Rolled Carbon Steel Prepunched Angle Iron Rings are used in joining duct work together. Conklin stocks diameters ranging from 3″ to 59″ manufactured by Midwest Metal Products. Larger sizes as well as Galvanized, Aluminum and Stainless Steel Rings are also available with very short lead times.
Many Fab Shops Use Angle Iron Rings with Vanstone Flanges
The Vanstone Flange is when you turn a 90-Degree Flange on the end of the Pipe. The Angle Iron Ring (Angle Iron Flange) slides over the Pipe and down to the Flange which then keeps it from falling off. Two Angle Iron Rings are bolted together to the each other making a connection. The alternative option would be welding the ends for the connection—much more costly and the access to get inside the pipe once installed would not be available.
These flanges are formed with Power Rotary Machine such as the Empire or Tennsmith Power Rotary Machine.