What happens if the low water cut off (LWCO) fails?

The low water cut-off (LWCO) is a critical safety device in steam boilers that monitors the water level within the boiler. If the LWCO fails, it cannot properly detect low water conditions. This failure can lead to insufficient water levels in the boiler, which is extremely dangerous. When the water level drops too low, there is a risk that the boiler components, especially the heating surfaces, can overheat. This overheating can cause the boiler to become pressurized beyond its safe operating limits, potentially leading to a boiler explosion.

The correct answer highlights the serious consequences of LWCO failure. The other choices do not reflect the potential hazards of a failing LWCO. A situation where the boiler operates efficiently would not occur if there is inadequate water supply. An automatic system shutdown is a function of the LWCO when it is operational and detects low water, so failure negates that safety mechanism. Lastly, the idea that air would escape the system naturally misrepresents the function of the LWCO, which is to maintain safe water levels, not manage air escape. Overall, the role of the LWCO is fundamental to boiler safety, and its failure can have catastrophic results.