Question 332Steam Plants - 1st Asst/Chief

The correct answer is B) a carryover from the boiler. Explanation: An unusual vibration in the main propulsion turbine unit, accompanied by a rumbling sound in the reduction gear, could be caused by a carryover from the boiler. This is because the boiler is responsible for generating the steam that powers the turbine, and any issues with the boiler, such as carryover of water or other contaminants, can disrupt the smooth operation of the turbine and reduction gear. The other options are incorrect because they do not directly relate to the specific symptoms described in the question. A labyrinth seal failure (A) or a reduction in condenser vacuum (D) would not necessarily cause the described vibration and rumbling sound. Overloading of the condenser (C) is also unlikely to be the cause of the issue.