🔍 Key Concepts

• Where oil can leak into fresh water in a diesel engine cooling system (think about components close to lube oil and pistons). • The difference between an expansion tank in a closed circuit and a drain/collection tank that receives return flow from machinery. • How gravity separation of oil and water** works and what kind of tank design/position is best suited for that.

💭 Think About

• Look at the flow paths in the drawing: which tanks receive water that has been in direct contact with pistons or components near lube oil? • Among the tanks listed in the answer choices, which ones are simply for volume/thermal expansion, and which ones look like they collect potentially contaminated return flow? • If you wanted to skim oil off the top of a tank, would you choose a small, high-mounted expansion tank or a larger, lower-mounted collection tank in the drain line? Why?

✅ Before You Answer

• Identify which tanks are high-mounted expansion tanks serving as header/pressurizing tanks versus low-level drain or collection tanks. • Confirm which line(s) in the diagram are labeled as drains or returns from areas where lube oil is present, especially around the pistons and telescoping pipes. • Before selecting your choice, make sure at least one of the tanks you pick is logically placed and sized so that oil can rise and be separated/skimmed from the fresh water.