Materials Performance

AUG 2018

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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44 AUGUST 2018 W W W.MATERIALSPERFORMANCE.COM COATINGS & LININGS G Volumetric ultrasonic thickness mea- surements performed on the ab- sorber column of a gas dehydration unit found several laminations and in- clusion clusters around the chimney tray. This unit had been in operation for 40 years. A fitness-for-service anal- ysis found that the defects were of considerable size and the component could not continue in operation un- less mitigating actions were taken. Possible remedial options were to replace defective plates, rerate, or provide a mechanical barrier to arrest hydrogen permeation. A polymer coating applied on the column's in- side diameter led to reduced hydro- gen activity that resulted in huge cost savings and continued safe operation. G a s d e hy d ra t i o n u n i t s (GD Us) a re primarily used in upstream operations to remove water from the raw natural gas. Before treatm ent, natural gas may b e saturated with water, which can cause downstream damage. Natural gas equip- ment with high water content in the gas stream is highly susceptible to aqueous damage mechanisms, freezing and piping damage at low temperatures, and methane hydrate formation due to the reaction of hydrocarbons with water. Damage mechanisms possible in GDUs include stress corrosion cracking (SCC) and wet hydrogen sulfide (H 2 S) damage that includes sulfide stress cracking (SSC), bli st erin g, hydrogen-induc ed crackin g (HIC), and stress-oriented HIC (SOHIC). Wet H 2 S damage occurs w hen there is increased hydrogen permeation due to increased H 2 S partial pressure. This is pos- sible at op erating conditions b etween ambient temperature and 300 °F (149 °C) and acidic or basic pH. 1 Excess hydrogen permeates the metal at inclusion clusters and l amination s, w hi ch creat e s over - stressed areas that e ventual ly lead to hydrogen blistering and/or cracking. NACE International guidelines recom- mend the use of organic or inorganic coat- ings, or corrosion-resistant alloys as barri- ers to corrosion. 2 These coatings form a physical barrier that isolates the metallic surface from corrosive environments such as wet H 2 S and other corrosion enablers. Using coatings that are hard, adherent, free of defects, and hydrophobic with low coef- ficients of friction protects interior and exterior equipment surfaces from corro- sion. 3 Such protective coatings are tested in h i g h - pre ssu re , h i g h - t e m p e ra tu re , a n d highly corrosive environments, and extend component ser vice life w hile lowering maintenance costs. Previous studies have demonstrated that wet H 2 S SSC, carbon dioxide (CO 2 ) corrosion, HIC, and other damage mechanisms can be mitigated in this manner. 3-5 Coating Application to Minimize Hydrogen Cracking in Gas Dehydration Units c e S a R e S pinoza, Sudhaka R Mahajana M , and Ryan d uBoi S , Pinnacle Advanced Reliability Technologies, Pasadena, Texas, USA

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