What does "Centerline-Stacked" mean in relation to tank construction?

• A. The bottom and top plates are bolted together
• B. The mid-thickness centerlines of plates in all shell courses coincide
• C. Plates are staggered for enhanced strength
• D. Shell plates are welded along the edges

Answer: (B)

The term "Centerline-Stacked" in the context of tank construction refers to the alignment of the mid-thickness centerlines of plates in all shell courses. This design strategy is essential for ensuring that the structural integrity of the tank is maintained. By aligning the centerlines of the shell plates, the forces acting on the tank can be distributed evenly, which aids in minimizing stress concentrations that may lead to structural failures.

This alignment also facilitates proper welding and helps in maintaining consistent wall thickness throughout the tank. Ensuring that the mid-thickness centerlines coincide contributes to a uniform appearance and performance of the shell, which is vital for the tank's long-term reliability in holding liquid products. This practice adheres to the design principles outlined in API 650, promoting safety and efficiency in tank construction.