What must be done to all parts of a boiler that are exposed to fire or hot gases?

In a boiler system, all parts that are exposed to fire or hot gases must be covered with water to ensure effective cooling and safe operation. This coverage is crucial because it prevents overheating of the boiler components, which can lead to structural failure or damage. Water serves as a coolant, absorbing heat, and thereby maintaining the integrity of the metal parts that might otherwise be subjected to extreme temperatures.

While insulating parts can be beneficial for energy efficiency and to control heat loss, it is not a necessary action for all exposed parts, especially those that need direct cooling through water. Repainting components helps with corrosion protection and aesthetic purposes but does not address the fundamental need for cooling in hot sections of the boiler. Maintaining constant airflow is essential for combustion efficiency but does not directly relate to the protection required for parts exposed to direct fire or hot gases.