Faculty Publications
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Item Failure Analysis of Cooling Tower Fan-Arm(Springer, 2020) Padasale, B.; Kumar, J.K.R.; Sondar, P.R.; Cadambi, S.; Hegde, S.R.This work presents failure investigation of cooling tower fan-arms commissioned in a chemical processing plant. The analysis aims at understanding the mechanism and root-cause of the failure. The investigation involves site visits, microstructural analysis, fracture surface analysis, hardness measurements, numerical stress analysis and experimental simulation. Work concludes that the fan-arms failed due to the lack of post-weld heat treatment, which caused localized stress-corrosion and pitting at critical locations that served as crack initiation sites. Fatigue loading condition and presence of residual stresses at the weld enabled easy propagation of cracks that led to recurring premature failure. Based on the root-cause and the mechanism identified in this analysis, proper pre-heating and post-weld heat treatment is recommended to relieve the residual stresses at the critical locations and thus to avoid/minimize such recurring failures in future. © 2020, ASM International.Item Failure Analysis of a Bucket Elevator Shaft(Springer, 2021) Gurudath, B.; Kumawat, K.K.; Tejaswi, V.; Sondar, P.R.; Rakshan Kumar, J.K.; Hegde, S.R.Present work investigates the in-service break down of a bucket elevator in a chemical processing plant. The elevator was used for lifting bulk Di-Ammonium Phosphate and broke down due to premature failure of a shaft made of EN19 steel. The investigation comprises a detailed metallurgical failure analysis involving site visit, visual inspection, fractography, and metallography. The investigation reveals that, about 2 years prior to the failure, the shaft was tack-welded to the sprocket hub and a gib-head key near the keyway to avoid the frequent loosening of the key. The inspection during the site visit confirms that the shaft-sprocket assembly was subjected to in-service jerky loading condition along with uneven stress distribution due to misaligned counterweight. The investigation concludes that a crack was initiated in the shaft at the heat affected zone of the tack-welded spot, propagated transversely by fatigue due to in-service cyclic loading, and terminated catastrophically by a brittle fracture during the service. Tack welding, coupled with uneven stress distribution in the shaft due to misaligned counterweight system, is adjudged the root cause of this failure. Suitable remedial measures are suggested to avoid such a failure in the future. © 2021, ASM International.