In a diesel engine jacket water cooler, with sea water cooling the engine jacket cooling water, what statement is true?

Correct Answer: Option A — The jacket water pressure is always kept higher than the sea water pressure, and in case of a jacket water cooler leak, the jacket water expansion tank level will increase.

Jacket water systems operate at higher static pressures than raw sea water cooling circuits per marine engineering design standards. Consequently, any heat exchanger tube degradation forces fresh water outward, manifesting as an rising expansion tank level.