Why do we preset the 2G?

Why do we preset the 2G?

• A. To offset distortion caused by multiple stringer beads.
• B. To offset distortion caused by single stringer beads.
• C. To offset distortion caused by heat input variations.
• D. To offset distortion caused by misalignment of joints.

Answer: (A)

When welding a horizontal pipe weld in multiple passes, heat causes expansion and, as the metal cools, shrinkage. Each stringer bead adds its own shrinkage, and the effects accumulate, tending to pull the joint out of true alignment. Presetting the joint means adjusting the parts in the opposite direction before welding so that, after all the heat cycles and multiple passes finish, the joint relaxes into the correct position. This pre-emptive correction specifically targets the distortion that comes from the cumulative shrinkage of several passes, which is why it’s the appropriate reason for presetting in a 2G weld. It’s not mainly about distortion from a single bead, heat input variations alone, or misalignment from poor fit-up, though those factors are addressed separately.

When welding a horizontal pipe weld in multiple passes, heat causes expansion and, as the metal cools, shrinkage. Each stringer bead adds its own shrinkage, and the effects accumulate, tending to pull the joint out of true alignment. Presetting the joint means adjusting the parts in the opposite direction before welding so that, after all the heat cycles and multiple passes finish, the joint relaxes into the correct position. This pre-emptive correction specifically targets the distortion that comes from the cumulative shrinkage of several passes, which is why it’s the appropriate reason for presetting in a 2G weld. It’s not mainly about distortion from a single bead, heat input variations alone, or misalignment from poor fit-up, though those factors are addressed separately.