Stress Concentration Tomography Services (SCT) PART 2: DID YOU KNOW?

Posted on
July 9, 2019 by

Stress Concentration Tomography Services (SCT) PART 2: DID YOU KNOW?

There are over 3 million miles of unpiggable pipelines worldwide. Monitoring the integrity of these ageing ferromagnetic pipelines poses a significant problem for pipeline operators. The costs of converting the pipeline for In-Line Inspection (ILI), considered to be the gold standard of pipeline inspection, are very high and in many cases this conversion process is not possible due to physical limitations of the pipeline. The alternative for integrity managers is to apply one or more of the inspection methods used in the External Corrosion Direct Assessment (ECDA) process. However, the ECDA process is lengthier than Pipeline Internal Gauge (PIG) inspection, is often more expensive when excavations are costed into the total price, faces more technical limitations and delivers less in-depth information on the pipeline wall condition than does an ILI inspection.

Developed by Speir Hunter Ltd. in collaboration with the University of Leeds, SCT™ is
a screening tool that can be deployed with ILI and ECDA processes to optimise the accuracy of results and to dramatically reduce inspection costs. It is considered by some well respected engineers in the industry to potentially offer a comprehensive solution for the inspection of unpiggable pipelines thereby eliminating the incentive to convert an unpiggable line for ILI inspection as well as to completely replace the ECDA process. This is why such notable figures have described SCT™ as a potential ‘game changing technology.’

SCT™ is a truly original method of non-contact inspection that assesses the integrity of a pipeline’s wall condition through the analysis of remotely collected magnetic data. SCT™ is non-invasive: the inspection does not require a change in any of the operating parameters of the pipeline such as pressure or flow rates. Furthermore, there is no need to place sensors on the pipeline to amplify the magnetic field or to conduct an excavation after inspection to calibrate results. The pipeline remains in its normal operating condition throughout the SCT™ inspection process.

During SCT™ inspection, the field operator walks directly above the pipeline carrying an array of sensitive magnetometers that remotely collects the pipeline’s natural magnetic field data down to nano-tesla level. Survey-grade GNSS equipment tracks the movement of the operator stamping cm accurate locational positioning information on the magnetic data 40 times a second as it is collected in real-time. This data is then downloaded into software that analyses the magnetic signatures detecting and quantifying all areas of abnormal localized stress in the pipeline wall.

SCT™ detects and estimates the stress caused by all types of metallurgical and mechanical defects (including Stress Corrosion Cracking (SCC) and weld defects) in the pipeline wall, irrespective of clock position and whether or not the defect is internal or external to the pipe. It is also the only inspection technology in the world that can concurrently identify the stress-levels of defects in a pipe whilst simultaneously mapping the pipeline’s depth of burial and lateral position. SCT™’s 3D Mapping feature provides the lateral position and depth of cover of the pipeline to sub-meter accuracy. This information can be used to detect geotechnical hazards, such as underground earth movement, before they cause pipeline failure and to identify segments of the pipeline where soil erosion has led to a dangerously shallow depth of cover.

SCT™’s deliverables also anticipate future regulatory demands on pipeline integrity management. For example, it can be used to detect the location of casings, changes in wall thickness and diameter and wrinkle bends. Stuck PIGs and illegal hot tapping can also be reported and all these aforementioned characteristics can be delivered from a single survey using the same data.


3-D Line Locating Ltd is a privately owned Buried Pipeline and Utility Locating, Hydrovac Services and Ground Disturbance Management company. For over 20 years, we have been at the forefront of the Damage Prevention industry in Western Canada. Although the industry has changed significantly over the last 20 years, we have been very fortunate to have been at the leading edge of the evolution and still maintain the highest levels of quality, accuracy, consistency and customer satisfaction in our industry.

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