As per ASME section I and section IV, a steam boiler operating at a pressure of ______ or higher is considered a Power Boiler.

The correct answer reflects the distinction made by the ASME regarding the classification of steam boilers. According to ASME Section I, a steam boiler operating at a pressure of 15 psi gauge (which equates to 103.1 kPa) or higher is classified as a Power Boiler. This classification is significant as Power Boilers are subject to different regulations, design considerations, and safety standards compared to low-pressure boilers.

When a boiler operates at or above this pressure, its potential to produce significant amounts of steam energy necessitates more stringent safety protocols to ensure safe operation and prevent failures that could lead to hazardous situations. This pressure threshold helps to define the scope of the ASME's standards, which are aimed at ensuring the safety and efficiency of such high-pressure boilers in operation.

While understanding the chosen answer, one realizes that pressures below 15 psi would categorize the boiler differently and often under less stringent regulations. This distinction helps professionals in the field understand the operational limits and the associated responsibilities when working with various types of boilers. Therefore, the classification as a Power Boiler at or above 15 psig is critical in the context of safety, engineering design, and regulatory compliance in steam boiler operations.