PSI - Issue 48

Mohammed Badr Alzeer et al. / Procedia Structural Integrity 48 (2023) 363–370 Mohammed Badr Alzeer/ Structural Integrity Procedia 00 (2019) 000 – 000

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For carbon steel and low alloy steel, the presence of sulphate (SO4 -2 ) is considered an aggressive corrosive factor, such sulphide corrosion which is very similar to hydrogen sulphide corrosion, an ineffective (weak) layer made of FeO oxides will act as a protective film due to the high absorption effect of sulphate ions on the inner surface of the pipe. This layer will prevent the surface from developing localized corrosion, the issue starts to arise as soon as the passive film is locally destroyed and its continuity is broken by the presence of corrosive chloride (Cl - ) ions, which causes active-passive galvanic cells to form and corrosion pits to form (Zhang & Lan, 2017). Since the flow velocity of a certain fluid is a critical factor that influences Microbiological corrosion, the sections that witnessed the harshest corrosion rates were located where the pipe is fully filled and the mean flow velocity is 0.7 m/s, which constitutes a typical speed to develop such corrosion, while it less likely in sections where fluid fell by gravity in which the pipe is partially packed, which was the dominant scenario when the pipeline had been used for light crude transportation between 1961- 1982 (Okonkwo & Mohamed, 2014). Cracks account for nearly a quarter of all identified anomalies. The fluctuating temperature of soil between cold and hot seasons makes the buried pipeline expand and contract, in addition to the operating pressure exerted on the pipeline which varied between 51 Bar (5,100,000 Pa) and 1 Bar (100,000 Pa) adding to it the technical state of the pipeline material which in most parts been in service for almost 50 years, and the corrosiveness of the carried fluid all those reasons create a typical environment for cracks propagation (Okonkwo & Mohamed, 2014). 6. Operating Conditions-Based Analysis 6.1 Analysis relating to Topography According to the 2008 MFL inspection, metal loss features’ frequency notably increased more towards the pumps (Banias) than the downstream sections (Homs), particularly within the segment between 534/24 and 554/10. By looking at the locations where the new API 5L X52 sections had been built from 1984 and later, and by reviewing the maintenance record, It was possible to get the conclusion that the corrodibility increases in such lower areas where the pipeline is more exposed to the corroding environment. Figure 3 maps out the frequency of the corrosion features in relation to the elevation profile of the pipeline.

Figure 3. frequency of the pipe body corrosion features with respect to the elevation profile.