If the insulation thickness is 1 inch, what should the flange overlap distance be?

• A. 1 inch
• B. 3/4 inch
• C. 2 inches
• D. 4 inches

Answer: (C)

The key idea is that insulation around a pipe joint with a flange must extend over the flange face enough to keep the thermal barrier continuous and cover the bolt area. The flange sits on top of the pipe insulation, and without a sufficient overlap, heat can escape through the exposed flange edge or around bolt holes. The overlap distance is chosen to provide enough material to wrap over the flange and seat against the surrounding insulation, without being so large that it interferes with hardware. For one inch of insulation, this overlap should be about twice the thickness, which is two inches. This amount ensures full coverage of the flange area and maintains the insulation’s effectiveness. Using a smaller overlap leaves gaps and reduces insulation performance, while a much larger overlap adds unnecessary bulk and could complicate installation.