Integrity assessment of tanks with microcracks in welded joints

Abstract

Tokom eksploatacije rezervoara za skladištenje tečnog ugljendioksida ukazala se potreba za ugradnjom dva nova priključka u jedno od danaca. Rezervoar je izrađen od mikrolegiranog čelika, a priključci od visokolegiranog austenitnog čelika. Za izradu novih priključaka izabrani su isti dodatni materijali i ista tehnologija zavarivanja, koji su korišćeni i pri izradi rezervoara. Ispitivanjima metodama bez razaranja zavarenih spojeva novih priključaka otkrivene su mikroprsline u zoni uticaja toplote mikrolegiranog čelika. Primenom postupka prikazanom u standardu BSI PD 6493 'Uputstvo za ocenu prihvatljivosti grešaka u zavarenim konstrukcijama', ocenjen je uticaj ovih mikroprslina na integritet zavarenih spojeva novih priključaka i time i na integritet rezervoara.During the exploitation of tanks used for storing liquid carbon dioxide there was a need to install two new connectors on one of the lids. The tank is made of micro-alloyed steel and its connectors are made of high-alloyed austenite steel. The same welding technology and added materials are used for both the tank and connectors. Non-destructive testing methods of welded joints in new connectors revealed microcracks in the heat-affected zone of micro-alloyed steel. By applying the procedure given in standard BSI PD 6493 'Manual for assessment of acceptability of flaws in welded structures', it is possible to estimate the effect of these microcracks on the integrity of welded joints in new connectors, and therefore their effect on the integrity of the tank

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