🔍 Key Concepts
• Think about what sludge in lubricating oil actually is made of (solid particles, moisture, breakdown products).
• Consider how contaminants can enter the crankcase of a reciprocating refrigeration/air conditioning compressor.
• Review the difference between viscosity changes, gas bubbles, and solid/foreign contamination in lube oil.
💭 Think About
• Which condition would actually introduce or create solid or semi-solid material in the oil, rather than just changing how thick or thin the oil is?
• Could a temperature change or dissolved refrigerant directly make sludge, or would they more likely affect flow, lubrication quality, or foaming?
• Which option clearly points to foreign material (like dirt, rust, or water) entering the lubricating system?
✅ Before You Answer
• Identify which option clearly involves foreign matter or moisture entering the oil, which is a common cause of sludge.
• Ask whether bubbles or lower viscosity alone would create sludge, or just alter lubrication characteristics.
• Eliminate any choices that mainly describe normal refrigeration-side conditions (suction line temperature, refrigerant behavior) rather than oil contamination.