What is a cross break in rectangular ductwork?

What is a cross break in rectangular ductwork?

• A. A turning vane used in straight ductwork
• B. A sealant used at duct joints
• C. An angle on all sides of a rectangular duct to increase rigidity and reduce vibration
• D. A dampers mechanism for balancing airflow

Answer: (C)

Cross breaks stiffen rectangular duct panels by adding angled folds along each edge. This creates a ribbed, box-like cross-section that increases the panel’s rigidity without needing extra material. The added stiffness helps the duct resist buckling and reduces vibration and noise as air moves through, especially over long spans or under higher pressures. It keeps the interior surface smooth and minimizes oil-canning that can occur when the duct flexes. This feature is about strengthening the duct, not about directing airflow, sealing joints, or balancing airflow.

Cross breaks stiffen rectangular duct panels by adding angled folds along each edge. This creates a ribbed, box-like cross-section that increases the panel’s rigidity without needing extra material. The added stiffness helps the duct resist buckling and reduces vibration and noise as air moves through, especially over long spans or under higher pressures. It keeps the interior surface smooth and minimizes oil-canning that can occur when the duct flexes. This feature is about strengthening the duct, not about directing airflow, sealing joints, or balancing airflow.