Which of the following is a common cause of thermal shock in boiler systems?

Thermal shock in boiler systems occurs when there is a sudden change in temperature, particularly affecting the materials and components of the boiler. This quick fluctuation can cause expansion or contraction of different materials at varying rates, leading to stress and potential damage such as cracking or warping.

Sudden changes in water temperature can occur due to various operational issues, such as rapid flushing of a water line or abrupt changes in the heating applied to the boiler. These situations can severely impact the integrity of the boiler surfaces and components.

In contrast, gradual temperature changes allow materials to adjust more uniformly, reducing the risk of stress or damage. Constant water flow rates maintain stable thermal conditions within the system and excessive boiler pressure primarily relates to operational safety rather than thermal shock directly. Therefore, the common cause of thermal shock is clearly linked to those sudden temperature changes.