| This text regards the failure of the inter cooler of CO; compressor in the China blue chemical ltd. as the research object. According to the operating conditions of the inter cooler, and survey for the water quality analysis and the eddy current testing, thickness detection, endoscopic detection, tube destructive testing and so on. Furthermore, we took samples on the failure tube to do the destructive test.By this method, we make sure the root cause of the heat exchanger failure. And it also provided the basis for design and site operation using of the new heat exchanger.The results of the study are as follows:①At low flow conditions, the segment between the intermediate plate cooler side angle position of the tube plate will appear the case of cooling water stagnation. Interstage cooler through the large margin of the original design, in order to ensure the long-term heat load balancing is controlled at low load operation at low flow rates is caused by the formation of the reasons for scaling the wall.②Cooling water at low flow rates, high temperatures prone to fouling.③In the lower flow rate of operation, and there is a certain stagnation region, lead chloride gathered.④Chloride accumulation and the right temperature, resulting in duplex stainless steel (UNS S31500) stress corrosion cracking.Judged from analysis of scales adhered on tube surface, the accumulation of chloride is too large, about7000ppm, a normal operation condition70times the normal value.Even if the field device scaling and viscous flow generated due nucleate boiling, but the chlorides gather70times the normal amount is unthinkable. Because, fouling caused by conditions must be gathered in a gap between the pipe and the dirt. If there is a gap between the pipe and dirt, a obvious of crevice corrosion (pitting) should be seen On the rupture position. However, most of the cracked part does not indicate a gap corrosion indication, and this fact shows that scaling is not reason for the chloride aggregation. |
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