Moisture in tanks

never heard of any one doing that ? Maybe just my limited knowledge of fill tanks , i only fill gun tube's

Can you put a few drops of water in a vacuum jar and then pull the air and see if it works? I don't know the science.

A lot of places will purge the tanks to be filled with the same type gas.

i dont know how bad a shoebox is, but using a yongheng with one of those cheap gold 'condensing' type filters and only filling indoors in the ac ive never seen one drop of water in a tank or a gun .. id say if youre seeing water or can hear it sloshing in a tank, disassemble it and dry it .. valve off, upright in a 120* garage for a day should do it lol ..

The only way to purge moisture from an SCBA tank is to depressurize, remove valve, invert tank & let it air dry or use a heat source (hair dryer type) like when tanks are hydroed. It's pretty rare to find moisture inside a tank even with nominal filtering. Dive shops & such have filtration & humidity guidelines that are prescribed by regulations. Over 30 years in the firefighting equipment industry & I'd never come across moisture in tanks that were filtered & filled according to guidelines! No need for a "vacuum" type process you were talking about.

why are people calling this a shoebox IT IS NOT A SHOE BOX this is completely different . a shoe box is a booster not a compressor .

We used to use vacuum pumps on our steel scuba tanks when I was diving. Works perfectly.

beerthief said:

why are people calling this a shoebox IT IS NOT A SHOE BOX this is completely different . a shoe box is a booster not a compressor . View attachment 479671

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Yep the only way that could be called a booster is it being fed Nitrogen from a regulated tank. Thats the only way my pumps get used to fill my guns

I would hesitate running a vacuum on a CF tank. They are not made to withstand a vacuum but only pressure.

Also, what's the purpose in the first place? HVACR techs do not pull a vacuum on large, easy to disassemble tanks that can be easily inspected.

They pull a vacuum to first remove refrigerant, then water and finally, test for leaks. If a tank has water inside it, blow it out and let it dry!

Panzerfaust said:

My bad, I started it, I don’t know why I called it that, possibly something I read before posting here.

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sorry if i came off as a bit rough .

Panzerfaust said:

If you actually run refrigerant through a vacuum pump , the insides of it would corrode terribly. They can stand trace amounts of it as there is always some left after it’s purged. I know this because I thought the same thing you wrote. I killed a 200 dollar pump
Servicing two cars. Almost every place that services auto ac systems will purge the refrigerant for you for free. The machines they use now recycle it , so they sell it to other customers getting full service. Anytime you get an ac system serviced be sure to tell the people you want new refrigerant , not the stuff there machine has recycled , it isn’t as effective as the new stuff.

When I read the part about not pulling a vacuum on a carbon fiber tank. The image of a train car tanker imploding like a submarine that went too deep when people hooked one of those huge vacuum trucks too it and throttled it up to full power. Have you ever seen that video on YouTube? It’s amazing.

Don’t need too, I already know water can’t remain as a liquid inside of any vacuum pulled down to -29. If you took a cup of water and put it in a vacuum chamber and pulled a vacuum on it the water literally boils at room temperature until it’s all vaporized. The constant vacuum will remove the vapor from the space. Just a drop of moisture inside the site glass of a set of manifold gauges will bubble like it’s boiling as the vacuum pulls down to the limit of the pump. Thank you for responding though. It seems to be unnecessary to do anything to the pcp tanks unless there is an unusual situation.

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I don't know why you assumed that I said to pull refrigerant through a vacuum pump?

We pull refrigerant and any water with the pump connected to a recovery tank, the tank pulls the refrigerant from the system.

The point is the VESSEL not the vacuum.

Metal SCBA tanks will handle 29-in. -Hg but it's doubtful a CF tank will hold across the flats. Ergo, tank cars:

Firewalker said:

The point is the VESSEL not the vacuum.

Metal SCBA tanks will handle 29-in. -Hg but it's doubtful a CF tank will hold across the flats. Ergo, tank cars:

View attachment 479751

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This is a bit more visual..




A tire is also designed to hold air in but we don't apply vacuum to them to remove water.


Allen

OK - there is a lot to unpack here . . .

First, the pressurized air system of our air guns is extremely different than that of a refrigeration system, with the most important difference being that a refrigeration system is a "closed" system and the air gun system is an "open" system.

In refrigeration, we need to get all the moisture out for it to work properly, and the method for that has already been described. Once we know we have a good sealed system with no moisture in it, we fill it with refrigerant and it does its thing - sealed as a closed system, at least until a leak develops. And then refrigerant leaks out, but moisture typically does not get in, except in cases where there are bad enough issue son the suction side (which is almost always still above ambient pressure when running).

But with the "system" of filling air guns, everything is different due to the open nature of it. Even if everything were to start off with absolutely zero water molecules in it (in both liquid and vapor forms) via whatever method one wanted to use (vacuum, nitrogen purges etc.), it would be possible for moisture to be introduced into it with the very first use of a pump to refill whatever reservoir. When that pumping refill happens, ambient air is drawn into the compressor, and if no action is taken with respect to reducing the amount of water vapor that remains in the air stream exits the compressor, remembering that the air will be hotter than ambient due to compression, some of that vapor will condense into liquid when it cools back down to ambient.

As @Gerry52 said, this is easy to prevent with proper filtration - usually with desiccants. But if no action is taken to actively filter out the water vapor, it is a certainty that over time liquid water will accumulate in the tank or reservoir. The amount introduced is each pumping session is small, but the majority of it stays in the tank or reservoir and more gets added every time the system is opened up on the pressurization side to add more air into it - which has to happen every so often as we are opening the system up on the depressurization side to use air for shooting.

There is more I could add, but that should start to make it clear.

Also, there is no need to pull a vacuum on a tank before it gets filled - as long as there is no liquid water present to start, the small amount of water vapor that exists in the ambient air in the tank is inconsequential - remember that if we are filling the tank with appropriately dried air, that starting level will be diluted 300:1 if filled to 300 bar gauge. But even if you did do that, the tank should have no issue withstanding 1 bar of negative pressure as they are so strong to begin with to withstand 500 bar of positive pressure - they could not handle that kind of negative pressure differential, but 1 bar of negative differential would be noise to our tanks. Remember that those huge train tanks that are shown collapsing are not made for pressure, but for liquids . . . (note / edit: I was told that some LP railroad tanks made for pressure have been imploded too, so I stand corrected on that specific point, but I still think our tanks would do fine)