North American Oil & Gas Pipelines

MAY 2018

North American Oil & Gas Pipelines covers the news shaping the business of oil and gas pipeline construction and maintenance in North America, including pipeline installation methods, integrity management innovations and managerial strategies.

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napipelines.com MAY 2 018 | North American Oil & Gas Pipelines 25 T here are four generally accepted classification levels of a buried pipeline's location; the levels reflect decreasing degrees of accuracy and re- liability. The most accurate, Level A, requires the pipe to be physically exposed, typically via digging, hydro or pneumatic excavation (a process known as "potholing"). Survey teams can then use GNSS or to- tal stations to accurately measure the 3D position of the exposed pipe. 4 Techniques for Level B location include using electromagnetic sen- sors to detect a pipe; the position is marked on the ground using paint or small pin flags that can then be measured by surveyors. Conventional electromagnetic detectors are fast and can reveal a pipe's location hori- zontally but they offer little information on its depth. Additionally, survey- ors must coordinate with the pipeline location crew so that markings can be measured before they fade or are removed. It's not unusual for survey crews to make multiple visits to a site to capture needed information. Level C location is based on visible evidence of underground assets such as manholes, meters, valve covers or utility pedestals. Surveyors can capture accurate location on these features, but the approach pro- vides no data on what is out of sight below ground. Level D locations are based on existing utility plans, as-built drawings or the aforemen- tioned tribal knowledge. While this is a common approach, it's very diffi- cult to assess if the information on older maps is accurate or complete. In particular, data on the depth of a pipeline is subject to question and may be affected by surface changes such as grading, cultivation or paving. The different location classifications provide a striking illustration of the costs associated with accurate information. While Level A offers the best accuracy, the cost to find and measure pipelines is high, especially when seeking pipelines beneath paved surfaces. Level D location data is es- sentially free, but comes with low confidence. Despite the cost and challenges, demand for accurate locations is strong and extends across multiple types of assets. It's opened the door for technological solutions that combine the speed and flexibility of elec- tromagnetic detection with instruments and software for precise position- ing and mapping. Companies are putting the technology to work—and keeping it busy. Four Levels of Accuracy and Cost

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