Question 31Motor Plants - QMED

The correct answer is D) Air entrained in the cooling water. In a closed cooling water system, the presence of air bubbles or air pockets can cause the water pressure to fluctuate. The entrained air can create compression and decompression zones, leading to unstable pressure readings. This is because air is compressible, unlike the incompressible cooling water, and the changing air volume can result in pressure fluctuations. The other options are incorrect because: A) An open vent would allow air to escape the system, stabilizing the pressure; B) A restricted water passage would cause a consistent pressure drop, not fluctuations; and C) A fouled sea chest would impact the flow rate, but not necessarily cause pressure fluctuations.