What does "thermal shock" refer to in a boiler context?

In the context of a boiler, "thermal shock" refers to the stresses and potential damage that can occur when there are abrupt temperature variations within the boiler system. This phenomenon happens because materials expand and contract differently according to temperature changes. When a rapid temperature change occurs, for example, if cold water is suddenly introduced to a hot boiler, it can create significant stress on the boiler components. This stress may lead to cracking or other forms of damage, which can compromise the integrity of the boiler and lead to safety hazards.

Understanding thermal shock is crucial for boiler operation and maintenance, as measures must be taken to avoid sudden temperature changes, such as gradually introducing water or controlling load changes carefully. This helps ensure the longevity and safe operation of the boiler. The other options do not accurately describe the specific issue related to thermal shock, focusing instead on other aspects of boiler operation that do not involve the damaging effects of rapid temperature variations.