Materials Performance

JUN 2019

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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54 JUNE 2019 W W W.MATERIALSPERFORMANCE.COM CM CORROSION MANAGEMENT The painting of field welds is always a concern as it is likely to differ from the equipment and spools that were coated under the controlled atmosphere of a paint- ing shop. 6 Field weld joints are usually painted by normal cleaning with a power brush, followed by a paint touch up with roller brushes. Any f laws or nonconfor- mances arising from this practice are likely to create a location for initiation of corro- sion in case of moisture ingress into the insulation . The humid conditions may result from operational conditions of the neighborhood, such as cooling tower drift, dripping water from overhead equipment, leaking f langes, steam traps, or unusual events such as rain, fire water sprinkles, chemical cleaning, hydrojetting, f lushing, steaming, etc. In such scenarios with inevi- table moisture ingress, use of an adequate painting system (primer, multicoat) can be an effective and viable last line of defense against CUI. Nevertheless, a balanced moni- toring approach considering the detailed history of the equipment, piping, tanks in terms of their operations, process, inspec- tions, reliability, and maintenance can pro- actively address the biggest portion of uncertainties with CUI. Finally, avoidance of CUI due to potential water dripping from overhead structures, as mentioned in the previous case, requires an RBI mindset, even during the design phase of the entire chemical process, operating systems, pro- cess equipment, as well as piping and struc- tural segments. 7 Figure 1 shows the modified map for some potential damage mechanisms that can be expected in the heater components, including tubes, casing, heat recovery coils, steam header, and reformer system, along with adherence to neighborhood-inf lu- enced damage mechanisms. Figure 2 shows the possible sensitivity analysis using a modified tornado diagram to indicate the propensity and associated outcome toward neighborhood-influenced damage mecha- nisms. Additionally, it shows applicable consequences, including financial and out- age impacts. 8 In other words, neighbor- ho o d-driven unc er t ainti e s can b e ad- dressed by adherence to site conditions, operation log books, process data, applica- ble damage mechanisms, as well as piping isometrics as well as process and instru- mentation diagrams. Conclusions 1) In addition to known environment- a ss o ci at ed d am a ge m e ch ani sm s (like environmental corrosion, envi- ronmentally assisted cracking, etc.), common neighborhood conditions (such as stray currents, 9 cooling tower drifts, and floor vibrations due to machinery), inspection and RBI teams should consider the historical records of unusual events in the neighborhood. These unusual neigh- borhood events include dripping water, chemical cleaning, steaming, hydrojetting, flange leaks, fire water sprinkling, spills, fires, explosions, relief valve pop-ups, repairs, etc. 7 As a best practice, the frequency and p a tt e r n of t h e s e re c o rd ke e p i n g should be made flexible for potential consolidation with an organization's RBI program. 2) Credibility and sensitivity of neigh- borhood envelope-containing equip- ment, piping, systems, loops, compo- nents, and stray currents 9 toward the equipment or segment under study should be considered, followed by a thorough review and evaluation as a part of RBI efforts. 3) Wherever feasible, painting systems (or at least primer) for piping and FIGURE 1 Damage mechanisms map for typical reformer-economizer heater system. FIGURE 2 Damage mechanisms sensitivity analysis for typical reformer-economizer heater system.

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