US Duct provides duct with flanges (also called angle rings or angle flanges) in black iron, galvanized, or stainless steel (SS) and with or without holes. The duct to which these flanges are attached is available in sizes 3" and up, and also in black iron, galvanized or SS. Construction methods range from laser welded pipe and mechanically lock elbows in lighter gauges to fully welded product in heavy gauge (even up to 1/4")—all depending upon the application.
This refers to a technique whereby a flange is used to mate 90-degree lips turned onto the pipe or duct component. In this method the flange is placed onto the pipe, the lip turned back and the flange left loose. Typically, the lip is ½” tall (or wide depending on your perspective) when the flanges are pulled together, the VanStoned lips of the pieces that are being connected, are pressed together to make a secure metal to metal connection. Because the flanges are loose on all pieces, alignment of the center-line of the components is easily accomplished. Standard Vanstone pipe lengths are a nominal 59”.
Welded flange refers to flanges that are welded to the duct. The faces of the flanges are the mating surface, as opposed to the Vanstone where the duct lips are mating. Full welded duct flanges have a continuous weld. Intermittently welded duct flanges mean that there is a weld at intervals around the duct. Standard welded flange pipe lengths are a nominal 60”.
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When aligning components with welded flanges, positioning against the centerline is important. Because the flanges are welded to the duct and cannot be 'rolled' it is important that the flanges be aligned to the centerline of the fittings and will, therefore, all lineup. There are two options for this alignment:
Either is acceptable and is a matter of choice (OR MORE IMPORTANTLY) to the existing duct where present.
When field fitting flange duct, and in the case of Vanstone flanges where the flange is left loose, the pipe is typically cut ½” longer than needed and then a ½” lip is hammered back at 90 degrees to the pipe by using the flange as an anvil. This is best accomplished by using deep throat vice-grips to hold the flange squarely on the pipe and far enough back to create the desired lip. In the case of welded flanges, the pipe is cut to length and then the flange welded in place. (Remember to line up the flange with the centerline.)
For ducting applications that require duct dimensions that are less than 20” in diameter, consider US Duct’s leak-free US Tubing option. US Tubing combines the best of flange and gasket connections with the convenience of a clamp together connection system.