I tried posting a reply to the PAG Olis - Do I need DEC? but couldn't. If I could, here's what I'd say ;-)
This is one of the best FAQ's I've ever seen - bar none. Clear, simple, and conclusive proof of the value of DEC Pag.
I wish I had a chemistry set that I could subject to high vacuum levels. If I had one I'd put 10 cc's of mineral spirits in a clear jar, drop the vacuum level to 30 microns and then conclusively show people that evacuation will not remove them.
It would go a long way to proving, very simply, that it's absolutely vital to remove mineral spirits when using them as a flushing agent.
In fact, if I had a set like that I'd be off trying all sorts of flushing agents... maybe it's a good thing I don't!
With a rig like that you could also demonstrate miscibility(?) between refrigerants and oils. Man, sometimes a picture is better then a 1,000 steps!
Best & Thanks;
Sometimes proving your theory does not produce the results that you are expecting. I give advice, make suggestions, recommendations, etc. and if customers don't want to hear it, that's fine.
Grove Automotive Group, Inc.
An Alabama Corporation
I commented on this study before, and I still have the same concerns. All this test shows is that DEC PAG has less ability to dissolve water than SEC PAG. Is this a good reason to choose one over the other or not?
As a refrigeration systems chemist, I know that there is desiccant in the system that has a much greater affinity for the moisture than the PAG. In a tug of war over water, the desiccant will win quite easily. The water in the system will hang out in the desiccant, not in the PAG or the refrigerant.
If you allow enough moisture into the system to make free water in the PAG, you would have to literally pour liquid water into the system. No one is going to allow this in real life.
If you were crazy enough to pour some liquid water into the A/C system, the DEC PAG will not absorb as much of the additional water as the SEC PAG, so you will get lubrication destroying free water sooner with DEC PAG than with SEC PAG. The SEC PAG will prevent free water from forming as it dissolves the additional water better. You can argue in this particular situation, DEC PAG is a poorer choice than SEC PAG. Since the whole scenario is not going to happen in real life, it doesn't matter.
The water absorbtion test in the FAQ doesn't tell you what you need to know to make a proper choice of PAG. The actual lubricity and chemical stability were not measured for these products, so there is no way to tell which one is working better in the compressor. To do the testing proerly, you would have to run a compressor test stand and sealed tube aging studies, and these would likely set you back several tens of thousands of dollars. This is what it takes to get a real answer as to whether DEC is better than SEC. The test in the FAQ makes some pretty pictures, but doesn't tell a chemist or engineer anything relevant as to how the oil will perform in a real system.
There are advantages of DEC PAG over SEC PAG as far as chemical stability goes, but in a real system you may or may not see the benefits. The same situation exists with engine oil where you can buy cheaper mineral oil or more expensive synthetic oil. Most people will not benefit from the more expensive synthetic, but some who have severe service needs may see the benefits and can make the economics work in their favor. Of course some people just want the best product regardless of cost, and if so then buy the DEC PAG. The SEC PAG may work just as well for less money, but that doesn't matter to the oil obsessed.
Your statement about mineral spirits needs some work as well. You don't measure high vacuum in inches, you measure it in absolute pressure units like microns. If you were able to reduce the pressure enough, you would boil away the mineral spirits very quickly. What you may want to say instead, is that if you pull a crappy vacuum, you won't be able to boil away the mineral spirits very quickly. Mineral spirits evaporates at atmospheric pressure (its used as a solvent in oil based paint etc.), so they will eventually be pulled out of a system if used as flushing agents. The speed of removal is the key you should focus on.
There are flushing agents used in commercial refrigeration and A/C that are composed of liquid HFCs and chlorinated solvents that clean systems and evaporate quite well. These are kind of expensive due to the liquid HFC component, and cost about $80 for a 2 pound container. You can get anything you want as far as really good flushing solvents if you don't mind paying for them.
Hi Test Specimen;
I think you missed my point. The water solubility test tells you absolutely, positively nothing about the advantages of DEC PAG over SEC PAG. Water solubility of the PAG is a non-issue in a real system. The water in the A/C system is not in the PAG, it is in the desiccant. This piece of work shows a clear effect, but the interpretation of the results is wrong. My problem is with the incorrect interpretation.
I have no vested interest in DEC versus SEC. The company I used to work for manufactured both types of PAG, as well as POEs, and they sold more DEC than SEC for auto A/C since they supplied the Ford OEM product. I tested both PAG products and am very familiar with how they perform. The performance of the lubricant has much more to it than the solubility of moisture. Both PAG products (as well as POE) can work well in A/C systems. There are hundreds millions of vehicles running on DEC PAG, and just as many hundred millions running on SEC PAG. If SEC was clearly worse than DEC, then someone forgot to tell those millions of SEC filled compressors to fail.
My problem with this test has been illustrated by your stated opinion - "it very clearly and simply shows (with pictures) the advantages of DEC PAG over SEC PAG."
This test shows no such thing. There is no advantage based on water solubility because A/C systems just don't get wet enough for the PAGs to show a difference. Even if they did get that wet, the test makes the wrong conclusion that excess water is more of a problem for the SEC PAG. It is not - excess water will be more of a problem for the DEC PAG as it will allow free water at lower amounts of added moisture than SEC PAG. Free water will cause problems in the system, and SEC PAG is better at preventing free water than DEC PAG.
The test that was run showed valid and accurate data. What the data means has been misinterpreted because it does not address any actual issues that are important in a A/C system.
The whole 'polymerized' statement is just plain technically wrong as well. If the PAG had 'polymerized', this is a chemical reaction, and would cause a permanent change to the properties of the PAG. I know that if the water had been removed from the SEC PAG after the test pictures had been taken, that the PAG would be chemically unchanged. The whole test was not good science, and no technical people at a lubricant manufacturer would be caught dead presenting this type of data with the interpretation that it showed the superiority of one product over the other. They would feel comfortable showing that the products behaved differently, but would not draw any conclusions from just this test about the different performance of the two products.
The water solubility test is a marketing dream - show something that looks like it has meaning and can be understood by the masses that clearly differentiates two products. It doesn't matter that it actually means nothing as to the actual performance of the product. People have been taught that pictures tell a thousand words, but pictures can certainly mislead as well as inform.
The evacuation test you ran on mineral spirits would give a similar result had you used R-11, the old flushing standby from years ago. R-11 can't be easily removed by vacuum either from a cylinder. I have seen it take days for R-11 to be pumped away by vacuum only. You had to break the vacuum with dry air multiple times to get the R-11 to be carried away in a reasonable time. If you go through multiple vacuum - air cycles, you'll be surprised at how much better mineral spirits will be removed. You need a carrier gas to pick up the vapor from the mineral spirits and efficiently carry it out of the container (or A/C system). Mineral spirits has a vapor pressure, and it will eventually be carried away by vacuum or by air blown through the system.
No argument here. This is why I suggested Marvin refocus his direction to studying the rate of solvent removal rather than saying it doesn't get removed at all by vacuum. There is a lot of middle ground between the liquid refrigerant flush Marvin prefers, and the mineral spirits flush he dislikes. It is possible to make a mineral spirits flush work well if the components you are flushing have no dead spots in the flow path.
Vacuum will remove mineral spirits and other low volatility flushes, but at much slower rates than solvents with higher vapor pressures. Depending on vacuum only is probably a bad idea, even with higher volatility flushes, because it is much more effective to use a carrier gas to remove the residual solvent. The commercial flushes are removed much quicker by blowing air through the system than by pulling a vacuum. Once almost all the liquid solvent is removed by air flushing, the vacuum will remove the residual vapor quite well. If you short the air purging time regardless of the flush type, there will be residual liquid flush solvent left in the system that may dilute the oil.
Honeywell and NuCalgon (using material supplied by DuPont) both sell non-flammable low toxicity flushing solvents with higher volatility solvents (patented HFC / transdichloroethylene blends), and they both recommend using air purging to remove the residual liquid. Vacuum alone just doesn't seem to get the job done, even with these 'evaporative' flushes.
Use plenty of air, "then" use plenty of air..When you're done, "use more air"....
Freedoms just another word for nothing left to lose
Am I in deep trouble again? Only thing I said was when using PAG, have to make sure the system is bone dry before pouring it in. That is true either in the lab or in the field, once PAG gets moisture in it, can't get it out.
I think that point was covered in the original article - that with DEC Pag you could get the moisture out whereas with SEC Pag you can't.
But I think we're in agreement - why would anyone put oil in a moist system in the first place :-)
Best & Thanks;
Nick no one is in trouble.
I do think the I'll take my ball and go home now attitude is amusing. Lab coat people make me chuckle all the time. While Test's comment could be true. I certainly see Marvin's point about getting someone to use a product. Which I think everyone has stated is a better choice. You know I don't care how I get someone of crack. As long as they put the pipe down that's what concerns me.
I honestly don't see where anyone did anything out of line. Holy cow people this is a forum to discuss stuff. Instead of running home because someone thinks differently. Try and help make others understand!
Enough baby sitting, I have to go fix a float on a toilet!
Oil - good
Moisture - bad
Solvents - bad
I appreciate and value the analysis from both the "real world" and the "lab world" environments.
I want to understand the chemistry and very much value and appreciate the "lab world" information. But as a tool manufacturer, I must apply this understanding to "real world" applications by listening to and seeking answers for my customer base.
No one wants to create confusion by pointing out that the number of relevant and irrelevant variables are huge. There is no magic bullet answer to flushing and flushing chemicals; just lots and lots of variables that we cannot just dismiss, but must understand and find a way to mitigate.
I jumped in on the Mineral Spirits issues as this "solvent remaining" issue is something we have been focussed on for some time. I don't think anyone disagrees that "solvent remaining" is a true issue.
I have put all the commercial flushing products and over the counter solvents in a jar and pulled vacuum, some boil then stop, some don't; even water. In my "real world" explanation it has to do with variables in pressure temperature relationship, latent heat of evaporation, and ambient temps. Which makes me believe that a vacuum pump cannot even remove a few ounces of water, given certain variables were to come into play.
How do you explain this to technicians who work on A/C systems without even having the understanding of such basic principles of A/C operation? If they understood these principles, they would understand that a vacuum pump is designed to remove the air and contained moisture (i.e. humidity). It's not the vacuum pump that didn't remove the crap, it's the technician.
Ha, I punched a hole in a Mason jar lid, soldered a brass tube to it, filled a pint jar 1/4 full with water, hooked up my vacuum pump and showed my kids I was holding a jar full of boiling water and acting like I was in pain. But let them feel the jar, it was cool to the touch. If water boils, you have humidity and the pump will draw that off.
New refrigerant, new oils, new problems, something about miscibility is required though some were preaching due to the sheer velocity of the refrigerant, good old mineral oil would work just as well. Certainly not adopted by anyone that I know of. Which brings about a question, when R-12 was first developed back in the 30's, were they having the same problems back then?
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