Materials Performance Supplements


Materials Performance is the world's most widely circulated magazine dedicated to corrosion prevention and control. MP provides information about the latest corrosion control technologies and practical applications for every industry and environment.

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VAPOR PHASE CORROSION INHIBITORS VCI slurry in protecting two tanks by eval- uating 10 ER probes before and after injec- tion. The achieved data declare a satisfac- tory success of VCI in minimizing soil-side corrosion by reducing the corrosion rate prior and after injection. It is important to mention that diffusion of VCI to reach the metal surface to be protected is a time process and is dependent on the aeration degree of the under-tank soil. That is the reason why VCI action is not instantaneous and takes some time to be visible through ER readings. 4 Cost Savings A business case was presented to the refinery management for 40 tanks that were identified for the project. The business case presented was based on the following assumptions: • Tank bottom plate condition is not known as no inspection had been done. • The chemical injection is to extend the life of the tank bottom plates. Hence, some plates may have already corroded to an extent of complete replacement. • Bottom plate repair strategy is either by jack up and complete rebottoming or inspection and patch repair. • The cost of both of these methods varies upon the size (diameter) of the tank to be repaired/replaced, with rebottoming cost almost 4 to 5 times patch repair cost. Therefore, even after chemical injec- tion, some repair is anticipated and the following assumptions are used for the cost savings calculation: • Eight tanks (20% of total tanks) may require rebottoming and jack up. • Thirty-two tanks may require patch up, but not to an extent as required without any chemical injection. Table 2 shows the difference in repair cost either by replacing the bottom f loor or by patch repair and injecting VCI under- neath 40 tanks. The benefits of using VCI rather than a repair route are in the following: • Technical/operations: The project has reduced the risk of plant slow down or shutdown as the reliability of the tanks has increased. FIGURE 7 Three-period rolling average corrosion rate of ER probes in TK-02. FIGURE 8 Three-period rolling average corrosion rate of ER probes in TK-03. TABLE 2. COST SAVING FOR VCI VS. FLOOR REPLACEMENT/PATCH REPAIR OF 40 ASTS Cost Description Cost (USD) Typical cost of rebottoming eight tanks (A) 10,400,000 Typical cost of patch repair of 32 tanks (B) 6,240,000 Typical cost of chemicals for 40 tanks (C) 2,808,000 Typical saving for 40 tanks [(A+B)-C] 13,832,000 8 JUNE 2018 MATERIALS PERFORMANCE CORTEC SUPPLEMENT TO MP 8 JUNE 2017 MATERIALS PERFORMANCE CORTEC SUPPLEMENT TO MP

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