Offline internal inspection in the Czech Republic
A natural gas leakage was detected on the unpiggable, high pressure DN 600 pipeline Kasejovice-Mikulášov in the Czech Republic after 50 years of operation. The pipeline was excavated and found to be suffering from extensive corrosion. The operator, therefore, decided to carry out an inspection on a representative 15 km section in order to check the actual condition of the pipeline system.
Conventional inline inspection (ILI) during operation was not feasible on this pipeline section, and therefore the inspection was carried out ‘offline’. An ultrasonic inspection tool was propelled through the pipeline section with a controlled speed by water.
The ILI results revealed severe general corrosion defects, mainly in the location near the Čížová village. The rest of the pipeline was not significantly corroded.
The operator obtained insightful answers regarding the actual pipeline condition, specifically regarding class, number, severity and location of defects. In addition to that, exact locations of circumferential welds, offtakes, bends and sockets were obtained. Also, a detailed pipe tally book was generated based on the ILI data.
Based on the mapping unit data, both vertical and horizontal pipeline profiles were calculated including exact geographical co-ordinates.
According to the ILI data, corrosion survey and material tests, a list of recommended urgent repairs was proposed. Also, an operation recommendations report was issued. By following the proposed practice, the pipeline section’s operation lifetime should not be limited.
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