Which joint type is the strongest in a boiler?

The longitudinal joint is considered the strongest joint type in a boiler due to its design and the manner in which it bears load. This joint runs parallel to the length of the boiler and provides continuous strength along the vessel. The pressure exerted within the boiler tends to run along its length; thus, a longitudinal joint is strategically positioned to handle these stresses more effectively than other joint types.

Lap joints, while useful in certain applications, tend to have weaker load-bearing capacity because they involve overlapping pieces of material. Butt joints, although generally strong, are sometimes less effective in high-pressure environments without additional reinforcement. In contrast, the continuous nature of longitudinal joints provides extensive coverage along the pressure axis, making them particularly suitable for maintaining the structural integrity and safety of the boiler under operational conditions.