Abstract
A major cost contributor of P91 pipe welding is the vital requirement of ensuring proper protection of the root or first pass of the weld from oxidation through the use of an inert gas blanket, i.e. backing gas. The necessity for oxidation protection negatively impacts the cost of both weld set-up and the actual welding process of P91 pipe fabrication. In an effort to decrease the associated costs of welding P91, Fluor Corporation has invested in significant research and extensive field-testing to develop the wire/gas mixture that contributes to the breakthrough in welding P91 with “No Backing Gas (NBG)”. Combining this novel technique with the semiautomatic GMAW-S (using inverter technology with a controlled transfer) eliminates all cost associated with the need to provide a backing gas, including installation of purge dams, backing gas, and man-hours associated with implementing these activities.
