Tubed elbow are constructed from non-seamed tubing that is mechanically bent. The elbows are available in 90, 60, 45 or 30 degrees, in 16,14 or 11 gauge. Tubed duct elbows are either made of galvanized or stainless steel, however, the stainless steel options only come in sizes 3”-6”.
US Duct tubed elbows are generally considered in applications for oil mist because they have no seam. Additionally, they are widely used in paper trim applications for the same reason.
The ends can be fitted with a rolled-lipped collar or an angle ring flange.
Because the segment geometry controls the final geometry, these elbows are available in any degree and any radius*.
*Radius means the height of the elbow and is a direct reference to the length of sweep — an important factor when considering the impact of air flow, static pressure and wear. Typical radii are 1xD (short radius), 1.5xD (Standard Radius) and 2.5xD (Long Radius). A 1.5xD radius means that a 4" dia. elbow has a 6" (1.5x4) radius. Another way to think of this is to set a 90 degree elbow on the floor and measure from the floor to the centerline of the elbow. (Be sure to subtract any straight portion of the elbow.) Divide this height by the diameter and you have the radius.