168. The term «oil foaming» in refrigeration practice, is used to describe what event?

Oil foaming occurs when dissolved refrigerant rapidly evaporates from crankcase oil, creating foam. Refrigerant can dissolve in oil during periods of low pressure or temperature, and a sudden pressure or temperature change causes the refrigerant to boil out of the oil. This phenomenon is distinct from moisture or air issues, and involves refrigerant leaving the oil, not oil leaving the refrigerant.