Overheating of tubes in a water tube boiler results if _______?

The correct response addresses a critical aspect of boiler operation: the effect of scale buildup on the interior surfaces of the tubes. In a water tube boiler, water is circulated through the tubes. If scale builds up on the inside of the tubes, it acts as an insulator, reducing the efficiency of heat transfer from the combustion gases to the water inside the tubes.

When heat transfer is impaired due to this insulating layer, the tubes themselves can overheat because the water content in them may not absorb the heat effectively. Overheating can lead to the tubes reaching dangerously high temperatures, which may compromise their integrity and lead to failure. This phenomenon highlights the importance of maintaining water quality and implementing regular maintenance practices to prevent scale formation.

In contrast, excessive water flow might help cool the tubes further, and an interrupted water feed could more likely lead to other issues, such as low water levels causing the tubes to run dry, rather than overheating. A restricted fuel supply generally results in inadequate heat generation, which would not typically lead to overheating of the tubes. Therefore, understanding the significance of scale in relation to heat transfer is key to recognizing why scale buildup is the correct answer regarding overheating in water tube boilers.