Is the longitudinal joint considered the strongest part of the boiler?

The longitudinal joint is not considered the strongest part of the boiler primarily because it is a seam where two sections of the cylindrical shell are joined together, typically running the length of the boiler. In most boiler designs, the circumferential joint, which goes around the boiler, is usually stronger. This circumferential joint has structural advantages due to the way pressure loads are distributed across the curvature of the boiler.

Additionally, the construction methods and welding techniques used in making longitudinal joints can introduce weaknesses, such as potential for stress concentration or fatigue over time. These factors contribute to the overall strength and reliability of the boiler under operating conditions.

In summary, while longitudinal joints are crucial for the integrity of a boiler, they do not provide the maximum strength compared to other components, particularly the circumferential joints.