girthweld
A circumferential weld that joins two cylindrical sections, such as pipes or pressure vessels, by welding around their perimeter. Girth welds are commonly used in pipeline construction.
girthweld: the ring that holds two pipes together
A girth weld is a circumferential weld that runs around the full perimeter where two cylindrical sections meet, joining them into a single continuous structure. In pipelines, it connects pipe spools end-to-end. In pressure vessels, storage tanks, and boilers, it seals the joint between shell courses or between the shell and end caps. The weld must achieve complete fusion around the entire circumference while meeting code requirements for strength, soundness, and leak-tightness.
Girth welds are typically made using either manual gas tungsten arc welding (GTAW), shielded metal arc welding (SMAW), or flux-core arc welding (FCAW), depending on wall thickness, material grade, and position. On large diameter pipes or vessels, the work is rotated slowly in the vertical or horizontal axis (sometimes called "rolling" the joint) to keep the weld in the optimal flat or downhill position, which improves bead quality and penetration. Fixed or non-rotated joints are completed in multiple passes, often requiring the welder to climb around the circumference several times as the weld builds from root pass to fill and cap passes.
The geometry and accessibility of girth welds create predictable defect patterns. Incomplete fusion and lack of penetration at the root pass are common when the gap between pipe ends is too large or too small. Porosity and lack of fusion in fill passes occur with contamination, incorrect shielding gas, or excessive travel speed. Because the entire weld must be continuous and uniform, defects discovered during radiography or ultrasonic inspection often require gouging out the affected section and rewelding, adding time and cost.
The term "girth" refers to circumference or the measurement around an object. Unlike a longitudinal seam weld that runs along the length of a pipe, a girth weld encircles it. In pipeline terminology, girth welds are sometimes called "circumferential welds" or simply "girth" when context is clear.
Girth weld quality is critical because the joint is under continuous hoop stress from internal pressure. Pipeline codes such as ASME B31.8 (gas) and B31.4 (liquid) mandate minimum shear area, minimum strength matching the pipe material, and post-weld heat treatment (PWHT) for many carbon steel and alloy steel applications. Pressure vessel codes (ASME Section VIII) impose similar or more stringent requirements. Acceptance criteria include visual inspection, dimensional measurement, radiographic or ultrasonic examination, and mechanical testing on test coupons welded under identical conditions.