Question 526Steam Plants - Assistant Engineer

The correct answer is D) The drains from lube oil coolers can be directed back to the main sump, the sludge tank or the lube oil purifier. This is correct because the lube oil system illustration shows multiple drain lines from the lube oil coolers, allowing the oil to be directed to different parts of the system, such as the main sump, sludge tank, or the lube oil purifier. This provides flexibility in managing the lube oil and ensuring proper circulation and purification. The other options are incorrect because: A) The gravity tank does not directly supply oil to the turbines and gears, but rather provides a backup supply; B) The gravity tank overflow line does not lead directly to the sludge tank; and C) The three-way temperature control valve is used to maintain the desired oil temperature, not to bypass the lube oil cooler.