Question 43 3AE01 - Third Assistant Engineer

The Correct Answer is C **Why option C is correct:** Option C states that the oil pressure is greater than the cooling water pressure. This design principle is mandatory for safety in marine engine coolers (oil or jacket water coolers). The primary purpose is to prevent catastrophic engine damage should a leak develop inside the cooler. If the cooling water pressure were higher, water (which can cause severe damage) would contaminate the lubricating oil system. By maintaining the lubricating oil pressure higher than the cooling water pressure, if a leak occurs, the oil will flow into the water system (where it can be detected), ensuring the engine lubrication system remains uncontaminated and functional until the problem is addressed. **Why the other options are incorrect:** * **A) The oil temperature is less than the cooling water temperature.** This is incorrect. Heat transfer requires a temperature differential, and the purpose of the oil cooler is to remove heat from the oil. Therefore, the **oil temperature must always be greater than the cooling water temperature** for effective cooling to occur. * **B) The oil pressure is less than the cooling water pressure.** This is incorrect. As explained for option C, maintaining the oil pressure lower than the water pressure is a dangerous design that would lead to water contamination of the lube oil system if a leak occurred. Safety standards require the oil pressure to be greater than the cooling water pressure. * **D) The oil flow control valve is always installed in the oil input line.** This is incorrect. While automatic temperature control can be achieved by throttling the flow of oil or water, typically, the control valve (a thermostatic regulating valve) is installed in the **cooling water line (usually the outlet) or bypass line**, regulating the flow of water to maintain the desired oil temperature, rather than throttling the main oil flow.