whether hermatic compressors previously used in system with cfc free refrigerants can the same compressor be used again with hfc refrigerants, if so please tell me process
The heat transfer devices (condenser, evaporator) were designed for the physical properties unique to a given refrigerant. Even if going to an HFC with similar propertes, you have an oil issue, and should check the expansion valve. Also, compressors have different capacities with different refrigerants.
You also have to look at the application; low temp, med. temp, AC, etc. to select the proper refrigerant.