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The article contains the comparative results of the experimental and calculated research of the strength of a pipeline with such defects as “metal loss” and “dent with groove”. Two coils with diameter of 820 mm and the thickness of 9 mm of 19G steel were used for full-scale pipe sample production. One of the coils was intentionally damaged by machining, which resulted in “metal loss” defect, the other one was dented (by press machine) and got groove mark (by chisel). The testing of pipe samples was performed by applying static internal pressure to the moment of collapse. The calculation of deterioration pressure was carried out with the use of national and foreign methodical approaches. The calculated values of collapsing pressure for the pipe with loss of metal mainly coincided with the calculation experiment results based on Russian method and ASME B31G. In case of pipe with dent and groove the calculated value of collapsing pressure demonstrated greater coincidence with Russian method and to a lesser extent with API 579/ASME FFS-1. In whole, all calculation methods demonstrate sufficient stability of results, which provides reliable operation of pipelines with defects.

No abstract

Pipe sections with curvatures exceeding the required specified values are often found during the pigging of major pipelines. Process parameters for repairs have to be defined in order to develop a maintenance project that also includes works to restore the specified status of the section found. A corresponding method is known for cases of relocation of an initially straight pipeline. The authors developed a method for determining process parameters for repairing pipelines with out-of-project axis curvature. The method is based on modeling the deformation of a pipeline with initial axis curvature; it takes into account the actual operating conditions of the pipeline and in-line inspection data. Examples of calculating process parameters for repairs and stress-deformed state of pipeline sections with out-of-specs curvature have been presented. The modeling results confirm the possibility of using the method for evaluating the repair process parameters, the length of the required trench exposure, and the magnitude and boundaries of additional digging-in or the need to lift the pipeline in order to determine the stress–strain state of the pipeline section to be repaired during execution and after the completion of repairs.

When performing in-line inspection of trunk pipelines, line pipe sections are detected with curvature exceeding the values required by specifications. To prepare a repair work project that entails bringing the pipeline into the standard conditions, it is necessary to determine the technological parameters of the repair. The corresponding technique is known for cases of moving an initially straight pipeline. The authors of the paper have developed the method for determining the technological parameters to repair pipeline with out-of-spec curvature of the axis. The method is based on simulation of pipeline deformation with the initial curvature of the axis, taking into account the actual operating conditions of the pipeline and in-line inspection data. Examples of calculations of repair technological parameters and stress-strain state of pipeline sections with out-of-spec curvature are given. The simulation results confirm the possibility for applying this method to assess the technological parameters of repair, the length of trench excavation, the size and limits of the pipeline additional burying or lifting, and to determine the stress-strain state of the pipeline section under repair during and after repair work.