contaminants in ammonia systems

I'm a relative newbie to the world of refrigeration so a little unsure where to look for some info. I'm trying to find out about ammonia, but the more people I talk to the more questions I seem to have!

What I'm looking for is information about the effects that contaminants in the refrigeration circuit have on ammonia systems. For CFC/HCFC/HFC systems there is info in the ASHRAE handbook about this e.g. moisture levels, but I'm having more than a little trouble finding similar information for ammonia. I know ammonia systems are a lot more tolerant than fluorocarbons but there must be some info out there somewhere - ?

Hi i have send you some info i hope can help you

Sabroeclaus , why don't you post those info here , so all of us can discuss it and have a look at it , maybe it's useful for the others to

Hi Johnny Rod,

You are correct about the water tolerance in ammonia. There are some limits though as to how much. I need to dig in my information for the exact numbers, but for a general discussion I will give you some basic info.

Refrigerant grade ammonia has a small percentage of water added to it for storage and transportation issues. This is due to the possiblility of pure ammonia causing corrosion stress cracking in carbon steel vessels. The water helps to reduce this effect.

Higher concentrations of water begin to change the pressure/temperature relationship. This is approaching the aqueous-ammonia solutions used in some absorbtion machines where ammonia is sometimes used.

Another contaminant to watch out for is CO2. This only applies when the ammonia system is being used on CO2 systems (breweries, or cascade CO2 refrigeration systems). CO2 and ammonia can form solids if the two mix. I think the solution is called ammonium carbonate. This is a mess.

Most of this information we all learn the hard way. If you find some information on other contaminants, I would like to see them also.

I will try to find what information I can and send you a message.

Best Regards,
US Iceman

I found some of the information I was looking for.

IIAR has a bulletin that discusses some of the specifications for refrigerant grade ammonia:

This is from Bulletin 110
Ammonia content (99.95% minimum)
Non-basic gas in vapor phase (25 ppm maximum)
Non-basic gas in liquid phase (10 ppm maximum)
water (33 ppm maximum)
Oil (2 ppm maximum)

As the % of dilution increases (more water/less ammonia) the saturation temperature for the aqueous solution increases. Therefore, to maintain the same evaporator temperatures with the aqueous solution, the suction pressure must be lowered (lower than the the normal expected pressure for 100% ammonia).

Air can also be considered a contaminant as a part of non-condensables that get into the refrigeration system. One portion of this argument is the air carries oxygen into the system. There have been some discussion about oxygen content promoting the stress corrosion cracking of the carbon steel vessel and piping.

The other part of the air argument is the increased discharge pressures due to the presence of non-condensable gases. Air is only one component of non-condensable gases. Some of the "gases" may be comprised of other vapors due to oil breakdown, ammonia breakdown, or other gases contained in the ammonia during charging of the system.

I have heard of propane vapors being found in the ammonia (someone used the wrong transport cyclinder, which had previously been used for propane).

Ammonia will dis-associate at high temperatures and in reaction with metal parts. So it is possible that some free hydrogen could be found.

Most of this is fairly simple to deal with. The worst one I have heard of is the CO2 and ammonia mixing.

That is about all I have. If you find other information, I would appreciate a copy of it.

Thanks,
US Iceman

The ammonia supplier should be able to provide a kit to test for water content in the refrigeration system.

Almost everyone has smelled the sharp, penetrating odor of ammonia, NH3. A more than a sniff of this toxic, reactive, and corrosive gas can make one very ill indeed. It can, in fact, be fatal. Ammonia is pretty nasty stuff. Nevertheless, it is also an extremely important bulk chemical widely used in fertilizers, plastics, and explosives and also as a refrigerent.
The melting and boiling points of ammonia, –77.7°C and –33.5°C, respectively.

It is also used in metallurgy for heat treating and combustion processes to control air pollution. I agree it can be dangerous, but then so can all refrigerants.

The others are just as bad, because they can sneak up on you in a room where a leak has developed. This is no fun (been there done that)! We should recognize that all refrigerants are potentialy fatal. That makes us work smarter.

I'll take ammonia systems over anything else. It does make a lovely air freshener though!

hi
I have some info but it is too big to send .is ther any way

I'l have to agree with US Iceman. My preferred refrigerant is ammonia. Like all refrierants, they are dangerous if you do not properly handle them. The same is true for propane and propylene.

As for the best source of ammonia refrigeration information check out http://www.iiar.org.

Ken

Hi guys, thanks for the replies. I have been trying to get hold of IIAR bulletins 108 and 110 but their shop crashed on me, will have another go.

As for the IIAR ammonia spec, I'm not sure what this is based on but I don't think anyone sells ammonia as dry as that, or at least not at the prices you'd be prepared to pay. Also like you say, dry ammonia contributes to SCC.

Spoke to a rather short-tempered lady at the IOR, that didn't get me anywhere really.

Any comments on oil logging? I believe the majority of ammonia systems use a low-temp receiver/header/vessel with flooded chillers (thermosiphon or pumped) instead of evaporators. So presumably the oil can collect in the low side vessel - but I guess oil return is easier then with fluorocarbons as it sinks not floats?

Will let you know what else I can find out.

Claus, can you upload your files and post a link for them? I presume they're the ones you sent me? If not I'lls ee if I can do it.

You are right in stating the oil sinks in ammonia systems. The density of the oil is higher than the liquid ammonia density. The difference in density causes the oil to sink.

Similar to the thermosiphon principle. Gas rises, liquid falls.

Oil will sink in any part of the ammonia refrigeration systems. Vessels, piping, or heat exchangers. Sometimes you will find a small vessel located below, and piped to the main vessel. This is an oil drain pot. Oil flows down the lower line connected to the bottom of the main vessel, while gas rises through the other line from the oil pot to the gas space on the main vessel (above the maximum liquid level in the vessel).

If the ammonia temperature is below freezing, ice will form on the oil drain pot. As the oil accumulates in the drain pot, the frost/ice formation will move upward. The bottom of the oil drain pot will be clear of frost due to the oil insulating the bottom of the oil drain pot. Liquid ammonia floats on top of the oil.

If you have these, be very careful when manually draining them. The most common accidents occur when oil pots are being drained. IIAR has an oil drain procedure that lists the steps and recommended piping methods.

The IIAR ammonia specification is for refrigerant grade ammonia. This is based on past thinking. This may change due the probelms encountered with SCC.

The other two grades of ammonia I am aware of are: Agricultural ( a little dirt and more water) and metallurgical (extremely clean and very little if no water content).

If the information from Sabroeclaus is too big for the attachments, I would be interested in getting a copy also.

Thanks.

Keep us posted on your progress.

Best Regards,
US Iceman

Quote:

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Originally Posted by kothari

Almost everyone has smelled the sharp, penetrating odor of ammonia, NH3. A more than a sniff of this toxic, reactive, and corrosive gas can make one very ill indeed. It can, in fact, be fatal. Ammonia is pretty nasty stuff. Nevertheless, it is also an extremely important bulk chemical widely used in fertilizers, plastics, and explosives and also as a refrigerent.

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Indeed, one of the nice things about ammonia is the fact that anyone with a sense of smell has a built-in leak detector. This is not the case for HFC, CFC, etc., which lack any sort of strong odor.

Yes, a leak on a large ammonia system in an enclosed space can be fatal to those working on it, but read the Material Safety Data Sheet for all the other refrigerants - under the same or similar conditions just about any of them can be fatal too. At least with ammonia there is a warning.

Hi Iceman. I was going to upload Claus' files to my webspace but one or both is covered by copyright I think. They are 1MB and 800kb and are quite a good dissertation of mositure in ammonia refrigeration - I could mail them on if these files aren't too big for you.

Still trying to get the bulletins out of IIAR...

I ran across some additional information on contamination issues.

If small quantities of R-22 (possibly others) get into the ammonia, a fine water powder can precipitate out and clog filters, strainers, etc.:eek:

This may occur if the refrigeration system was originally used with R-22 (steel pipe of course) and converted to ammonia due to the refrigerant management protocols. Or, if R-22 (or other HFC, etc.) leaked into an ammonia system used for process cooling.

Since it appears you are in the refrigerant manufacturing business, do you have an ammonia system used to cool part of your process plant?:confused:

Another source to consider.

Best Regards,
US Iceman

I realise this is an old thread but it caught my eye regarding the R22 in ammonia.

We recently had some leaks on a spiral blast freezer with a thermosiphon ammonia coil constructed from aluminium and installed about ten years ago. Pinhole holes had developed in the evaporator coil tubes, four over a period of six months. The leaking tubes were cut out and inspected and a bluey green sludge was coating the inside of the tubes along with a fairly even sprinkling of pits where corrosion cells had set up under the sludge. Obviously some of the pits were full penetration hence the leaks! The sludge was analysed and found to be ammonium hypocyanide (if memory is correct) which is a known byproduct of ammonia which has been contaminated with R22, is highly toxic and very dificult to remove. The evaporator coil was replaced at a cost of around €50,000. How the R22 got there is a mystery but must have been a ****-up by someone at sometime who forgot what came out of which cylinder. We installed an ammonia purifier which is slowly collecting the residual sludge powder from the system. We are still trying to find a suitable method to analyse the system to monitor the levels of contamination and avoid a repeat of what happened previously.

In my experience its fair to say that in the past some of the "old school" ammonia guys were not too concerned about the cleaniness of a big system when it was installed. They made sure it was fully pressure-tight and were pretty good about swarf and debri but water and non-condensables would be absorbed quite happily or the purger would deal with it. To be fair Im talking about big systems; 5, 10, 20+ tons of ammonia. The other side is of course that even a 1-2% power eficencey increase or decrease on a system doing 3000kWR is alot of money!

Hi garyb,

Quote:

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...bluey green sludge was coating the inside of the tubes

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I'm not one to argue with a chemist, but this also sounds like some leaks I have seen where brass and/or copper were present at the leak.

Were the pinhole leaks developing from the inside or outside of the tubes? Did you cut out an affected area to see if the corrosion site was internal?

Has anyone checked the CIP washing fluid for the coils to see if the cleaner is compatible with the grade of aluminum used in the coil?

The pinholes were on the inside of the pipe - the ammonia reacted with the R22 to create a corrosive compound and proceeded to eat its way to freedom! The leaks were all several rows down and the surrounding fins had to be excavated to allow a short section of pipe to be removed and cut in half.

Hi, hope I can contribute with a little help because I am also ammonia guy ;)

Here are some links:

About ammonia:
http://www.airgasspecialtyproducts.c....aspx?PID=1753

About training for ammonia operators:
http://www.ammoniatraining.com/News.htm

One page with a lot of good stuff from Arta:
http://www.nh3tech.org/Index.html

Page with basic chemistry what we have to know:
http://www.chemtutor.com/index.html

Safety and health:
http://www.osha-slc.gov/SLTC/ammoniarefrigeration/

One very good page about Refrigeration:

Quote:

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XV c.b.C. First mention of making ice, in ancient Egypt, by night-cooling, for refreshment and fever fight.

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http://imartinez.etsin.upm.es/bk3/c1...#_Toc101323302

At the end guys, I have to ask you something:

Why you are so "shamefaced" to put some of your good links here for others :confused:

Hope you'll enjoy.

Best regards,

Josip :)

I've not come across R22 and ammonia reacting, would be interested to know more about what you found. As for the sludge, can you find out what it was? Blue/green does sound like copper if it's a vivid colour, but aluminium salts are often pale blue-green. As for checking the amount of R22 still present, if you can find a lab that can do ammonia analysis they should be able to do something for you. It's not something that would normally be analysed for, but if they have a method that looks for air gases then they might be able to modify it to look for R22.

Quote:

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Originally Posted by Johnny Rod

I'm a relative newbie to the world of refrigeration so a little unsure where to look for some info. I'm trying to find out about ammonia, but the more people I talk to the more questions I seem to have!

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I have a printed document from Sabroe about contamination in ammonia systems. I wonder if it might be the one SabroeClaus has sent to you.

However, as you are just up the road from me, I can let you have a look. PM me if you want and let me know the content of Claus' stuff and I'll see if it is a different document.

Steve

You can go to IIAR website and find anything you need on NH3

HI JOHNNY ,
Among all the ill-effects of Ammonia, it is can deliver high capacity at low displacements,green refrigerant and probably poses less problems on oil recovery from system etc.

D.D.KORANNE

Hi appreciate that this is an old thread but it seamed appropriate and has some handy links herein.

On this subject has anybody come accross moisture reactions resulting in Clathrate Hydrate. This is apparently where acid oxides react with the ammonia to produce an ammonium salt seen as a blackish sludge.

Does anybody have experience of this phenomina and if so how common is it and what sort of moisture levels is it likely to need to be present ?

Attachment 7151 Problem in ammonia refrigerfation system in beverage industry:
the attached image is of vapour outlet line of a carbocooler in a beverage industry
I am facing the problem of either contamination carbon dioxide with ammonia or caustic vapours in ammonia, the line size is 100 NB which is blocked with the salt like crystals
can anybody will help me what could be the exact cause for this?

My suggestion is to get a sample of this to a lab and get it analyzed. Next, get a couple of liquid ammonia sample (off the receiver and off the evaporator). Also get an oil sample under pressure. You will need to get some stainless steel pressure containers (we used to call them sample bombs, but I don;t know about now) of about 0.5l each.

The lab can tell you what you have there and working with a metallurgist and a chemist, you may well get to the bottom of this.

This will not be cheap, but you need to get to the bottom of this. I have dealt with a contaminated low temperature large system in a petro-chemical plant and we wound up dumping 20,000# of NH3 as a hazardous waste.

Ken

Hi umesh.
I have seen similar junk build up in ammonia systems , and stemmed from contaminated oil and wrong oil in system, a combination of water and additives in oil separating out at expansion point.

When you find out what happened I'd be very interested in the information! I think we'll be seeing a lot of CO2/NH3 cascades in the next five years.

Off topic - needed removing

Try to burn it with a lighter.
If it transform from solid to gas, it is ammonium carbamates .....

Almost looks like waxing to me. When Solvent Refined Paraffin oil is used in a DX system, it can cause the wax to fall out and solidify in the lines.
Carbon dioxide and ammonia creates a white sand-like substance, calcium carbonate which would tear up your compressors more than build up in one location.