Dose Anybody know Auto Refrigeration Cascade System

[ernestlin]

Hi, everybody! I set up a three stage ARC system to achieve the -180 F box temperature, and the refrigerant was chosen as R404A\R23\R14 mixture, the lubricating oil is synthesize POE. When run this system, I found the evaporate temp. fluctuated in a wide range, after checked the system, it has been found there was a blockage in the line by the sticky oil. I think the oil is the big problem. So, does anyone know which type oil should be used in this ARC system? Any input is appreciated!

best Rgds

ernest.

[ernestlin]

nobody knows, I may solve it by myself...

[Huynh Ba Dat]

This is difficult

[TXiceman]

The systems I have run at such low temperatures used oil free compression on the low stages. If we did not use oil free, we used tandem carbon bed absorpsion oil separation on the compressor discharge.

For alternate oils, you might contact CPI Engineering in Michigan, USA.

[Peter_1]

They mostly add a litlle bit refrigerant with a boiling point higher then those you have used wich cleans/flushes the lines.
This refrigerant will flow as a liquid through all the separating traps of the ARS.
It's not used as a refrigerant but as as some sort of cleaning agent.

[TXiceman]

We use to do that when we had R-12 around. Worked great to get oil to come back in a low temp R-22 system. What would you suggest on this system.

Ken

[NoNickName]

POE viscosity is given in centistokes at +25° (or +40°C sometimes).
Unfortunately viscosity of a liquid is a function of temperature. a 150cSt POE oil at +40°C has a viscosity of 1200 to 1500cSt at -20°C.
The resulting molasse easily clogs channels and orifices.

[Cofreth]

I have tried using Penthene for cascade system.

[ernestlin]

Tks for your good information, pals!
Cofreth, what's the Penthene oil? Could you tell me the detail? Tks again.

ernest

[Ybb]

I've also used a small amount of pentane but that was with mineral oil not poe. Wikipedia has info on it but I can't post the link.

[TXiceman]

Did you contact CPI Engineering in Midland, Michigan. The blend oils for all sorts of applications.

Ken

[ernestlin]

Thanks for your information.

[ultralo1]

Try a little instrument grade propane, sulfer content less than 20ppm. Also you could try adding an ounce or two of R134a into the last stage. Definatly add an oil seperator on the last stage.

[Rob S]

Just wondering what your solution was?
And in what stage was the oil flogging up at? Because you shouldn't have any oil carry over into the 2nd or 3rd stages.