Flanges can be loose (vanstoned) or welded to the pipe/components depending on your needs!
Duct provides duct with flanges (angle rings) in black iron, galvanized or SS and with or without holes. The duct to which these flanges are attached it available in sizes 3" and up, and also in black iron, galvanized or SS. Construction methods range from lock seamed pipe and mechanically lock elbows in lighter gauges to a fully welded product in heavy gauges (even up to 1/4") - all depending upon the requirements of your application.
