Abstract
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 was 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 AISI Type 316, ASTM A 193 GR. B7 and ASTM A 194 GR. 8M. The causal factors for the fastener’s 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 gaskets instead of spiral wound metallic stainless steel AISI 316 gaskets as per design. Consequently, chemical incompatibility of the gasket led to flange surface crevice and localized corrosion.
