Which of the following statements about boilers is correct?

A hot boiler will continue to generate steam after the fires are secured because it retains the heat generated from the burning fuel. This residual heat is sufficient to continue converting water into steam for a period of time, depending on the boiler's design, the amount of water inside it, and the insulation properties. This phenomenon is often referred to as the boiler's heat retention capability, which allows for steam production even when the fuel supply is cut off.

Understanding this aspect of boiler operation is essential for managing boiler safety and efficiency. For example, when the fires are secured, the operator must still monitor the system to prevent overpressure situations, as the steam generation can continue despite no active combustion.

While there are other options provided, they do not accurately reflect the operational characteristics of a boiler. A cold boiler being unable to generate steam is a more straightforward concept; without active heat from combustion, it cannot produce steam. The notion that boilers can only generate steam at full capacity ignores the fact that they can operate at varying loads. The requirement for a boiler to always be under pressure to function does not hold, as boilers can operate at atmospheric pressures under specific conditions without generating steam, albeit not in the usual operational context.