12 KB249 KB12 KB200020242007Celin, RomanKmetič, Dimitrijštevilka:34 straniletnik:41str. 151-154ISSN:1580-2949COBISSID:607658URN:URN:NBN:SI:doc-OBE3H8EAenInštitut za kovinske materiale in tehnologijeMateriali in tehnologijecevovodipreizkušanjeprelomiutrujenost materialovA wet-steam pipeline fracture| Prelom cevovoda za vlažno paro|The operational reliability of a system determines the systemćs availability and costs during its lifetime. Taking care of the reliability usually starts with knowledge of the operating conditions that need to be considered during the design, fabrication and maintenance of the system. In the case of a system or component failure, it is necessary to know the causes and the degradation mechanisms. An analysis of a fractured low-pressure wet-steam pipeline from a heat exchanger was performed. The fracture was located in the fillet weld's heat-affected zone. Visual testing, chemical analysis, hardness measurements and metallographic examinations were carried out. The fracture surface was quite damaged, and so the number of fatigue-crack propagation cycles could not be determined. An examination of the microstructure revealed that the fatigue crack occurred in the heat-affected zone, where the plasticity and toughness had been diminished due to the material overheating at the welding. As a result of the fracture analysis the industrial facility concerned extended the scope of its inspection of wet-steam pipelinesZanesljivost obratovanja je lastnost sistemov ali komponent, ki določa njihovo razpoložljivost in stroške v trajnostni dobi. Skrb za zanesljivost je tudi poznanje pogojev obratovanja, ki jih je treba upoštevati med konstruiranjem, izdelavo in uporabo sistema. Pri okvari sistema ali komponentepa je treba natančno poznati vzroke in mehanizme degradacije. Zaradi tega je bila opravljena analiza preloma nizkotlačnega cevovoda za vlažno paro izmenjevalnika toplote. Prelom je nastal v toplotno vplivani coni zvarjenega spoja. Izvedena je bila vizualna kontrola, kemijska analiza, meritve trdote in metalografska preiskava. Površina celega preloma je bila precej poškodovana, zato na njej ni bilo mogoče ugotoviti v koliko korakih je nastala utrujenostna razpoka. Preiskava mikrostrukture je odkrila, da se je prelom cevi izvršil v območju, kjer je bila plastičnost, z njo pa tudi žilavost, zmanjšana zaradi spremembe mikrostrukture pri varjenju zaradi pregretja materiala. Na osnovi rezultatov analize preloma je bil v industrijskem obratu povečan obseg kontrole cevovodov za mokro paroTEXTznanstveno časopisjejournalsSlovenian National E-content AggregatorNational and University Library of SloveniaInštitut za kovinske materiale in tehnologije