Case Study

Long-Seam Pipeline Crack Inspection in Liquid Propane

The Challenge

A North American operator required an inspection of a liquid propane line critical to the company’s business. Liquid propane is an extremely difficult environment for conventional ultrasonic inline inspection (ILI) methods. The medium’s volatility can cause variations in sound velocity from 1,520 mph (680 m/s) to as high as 2,235 mph (1000 m/s), depending on pipeline pressure and temperature. This large swing degrades the accuracy of ordinary tools and can render them ineffective. The pipeline’s nominal 6" ID and thin walls were further constraints. 

The Solution

After careful evaluation of its options for inspecting the 61.78 mile line, the operator chose NDT Global’s Evo Series 1.0 UC ultrasonic crack inspection tool. This tool offers unsurpassed axial resolution of 1.5 mm (0.06 in), and circumferential resolution of 7 mm (0.27 in). The tool detects and sizes cracks and crack-like features using industry-leading ultrasonic technology. Ultrasonic crack inspection enables early detection and sizing of irregularities. This allows the pipeline operator to take appropriate measures to avoid pipeline failures caused by cracks. Purpose-made configurations detect axial and circumferential cracks, with an option to perform combined metal-loss and crack detection. EVO tool capabilities also include crack-depth profiling, for accurate assessment, and absolute depth sizing. NDT Global applied its deep knowledge base and extensive experience with liquid propane lines to identify the necessary angle of inspection required to conduct an accurate, ultrasonic ILI run in this challenging medium. 

The Results

High-accuracy NDT Global inline inspection revealed hundreds of crack-like anomalies requiring operator attention. Most of these were lack-of-fusion defects typical in long-seam ERW pipe. Nearly 100 dents were also reported. All of the reported crack-like and crack-field features were calculated in absolute depths. Inspection accuracy was confirmed by the unity plot, which showed a 97% correlation of field investigation and inspection results. 

NDT Global provided the operator with a comprehensive, on-time, post-inspection Pipeline Integrity Assessment that included a detailed, in-depth analysis of data collected from the ILI run, as well as insights to pipeline condition, repair, and maintenance. Proven, proprietary algorithms maximized data accuracy.

Close correlation of field investigation and inspection results, along with insights from NDT Global, enabled the operator to design and implement a more aggressively proactive pipeline integrity management program. This inspection enabled the operator to substantially reduce ongoing operational risk. 

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