دانلود رایگان مقاله خوردگی تنشی در صفحات Type.316l از یک مبدل حرارتی

ABSTRACT

In Jam petrochemical complex (JPC), Iran, the plates (ASTM A.240 Type.316) of some heat exchangers have been damaged due to the occurrence of cracks at the sitting place of gaskets. A comprehensive failure analysis including the chemical analysis, visual inspection, optical microscopy and scanning electron microscopy (SEM) of the cracks spread over the plates together with the energy dispersive X-ray spectroscopy (EDS) of the corrosion products and the measurement of chloride and sulfide ions content of the process water were employed for the examination of the failure mode and its causes. The obtained results indicate the building-up of the chloride and sulfide ions at the crevices between plates and gaskets at high temperature leads to stress cracking corrosion (SCC) of the plates. Moreover, the simultaneous presence of chloride and sulfide in the media hastens the SCC failure in the heat exchanger plates.

4. Conclusions

In this study, the principal causes of corrosion failure in the plate heat exchanger (PHE) of Jam Petrochemical Complex (JPC), Asalouyeh, Iran, were evaluated via visual inspection, optical and scanning electron microscopy, energy dispersive Xray spectroscopy (EDS), thermo-scan analysis, and measurement of chloride and sulfide content of the waters. It was found that the chloride ions build-up in crevices formed between plates and gaskets (at high temperatures), is the main reason for the occurrence of SCC. The suspended soil of the service water settled in the crevices between gasket and plate and provides a favorable position (dead zone) for building-up of the chloride ions. When the level of chloride ions in the water is low, the evaporation of water in the crevices leads to chloride ions build-up. Moreover, the high temperature of the transport water outlet and cooling water inlet results in the acceleration of this building-up. By chloride ions concentration in the crevices, the pitting corrosion under gasket seat occurs. In addition, the simultaneous presence of chloride and sulfide ions intensifies the SCC failure in the heat exchanger plates.