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T.D. Williamson's technology assists operator

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World Pipelines,

Due to growing regulation and industry requirements, pipeline operators are redoubling their efforts to mitigate cracks. As a result, demand for inline inspection (ILI) crack tool technology that can detect and size defects, such as environmentally-assisted cracking (EAC) and seam weld anomalies, is also on the rise.

However, identifying the most effective ILI tools and techniques can be challenging. Most options have limitations that keep them from providing a complete picture of anomalies and their potential risks. For example, hydrostatic testing will miss defects below a critical length, depth, and width. In addition, due to it being a one-time pass/fail test, this does not provide information about the type of defects that remain in the pipe and how they may have grown as a result of such testing.

Ultrasonic crack detection (UTCD) is another alternative. However, because it requires a liquid couplant, UTCD cannot be used in natural gas or light-grade liquid pipelines without making significant and costly operational compromises, such as batching, reduced product throughput, and post-inspection line drying of natural gas lines.

Pipeline operators are increasingly turning to electromagnet acoustic transducer (EMAT) technology to overcome the above limitations. Since EMAT technology produces a larger guided acoustic signal into the pipe wall compared to other acoustic techniques, it provides a different approach for detecting and sizing cracks. Merging EMAT data with additional integrity data that is produced by a multiple dataset tool that combines multiple ILI technologies on a single inspection device, provides improved characterisation of detected anomalies.

By running the SpirALL® EMAT tool and the multiple dataset (MDS) platform from global services provider T.D. Williamson (TDW), a pipeline operator in the US was able to address the most critical threats to the pipeline’s integrity and prioritise repairs.

Finding flaws in long seams

Following a long seam failure and release of approximately 5 000 gallons of liquid propane, the operator required a comprehensive seam assessment to identify and prioritise the repair of cracks on its 16 in. low-frequency electric resistance welded (LF-ERW) pipeline. Not only was the inspection necessary to satisfy the company’s own integrity management programme, the operator needed to prove to the Pipeline and Hazardous Materials Safety Administration that the pipeline could operate safely atpre-failure, maximum operating pressure (MOP).

Both internal and regulatory goals were met by deploying the 16 in. SpirALL EMAT tool and MDS platform.

Identifying and prioritising the most critical defects

The SpirALL EMAT technology generated the primary data used to detect and size cracks in the LF-ERW long seam. Results revealed numerous seam anomalies that were confirmed in the field as hook cracks and lack of fusion.

According to Sean Moran, TDW EMAT Product Manager, SpirALL EMAT and MDS technology “advances analysis capabilities by utilising various data collected by multiple technologies to improve the characterisation of cracks.” He continued: “in addition, by leveraging EMAT and MDS, we discover interactive threats that individual technologies are unable to identify.”

Adapted from press release by Anna Nicklin

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