What is required for a boiler to be classified as a high-pressure boiler?

A boiler is classified as a high-pressure boiler when it operates at a pressure exceeding 15 pounds per square inch gauge (psig). This standard is important in differentiating between low-pressure and high-pressure steam boilers, as the operational risks, safety requirements, and regulatory standards differ significantly.

While a pressure exceeding 100 psig could certainly qualify as a high-pressure boiler, the minimum threshold is defined by the 15 psig standard. Therefore, it's crucial to recognize that any boiler operating above this pressure must adhere to higher safety standards and regulations. In this context, temperature is not the sole determining factor for classifying a boiler; instead, it is the pressure that primarily defines the classification.

Thus, the answer indicates that the key criterion for designating a boiler as high-pressure hinges on surpassing the 15 psig mark, reinforcing the importance of understanding pressure measurements in boiler operations and classifications.