Gaining a Granular View of Girth Welds with In-line Inspection

Metal loss occurring at girth welds can be difficult to characterize. Knowing the difference between weld signatures is paramount to characterizing anomalies and determining urgency for repair. The ENTEGRA^® True Ultra-High Resolution In-Line Inspection system reveals girth weld anomalies in impressive detail. In the cases described below, detailed True UHR ILI findings corresponded very closely with field examinations, showing that True UHR ILI can help improve understanding of girth weld anomalies and lend greater confidence in conclusions drawn from ENTEGRA data analysis.

Understanding weld signatures

Figure 1 provides a quick comparison of how different girth weld issues may appear in an ILI data visualization. A sound weld (left) will appear as a relatively continuous line. When there is something interfering with the weld, ILI visualization will indicate volumetric loss along the thickness of the weld, which appears as a break in the weld bead (center). If that volumetric loss is contained to the weld only, this is likely a construction-related anomaly, as it does not extend into the body wall thickness of the pipe itself. A corrosion-related signature — which may be internal or external — will indicate a greater volumetric loss over a longitudinal distance extending beyond the bounds of the weld bead.

Figure 1

Figure 1: Comparing Weld Signatures

The data on the left shows a sound girth weld with a continuous weld bead around the full circumference. In the center, the data reveals a disruption in the weld bead path, but the volumetric loss does not extend longitudinal outside the weld bead limits, indicating a construction-related anomaly. The data on the right shows volumetric loss that is present within the weld bead but also extends longitudinally outside of girth weld into the body wall thickness, this is indicative of a corrosion type metal loss feature.

A closer look at corrosion metal loss

The ENTEGRA True UHR ILI system provides an unprecedented level of detail for visualizing girth weld issues. This is accomplished through a combination of robust data gathering with our proprietary ILI tools and expert, human-led data analysis. In the example described here, we encountered a line with multiple areas of metal loss that required in-depth characterization.

The first area analyzed (Figure 2) involved external metal loss, but True UHR ILI further revealed important pinhole features. The ENTEGRA analysis indicated corrosion extending into the body of the pipe with a predicted pinhole depth of 50%. Field inspection closely matched the prediction, determining a loss of 58%.

Figure 2

Figure 2: External Metal Loss – Pinhole at Girth Weld

Caption: The True UHR ILI system revealed pinhole features within this external metal loss. Predicted at 50%, the actual depth was 58%.

Another location on this same line showed a longitudinal area of metal loss. True UHR ILI analysis indicated a thicker area of metal loss on one side of the weld, which was confirmed by field inspection. ENTEGRA analysis predicted a 50% depth of corrosion, and the field measurement confirmed it at 42%.

Figure 3

Figure 3: External Metal Loss at Girth Weld

Caption: Another location on the same pipeline featured a longitudinal area of metal loss with 50% depth of corrosion. The True UHR ILI imaging revealed a thicker area of loss on one side of the weld, which was confirmed by field inspection.

A closer look at construction-related metal loss

ENTEGRA True UHR ILI is capable of revealing just as much detail about construction-related girth weld anomalies.

In this example, we used different data visualizations to fully characterize a construction-related issue. In Figure 4, the girth weld is visualized top-town (top image) and from the side (bottom image). These views are compared with an X-ray of the weld, pictured in the center. In ILI data visualization, the blue coloration indicates a healthy weld. Red areas correspond with valleys seen in the side-view of the weld and the black spots appearing in the X-ray. In the X-ray, white areas indicate volumetric gain — areas of slag or excess material around the weld. These correspond with peaks seen in the side view. Across all three types of visualization, findings are consistent. Further analysis revealed that the red coloration/valleys/black voids seen in each image respectively were areas of volumetric metal loss in the pipe itself. This finding was confirmed by field examination.

Figure 4

Figure 4: Internal Weld Bead with Volumetric Loss

Caption: A bird’s-eye view (top) and side view (bottom) of a girth weld. Blue coloration indicates a healthy girth weld. The red coloration (top) and dips (bottom) indicate volumetric loss. The deepest valleys and reddest areas correspond to dark spots seen in an X-ray of the weld (center), which are volumetric drops in pipe material.

The value of such a detailed view is really brought to life in one final example. As in the previous example, Figure 5 shows a bird’s-eye view (top) and side view (bottom) of a girth weld captured with the True UHR ILI system. Analysis identified a section of interest, circled. Figure 6 shows the section of pipe that was removed for further inspection, revealing a small weld flaw, with a 3.7 mm (0.145”) opening and 30% loss, relative to the weld bead thickness.

Figure 5

Figure 5: Internal Weld Bead with Volumetric Loss

Figure 6

Figure 6: Pipe View of Internal Weld Bead with Volumetric Loss

Caption: Top and side views of a girth weld indicated a small area for further investigation (Figure 5, circled). Inspection revealed a girth weld flaw with a 3 mm (0.145”) opening and 30% loss (Figure 6), demonstrating the incredible level of visualization detail possible with True UHR ILI.

You can’t put your eyes on every girth weld in your pipeline, but the ENTEGRA True UHR ILI system may be the next best thing. With True UHR ILI, you can have a clear picture of girth weld health without costly digs.