PSI - Issue 5

Chmelko Vladimír et al. / Procedia Structural Integrity 5 (2017) 614–619 Garan, M., Chmelko, V./ Structural Integrity Procedia 00 (2017) 000 – 000

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0 2 h k c    , (3) where k and c 0 are the constants of environment in which the corrosion defect is and  is time in seconds. For the known depth and geometry of the defect, it is possible to calculate the deformation pressure of the weakened pipeline according to known standards DNV-RP-F101 or ASME-B31G by Cosham (2001). These criteria are conservative, so it is possible to specify the actual destruction pressure by computer modeling (see Fig. 3)

Fig. 3 Modeling destruction pressure in the pipeline with the corrosion defect The role of the pipeline monitoring system with corrosive defects and additional stress can be summarized in 3 main steps  To measure actual pipeline loads (including additional stress, e.g. from sloping slope, submerged subsoil, ...) near corrosion defect  Calculate the actual depth of corrosion defect based on the known depth since the last inspection according to the model of its propagation in the environment under stress  To assess the actual safety of the pipeline cross-section against destructions according to the standards of DNV, ASME, or according to the actual value of the stress and real destruction pressure In-time monitoring system pursuing the fatigue damage and vibrations was installed on the gas pipeline of the transit courtyard in year 2011. This monitoring system continuously evaluates increments of the fatigue damage in 9 critical cross-sections. The cyclic properties were acquired by direct cyclic tests on the specimens of materials created from material of the pipeline. Through the application of the monitoring system, many data and interesting findings have been obtained about the behavior of the pipeline yards of the gas pipeline compressor stations. From the point of view of the integrity and security of pipeline operation, it was most important when the monitoring system recorded high descent of the mean value of the overall loading (Fig. 4). From the measured data was possible to identify the reason of that descent – the main reason was the addition bending stress that has appeared as result of the subsoil decrease because of the effect of previous more raining period. The occurrence of non-standard operating situations is difficult to predict, thus fulfilling the standard of EU Directive 37/1998 on impact assessment so called non-standard operating situations for the safety of further operation can be accomplished, using the mentioned monitoring systems. Other benefits of deploying monitoring systems are 4. Industrial applications and conclusion