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Pipeline Technology Journal 2-2015

Latest developments and news from the pipeline industry

ASPECTS OF PIPELINE INTEGRITY Exact knowledge of pipeline condition is the main factor of pipeline integrity. Intelligent pigs on the highest level of available technolo- gy provide pipeline operators with necessary information e.g. loss of wall thickness, existence of cracks, dents or ovalities. Based on the experience of previous intelligent pigruns we expected app. 5 necessary repairs, due to results of metal loss and profile intel- ligent pigruns in 2010, but the fact was the necessity of more than 40 repairs. Due to lack of budget for replacing of pipes or steel sleeves, we were forced to find a cheaper repair method. As costs for excavat- ing pipeline defects are often multiple of the repair costs themselves, there was the aim to find a really durable repair system. As pipeline pressure cannot in any case be reduced to zero bar for application of repair systems, they also have to respect this circumstance. DURABLE REPAIR SYSTEMS As none of the available composite repair systems was certified for more than 20 years life time, we decided to give suppliers the oppor- tunity to gain such an approval for durable (> 100 years) service time by testing their products on our test stand, according to strict regula- tions of the TÜV-Süd of Germany. Three international providers used the chance to apply their products on test pipes with previously specified and inserted defects. Some of our engineers suggested to develop an own repair system in addition and got the approval of the AWP - management. DEVELOPMENT Due to the high tensile strength and elastic modulus, the use of car- bon fibre was very soon identified as the best option, as the main target was to not exceed the yield strength within the failure, even at the maximum allowable pressure (MAOP) of the unaffected pipe. Contacts to carbon- and resin suppliers were established and ade- quate products were selected and some test applications performed. In parallel utilized materials were tested with reference to e.g tensile strength / elastic modulus, glass transition temperature, ageing and hardness. Based on the test results of the composite tests, a calculation algo- rithm for the calculation of necessary number of carbon layers, which also had to consider pipeline pressures higher than zero bar during application, was developed. TEST After inserting of specified defects, strain gauges were applied inter- nal and external of the pipe wall in the defect areas, as well as on the unaffected pipes. Before application of repair systems the pipes were pressurized up to 32 bar. To identify the supporting action of the different repair sys- tems, step tests were executed after full curing of the repair systems. For this pressure was raised in steps of 10 bar up to MAOP of unaf- fected pipes and extension values within the defects were compared to that of unaffected pipes. Figure 3 Adria-Wien Pipeline (AWP) hydraulic profile RESEARCH / DEVELOPMENT / TECHNOLOGY 32 PIPELINE TECHNOLOGY JOURNAL

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