Question 212Steam Plants - 1st Asst/Chief

The correct answer is A) they require more water flow since they are exposed to the greatest heat. In most marine boilers, the first few rows of generating tubes, called the screen or furnace row tubes, are made larger in diameter than the rest of the generating tubes. This is because these tubes are directly exposed to the highest heat from the burners, and they need to carry a greater volume of water to prevent overheating and potential tube failure. The larger diameter allows for increased water flow to absorb the intense radiant heat, which is critical for the overall efficiency and safety of the boiler system. The other answer choices are incorrect because they do not accurately describe the primary reason for the larger diameter of the screen or furnace row tubes. Options B, C, and D describe secondary functions or features of these tubes, but do not address the key reason for their larger size.