Question 55 QMED03 - Oiler

The Correct Answer is A. **Why Option A is Correct:** The term "oil foaming" specifically refers to the rapid and often turbulent process where refrigerant, which is highly soluble (miscible) in lubricating oil, comes out of solution when the pressure rapidly drops. This commonly occurs in the compressor's crankcase, especially during startup after a long shutdown or during sudden drops in suction pressure. The liquid refrigerant, trapped within the oil, suddenly boils (flashes) as the pressure above the oil surface decreases, causing the oil level to rapidly rise and appear foamy, similar to the foam on a carbonated beverage being opened. Therefore, it is the **release of miscible refrigerant from the lubricant in the crankcase**. **Why the Other Options are Incorrect:** * **B) sudden evaporation of entrapped moisture from the crankcase lubricant:** While moisture is undesirable and can cause issues, its sudden evaporation (flashing) is generally referred to as "acid formation" or simply "moisture contamination issues" and does not define the large-scale turbulent process known as oil foaming. * **C) sudden evaporation of entrapped air from the refrigerant liquid:** Air (non-condensable gas) dissolved in the refrigerant can cause performance issues, but "oil foaming" is strictly related to the interaction between the oil and the refrigerant. Air typically causes increased head pressure and is not the primary mechanism behind crankcase oil foaming. * **D) release of dissolved lubricant from the refrigerant in the crankcase:** This statement is incorrect because the process being described (foaming) involves the refrigerant leaving the oil, not the oil leaving the refrigerant. Furthermore, oil is necessary in the crankcase, and its presence is the foundation upon which the refrigerant foaming occurs.