Faculty Publications
Permanent URI for this communityhttps://idr.nitk.ac.in/handle/123456789/18736
Publications by NITK Faculty
Browse
Search Results
Item Failure of a Cooling Water Pump Shaft(Springer, 2021) Sondar, P.R.; Kumar, J.K.R.; Chawla, S.; Dsilva, P.C.; Hegde, S.R.This study investigates the failure of an industrial cooling water pump which experienced a drive shaft failure. As per the fail-safe design, during adverse loading of the shaft, key should fail by shear. The key, if fails, can be easily replaced to resume the operation of the pump. However, this investigation reveals that both the key and the shaft failed due to materials processing issues. A detailed failure analysis was carried out including design calculations, visual inspection, dye penetrant inspection, magnetic particle inspection, hardness test, microstructural analysis, and fractography. The study found that the hardness of the shaft varied radially from the core to the surface. The subsurface of the shaft near the keyway, happened to be significantly softer than the key. During operation, the keyway widened by plastic deformation and caused rattling of the key. Due to rattling and vibration, the key developed numerous fatigue cracks and eventually failed by crack linkages. The shaft eventually failed by torsional shear near the midpoint of the keyway. The analysis adjudged hardness variation in the shaft due to materials processing issues as the root cause of the failure. © ASM International 2020.Item Premature failure of superheater tubes in a fertilizer plant(Elsevier Ltd, 2021) Dsilva, P.C.; Bhat, S.; Banappanavar, J.; Kodancha, K.G.; Hegde, S.R.This work presents an unique premature failure of steam superheater tubes in a fertilizer plant. The heat exchanger tube bundle made of SA 213 grade T11 steel suffered from wall thinning in the vicinity of baffles causing reduction in wall thickness of the tubes leading to perforation and leakage of steam from the tube-side into the shell-side during service. The work presents details of metallurgical failure analysis involving: site inspection, visual inspection, chemical analysis, X-Ray diffraction, microstructural analysis, and computational fluid dynamics analysis. The qualitative and quantitative chemical analyses and X-Ray diffraction carried out on superheater residue followed by microstructural analysis of failed tubes confirmed that the tubes suffered from aggressive corrosion attack at certain locations due to hot flue gas carrying alkaline salts and refractory fines. To understand the mechanism of thinning and the reasons for the tube bundle failure only at certain locations, a detailed CFD analysis was carried out on model of the heat exchanger which simulated the flow pattern of the hot gas. The analysis comprehensively demonstrates that the hot gas carrying both corrosive and erosive species caused erosion-corrosion of the tubes in the vicinity of tube-baffle junction that lead to wall thinning and subsequent failure of the tube bundle. Suitable remedial measures are suggested to minimize such failures in future. © 2020 Elsevier LtdItem Failure Analysis of Reciprocating CO2 Compressor(Springer, 2021) Dsilva, P.C.; Shetty, P.; Sondar, P.R.; Ganesh Kumar, B.; Hegde, S.R.This work presents failure analysis of a heavy-duty, four-stage, double-action, reciprocating CO2 compressor, which resulted in the shutdown of an ammonia plant. The failure occurred in the fourth stage of the compressor, during which the piston rod, piston rings, a suction valve, and associated valve cage are found fractured. The failure analysis includes details of site visit, visual inspection, dye penetrant test, fractography, and microstructural analysis. Furthermore, Xanthoproteic test was conducted on the extracts of the failed piston rings that confirmed the presence of bacterial cellular protein. When the morphology of the failed piston ring was studied using a scanning electron microscope, unique degradation features and the presence of bacterial metabolic products were observed conforming to the growth of bacteria. In-service biodegradation of the piston ring material (polyether ether ketone composite) is adjudged as the root cause for the compressor failure. © 2021, ASM International.