The question I have posed for today's blog is are girth welds needed in composites? I need to start by defining girth welds as type of weld that is used to make a perfect sealing of a joint after several passes. The first weld pass which the welder performs is called a root pass, and this is done at a difficult speed as it is see as the most difficult pass. Next is the hot pass, which is seen as when you fill the thickness of the weld. The third process is the cap pass, which is done to complete the process of the welding by covering the joint.Composite materials are not like steel, as such they do not require welding, as they are manufactured in a different process. As for the selection of the welding process, it starts with the mode of application:
1. Manual arc welding – gas tungsten arc welding & shielded metal arc welding
2. Semi-automatic arc welding – gas metal arc welding, flux-cored arc welding & submerged arc welding
3. Mechanized arc welding
4. Automatic arc welding – forge welding (friction welding & flash-butt welding), laser-beam welding
The mode of welding or the standards set for girth welds are determined by:
1. The method of pipe manufacturing process;
2. The length of the pipeline/cost;
3. The joint strength of the pipes which depends on the base material;
4. The pipe wall thickness;
5. The pipe diameter;
6. The joint strength based on the external conditions;
7. The workmanship of the welder;
8. The environmental factors;
9. The terrain in focus.
For pipes, there is DNV-RP-F118 standard that is used for the qualification and verification of pipe girth welds. For composites, you need to look at the manufacturing process.
