Materials and Corrosion 2011, 62, No. 10 Acidic/caustic alternating corrosion on carbon steel pipes 969 1708° quench oil (Qo) diluted steam(DS) 195C,0725MPa 1702°C,0.706MPa QO Figure 2. External appearances of the Qo/dS heat exchanger:(a)total appearance of eight sets, (b)streamline diagram of two heat media, (c)four arrays of pipes, and(d) heat exchange mode pressures of these two heat media before and after heat exchanges more, the failure pipes, whose inlets had already been blocked are also listed in Fig. 2b with plugs after being detected perforation to avoid further In this event, failure mainly occurred in the heat exchanger leakage of QO, dominantly accumulated in the lower two arrays B. Figure 3a presents the scaling morphology of leaked Qo(Fig. 3c and d), while the upper two arrays of pipes were nearly companied with yellow sulfur sublimating from it on the pipes' free of failure, seen in Fig. 3b. With regard to the concrete failure surfaces caused by perforation of some specific pipes. What is pipes, Fig. 4a and b, respectively, displays the macroscopic Figure 3. External appearances of the failure Qo/DS heat exchanger B: (a)scaling of leaked Qo, (b)upper two arrays of pipes, (c)lower two arrays of pipes, and(d)locations of failure pipes www.matcorr.com o 2011 WILEY-VCH Verlag GmbH& Co KGaA, Weinheimpressures of these two heat media before and after heat exchanges are also listed in Fig. 2b. In this event, failure mainly occurred in the heat exchanger B. Figure 3a presents the scaling morphology of leaked QO accompanied with yellow sulfur sublimating from it on the pipes’ surfaces caused by perforation of some specific pipes. What is more, the failure pipes, whose inlets had already been blocked with plugs after being detected perforation to avoid further leakage of QO, dominantly accumulated in the lower two arrays (Fig. 3c and d), while the upper two arrays of pipes were nearly free of failure, seen in Fig. 3b. With regard to the concrete failure pipes, Fig. 4a and b, respectively, displays the macroscopic Materials and Corrosion 2011, 62, No. 10 Acidic/caustic alternating corrosion on carbon steel pipes 969 Figure 2. External appearances of the QO/DS heat exchanger: (a) total appearance of eight sets, (b) streamline diagram of two heat media, (c) four arrays of pipes, and (d) heat exchange mode Figure 3. External appearances of the failure QO/DS heat exchanger B: (a) scaling of leaked QO, (b) upper two arrays of pipes, (c) lower two arrays of pipes, and (d) locations of failure pipes www.matcorr.com
2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim