What might happen if the water level in a boiler drops below N.O.W.L.?

When the water level in a boiler drops below the Normal Operating Water Level (N.O.W.L.), one of the primary risks is that the boiler can begin to overheat. This occurs because the water acts as a coolant for the boiler's heating surfaces. With insufficient water, areas of the boiler can reach excessively high temperatures, leading to potential damage such as warping or rupturing of the metal components. If this condition persists, it can cause catastrophic failure of the boiler.

The risk of overheating is a critical concern as it can result in a complete boiler failure, which may have serious safety implications for personnel and equipment. Proper monitoring and control systems are implemented in boilers to prevent this situation, ensuring that the water level stays within safe operating limits to mitigate the associated risks of low water levels.