Hi, I am new to this ocean of knowledge and experience.
I am little bit experienced in R11 centrifugal water cooled chiller operation and maintenance. Handled various breakdowns like bearing seizure due to oil failure, impeller eye bolts broken, impeller damage etc. etc. Repiared and reconditioned various parts and used.
Now, we are in the process of phasing out these units with R134a screw chiller.
Many questions are in mind. Over the time, I will be sharing those.

Why viscosity of refrigerant oil drops down so sinificantly immediately after use. ***** in oil brings down viscosity. But, even if ***** is driven out by moderate heating of fesh oil, viscosity is about 50 %.