Flange system is one of the two ways to produce flange connector. Low cost, sealed well, easy to
install. So, it is a good choice to make the ventilation ducts for small cross-sectional area. The
TDF flange ventilation ducts can be largely produced by the factory. It is a high efficient design. If
with the Pittsburgh Lock Machine, Notching Machine, Grooving machine, there would be a fully
automatic product line. And all of the machine can be sent to the place where need the flange
ventilation ducts. Then, it will be convenient for the user.