First, the production method:

Then the diameter of the size, the number of knots, the radius of curvature of the data to carry out each section of the expansion, and then relatively re-welded web.

Second, the brief introduction of ventilation pipe:

The vent pipe is hollow for the pipe duct duct, mostly round or square. Ventilation pipe production and installation of the plate, profiles and other major finished materials, should be consistent with the design and related products, the current national standards, and application of factory inspection certificate, the material approach should be based on the current national standards for acceptance. Ventilation ducts are generally: marine ventilation pipe with positive pressure ventilation pipe and negative pressure ventilation pipe and PE film ventilation pipe.