Moisture Buildup in Shop Compressor Debate

You're right, but what difference does it really make.

Any condensed water means the air is at 100% RH and the inside of the tank will rust.

You could humor them. Cause it really doesn't matter.

They still have to drain the tank!!!!!!!!!!!!

While I was there they had me look at a 40 gallon automotive type propane tank they were not sure if it was still good to use.

Well it's still at least 2/3 full plus the valves and gauge work so I told them I would trade them $25 off my work for it.

They were going to shot a hole in it with a rifle and let it bleed out so they could scrap it and maybe get $2 for the metal. BTW I figure it has at least 25 gallons of fuel in it worth around $2.30 a gallon right now.

That'd be a good youtube video for the Darwin awards...

They have been trying for a Darwin awards nomination for as long as I have known them.

Gotten close a few times but still nothing granted a written account of their failed attempts would make for darn good read!

It sounds like you need a smarter class of friends, but then what else is new in a world of technological (and other) superstition?

You are, of course, correct. The same amount of air of the same humidity temperature and pressure will have the same amount of water within.

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There is a chance that the initial indication will erroneously suggest they are correct (and you mistaken). If the amount of condensation is checked immediately after the compressor has completed filling the tank, the air could be meaningfully warmer using the new compressor for reasons such as the more rapid pressure increase and reduced time for heat transfer should result in a higher temperature and therefore more capacity to hold water vapor .... so probably less condensation.

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If an accurate comparison is to be made (perhaps for their education), sufficient time should be allowed for the tank to cool.... probably that additional ten minutes required of the old compressor.

It's probably using less electricity too.

Tell them that if they use the air to drive a turbine, they can generate free electricity.

Well we are discussing it at the moment and physics be damned this ones is going to be better.

It's faster, pumps up to a higher pressure and costs more than the old one.

Well, in my mind, just being faster makes it better...especially if they plan on using pneumatic tools. More pressure never hurts either.

I like to go along with things like this, and be just as outraged at the results....then lead the charge back to the salesman that told them all these lies to make the sale....and let havoc ensue....sometimes it leads to a better unit at a discount...lol

Prepare to keep arguing...

To prove they're right, they will fire up the new compressor in Jan, and show you how much less water is in it, compared to the old compressor in August.

Do these fellows drive fast? As in drive faster, get there earlier, you burn less fuel 'cause the engine doesn't run as long.

How is that working out for them?

Works great! Infact they are so efficient that they can spend 3/4 of today redoing what went wrong yesterday because they tried to get a full days work done in 1/4 of the time that it needed.

I haven't drained the tank on my compressor for at least 3 years.

They put the stupid thing under the tank, at the lowest point.

I'd drain it more often if the drain were on the top where it would be easy to get to.

_{Note to self: "LynDoor}™_{Industries announces revolutionary top mounted tank drain". Get product development on this soon!}

Well, if it's in Arizona you probably don't get condensate. If it's at your other place, it's probably frozen anyway.

The top drain idea would actually work.

All they would have to do, is create a low spot in the compressor tank, with a hose running up to the valve. It would work just like a pump up garden sprayer.

Ok, I was joking.

All I'd need to do is plumb the drain out from under the tank so I could turn the valve without sticking my hand under the tank,which I can't do without lifting it up.

The only thing I use it for is inflating bicycle tires now anyway.

#19: sounds like you have dangerous friends. I hope they don't live in town.

Nicest people you could ever know! Not the smartest or fastest learners or most organized but nice.

Similar problem as well. They have no water issues until the level in the tank gets higher than the air fitting thats connected to the lowest point that feeds their shop system.

Once it gets above there the main venturi cyclone separator starts peeing all over everything and the inline dryer elements plug up followed by the air tools and plasma cutter blowing out slobbering jets of water mist.

They would drain the tank more often but then well you know that valve is hard to get at and when the tank is not 3/4 full of water the compressor takes so much longer to catch up which of course means its also pumping even more wet air into the system for even longer.

relative humidity in depending mainly upon temperature and pressure of the system.
in our case as pressure increases ,relative humidity will also increase until it exceeds saturation pressure ( over saturation) . So water will start to condensate regardless of air velocity . if no chance for water vapor to condensate in air tank because of high flow speed , it will condensate in air service lines.
all pneumatic appliance will be rusted ,and corroded , finally too much losses will be gained

You are partly right, but the filling time matters because the air cools in the tank, and it is the cooling that causes the water vapour to condense. More water will condense over time.

The water vapour is in the atmosphere, but usually well below 100% RH. Meaning the dewpoint is also well below the ambient temperature.

Compressing the air increases the temperature, and also the dewpoint to above ambient temperature. (The RH does not change by much). The RH only increases when the air cools and becomes 100%RH at the dewpoint when condensation occurs as the temperature drops to ambient. This will first happen in the tank. The tank will eventually fill with water unless it is drained.

The drain connection must be at the lowest point of the tank if the water is to drain by gravity. Or insert a pipe into the tank from above to reach down to the bottom, so that water will be pushed up the pipe by air pressure.

A manual drain operated frequently (as often as necessary), or fit an automatic drain. Simple ones work off a timer, others work off water level.

If the water is not drained, the tank will fill up (reducing the available air volume) eventually water rises to the outlet pipe and slugs of water will be picked up and flood into the system.

At busy times the air will not be in the tank long enough to condense, especially if already half full of water. The air will be 100%RH and enters the pipework system and cools causing water to appear everywhere. It will collect by gravity at all low parts of the system, and unless drained, will be picked up and thrown at the final product.

To avoid water problems, you must first cool the air at source to near ambient with an after-cooler, but preferable to a temperature below ambient with a fridge dryer. The choice will depend on a cost/benefit exercise of drying costs set against down-time and product spoilage.

They are average guys working on typical stuff any common farmer/ home mechanics work on.

No manufacturing is being done. In most cases their shop compressor might see 1 - 2 hours run time in a week which gives the air plenty of time to drop its water in the tank.

They like to think they are big time operators and spend money as such but to be honest they are not and rarely can they afford to spend money on what they do as is.

Knowing them they spent $2000 on a compressor system that I could have found for about half that price to replace a worn out compressor head on their old system that I could have gotten them new for around $400 that would have lasted them the rest of their lives.

I guessing that next time I visit they will have the new system tied directly into the old tank so it has to fill 160 gallons of reservoir instead of just 80 and they will be complaining that it's taking twice as long to pump up.

Great!. If they are happy why worry. I've explained how to avoid wet air problems.

The simplest remedy without spending much money is to fit a manual drain and empty the tank before starting work, and again after finishing work.

They don't do preventative maintenance.

They don't have time too because they spend all day fixing everything that broke due to its never being maintained properly.

I don't think "insert a pipe into the tank from above to reach down to the bottom, so that water will be pushed up the pipe by air pressure" is practical. I'm not about to cut and weld on my compressed air tank.

I am going to plumb the bottom drain out to the edge of the tank the next time I clear all the junk around it enough to lift it up. That's a good idea.

Nothing fancy like Fredksi suggested, just move the valve to where I can get to it..

"Nothing fancy like Fredksi suggested, just move the valve to where I can get to it.."

Now how is that going to work? You will never justify buying a $2000 air compressor with that sort of attitude.

I don't need a $2,000 compressor. Bicycle and vehicle tires are all I ever use the one I have now for. I don't even use a rattle wrench enough to need a compressor.

I've mostly outlived my usefulness when it comes to work. I did put a new battery in my pickup this weekend.

I even sold my car hauler to a friend last month.

I don't want anyone to drill holes in their tank.

Use one that is supplied with the tank. Most tanks I have come across have inlet and outlet connections, pressure gauge and safety valve connections, and a drain hole.

Just make sure the drain hole is at the lowest point when installing the tank. But if not, then poke a pipe to reach the bottom of the tank through one of the upper holes if spare, or fit a Tee piece.

Nope, no drilling/welding.

A simple 90 in the bottom fitting and a one foot run of tubing will do it.

If this new compressor manages to compress and store the air at a lower temperature, wouldn't that mean there would be less carry over of moisture?

Doesn't warmer air have the capacity to hold more moisture, than cooler air?