Crack assessment criteria for ship hull structure based on ship operational life

Nair, Ajit; Sivaprasad, K; Nandakumar, C. G.

doi:10.1080/23311916.2017.1345044

Cited by 13 publications

(2 citation statements)

References 12 publications

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“…Chemco International [29] mentions for a coated ballast tank a rate of corrosion of about 0.22 mm/year. The crack assessment criteria study of Ajit Nair et al [30] referred to Beghin [31] who proposed a rate of corrosion for unprotected ballast tanks of 0.4 mm/year and for coated ballast tanks at 0.2 mm/year. Gudze and Melchers [32] conducted an experimental trial using unpainted mild steel coupons exposed inside the seawater ballast tanks of an operational naval ship.…”

Section: Discussionmentioning

confidence: 99%

Accelerated Ballast Tank Corrosion Simulation Protocols: A Critical Assessment

Willemen,

De Baere,

Baetens

et al. 2024

Materials

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In the realm of accelerated testing within controlled laboratory settings, the fidelity of the service environment assumes paramount importance. It is imperative to replicate real-world conditions while compressing the testing duration to facilitate early evaluations, thereby optimizing time and cost efficiencies. Traditional immersion protocols, reflective solely of full ballast tank conditions, inadequately expedite the corrosion process representative of an average ballast tank environment. Through the integration of immersion with fog/dry conditions, aligning the test protocol more closely with the internal conditions of an average ballast tank, heightened rates of general corrosion are achieved. This augmentation yields an acceleration factor of 7.82 times the standard test duration, under the assumption of a general corrosion rate of 0.4 mm/year for uncoated ballast tank steel, with both sides exposed. Subsequently, the fog/dry test protocol, albeit only resembling the environment of an empty ballast tank, closely trails in terms of acceleration efficacy. The fog/dry test protocol offers cost-effectiveness and replicability compared to the AMACORT CIFD-01 protocol, making it a strong competitor despite the relatively close acceleration factor.

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Section: Discussionmentioning

confidence: 99%

Accelerated Ballast Tank Corrosion Simulation Protocols: A Critical Assessment

Willemen,

De Baere,

Baetens

et al. 2024

Materials

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“…Nair et al 24 presented criteria for assessment of cracks based on inducement factors which influenced crack initiation in the hull structure even during the early stages of operation. Detectable cracks identified during inspection were analyzed to determine the inducement factor and the underlying causes for such crack initiation corresponding to the ship operational life.…”

Section: Literature Reviewmentioning

confidence: 99%

Efficient fatigue assessment of the upper and lower hopper knuckle connections of an oil tanker

Özgüç

2020

Proceedings of the Institution of Mechanical Engineers, Part M:

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The fatigue of structural details of ships is of great importance in the maritime industry as they can lead to cracks which can jeopardize structural integrity. The hopper knuckle is among the most vulnerable areas in a ship with respect to fatigue damage. Analysis of the hopper knuckle has become mandatory for tankers in the Class Ship Rules and in the International Association of Classification Societies Common Structural Rules. Along with the fatigue damage record of the vessels, the fatigue analysis of the hopper knuckles is essential to ensure that the vessels have sufficient fatigue strength. In the current work, fatigue calculations are performed of the upper and lower hopper knuckle connections within midship of the oil tanker using simplified fatigue calculations based on Det Norske Veritas (DNVGL) Classification Note No. 30.7. The fatigue analysis is based on 25 years of operation in worldwide wave environment. A cargo hold model (½ + 1 + ½) amidships and a local finite element model of the hopper knuckle are generated. The local model provides relevant hotspot stress for fatigue life calculations. The results from the hopper knuckle fatigue analysis show that the vessels may expect fatigue cracks at lower hopper knuckle before the vessel reaches its design life of 25 years. Based on the findings, it is recommended to fit soft brackets and close scallops at the lower hopper knuckle on selected common frames in all cargo holds.

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