For pressure vessel shell plates, the rolling direction is usually which?

• A. Around the circumference
• B. Diagon al to the length
• C. Along the length
• D. In the least favourable direction

Answer: (A)

The rolling direction is chosen so that the plate’s direction of grain flow, created by the mill’s rolling, aligns with the direction that carries the main stresses in the shell. For a pressurized vessel, the hoop (circumferential) stress is the largest, so placing the rolling direction around the circumference makes the material’s strongest/most ductile orientation align with the hoop load. This improves resistance to hoop loading and aids forming into a circular shell, while keeping the weld seam along the axis where properties are well-suited for welding. If the rolling direction were along the length or diagonal to it, the material would be less optimized for the dominant circumferential stresses. The least favourable orientation is avoided.