What might happen if scale is allowed to build up in a boiler?

When scale builds up in a boiler, it acts as an insulator on the heat transfer surfaces, impairing the efficient transfer of heat. This insulative layer can lead to localized overheating of the metal components because the combustion gases continue to deliver heat, but the scale prevents proper heat dissipation. As a result, the temperature of the boiler surfaces can increase significantly, potentially leading to damage such as cracking or even failure of pressure parts.

Further complications arise as the scale reduces the efficiency of the boiler system. The boiler must work harder to achieve the desired steam output, which affects overall performance and efficiency. This inefficiency increases fuel consumption, ultimately leading to higher operational costs. Hence, the statement about scale causing overheating and inefficient performance accurately highlights the risks associated with scale buildup in boilers.