lt is generally accepted that high-pressure steel pipelines provide the safest and most economical means to transport large quantities of crude oil, products and natural gas. Thus, several millions of kilometers of high-pressure liquid and gas pipelines have been installed all over the world and the infrastructure is growing every year. However, just like any other technical component, pipelines age and can deteriorate. As a result, flaws can appear in the pipe wall and, it undetected, grow until the pipeline fails. These flaws must therefore be identified before they endanger the integrity of the line. Safety as well as the need to protect the asset is of paramount importance. Pipelines are not easily accessible. Onshore pipelines are usually buried underground, offshore pipelines under water. Special testing equipment had to be engineered. This paper will provide a short overview regarding the physical principles applied and the technologies available in order to inspect pipelines by in-line inspection tools. These devices, also termed intelligent pigs, can survey the entire area of the pipeline they inspect in a single run. Pipeline lengths of up to several hundred kilometers can be covered. Depending on the type of tool used, they will detect, size and locate flaws in the pipe steel, such as metal loss, geometric anomalies or cracks. There are also tools available that survey the pipeline route, providing data on the pipeline coordinates and possible pipeline movement. Recently, the issue of detecting stress corrosion cracks in line pipe has grown in importance. The tools are pumped through the line and do not require their own drive. The data collected during a survey is critical input for integrity assessment and fitness-for-purpose procedures relating to the pipeline section inspected. Baseline surveys are often performed after construction of a pipeline as part of the quality assessment procedures and in order to obtain data for later comparison. The paper will also introduce the latest generation of high-resolution ultrasonic inspection tools designed for metal loss and crack detection as well as sizing. These intelligent pigs inspect both the volume or body of the pipe and the heat-affected zone. State-of-the-art technology allows these tools to inspect at greater speed, cover longer sections of pipe than earlier generations. lmproved data handling and optimized software design ensure shorter reporting times. Ultrasonic tools are characterized by their ability to provide quantitative data. They incorporate an unsurpassed level of sensitivity and accuracy of measurement compared to other technologies applied in the field of pipeline inspection. The paper will cover the non-destructive testing principles applied and introduce the components of the inspection tool. Tool and defect specifications will be introduced and explained, as well as the data analysis procedures, including the issues of data compression and data reduction. Finally, examples of flaws and defects found by the tools will be shown.
Quality assessment and inspection of steel pipelines
2003
10 Seiten, 9 Bilder, 1 Tabelle, 10 Quellen
Aufsatz (Konferenz)
Englisch
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