Duct processing is divided into two kinds:

1、  ordinary angle steel welding flange: angle steel cutting must ensure  that the flange size is a positive deviation, followed by flange welding  shall not have slag, pores, bite, etc., flange side length, diagonal  size, flatness Must meet the design requirements (see GB50243-2002); flange hole must ensure passability.

2、  cutting flange: cutting flange in addition to meet the above  requirements, should pay attention to the flange at the silicone seal at  the plug.