WELDING METHOD FOR PIPELINE INCLUDING CHECK VALVE

To provide a pipeline joining method by which chattering can be prevented, and weld quality can be stabilized.SOLUTION: A method for joining a first pipeline 102a which is a pipeline on an upstream side and a second pipeline 102b which is a pipeline to be introduced to a primary side of a check valve 104 by welding includes: a step at which a branch pipeline 102d for releasing atmospheric pressure is provided on the first pipeline, and opening control means 110 for performing closing or opening control of the branch pipeline is connected to the first pipeline; a step at which end faces of the first pipeline and the second pipeline are abutted against each other; a step at which a pressure of a back shield gas in the first and second pipelines is set to a first pressure higher than a check valve opening pressure, and the check valve is opened so as to replace the interiors of the first and second pipelines with the back shield gas; and a step at which a pressure of the back shield gas in the first and second pipelines is set to a second pressure higher than atmospheric pressure and lower than the check valve opening pressure, and in the state that the check valve is closed, the first pipeline and the second pipeline are welded.SELECTED DRAWING: Figure 2 【課題】チャタリングを防ぎ、溶接品質を安定化できる、配管の接合方法の提供。【解決手段】上流側の配管である第１の配管１０２aと、逆止弁１０４の一次側へ導入する配管である第２の配管１０２ｂとを溶接により接合する方法であって、第１の配管に、大気圧開放する分岐配管１０２ｄを設け、該分岐配管を閉止又は開度調整する開度調節手段１１０を接続するステップと、第１の配管と第２の配管の端面同士を突き当てるステップと、第１と第２の配管内のバックシールドガスの圧力を、逆止弁の開弁圧力より高い第１の圧力に設定し、逆止弁を開いて、第１及び第２の配管内をバックシールドガスで置換するステップと、第１と第２の配管内のバックシールドガスの圧力を、大気圧より高く逆止弁の開弁圧力より低い第２の圧力に設定し、逆止弁を閉じた状態で、第１の配管と第２の配管とを溶接するステップと、を含む。【選択図】図２