The TesTex developed automated scanning rig known as the Line-Cat is based on the principles of the Low Frequency Electromagnetic Technique (LFET). It was designed to quickly and accurately scan piping of 3” or greater diameter. This inspection is performed from the pipe O.D. (outer diameter).

Side view of Line-Cat rig showing different diameter configurations

About the Line-Cat
A remote controlled magnetic wheeled crawler is used to propel the Line-Cat system making it capable of traveling up to 10 feet per minute. It has a contoured top shell that supports and stabilizes the main sensor array. The sensor array itself, is made up many scanning pods that contour to the actual geometry of the pipe via a flexible coupling system. The system is sufficiently designed to travel around bends and over welds. All components of the Line-Cat are designed to withstand Arctic conditions down to -40° Fahrenheit. In addition, the Line-Cat is shippable via overnight carriers.

16 channel waveform from Line-Cat revealing flaws in pipeline

LFET vs. EMAT and A.U.T.
The Line-Cat system was field tested on sections of two insulated crude transit pipelines on the North Slope of Alaska, during the fall of 2006. The insulation was removed from both pipelines. One of the pipelines was found to have anti-corrosion tape, while the other was bare. These sections were tested with the Electromagnetic Acoustic Transducer technique (EMAT) and Automated Ultrasonic Thickness (A.U.T.) as well as LFET. Although A.U.T was able to give actual thickness readings, it had a very slow scan rate. EMAT displayed scan rates faster than the A.U.T., but the LFET was by far the most productive. Both EMAT and LFET demonstrated a 100% POD (probability of detection) for 25% wall loss isolated pitting at a 3:1 aspect ratio. EMAT displayed a reduction in the scan rate over the tape-covered section, from 1000 ft per day on uncoated piping to 500 ft per day on tape-coated piping. The scan rate of LFET remained unchanged over the tape-coated piping (approximately 10 ft per minute). Also, LFET has a false positive overcall rate of less than 1%. The results of the field test were such that the Line-Cat’s LFET Technique was the only method that could work efficiently through the tape coating and had the highest overall productivity for the job. The results of the field test can be seen in the linked article written by Mr. John J. Nyholt of BP Americas.

Click to read the TNT Article featuring the Line-Cat