dumped. How much of a problem is this really?

It's not a money scam issue in my case, a fill is a fill and I bought several prepaid fill cards.

 

[WB2GLP]

They are draining to 0 psig to blend directly in the tank. Doing so requires a lower initial o2 fill pressure before topping with air. It may also allow the operation to use a chart for blending rather than software.

 

[syntaxerrorsix]

It's already been covered but if the shop isn't boosting O2 or dumping the same mix back in it will be easier for them to drain the tanks.

Moisture? Probably not.

 

[guruboy]

Also, unless you are somewhere super humid, moisture in the air really probably isn't that bad. It's not like everything around you is rusting instantly due to exposure.

 

[boulderjohn]

As a gas blender, I prefer to start with an empty tank as well. Not because I'm lazy, but because I use partial pressure blending and don't have a booster pump.

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.

 

[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.

not true. I use partial pressure blending, boosting helium but not oxygen. When the oxygen source tank gets low, it is relegated to the nitrox stick until empty.

although draining a little nitrox is not a big deal, it is unnecessary...draining helium is expensive and is also unnecessary

 

[syntaxerrorsix]

not true. I use partial pressure blending, boosting helium but not oxygen. When the oxygen source tank gets low, it is relegated to the nitrox stick until empty.

Uh, the Nitrox stick is continuous blending not partial pressure blending.

 

[nimoh]

Uh, the Nitrox stick is continuous blending not partial pressure blending.

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