compressors

[hauss]

The reason I leave my air in the tank of my compressor is I have a 80gal. tank set at 175psi and living in california {sky high electricity} it just seemed to be the practical thing to do.I have a ball valve at the tank so lines are not under pressure . Just wondering what others are doing

[patrickt]

Originally Posted by hauss

The reason I leave my air in the tank of my compressor is I have a 80gal. tank set at 175psi and living in California {sky high electricity} it just seemed to be the practical thing to do.I have a ball valve at the tank so lines are not under pressure . Just wondering what others are doing

Not living in CA.

[LMH]

Mine leaks slowly, so by the time I need it again, there’s no air to start with.
Larry

[kevins2]

Mine leaks a bit also, but I'd empty the tank anyway due to condensation. Amazing how much water comes out of the tank when it drains on a humid day. If I was painting or doing anything other than cleaning, filling tires or clearing debris, I'd get a filter.

Kevin

[cycleguy55]

Originally Posted by kevins2

Mine leaks a bit also, but I'd empty the tank anyway due to condensation. Amazing how much water comes out of the tank when it drains on a humid day. If I was painting or doing anything other than cleaning, filling tires or clearing debris, I'd get a filter.

Kevin

Presumably a filter with a water separator.

[LMH]

I use a filter and water separator on mine. I drain it from the bottom periodically as well, though there’s not much water in it usually. Very dry here.
Larry

[hauss]

Originally Posted by patrickt

Not living in CA.

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[Ozzie Goat]

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[hauss]

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[olddog]

Hauss,

I doubt leaving air in the tank is an issue, other than the moisture concern. Well it does push on the check valve(s) that prevent(s) the air from blowing back though the compressor. Moisture is what works on corroding the tank. Once the tank has corroded to the point it cannot hold the pressure that is in it, the failure of the tank happens, which is ugly.

The tank should have a drain valve for blowing out condensate. I would blow it down when I quit using it. Then blow it down again the next day or a few hours later, to get what continues to form as the tank cools. Anytime there is a drop in ambient temp (that drops the air temp in the tank) more condensate can form. Which is why I like the idea of blowing the condensate down on a cool morning.

The air tanks in the plant I work at were installed in 1969. They are in service 24/365, except for servicing the PRVs. The big difference is that we have driers located between the pressure tanks and the compressors. The air in those tanks is always around a -10 F dewpoint. No moisture in the air tanks, and they have lasted 50 years.

[hauss]

I have worked in the hvac industry for over 30 years, and have used compressed air to operate controls, and never have seen a tank fail because of moisture. I have seen the welds crack from fibration of the motor and compressor that was mounted to the tank.Never have they exploded, just leaked air and would wear out the compressor.Also by saving the air I am introducing less moisture to the tank.I also drain the water from the tank after use.

[olddog]

I never said the typical failure of a tank is an explosion. What I have seen is rust eats away, where the water sets. When a hole opens up, if your lucky, it just blows all the air out. Pieces of the corroded tank flinging through the air, with jagged sharp edges, is ugly if it hits you, and that can happen.

Again, if you keep the water out of the tank, no problem. Water forms when the air temp in the tank drops bellow the dew point of the air that is in the tank. All the new tanks I have seen inside are painted or coated to protect them from corrosion. I expect its a moot point as long as that coating stays in tack. At some point, moisture will get past it and start working on the metal. Since you never know when that is, it is best to keep the moisture out, the best you can.

I expect you have way less humidity and temperature fluctuation in California than I do in Ohio. I think you are fine.

[hauss]

I am fine and thank you for thinking so. The reason I even posted I was trying to share some reasons to keep the air in the tank and remove some of the myths of why it was harmful to do so. Remember you said your air has more humidity than mine so if you used less air{keep air in tank} you would have less moisture .

[olddog]

Hauss,

I thought you were asking for confirmation that what you were doing was not going to cause a problem. I did not realize you were trying to educate the world that leaving air in the compressor tank is fine and therefore a waste to drain.

Your premise that the more air you pump into the compressor the more moisture you pumped in is true, but that does not apply to a static tank of trapped air. A static tank of trapped air at 10 bars of pressure has about 10 times as much air in it as an empty tank at 1 bar (atmosphere). Also the higher the air pressure the higher the dew point. So when you leave the tank pressurized, it has more air in it with a higher dew point temp. It is more likely for water to form condense, if it is left with air trapped in it.

Your stating that by leaving air in it you would have less moisture is miss leading at best. The next time you start the compressor up and it does not have to pump all that air back in, then at that point in time you have put less air into the compressor. However when you shut it down and let it sit, there was more moisture in the tank while it sat, than it would have had had you blown it down.

When you stop the compressor, the air that is in the tank has had it temperature (adiabatic compression) and the dew point temperature increase. As the air temp drops, moisture forms when the air temp drops down to the dew point temp. You blow that moisture out. If you then blow down the tank to 0 PSIG. The dew point of the air in the tank drops with pressure. Now the remaining air in the tank is much drier than the air was when you pumped it into the tank. Remember you pumped air in and then blew water out, so that air absolutely has less moisture in it. While it is still compressed, it remains very close to the dew point temp. After it is decompressed it is much drier.

So I disagree that leaving the air in the tank is actually putting less moisture in the tank, while it sits. It is not the best way to leave the tank. It is always going to be less chance of moisture forming in the tank if you blow it down and more chance if you do not.

I still think you are fine. I would not recommend doing this in an area where the temp may drop below freezing, after you shut the compressor off. I have seen chunks of ice form.

[Jaydee]

When they fill scuba diving tanks, they remove all the moisture before filling as it's dangerous to breath compressed air with moisture. So your mouth feels really dry whilst diving. I wonder if you can fit a moisture trap before the compressor? JD

[razerwire]

I have an electric valve on bottom of tank. You can set the time in-between when it opens and how long it opens. Both would be set for your location. There are days when conditions are just right and there is a lot of moisture in the air, I can tell by water coming out when valve opens. I never have to even think about my compressor and water problems. Have water separators at each outlet and filters to protect my air tools but found out long time ago they are not need. Compressor has been in garage for twelve years and most of air tools are 30 years old with no problems. FWIW

[cycleguy55]

Originally Posted by Jaydee

I wonder if you can fit a moisture trap before the compressor? JD

While it may be reduced by 'pre-condensing' and removing the water from the air before it hits the reservoir tank, I'm not convinced that would entirely solve the problem. As the water condenses upon contact with the cooler walls of the air tank you may still have further condensation.

[Jaydee]

With SCUBA air there is zero moisture therefore no moisture to condense. But it would be a very expensive filter to fit to a average compressor. I think if you drain your tank occasionally and have a moisture filter then there will be no problems. JD