how can i correct the dilution of the oil lubricant when i use hydrocarbons?

Helo everybody!

I have been working with natural refrigerants base hydrocarbons. Sometimes i have had problems because you know the hydrocarbons in general are compatibles with almost all oil lubricants becuse its nature. The oil mix suffer a dilution and also change the viscosity and the density... I have read that if i use this kind of refrigerants i have to correct the low viscosity for to insure that the compressor will work correctly. My question is how can i know exactly the exact viscosity that i have to use for to correct it??? i mean it´s depend of many factors like capacity and the quantity of refrigerant, etc or not? So how can i insure that i have the optime viscosity of the lubicant capable to correct the viscosity for the dilution that make the hydrocarbons to the oil?

Thanks...

The amount of dilution changes with pressure and temperature of the oil/refrigerant mixture. An oil manufacturer should have the dilution information.

The compressor manufacturers also have a minimum requirement for viscosity for their compressors. Therefore, what you need to know is:

The refrigerant vapor pressure present at the oil supply pressure/temperature. For a screw compressor this is typically discharge pressure. For a recip. compressor the oil exists at suction pressure.

Based on the condition of the oil supply to the compressor you have to check the oil dilution at that pressure and temperature. Based on the dilution the viscosity will be reduced.

You have to ensure the correct oil viscosity is used to provide a sufficient viscosity (diluted) for the compressor at that operating condition.

This applies to other refrigerant or oil combinations also.

Hello Iceman, thanks for your answer...

Hello Iceman, thanks for your answer...

Quote:

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Originally Posted by US Iceman

The amount of dilution changes with pressure and temperature of the oil/refrigerant mixture. An oil manufacturer should have the dilution information.
I think so, but the problem is that i have been working with a new mixture, so nobody have this information, so i have to work for to obtain it.

The compressor manufacturers also have a minimum requirement for viscosity for their compressors. Therefore, what you need to know is:

The refrigerant vapor pressure present at the oil supply pressure/temperature. For a screw compressor this is typically discharge pressure. For a recip. compressor the oil exists at suction pressure.
Yes, i think i will consider it, it will help me a lot

Based on the condition of the oil supply to the compressor you have to check the oil dilution at that pressure and temperature. Based on the dilution the viscosity will be reduced.

You have to ensure the correct oil viscosity is used to provide a sufficient viscosity (diluted) for the compressor at that operating condition.

This applies to other refrigerant or oil combinations also.

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Yes it is, the question is how can i check or measure the dilution of the oil (remember that it is a new mixture, so, nobody have this information, i have to obtain it or directly the viscosity for to see the change and correct it). I think i have to desing an experiment and a instrument to simulate the conditions (T y P), but i cannot imagine how can i measure it without lost the gas in the mix (refrigerant/oil) while i handle it to move to the viscosimeter or something like that...

I don´t have an special apparatus for to check it, but i think i can make it... or what do you think?


If i could measure the viscosity of the mix at T and P how you say i think i could relate it with the dilution factor. It is what i would like to do...

Thanks for your comments
María Elena

make sure the suction return to compressor does not get liquid flooded. Pass it in a heat exchanger with condenser make use of waste cooling and heat suction.

Contact CPI Engineering in Michigan. They custom blend oils and can provide data for their oils and the dilution data. If it is a new custom blend, they can run the test for you on the dilution.

Ken