A miniature boiler has an inner diameter (ID) of shell of up to how many inches?

The definition of a miniature boiler is specifically tied to its physical size, particularly the inner diameter of the shell. A miniature boiler is classified as a boiler with an inner diameter of the shell not exceeding 16 inches. This classification is essential because miniature boilers are subject to different regulations and safety standards compared to larger boilers.

Understanding this regulation helps clarify that the correct answer aligns with the established criteria within the industry. The size limitation is designed to ensure proper design, safety, and operational performance specific to smaller boilers, which often serve different applications than larger units.

The option indicating 16 inches is, therefore, accurate as it reflects the maximum permissible diameter within the definition of a miniature boiler. Understanding the classification of boilers based on diameter is vital for professionals in the field to ensure compliance with safety codes and regulations.