Suppose a diesel engine is fitted with seawater-cooled lube oil and jacket water coolers. What statement is true concerning the system operating pressures?

Correct Answer: Option D — The jacket water pressure is maintained higher than the sea water pressure in the jacket water cooler, and the lube oil pressure is maintained higher than the sea water pressure in the lube oil cooler.

Maintaining higher pressure on the process side (lube oil and jacket water) than the seawater side is a critical safety requirement. In the event of a tube leak, this pressure differential ensures that process fluids leak into the seawater, preventing seawater contamination of the engine's critical lubrication and cooling systems.