What is the maximum angle for a field fabricated double cut mitred offset as per SMACNA standards?

The maximum angle for a field fabricated double cut mitred offset, according to SMACNA (Sheet Metal and Air Conditioning Contractors' National Association) standards, is 30 degrees. This specification is in place to ensure that the offset can be made while maintaining structural integrity and ensuring good airflow in ductwork systems.

Mitred offsets are used to create smooth transitions in duct systems, and establishing a maximum angle helps prevent excessive turbulence, which can hinder the efficiency of the HVAC system. A 30-degree offset strikes a balance between creating effective ductwork transitions and maintaining the ability to fabricate and install these transitions in the field without excessive complexity.

Field fabrication poses unique challenges, and adhering to established guidelines helps ensure that the workmanship aligns with industry standards, facilitating proper installation and optimal system performance.