The easiest way to buy Nordfab flanged ducting systems. Ducting USA is a leading Nordfab flanged ducting distributor. We don't just sell this stuff, we install it. So, we can help guide you to find the flanged ducting system you need. Flanged ducting refers to a technique where flanges are placed onto the pipe, with the lip turned back at 90 degrees and left loose for a secure metal-to-metal connection when the flanges are pulled together and the ducting lips are connected.