Stress corrosion cracking failure of a SS 316L high pressure heater tube

A service failure by environmentally induced cracking in austenitic stainless steel 316 L is presented in this work. Extensive research has been carried out on stress corrosion cracking of different materials and environment combinations by various established experimental procedures. The list of alloy/environment combination that causes stress corrosion cracking is continuously increasing. Stress corrosion cracking is a great concern in corrosion resistant alloys exposed to aggressive environments. Stainless steel 316 L material used as high pressure water heater tube failed by stress corrosion cracking was evaluated by various metallurgical characterisation techniques. Results and apparent causes leading to failure were explained in detail

Failure investigation of a cooling coil tube in zinc roaster furnace

The failure analysis of a cooling coil tube employed to extract the sensible heat of roasted zinc sulfide ore in a fluidised bed furnace type roasting unit was reported. The coils are prone to service degradation and subsequent failure due to the extreme operating conditions (920-960 degrees C). Severe corrosion attack and cracks were seen on the outer surface of the tube upon visual examination. The optical microscopy performed at the crack tip confirmed the deformation induced pearlitic banded structure. The corrosion products at the failure regions were rich in iron and zinc as revealed in the analysis by SEM with EDS. The galvanic corrosion between Fe and Zn is found to be the primary cause of the failure. It is hypothesized that the type of corrosion is possible with the zinc oxide acting as cathode with reference to the coil tube's outer surface. The selective corrosion resulted in the preferential corrosion attack and led to the premature failure of the tube. (C) 2017 Elsevier Ltd. All rights reserved

Non-polio enterovirus association with persistent diarrhea in children as revealed by a follow-up study of an Indian cohort during the first two years of life

Background: We recently reported significant association of non-polio enteroviruses (NPEVs) with acute diarrhea in children. Persistent diarrhea (PD) remains a major cause of morbidity and mortality in infants below two years of age in developing countries. Understanding age-dependent frequency and duration of NPEV infections is important to determine their association with persistent diarrhea and disease burden. Objectives: A cohort of 140 infants was followed for 6 months to 2 years of age to determine the frequency, duration, and association with PD of NPEV infections in comparison with rotavirus and other agents. Study design: Stool samples were collected every 14 days, and diarrheal episodes and their duration were recorded. Enteroviruses were characterized by RT-PCR and VP1 gene sequence analysis, rotavirus by electropherotyping, and other agents by PCR. Results: Of 4545 samples, negative for oral polio vaccine strains, 3907 (85.96%) and 638 (14.04%) were NPEV-negative and NPEV-positive, respectively, representing 403 (8.87%) infection episodes. About 68% of NPEV infections occurred during the first year with every child having at least one episode lasting between four days and four months. Approximately 38% and 22% of total diarrheal episodes were positive for NPEV and RV, respectively. While about 18% of NPEV infection episodes were associated with diarrhea, 6% being persistent, 13% of total diarrheal episodes were persistent involving infections by monotype NPEV strains or sequential infections by multiple strains and other agents. Conclusions: This is the first report revealing NPEVs as the single most frequently and persistently detected viral pathogen in every PD episode. (C) 2014 Elsevier B.V. All rights reserved