[speede5]

Originally Posted by MARTINSR

The filters or "separators" aren't perfect. The problem is compressed air has SOOOO much moisture in it. The filter has a LOT of work to get it out. First the air needs to be cooled, then ran thru the filter.

That is one of the questions I have, how much better could it be? Have you watched the video at the link I provided?

We are talking much more than a "filter", shooting with the nirtogen virtually eliminates static electricity!!!! The nitrogen is heated to the perfect temp. The atomization of the paint is controled by this process and not the as much the gun! They shoot the product with what looks like zero reduction! It looks like he is pouring paint right out of the can into the gun!

VERY interesting stuff.

Brian

That was an interesting video. Thats a lot more than just using compressed nitrogen from a bottle. That looks like something that would only be profitable for high volume manufacturing. I have to say again that anyone spraying as a hobby is best of sticking with air. If you can afford to play with nitrogen you should spend more money on tools and stuff.

But I would be interested in seeing it firsthand.

[MARTINSR]

Originally Posted by scrimshaw

Brian

I didn't watch the video, spraying paint is not something I do I leave that stuff to the experts.

I felt I must comment on something you said


The fact is compressed air is dryer than the ambient air that is being fed into the compressor. Anyone who has used a compressor should know this because the last thing he/she should do after shutting the compressor down is drain the water out of it and the filters/traps in the lines. This should tell you there is LESS water coming out of the compressor than going into it. Compressing air lowers it's dew point making it unable to hold the same amount of moisture.

The reason it is a problem in compressed air machinery is because it can't exist in the compressed air in as much of a quantity as the ambient air and therefore gets displaced as condensation in the tank, lines and tools and will get occasionally displaced and blown out with the compressed air thus ruining your paint job.

Having said that it does not remove ALL the moisture and I can certainly understand there is more reason to use Nitrogen on painting and other processes that are H2O intolerant but having done a bit more research on the tire issue I am convinced that it is another marketing scam to make us pay for something which we presently get for free!!.

So let me get this straight, for us non-scientist types, compressed air has less moisture but the "container" it is in holds all the moisture that the air once held. Does that sound right? So, all the moisture that the air held before it was jambed into the tank and lines is now "out" of the air, but still in the tank and lines.

Ok, so the water trap isn't trapping moisture from the compressed air, but simply moisture in the tank and lines. I don't see how that changes anything other than the simple statement that "compressed air has more moisture". Ok, sounds reasonable. So, in the same given square footage of air, you have compressed air, and you have ambiant air, the compressed air would have less moisture within it but the same amount of moisture would exist in both containers, right?

On the video, watch it, it is very interesting how it eliminates static charge. It may very well be snake oil, but I see high end shops and manufacturing using it.

Brian

[powerrodsmike]

Originally Posted by scrimshaw

The fact is compressed air is dryer than the ambient air that is being fed into the compressor. Anyone who has used a compressor should know this because the last thing he/she should do after shutting the compressor down is drain the water out of it and the filters/traps in the lines. This should tell you there is LESS water coming out of the compressor than going into it. Compressing air lowers it's dew point making it unable to hold the same amount of moisture.

The reason it is a problem in compressed air machinery is because it can't exist in the compressed air in as much of a quantity as the ambient air and therefore gets displaced as condensation in the tank, lines and tools and will get occasionally displaced and blown out with the compressed air thus ruining your paint job.

I know the opposite to be true.

I know that compressing air makes it warm...warm air carries more moisture, the only time that the warm compressed air loses it's water is if the walls of the tank and pipe are cooler than the compressed air, (or the air cools down), ..then the moisture condenses on the walls of the tank and runs down to the bottom...Obviously all the air in the tank will never touch the walls of the tank, so some moisture goes out the lines.

(rain works on much the same principal)

Anyone knows on a hot day, you get moisture in your lines, because the pipes and tank are not cool enough to condense the moisture out.

The moisture problem is compounded with a small compressor, working double time to keep up and heating the air even further.

Some water traps and air dryers operate on a condensing principle, while others use a centrifugal force to spin the heavier water out...(just about all of those polycarbonate bowl water traps do it that way,,,watch the air swirl the moisture down the sides of the glass bowl the next time you are pondering your air lines.)


Moisture in lines is a well known, well documented enemy of a good paint job..If nitrogen does not carry moisture, then that in itself is reason enough to consider it for a production shop.

(I'm still unclear on that flammable thing though... J/K)

Later, mikey

[scrimshaw]

Sorry guys my post was confusing, brief and wrong in places, here is a paragraph that explains it better than I.

The compressor is seldom given credit for removing the bulk of the moisture in compressed air.

The greatest amount of water will be removed from the air by compression and subsequent natural cooling. If the relative humidity is 50% at 70 deg. F the free air will hold .0725 gallons of water in vapor form per 1000 SCF. When the air is compressed to 100 PSIG and naturally cooled back to 70 deg. F. although saturated it will hold .0182 gallons per 1000 SCF. Twice as much water has been removed as the amount that remains. If this air that is saturated at 70 deg F and 100 PSIG were discharged back to atmosphere the relative humidity would be approximately 12 .5 %. The amount removed by compression would be greater if the relative humidity were higher but the air returned to atmosphere would still be 12.5% RH.
http://www.ifps.org/Education/WhitePapers/AirDryers.htm

Basically this means that if you look at a cubic foot of air inside a compressor it has more vapor than a cubic foot outside the compressor because that cubic foot of space contains say 10 times the amount of air (or whatever the comp. is set at), but it will contain less than 10 times the vapor. So what I should of said was if you look at the compressed air after it exits the tool and returns to atmospheric pressure it will be much dryer than when it went in to the compressor, and yes the compressed air can be saturated with moisture when it comes out of the lines, although this depends on many factors such as the exit pressure versus the compressor pressure, temp. difference etc.

My apologies to Brian for correcting him. I hope this post is clearer.

And I would like to say again that my skepticism with Nitrogen is not with painting or any other other use of compressed air versus Nitrogen use EXCEPT using it in tires.

[powerrodsmike]

The point that you are missing is missing in that quote as well.


The "compressor" does not remove moisture. The act of compression by itself does not remove moisture.

The tank and lines or atmosphere are where the air will "naturally" cool..(their word, not mine).
If you have no tank, dryer, or intercooler or your lines are not able to cool, then the only place for the compressed air to "naturally" cool is when it exits the end of the hose into the low pressure atmosphere...and we all know that when it does that, the water falls out like rain. If the end of you hose has a spray gun on it, the water mixes with your atomized paint and f's up your paintjob.

Spend any time at all working with a compressor and you will see what I'm talking about.

If the compressor removed the water you'd be draining the compressor, not the tank or lines.


later, mikey

[scrimshaw]

Powerrodsmike wrote

The point that you are missing is missing in that quote as well.


The "compressor" does not remove moisture. The act of compression by itself does not remove moisture.

The tank and lines or atmosphere are where the air will "naturally" cool..(their word, not mine).
If you have no tank, dryer, or intercooler or your lines are not able to cool, then the only place for the compressed air to "naturally" cool is when it exits the end of the hose into the low pressure atmosphere...and we all know that when it does that, the water falls out like rain. If the end of you hose has a spray gun on it, the water mixes with your atomized paint and f's up your paintjob.

Spend any time at all working with a compressor and you will see what I'm talking about.

If the compressor removed the water you'd be draining the compressor, not the tank or lines.

I am not missing any point and I never said 'the act of compression itself removes moisture' (and it doesn't say that in the paragraph it just assumes the reader understands the tank is included) but it is a vital part of the process. What I said was compressed air is unable to hold the same amount of moisture and yes it is correct to say that the drop in temp. from compressor (your strict definition!) to tank and lines (my implied general definition!) is what condenses the vapor back to water. But I think the point you are missing is that the lines and tank MUST be cooler than the compressor and the air that comes out of the compressor and so WILL naturally cool the air in any normal shop set up. If this was not true two things would happen. First your compressor would seize from not being able to cool itself (All shop compressors I know are air cooled). Second you and everything else in your shop would get very hot very quickly. (It would also violate the law of thermodynamics that explains why air is heated when it gets compressed because the energy put into it.)

Obviously when I wrote 'compressor' I was including the tank and lines as this is part of the whole set up, if this was not obvious in my post then I apologize once more for being too brief!! If we must be technically correct what myself and most people think of as a 'compressor' consists of a compressor, motor, tank and various plumbing and wiring but lets be real here have you ever seen a compressor used without a tank, and lines connecting the compressor to tank in any mechanics shop.

Putting all the science and theory aside, what it comes down to is this. Everyday when I have finished using my compressor/motor /tank/lines I let the compressed air out of the tank then DRAIN THE WATER FROM THE BOTTOM OF THE TANK AND ALL TRAPS. Where does this water come from? It comes from the ambient air that has been through the compressor/tank set up. Therefore the air that comes out of the compressor is dryer than the air that went in.

Now is this clear enough and can we stop arguing so I can go do some work on my car!

[MARTINSR]

Boy, I am dense, I just got what you two are talking about. OBVIOUSLY, when the air is leaving the tank, it has left some moisture behind, the water at the bottom of the tank is the proof. The thing is, again, this is a non-science type (but I love it, so I am reading your posts with vigor ) the air leaving the compressors hose has less moisture than the ambient air in the room given the same volume. That is a fact, however, that air is jammed into a smaller area thus that smaller area has MORE moisture than the same area of ambient air in the room! So, in layman's terms and simple common sense for the non-scientist type the compressed air has more moisture. It is that "jammed together" air that is rushing out of the gun breaking the paint up and blowing it all over the object being painted. THAT "jammed together" air is full of moisture (if it hasn't been removed).



Non-compressed air question, just for general knowledge:
So let me ask this, hot air doesn't carry any more moisture than cold air given it was taken from the same ambient air. The hotter air just "looks" like it has more because the water molecules all bunched up together in the hotter air and we can see the moisture. Whereas the cold air has the same amount of water molecules in it, they are just dispersed throughout the air and we can't see it. Does that sound right?

Brian

[powerrodsmike]

The compressor is seldom given credit for removing the bulk of the moisture in compressed air.

That statement is totally misleading.

I'm not missing anything about the fact that water in lines messes up paint jobs, tools and is a general nuisance. I also know how to get the water out.

I know why it works, and even said so in my post. Which you quoted, then ignored..

I'm not assuming that a compressor is all of the tanks and associated plumbing.. I've seen many compressors that are consant run or on demand units that are stand alone units with very small or no tank at all. Alot of guys run those little pancake compressors which have a very small tank and if you try to use them for very long , you get water at the end of the hose.

.My 7.5 hp Kaeser has a 2 gallon tank. I plumb it into a much larger remote tank where the air is allowed to cool and the water condense out.. I have very little problem with water in my lines.





I had a 15 hp rotary compressor...with no internal tank at all.


There are times when the tank and lines are not cooler than the compressed air, I included that scenario in the post that you quoted as well.




You seem intent on saying that it is a non issue, and seem to imply that there is no real reason to use the nitrogen spraying system that is the subject of this thread. You are saying that because the air comes out of a compressor drier than when it goes in, that's good enough.
(otherwise, why do you keep posting stuff about dry air and compressors?)

You keep talking about how folks filling tires with nitrogen is snake oil and a scam., and how it is not necessary. If moisture in tires presents problems, then why would you not want to find a way to get rid of the problem.

I know that cleaning rust off of rims so the beads will seal is a PITA.

I'm done arguing. I have work to do as well.


Later, mikey

[powerrodsmike]

Originally Posted by MARTINSR

Boy, I am dense, I just got what you two are talking about. OBVIOUSLY, when the air is leaving the tank, it has left some moisture behind, the water at the bottom of the tank is the proof. The thing is, again, this is a non-science type (but I love it, so I am reading your posts with vigor ) the air leaving the compressors hose has less moisture than the ambient air in the room given the same volume. That is a fact, however, that air is jammed into a smaller area thus that smaller area has MORE moisture than the same area of ambient air in the room! So, in layman's terms and simple common sense for the non-scientist type the compressed air has more moisture. It is that "jammed together" air that is rushing out of the gun breaking the paint up and blowing it all over the object being painted. THAT "jammed together" air is full of moisture (if it hasn't been removed).



Non-compressed air question, just for general knowledge:
So let me ask this, hot air doesn't carry any more moisture than cold air given it was taken from the same ambient air. The hotter air just "looks" like it has more because the water molecules all bunched up together in the hotter air and we can see the moisture. Whereas the cold air has the same amount of water molecules in it, they are just dispersed throughout the air and we can't see it. Does that sound right?

Brian

No.


Warm air will carry more moisture than cool air, that's why we have rain. Warm moist air rises up and meets cool air, where water vapor condenses and falls on us.


Mikey

[MARTINSR]

Originally Posted by powerrodsmike

No.


Warm air will carry more moisture than cool air, that's why we have rain. Warm moist air rises up and meets cool air, where water vapor condenses and falls on us.


Mikey

Mikey, why is it you talk about brownies and stuff when you were younger? I was the straightest non smoking, non skipping class nerd you would have found in school and I don't remember any of this stuff knowing damn well they taught it!

Ok, I am going out in the rain to the garage and work on a project.

Brian

[scrimshaw]

What -- you expect me to leave it at that!!!

Brian first your question about warm air being dryer than cold air.
The answer is it depends. While warm air is capable of holding more moisture, simply warming it up will cause the air to expand and keep the same amount of moisture so there is now less moisture per cubic foot than previously so we can say it has less relative humidity (drier). Only if there is water available for evaporation (lake, puddle, bucket of water, etc) can the air possibly contain more moisture than previously. So with regards to a workshop heating the air, assuming no standing water, will dry the air out (obviously).

Mike

I have to say you did not read my last post properly or any of my posts. You said

You seem intent on saying that it is a non issue, and seem to imply that there is no real reason to use the nitrogen spraying system that is the subject of this thread.

Here is a comment I posted in the last thread

And I would like to say again that my skepticism with Nitrogen is not with painting or any other other use of compressed air versus Nitrogen use EXCEPT using it in tires.

and in an earlier post

Having said that it does not remove ALL the moisture and I can certainly understand there is more reason to use Nitrogen on painting and other processes that are H2O intolerant but having done a bit more research on the tire issue I am convinced that it is another marketing scam to make us pay for something which we presently get for free!!.

.

Most of your post says EXACTLY what I have been saying -- that in a workshop environment compressed air will give up it's moisture when it cools leaving behind water in tanks and lines, we can all agree on this. (Frankly I don't know why you keep saying I am in disagreement most of you post reinforces what I am saying and I hate arguing about details.) Personally I have never seen a compressor used without a tank, even if the compressor is not physically attached there is always some reservoir somewhere in the system otherwise like you said they would run continuously. I am not saying it does not exist simply that it is not the normal workshop set up. Here is the part I have an issue with and the part that I tried to explain in my last post.

There are times when the tank and lines are not cooler than the compressed air, I included that scenario in the post that you quoted as well.

This is simply NOT possible in the normal workshop compressor/system set up. If what you said was true it would mean the ambient air is the same temp. as the compressed air and like I explained in my previous thread this would seize the compressor which requires cooler ambient air to cool itself. The picture you posted clearly shows cooling fins on your compressor that are there for a reason. One of the laws governing gases is that when you compress them they heat up considerably(think diesel engine) so compressed gas MUST be hotter than the air being used to feed the compressor. Unless you are heating the tank and lines with a separate system then the temp of the machinery will be somewhere between the temp of the compressed air in the piston and the ambient air in the room, therefore it WILL cool to some degree.

Alot of guys run those little pancake compressors which have a very small tank and if you try to use them for very long , you get water at the end of the hose.

This is because the small tank does not take long to 'overflow' and the water in it is being picked up by the turbulent air in the tank and pushed out.
You said

You are saying that because the air comes out of a compressor drier than when it goes in, that's good enough.

YES When it comes to filling tires that is exactly what I am saying.

[MARTINSR]

You two guys are just blowing a bunch of hot air.

Brian

[scrimshaw]

Not blowing hot air, just incoveniencing lots of electrons.!

Here is something else I didn't mention. Are you sick of this yet?? I almost am but whilst waiting for some epoxy to dry I wanted to clarify a point I made to your first comment. I know I am a PITA but just bear with me on this one.

Lets say your compressor is set at 100PSI and your regulator is set at 50PSI This means that the air in the line after the regulator is now capable of holding twice(edit-not sure about this now it may not be exactly twice) the moisture as the air in the tank was. (I am assuming equal temps throughout, not real world if the compressor is busy but is close if you let the air sit awhile, hope you get the point.) The ONLY way you can get moisture out of the air now, is by either compressing it back to over 100PSI or reducing the temp. of the air. This is why aircraft use Nitrogen in tires. Very cold up there (as the occasional refugee can attest to!!http://cbs5.com/local/SFO.stowaway.w...457702.htmland )not enough time to warm up the tire before landing, wouldn't do for a chunk of ice to be rolling around in the tire on touchdown.

Point I am trying to make is the air coming out the line might be far from saturated and will almost always be drier than in the tank. This is what I was trying to say before to you.
Edit again.
ONCE AGAIN this does not mean I am saying Nitrogen in a painting system is a waste of time.(Thought I should put this in for Mike's benefit ) I am simply trying to explain my point that air that goes through a compressor/tank system that exists in a normal shop environment will go through a drying process.

[powerrodsmike]

[QUOTE=scrimshaw]Not blowing hot air, just incoveniencing lots of electrons.!

Here is something else I didn't mention. Are you sick of this yet?? I almost am but whilst waiting for some epoxy to dry I wanted to clarify a point I made to your first comment.[QUOTE]


I always thought that epoxy cured...not an evaporative process like drying tomatoes in the sun but a chemical one...


Ok... you've said we agree enough for me to believe it.


Brian- I used to eat the brownies and watch Mr Rogers...

Later,
Mikey

[MARTINSR]

Hey Mikey, you sure have a nice compressor setup there.

Brian