PSI - Issue 33

J.L. González-Velázquez et al. / Procedia Structural Integrity 33 (2021) 221–228 J.L. González-Velázquez et al. / Structural Integrity Procedia 00 (2021) 000–000

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shape, size, and distance between inclusions affect the susceptibility to HIC. Peng et al. (2020), Kim et al. (2008), and Rahman et al. (2019) showed that large inclusions are prone to trap more hydrogen, increasing HIC susceptibility, and concluded that the shape, size, and separation between non-metallic inclusions could be considered as critical factors for HIC propagation. The relationship between HIC and NMI has been a concern among the pressure vessel users in the oil and gas industry, leading to the necessity to assess the impact of NMI on the Fitness-For-Service (FFS) of pressure vessels, but because of the absence of a specific assessment procedure NMI are usually evaluated as laminations. The detection of zones of closely spaced NMI in pressure vessels is typically done by conventional straight bean ultrasonic inspection in Scan-C mode, being a common practice by the inspectors to report them as laminations. Gomera et al. (2010) and Sudakov et al. (2010) observed that indications of continuous laminations are indeed the accumulation of NMI in hot rolled carbon steel plates. González et al. (2006) analyzed the mechanical behavior of non-coplanar pressurized laminations in carbon steel pipes and observed that the laminations might be interconnected by plastic deformation provided they are close enough, creating a larger damaged area. The FFS assessment of pressure vessels containing laminations is done by Part 13 of API 579 -1/ASME FFS-1- 2016 (API 579). However, the assessment criteria of API 579 generate strong questioning by the equipment’s Owner/User regarding the validity of the rejections, and often, FFS engineers are requested to provide technical argumentation for their modification due to the high financial consequences that such rejections imply. González et al. (2004) determined that the strength of cylindrical shells containing non-coplanar laminations is little dependent on the lamination size, so the FFS assessment of zones containing groups of NMI can be done by methodologies similar to those of laminations, but with less strict assessment criteria that may lead to less conservative assessments. This research aims to adapt the FFS assessment procedure and criteria presented in Part 13 of the API 579-1/ASME FFS-1 standard for the assessment of indications typified as “zone of non-metallic inclusions” in pressure vessel shells made of low carbon steel.

Nomenclature c

lamination dimension in the circumferential direction

inside diameter of the component

D

FCA future corrosion allowance FAD failure assessment diagram L h depth of the indications to the external surface L msd spacing to the nearest major structural discontinuity L s lamination-to-lamination spacing L w spacing to the nearest weld joint LOSS amount of uniform metal loss at the time of inspection MAWP Maximum Allowable Working Pressure MAWP r reduced Maximum Allowable Working Pressure s lamination dimension in the longitudinal direction t c corroded wall thickness t min

thickness required to support the internal pressure in the vessel

minimum measured thickness nominal thickness of the component Wall thickness away of lamination

t mm t nom

t rd