Which condition can lead to overheating of boiler tubes?

A low water condition in a boiler can lead to overheating of boiler tubes because the water serves as a cooling medium for the metal surfaces of these tubes. When the water level drops below the safe operating level, there is insufficient water to absorb the heat generated during operation. This results in the tube surfaces being exposed to higher temperatures than they are designed to withstand. As a consequence, the metal can become overheated, potentially leading to failure, ruptures, or even explosions due to the thermal stresses and the risk of overheating can severely compromise the integrity of the boiler.

In contrast, a high water condition can cause water carryover into the steam lines, while normal water conditions ensure that the boiler tubes maintain an adequate level of water for effective heat absorption and overall safe operation. Low pressure conditions might affect the system's efficiency but would not specifically relate to overheating of the tubes in the same manner.