Subsea 7 invites proposals or technologies from organisations and experts to improve the quality of weld start/stops in Pulsed Gas Metal Arc Welding (PGMAW).
The proposed welding technology (or augmented secondary source) would be able to improve the control of arc stability and weld geometry, thereby reducing the risk of weld flaws at weld starts and stops.
Currently, Pulsed Gas Metal Arc Welding (PGMAW) is utilised to weld pipes together in a multi-pass process. Initiation of the weld starts at the top of the pipe but because of the synergistic nature of the PGMAW, the arc initiation and the filler metal addition cannot be controlled separately. Therefore, following arc initiation, a weld pool is formed prior to the weld torch traversing round the pipe circumference and subsequently a crater is formed as the arc is terminated at the end of the weld pass at the bottom of the pipe. These start/stops require mechanical grinding to a smooth and tapered geometry to enable subsequent weld passes to form the final welded structure. Typically welding is performed using discrete passes of weld metal of about 3mm in height.
The following characteristics should be considered in the final technology offering:
Elimination of grinding
Suitable for fully automatic deployment
Required equipment should be compact and non-intrusive as far as is practical
Should not increase welding time
Key success Criteria
Suitable for carbon steel, clad and Corrosion Resistant Alloy (CRA) metallic materials in wall thicknesses 6-45mm and diameters 150-500mm
Minimal susceptibility to weld flaws in start/stop locations