The MOST important aspect of installing the first course of jacketing on a vertical vessel is that it MUST be

• A. Installed level
• B. Installed plumb
• C. Aligned with seam
• D. Centered on weight

Answer: (A)

The first course sets the horizontal reference for the entire jacket, so it must be level. When this initial wrap is true, every subsequent course stacks neatly at a consistent height around the vessel, keeping seams and edges aligned, and ensuring gaskets, clamps, and flashing fit properly. If that base course isn’t level, later courses will sit unevenly, creating gaps, misaligned joints, and fit problems around flanges or nozzles, which can lead to leaks and weathering failures. Plumbness and seam alignment matter, but they depend on a solid, level starting point to maintain overall geometry and a uniform, durable jacket. Centering on weight isn’t a practical factor in establishing the first course.