American Society of Mechanical Engineers (ASME) Practice Exam 2025 - Free ASME Practice Questions and Study Guide

The component regarded as the weakest part of a fire tube boiler is typically the flat surface supported by stays. This is because the flat surfaces of a fire tube boiler, such as those in the firebox or where the tubes are located, experience significant stress due to pressure and thermal expansions. These surfaces are supported by stays, which are elements that help maintain the integrity of the structure but can become weak if they corrode over time or if improper loads are applied.

Additionally, flat surfaces are less resistant to bending stress compared to cylindrical surfaces found in other components like the steam/water drum. The design and operating conditions place considerable strain on these flat surfaces, making them susceptible to failure under extreme conditions. Therefore, this characteristic renders them the weakest link in the overall system of a fire tube boiler.

In contrast, the steam/water drum is designed to withstand high pressure and typically incorporates stronger materials. The water column is specifically engineered for stability and monitoring water levels, and safety valves are built to release pressure safely to prevent system failure. Consequently, none of these components face the same types of potential weaknesses as the flat surface supported by stays.