The standard 90˚ bends are fitted with sheet angles, have
an inner and outer rounding, and the entire product is braced
by cross-wise ribbing.
The bends are recommended for high air velocity and/or higher
pressure ventilation systems and greater sizes of side b > 400 mm.
The standard radius is r = 120 mm. The standard angle is a = 90˚.
Typical applications of the bends include rerouting the ductwork
by 90˚ with the same clear cross-section.
