What can lead to boiler thermal shock?

Boiler thermal shock is primarily caused by rapid temperature changes within the system. When there is a sudden input of cold water into a hot boiler or a quick change in operational status, such as a sudden shutdown, the temperature differential can lead to stress on the boiler materials. This stress occurs because different parts of the boiler may expand or contract at different rates depending on their temperature, which can result in cracking or warping of the material.

In contrast, slow heating of water provides a gradual temperature increase, allowing materials to expand uniformly and is less likely to result in thermal shock. Continuous operation at high pressure does not itself cause thermal shock, rather it may lead to other operational issues, but does not create the rapid temperature changes associated with thermal stress. Low water levels in the boiler can lead to overheating and stresses from insufficient water for cooling but are not a direct cause of thermal shock in terms of rapid temperature changes affecting structure. Thus, the focus on sudden water input or operation disturbances highlights the critical nature of managing temperature gradients to maintain boiler integrity.