View Full Version : Decrease of the viscosity oil with hydrocarbons mix...

26-04-2007, 11:38 PM
The oil mix suffer a dilution and it affect the viscosity and the density. I have read that if i use hydrocarbons as a refrigerant, i have to correct the decrease of the viscosity for to insure that the compressor will work correctly. My question is how can i correct it, how can i know the exact new viscosity that i have to use for to make up for it?

27-04-2007, 12:52 AM
I am not sure I understand the question.
In a system that is not operating the refrigerant will migrate to the coldest spot. If it migrates to the compressor crankcase it will be absorbed into the oil. When you start the compressor the crankcase pressure immediatley drops causing the refrigerant to boil out of the oil. This causes the oil to foam. The viscosity and density of the oil are reduced. The result is to starve the bearings of oil and you damage the compressor.
To stop this you use a crankcase heater. While the compressor is off the heater is on to make sure that the oil in the crankcase is warmer than any other part of the system. This keeps the refrigerant out of the oil.
Could this be what you are asking?


27-04-2007, 04:54 PM
Specific oil blends are used for specific refrigerants. For a hydrocarbon refrigerant, the oil dilution becomes a major concern. The oils we use on hydrocarbon refrigerants are mostly a polyglycol based lubrcicant. We use several different viscosity oils, depending on the exact application.

If you are trying to determine a specific oil for an application, the first palce to look is the compressor manufacturer for his recommended or approved oil to use in his compressor. You can also contact CPI Engineering In Midland, Michicgan.

In addition to oil dilution, you need to look at the oil vapor pressure. Too low and you will have excessive oil loss from the compressor due to vaporized oil.

WHat type of compressor are you using for you application.

A word of caution from years of experience, do NOT mix oil manufactures in one system. With the synthetics I have seen this create problems a number of times. If you change the oil in a machine, be sure and drain all of the low points very well before you add the new oil. Run for 48 hours and dump the oil charge and recharge with fresh oil again.

Most of the oils we sell are blended for us by CPI.