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Failure Of In-Service Stainless-Steel Chemical Storage Tanks Fasteners And Gaskets – A Case Study

The Joint Operation (J.O) Wafra Oilfield is in the west central part of the Kuwait-Saudi Arabia Neutral Zone. The Wafra oilfield produces light and heavy oil and export it to its various customers after processing. Upstream field consists of various Sub Centres where crude, oil and water being separated, and the separated crude transported to the main gathering centre for further processing in two different trains. The produced water being disposed/injected via water disposal & injection facilities after treatment. 

Product Number: 51322-18105-SG
Author: A/Rahman Al-Ghamdi, Yousef Bahbahani, Manickavasagan Sabesan, Tariq Kamshad, Salem Al-Qahtani, Bakheet Al-Yami
Publication Date: 2022
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This paper demonstrates a case study associated with the improper installation of non stainless steel materials in chemical tanks against design specification, which explicitly called for the use of stainless steel fasteners and gaskets. An operating facility required the substitution of current chemicals with new ones, and as part of the management of change (MOC) process, the cleaning and inspection of the tanks were required. Internal visual inspection (IVI) of the tanks revealed severe corrosion of the tank internal fasteners, including fasteners supporting structural elements of the tank central periphery. Positive Material Identification (PMI) testing was conducted and concluded that chrome-manganese bolt nuts were used during construction stage which does not match with the design recommended material which is stainless steel ASTM Type 316 (S31600), ASTM A193 GR. B7 (a hardenable Cr-Mo steel) and ASTM A194 GR. 8M (S31600). The causal factors for the fasteners corrosion were determined to arise from galvanic corrosion from using dissimilar materials alongside very corrosive environment. Similarly, it was observed that all tanks manway suffered from localized and crevice corrosion due to the use of non-asbestos gasket instead of spiral wound metallic stainless steel Type 316 gasket as per design. Consequently, chemical incompatibility of the gasket led to flange surface crevice and localized corrosion.

This paper demonstrates a case study associated with the improper installation of non stainless steel materials in chemical tanks against design specification, which explicitly called for the use of stainless steel fasteners and gaskets. An operating facility required the substitution of current chemicals with new ones, and as part of the management of change (MOC) process, the cleaning and inspection of the tanks were required. Internal visual inspection (IVI) of the tanks revealed severe corrosion of the tank internal fasteners, including fasteners supporting structural elements of the tank central periphery. Positive Material Identification (PMI) testing was conducted and concluded that chrome-manganese bolt nuts were used during construction stage which does not match with the design recommended material which is stainless steel ASTM Type 316 (S31600), ASTM A193 GR. B7 (a hardenable Cr-Mo steel) and ASTM A194 GR. 8M (S31600). The causal factors for the fasteners corrosion were determined to arise from galvanic corrosion from using dissimilar materials alongside very corrosive environment. Similarly, it was observed that all tanks manway suffered from localized and crevice corrosion due to the use of non-asbestos gasket instead of spiral wound metallic stainless steel Type 316 gasket as per design. Consequently, chemical incompatibility of the gasket led to flange surface crevice and localized corrosion.

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