Water inside of ammoniac refrigeration system

[Nicolás Vera V.]

Please would you advice how I could meassure how much water has the ammoniac in a refrigeration system.

Thanks in advance.
Best regards,

Nicolás Vera.

[US Iceman]

I'm assuming your system is not an ammonia absorption system.

Do you suspect you have a large quantity of water already in the system? What are some of the problems you are seeing?

In general, if water has been introduced into the ammonia, the boiling temperature/pressure relationship will change.

As more water is added to the ammonia, the suction pressure at the compressors will need to be operated at lower pressures to maintain the desired evaporating temperatures.

What you might see is this; If the suction pressure is at the same pressure as normal, but you cannot maintain the cold temperatures you normally do, water can cause this. Water in ammonia increases the boiling temperature. To maintain the cold temperature you have to run much lower suction pressures at the compressor.

If I can find a chart for you, you can tell how much water is in the ammonia by the change in pressure you will need to operate at.

Now there is one thing to be careful of, oil in the evaporators can cause the same thing.

I'll look for the chart and try to post it.

[US Iceman]

Here is a link to another thread that was discussing some of the same problems.

http://www.refrigeration-engineer.co...ead.php?t=4373

[US Iceman]

OK, I found one piece of information that directly relates to your question.

Here is a link to a short technical article.
http://www.hantech.com/documents/PDF...AmmoniaSys.pdf

The units are in IP, but with a little conversion you can find the information you are looking for.

I hope that helps you.

[Johnny Rod]

If you want the moisture content to be measured, you should speak to your ammonia supplier to see if they can do this for you. Otherwise see IIAR bulletin 108, if you are able to get the test equipment it's the simplest test method.

As Iceman says, oil can give the same effect of reduced pressures.

[Paulajayne]

One way that MIGHT give you indication of water is to look for emulsification of the oil - depends on the sight glass but you need to clearly see the surface of the oil with the comps not running.

Mind you nothing beats testing.

Paula

[refteach]

One quick way of checking the amount of water in the refrigeration system is that the oil in an ammonia system will absorb a percentage of the water that is in the system. There is a fairly easy way to check, take a sample of oil and put it on a hot plate warm it up to the boiling point of water, if there is water present in the oil it will snap and pop just like a deep fryer, this is known as the Crackle test for oil. I read there is even have a way of gauging how much moisture is present by the size and quantities of bubbles at a certian temperature. Check on www.noria.com I believe that is where I originally read about the test, they also have alot of information on oil analysis that can be helpful in the future.

[Andy]

One quick way of checking the amount of water in the refrigeration system is that the oil in an ammonia system will absorb a percentage of the water that is in the system. There is a fairly easy way to check, take a sample of oil and put it on a hot plate warm it up to the boiling point of water, if there is water present in the oil it will snap and pop just like a deep fryer, this is known as the Crackle test for oil. I read there is even have a way of gauging how much moisture is present by the size and quantities of bubbles at a certian temperature. Check on www.noria.com I believe that is where I originally read about the test, they also have alot of information on oil analysis that can be helpful in the future.

Hi refteach

I have heard of hydro cracked mineral oil, would this be a similar process.

Kind Regards Andy

[refteach]

Hi Andy

Hydro Cracked mineral oil refers to a method of dewaxing the base stock oil. Standard napthenic base and parafin base stock oils are normally solvent stripped of wax (texaco capella), hydrocracked oils have hydrogen applied at high temperatures and pressures to change the parafin in the oil and improve the base stock. These base stocks are usually refered to as group II base stocks and are the basis for the severly hydrotreated ammonia refrigeration oils which have better properties and longevity in the systems compared to the older solvent refined oils.

[US Iceman]

Here is another method that may provide better details.

http://www.airgasspecialtyproducts.c...cold%20flo.pdf

and,

http://laroche.solarvelocity.com/Page1744.aspx

If you want to, you can do some searching on related pages of this site for other good information.

[Andy]

Hi Andy

Hydro Cracked mineral oil refers to a method of dewaxing the base stock oil. Standard napthenic base and parafin base stock oils are normally solvent stripped of wax (texaco capella), hydrocracked oils have hydrogen applied at high temperatures and pressures to change the parafin in the oil and improve the base stock. These base stocks are usually refered to as group II base stocks and are the basis for the severly hydrotreated ammonia refrigeration oils which have better properties and longevity in the systems compared to the older solvent refined oils.

Refteach

thank you, very interesting

Kind Regards Andy

[Johnny Rod]

Oil analysis won't tell you if the refrigerant is wet or not.

[refteach]

True, it will not give you an accurate amount, however if you think you might have a problem with moisture in a system, oils can absorb a percentage of that moisture in the system and an oil analysis will be a representative amount.

We have found the oil analysis on a system shows moisture, there is a good chance that the refrigerant will also show moisture. Then depending on the oil, it will show more or less than the system. As a whole hydrocracked oils do not readily absorb moisture, where as napthenic bases will absorb more. PAO oils will not absorb as much as the napthenic and POEs will actually pull moisture from a drier core.

Kind of an interesting experiment is to take samples of oil in clear jars, mix equal amounts of oil and water in them. Shake them until it looks like salad dressing. let them settle out, let them return to their original components and see which absorbs more also measure the length of time it takes for them to separate . Do this with POE it is REALLY interesting. This is sort of a "do it yourself" miscibility test.

[Johnny Rod]

We have found the oil analysis on a system shows moisture, there is a good chance that the refrigerant will also show moisture. Then depending on the oil, it will show more or less than the system.

There is a massive over-reliance on oil analysis to tell you about moisture (and acid) in the refrigerant. Your points are valid as far as different oil types have different affinities for water, but there are too many factors to consider to really make this accurate to any degree. Add to this the solubility of water in ammonia.

[refteach]

I definately agree, and unfortunately many ammonia systems that I have been asked to trouble shoot rarely see a vacuum pump when the servicing the equipment. Most purge the unit and they are on their merry way. What I have found on ammonia systems is I will empty a low temperaure sump and look at what is in the oil and sludge, at low temperatures, water has distilled out of the ammonia and from there I will recommend taking further more accurate samples to see how much is there.