جستجوی مقالات مرتبط با کلیدواژه « failure analysis » در نشریات گروه « مهندسی شیمی، نفت و پلیمر »

The boilers and other equipment utilized for steam generation suffer from a wide range of failure mechanisms particularly metallurgical failures, e.g. creep, graphitization, spheroidization and also different types of corrosion. In the current work, the causes of corrosion and premature failure of a carbon steel boiler bank tube used in an oil refinery was investigated by different microscopical and analytical techniques. The results showed that the main failure cause of the tube was localized corrosion which was happened due to formation of silicate deposits formed on the internal surface of the tube and consequently its caustic corrosion. At the end, some suggestions are given to mitigate such corrosion and failures.

The use of carbon steel is conventional for the transmission and distribution of treated natural gas. In order to control the internal corrosion of the gas transfer pipelines, the moisture content is removed in dehydration unit. In addition, the amount of CO2 gas is limited to less than 2%. In this study, the cause of the failure of an 8-inch gas distribution pipeline is investigated. The pipeline was not in service for two years and then it was in operation for 6 years before the failure. Microscopic examinations, as well as chemical analyzes such as EDS and XRD, were used to determine the possible mechanisms of damage. In addition, the NORSOK CO2 corrosion model was used to determine the corrosion rate in operating conditions. The results showed that corrosion caused by carbon dioxide is the most likely cause of internal corrosion of the pipeline and the occurrence of the leakage.

Cupronickel 90-10 is one of the most applicable Cu-based alloys which possess suitable corrosion resistance and strength and is employed extensively in marine industries particularly in the boilers and heat exchangers. Generally, the tubes of water cooling systems especially those use seawater as cooling medium are made of this alloy. In this paper, the causes of premature failure of a cupronickel (90-10) condenser tube used in a cooling system of an oil refinery in the south of Iran have been studied by different microscopical and analytical methods, e.g. X-ray fluorescence spectroscopy (XRF) and X-ray diffraction (XRD). The results showed that pitting corrosion on the internal surface of the tube was the main cause of its failure which was a consequence of the stagnant of the tube by external solids and preparation of an appropriate environment for the activity of microorganisms, hence, microbial corrosion.