What is the significance of a steam boiler's design pressure?

The steam boiler's design pressure is vital as it represents the maximum pressure at which the boiler is designed to operate safely. This design pressure ensures that the structural components of the boiler can withstand the internal pressures without risking failure or catastrophic incidents.

Operating a boiler above its design pressure can lead to excessive stress on the materials, potentially resulting in leaks, ruptures, or explosions. Therefore, understanding this maximum pressure is crucial for safe operation and compliance with safety regulations.

While other factors in the options might be relevant to boiler operation or performance—such as minimum operating pressures, fuel types, or energy efficiency—the design pressure fundamentally outlines the safe operational limits of the boiler, making option B the accurate choice.