767 KB0 KB201320252024Avsec, JurijStrušnik, Dušanletnik:17številka:iss. 1str. 11-19ISSN:1855-5748COBISSID_HOST:199750147URN:URN:NBN:SI:doc-RP0RZC2HenFakulteta za energetikoJET on-lineJournal of energy technologyammoniaamoniakcevicoolingcrackshlajenjerazpoketubesDamage analysis of condenser cooling tubes in a thermal power plant| Analiza poškodb hladilnih cevi kondenzatorja v termoelektrarni|A steam turbine condenser (STC) is a surface, shell, and tube type vacuum condenser, cooled by a water system supplied from a river. The STC consists of two water passes and two water flows. Its condenser shell is constructed from carbon steel, and contains 4910 cooling tubes made of CuZn28Sn1As brass, each with dimensions of 23.0 x 1.0 mm and a length of 6,400 mm. Three new steam dump devices (SDDs) have been installed on the condenser. Two SDDs are designated for high-pressure (HP) steam, while one is allocated for intermedia-pressure (IP) steam. The primary function of the SDDs is to divert steam from the boiler through the bypass system into the STC. The bypass system is utilised primarily during start-up, shutdown, and for managing excess steam transfer. The Commissioning and Trials Board conducted tests on the new SDDs, which lasted for five hours. However, during the commissioning phase, high condensate levels in the STC caused trips. Additionally, online monitoring indicated high condensate conductance. Upon opening the condenser water chamber doors and filling the steam side of the condenser with water, it was discovered that twenty-eight of the cooling tubes were leaking. These leaking tubes were subsequently plugged. For further analysis, four cooling tubes were extracted, and two condensate samples were obtained. While extracting the cooling tubes, the other tubes were inspected visually using a borescope to assess their internal condition. The analysis results indicated that all the cracks on the extracted tubes were located approximately 5 mm from the tube sheet on the front side of the condenser, where the cooling water inlet and outlet are situated. Furthermore, grooves were observed on all the other tubes at the same location, characteristic of stress-corrosion cracking influenced by ammoniaKondenzator parne turbine (STC) je površinski, lupinasti in cevni vakuumski kondenzator, hlajen z vodnim sistemom, ki se dovaja iz reke. STC je sestavljen iz dveh vodnih prehodov in dveh vodnih tokov. Ohišje kondenzatorja je izdelano iz ogljikovega jekla in vsebuje 4910 hladilnih cevi iz medenine CuZn28Sn1As, vsaka z dimenzijami 23,0 x 1,0 mm in dolžino 6400 mm. Na kondenzatorju so bile nameščene tri nove naprave za izpust pare (SDD). Dva SDD-ja sta namenjena za visokotlačno paro (HP), eden pa je dodeljen za paro srednjega tlaka (IP). Primarna funkcija SDD je preusmeritev pare iz kotla skozi obvodni sistem v STC. Obvodni sistem se uporablja predvsem med zagonom, zaustavitvijo in za upravljanje presežnega prenosa pare. Komisija za zagon in preskušanje je opravila teste novih SDD, ki so trajali pet ur, vendar so med fazo zagona visoke ravni kondenzata v STC povzročile izklope. Poleg tega je spletno spremljanje pokazalo visoko prevodnost kondenzata. Ob odpiranju vrat vodne komore kondenzatorja in polnjenju parne strani kondenzatorja z vodo je bilo ugotovljeno, da pušča osemindvajset hladilnih cevi. Te puščajoče cevi so bile nato zamašene. Za nadaljnjo analizo smo ekstrahirali štiri hladilne cevi in pridobili dva vzorca kondenzata. Med ekstrakcijo hladilnih cevi so bile druge cevi vizualno pregledane z uporabo boroskopa, da se oceni njihovo notranje stanje. Rezultati analize kažejo, da so vse razpoke na izvlečenih ceveh približno 5 mm od cevne pločevine na sprednji strani kondenzatorja, kjer sta dovod in odvod hladilne vode. Poleg tega so na vseh drugih ceveh na istem mestu opaženi utori, značilni za napetostno korozijsko razpokanje pod vplivom amonijakaTEXTznanstveno časopisjejournalsSlovenian National E-content AggregatorNational and University Library of SloveniaUniverza v Mariboru, Fakulteta za energetiko