Flange overlap should be placed at what distance relative to insulation thickness?

• A. Half the thickness
• B. Twice the thickness
• C. Same as thickness
• D. Three times thickness

Answer: (B)

The distance for flange overlap is chosen to keep a continuous thermal barrier across the joint. You want enough insulation to cover the flange faces and bolt area even after the joint is bolted and any compression occurs. Placing the overlap at twice the insulation thickness provides that coverage on both sides of the flange, helps compensate for material compression during assembly, and minimizes heat loss or cold-bridging at the joint. If the overlap were only equal to or less than the thickness, gaps around the bolt area could form. An overlap of three times thickness isn’t necessary and would waste material, whereas twice the thickness strikes a practical balance.