Internal pressure in a pipe generates the highest stresses along which weld orientation?

Internal pressure in a pipe generates the highest stresses along which weld orientation?

• A. Longitudinal weld
• B. Circumferential weld
• C. Fillet weld
• D. Butt weld

Answer: (A)

Internal pressure pulls the pipe wall in two principal directions: around the circumference (hoop stress) and along the length (axial or longitudinal stress). The hoop stress is the larger of the two, so the shell is most strongly stressed in the circumferential direction. When you look at weld orientation, the way the weld plane is cut relative to those stress directions matters. A longitudinal weld runs along the length of the pipe, so the hoop-induced tension tends to act in a way that concentrates stress at the weld throat along that seam, producing higher effective stress there. A circumferential weld, whose plane encircles the pipe, tends to carry load more by axial tension distribution around the circumference, where the stress is not as concentrated in a single weld location. Therefore, the longitudinal weld is the orientation that experiences the highest stresses under internal pressure.

Internal pressure pulls the pipe wall in two principal directions: around the circumference (hoop stress) and along the length (axial or longitudinal stress). The hoop stress is the larger of the two, so the shell is most strongly stressed in the circumferential direction. When you look at weld orientation, the way the weld plane is cut relative to those stress directions matters. A longitudinal weld runs along the length of the pipe, so the hoop-induced tension tends to act in a way that concentrates stress at the weld throat along that seam, producing higher effective stress there. A circumferential weld, whose plane encircles the pipe, tends to carry load more by axial tension distribution around the circumference, where the stress is not as concentrated in a single weld location. Therefore, the longitudinal weld is the orientation that experiences the highest stresses under internal pressure.