What defines a "boiler explosion"?

A "boiler explosion" is defined as a catastrophic failure that results from a rapid increase in pressure within the boiler system. This type of explosion can occur when the pressure exceeds the design limits of the boiler structure, often due to a failure in pressure control mechanisms, water level control, or overheating that leads to excessive steam production. The explosive failure can cause severe damage to the boiler and its surroundings, posing significant safety risks to personnel and equipment.

In contrast to the correct answer, the other choices describe situations that do not meet the definition of a boiler explosion. Minor pressure fluctuations would not lead to a catastrophic failure, mechanical failures in pumps do not directly relate to the characteristics of boiler explosion, and overheating issues, while serious, typically do not result spontaneously in an explosion unless they significantly contribute to a failure of pressure containment in the boiler. Thus, they are not representative of the specific and severe nature of a boiler explosion itself.