Abstract
Two segments of transition oil pipeline DN500 and DN700, operating since 1980, were subjected to full-scale pressure testing. In 2000, corrosion defects were found on both pipelines - the two corrosion defects on the outside wall of DN500 pipeline, and the one corrosion defect on the inside wall of DN700 pipeline. Both pipes were sleeve reinforced to increase the safety and reliability of the lines. The DN500 pipeline used the Cold Lock sleeve - the steel sleeve with a composite filling. On the other hand, the DN700 pipeline used the Clock Spring composite sleeve. In 2020, after two decades of operation with sleeve repairs, both pipelines were dug out, removed from operation and used for full-scale pressure testing to determine the residual strength sleeves repairs and to compare the efficiency of the sleeves. The full-scale test included three stages of loading. The first step was continual loading up to the yield strength of pipelines. The second step was the fatigue pressure test at 2-6,3 MPa with a total of 10 000 cycles. The third step was the burst pressure test. The stress-strain behavior was measured with help of strain gauges placed on the pipeline surface and on the surface of sleeves. From strain gauge measurement, it was found that both sleeves still have a remarkable residual strength even after two decades of operation. However, the Cold Lock sleeve has a higher efficiency compared to the Clock Spring sleeve, as it showed lower strains during loading. The test method, procedure and results will be fully discussed in the proposed paper.
Published Version
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