Unlike the 1-stage online process, where the preformed spiral pipe is directly finish-welded, the 2-stage process separates forming and finish-welding. In the first stage, the pipe is formed and continually tack-welded at high speed. In the second stage, the pipe is finish-welded using submerged-arc welding technology. There are two key advantages of 2-stage spiral pipe welding machines in comparison to the 1-stage online process: improved quality and higher productivity.