View Full Version : Chemistry of Contaminants

10-09-2005, 12:02 PM

Recently in the British trade press, BOC maintained that, in their estimation, 30% of the refrigerants contained in British industrial refrigeration systems are contaminated - presumably with moisture, various mixtures of acids etc.

Personally, I?m not surprised by this claim, and I expect that to include A/C systems as well, but the point is that as a technical practitioner of many years in this business, I suddenly realised that I have a very patchy knowledge of the chemical process involved in the degradation of various compounds of Fluorine, Chlorine and Hydrogen in contact with water inside an hermetic system.

In other words,

How, chemically, does acid form from water and CFC / HCFC / HFC?
How does it multiply in the system?
What, apart from copper plating etc., are the effects of electrolysis in concentrating this soup?

Can anyone with a knowledge of chemistry enlighten me?

mac game (http://macgame.org)

10-09-2005, 11:19 PM
Hi Argus , I will try to explain from my humble knowldge in chemistry

Let say we have R12 + moisture (water)
HCFCL2 + H2O -------> HF + products (HCCL2O)
HF= Fluodoric Acid ( Acide fluoridique in french)

The HF will react will the oil (what matter the oil acidity is , it will act like a base , because comparing it to pure acid HF , it's acidity seems negligeable)
The basic formula of almost all oils contains this string -COOH so we can say what matter the oil is it (----------)-COOH

So as HF reacts with an oil
HF + (---------)-COOH ------> H2O + (products containing fluor)
The H2O formed from this reaction will react again with the R12 and this thing continues

We can say that what the concentration is the ratio of acidity of the oil , as it's acidity rises , the reaction between it and the acid formed from the first reaction will give less H2O with less cycles of the 2 reactions , the H2O formed from the second reaction will decrease contiously .

Hope this helps
Best regards

Johnny Rod
12-09-2005, 01:05 PM
Hi Argus

It's my article you've seen, I was wondering if it would come up on here! I've found a lot of good fridge guys who don't know a lot about this sort of thing, you're far from being on your own. The samples came from all sizes of system, from a number of tonnes down to one guy who put the whole system charge in the sample cylinder.

I'll keep this brief but reply with questions, I don't want to overload you or bore you to sleep.

Moisture leading to acids in chillers has a couple of main routes, which are the refrigerant and the oil. POE oils are the worst for it, but in general moisture plus oil and some heat in the compressor starts degradation to give organic acids. If you have a regime of oil monitoring you'd see this increase with time. Moisture can also break down the refrigerant in hot areas like the compressor discharge, this is more of a problem for CFC/HCFCs than for HFCs as the chlorine comes off the refrigerant more easily than the fluorine.

In non-DX systems (or shell and tube evaporators with refrigerant tube-side) the contaminants should circulate the whole system, though with flooded-type systems where vapour is drawn off a vessel of some type on the low side, contaminants build up in the low pressure liquid.

I don't know a lot about copper plating, most people will tell you it's all about excess moisture, but the process starts with oxidation of the copper from internal surfaces. This is made worse by air, acids, and inorganic chlorides which can come from brazing flux etc.

Acids, particularly inorganic ones, will cause corrosion, though in fridge systems they are usually only at trace levels. The biggest problem is that they can cause the motor insulation in hermetic compressors to degrade and cause a burnout.

The only thing I don't really have any numbers on is non-condensable gases, so far very few people have asked me to look for these, so no idea how big the problem is.

Hope this helps


12-09-2005, 10:29 PM
Hi Johnny as it was you article , would you be kind and post it here so i can read it . . .

Thanks in advance and best regards

Johnny Rod
13-09-2005, 02:10 PM
See if this works:


There were edited versions in some of the trade press. I didn't write it myself and there are one or two things I don't like, but it seems to have generated a bit of interest. Not something a lot of people think about, I think.

15-09-2005, 09:30 AM

Thank you both for the interesting replies.

As I said previously, I?m not surprised by what appears to be an endemic level of contaminants in commercial systems.

It seems to me that a combination of recent technical and commercial changes has exacerbated an old problem. Given the restrictions on HCFCs, synthetic oils are now almost universal in new systems of all types in this country, and also I suspect in the EU and elsewhere; the population of older equipment using ODS gases and hence mineral oils are dwindling. Combine this with the quality of installation hygiene, especially in the small split-system market and you have a rich breeding ground for a bank of contaminants.

There are a number of things that are unexplained:

Is this bank of contaminated systems growing, reducing or remaining static?
Apart from reduced system life, what?s the impact on running costs and system efficiency?
How much is it costing?

And finally, does it matter?

In other words, it?s probably always been there - have we learned to live with it and operators accept the cost and implications of increased service outlay?

ecig forum (http://vaporizer.org/forum/electronic-cigarettes/)

15-09-2005, 07:38 PM
Thanks Johnny for posting the link

15-09-2005, 07:46 PM
Hi Argus . . .
I think the bank of those contaminated systems is growing , because the precaution and the presevative maintenance done to provide contamination or to discover a contaminated system is still very low in percentage of the total of the systems working , mentioning split units which are spreading widely .

The impact from running coasts for unapproved blends comes from the inefenciency of the unapproved blend t self , it just isn't a good refrigerant , which makes the unit to work for more time . . . and an unapproved blend has usually problems with the system pressure because the total pressur in the system is equal to the partial pressure of each refrigerant of the blend , so a faulty blend perturbates the pressure of the system.

As for high level moisture , appart from killing the system gradually , we come back to the pressure issue , the system is designed to work in maximum efficiency with refrigerant and oil only , add to them the pressure of the moisture , that perturbate the pressure of the system (in my opinion not in a very significant way because of the little ammount of moisture comparing it to the refrigerant) but it affects the efficiency .

Best regards

Johnny Rod
19-09-2005, 11:53 AM
Some good points and questions indeed. I can't tell you how the situtaion is changing, I only have stats for the last year to hand I'm afraid.

The majority of chemical analyses will indicate problems relating to reliability, so e.g. if I told you that you had a moisture problem, it wouldn't make a (big) difference to efficiency or capacity of the system. As an aside, I think ammonia systems are the only ones where high enough proportions of water are seen to affect vapour pressures. The elements relating to efficiency are oil and air contamination, and out-of-spec blends though that's a bit less clear.

Oil is a bad refrigerant and floats in flooded evaporators. This can lead to significant losses due to evaporator fouling; for example, in one of our own systems with shell-and-tube evaporators (refrigerant shell-side) oil logging had reduced capacity by 10-20%. Air collects in the condenser raising the pressure (and thus motor power) and taking up space. This has a penalty roughly equivalent to the air content, e.g. if you took a sample from your condenser and it had 10% air in it, condenser capacity would be expected to be down around 10%.

How much this is costing people I don't know, and quite often a system has more than one problem e.g. it could also be undercharged so it takes another hit on efficiency.

Does it matter? I guess these problems have always been around, but it doesn't make some of them any less serious. We do see a good number arising from installation which lead to equipment failures which, once rectified, are often fine for a long time as the systems are now clean and dry. In estalished running systems there are plenty where nothing is checked until it falls over, which can be a big problem for factories with continuous manufacture - some people lose thousands a day if something stops their production. Have we come to live with it? Probably, but should we?

19-09-2005, 12:16 PM
Maybe some law should be made for dig units , let's say 5 tones and up to be checked for chemical contaminents regulary , to check all units that's hard to do , specially with the expending market of mini units

US Iceman
19-09-2005, 01:13 PM
Hi Johnny Rod,

Flooded shell-side evaporators do act as a distillation device for the oil. As the liquid refrigerant continues to boil off, the oil concentration increases. Additional liquid refrigerant replaces the boiled off liquid and this continues until the oil concentration seriously affects the cooling capacity.

The oil can be recovered at the interface layer (oil and liquid refrigerant layer), but this usually means the chiller would have connections on the shell-side for doing so.

One way of performing this was discussed in the link below:


The thread highlights a situation concerning the various facets involved in refrigeration we all need to know. Chemistry, reactions, methods of removal, clean-up, etc.

This is on top of the knowledge required for refrigeration systems alone, electricity, plumbing, installation techniques, etc., etc.

This tends to show the extent of the information required to make good decisions for keeping the system operating at the highest efficiency level.

Ultimately, the situation can often be condensed to several areas:

1) Someone does not know what to do or how to fix it

2) Money will not be spent to correct the problem

3) Or, someone does not care

The latter two are the most serious to change.

The first statement above is the easiest to change. Whenever anyone encounters a new problem they will need to ask questions and apply what they already know.

Personally, I would like to thank Argus for bringing this subject up in the first place. This is a fascinating subject that should be documented and explored further.

Best Regards,
US Iceman

Johnny Rod
28-09-2005, 10:40 AM
Hi guys, been away for a while.

Until I got into this field I didn't know how much was involved in refrigeration, you really have to cover a range of stuff to work properly on just one system. But like you say, someone either does or doesn't know or care what to do about problems.

On the subject of refrigerant contamination specifically, I've found there is a great reliance on the fact a piece of kit hasn't stopped yet, and on oil analysis alone, which is one reason I have some stats but not that many on the state of the fridge systems out there. Some people seem to prefer to work in the dark! I do talk to a number of people who are sure that they've been in the game long enough that they don't need to be told anything new, but I've been working in chemistry for 14 years and I'm always ready to learn something new - I'd be almost 14 years behind otherwise. Conversely of course I've been told lots of things I already knew.

The thrust of the press release was to try to highlight that a lot of people could be missing a trick here without realising it, another spanner in your toolbox is never wasted. I get the impression that in the US they're a bit more switched on than we are in the UK about problems of contaminated refrigerant in chillers.

What do you think? Most people here will have been in refrigeration a lot longer than me.