How are tank welds categorized in API 650?

• A. By location only
• B. As circumferential or vertical seam welds
• C. By thickness
• D. As primary or secondary welds

Answer: (B)

Tank welds in API 650 are categorized specifically as circumferential or vertical seam welds, reflecting the orientation of the weld relative to the tank's structure. Circumferential welds are those that run around the tank, typically connecting the bottom and side shells or the side shells with other sections, while vertical seam welds run vertically along the height of the tank.

This classification is critical in the design and construction processes, as different types of welds can have varying stresses and performance characteristics. Understanding the distinction between these weld types helps in determining the appropriate methods for inspection, quality control, and ensuring structural integrity throughout the life of the tank.

Other categorization methods, such as by location, thickness, or the designation of primary versus secondary welds, do not fully capture the fundamental differences in weld function and placement that are essential to tank design as outlined in API 650. Thus, the classification into circumferential and vertical seam welds succinctly addresses the significant aspects of welding in tank construction.