What is one of the primary risks associated with scale buildup in a boiler?

One of the primary risks associated with scale buildup in a boiler is that it reduces efficiency and can cause overheating. Scale, which is primarily composed of minerals like calcium and magnesium, forms when hard water is heated in a boiler. This deposit acts as an insulating layer on the heat transfer surfaces, which disrupts the efficient transfer of heat. As a result, the boiler must work harder to achieve the desired temperature and pressure levels, leading to increased fuel consumption.

Moreover, if the scale buildup persists, it can actually cause the metal in the boiler to overheat due to the lack of adequate heat absorption. Overheating can lead to serious issues such as equipment failure, ruptures, or catastrophic boiler explosions if not monitored and addressed properly. The efficiency drop also means higher operational costs, making addressing scale buildup essential for safe and economical boiler operation.

The other options fall short because while increased fuel consumption is a consequence of efficiency loss, it doesn't directly highlight the overheating risk. Enhancing water quality is incorrect, as scale buildup is detrimental to it. Corrosion of the outer shell is a separate issue typically linked to different factors, such as chemical imbalances or inadequate maintenance rather than scale alone.