Large diameter thin wall welded pipe has been the problem of the industry, because the ratio of wall thickness to outer diameter is bigger, in the process of forming of thin wall pipe, the edge will form "bulge" and " fold", which affect the quality of HF welding and easy to occur overlap welding, solder skips and lack of welding. After years of our practice and research, this problem has been solved well.

For the φ273*3mm unit provided for Pakistan, trial run was successful, and received favorable comments from users.