In the EC the oxide film is mechanically removed from a metallic substrate.

1. Estimation of Flow Accelerated Corrosion (FAC) in Process Piping Using CFD Software and Low Temperature Experimental Determination of FAC.

2. This presentation includes idea about Flow Accelerated Corrosion (FAC), FLUENT analysis of KANUPP feeder in order to find FAC in them and experimental work regarding to study FAC at low temperature.

3. Flow Accelerated Corrosion (FAC) is a process in which a normally protective oxide coating dissolves into a rapidly moving water, or a water/steam mixture. • Principal parameters on which FAC depends are temperature, pH, oxygen content, and water velocity. • This phenomena was identified as a result of research in France, Germany, and the United Kingdom over the past twenty years.

4. FAC and Erosion Corrosion (EC) are normally considered same which is wrong. The differences involves the mechanism by which the protective film is removed from the metal surface. • In the EC the oxide film is mechanically removed from a metallic substrate. • In the FAC process, the protective oxide film is not mechanically removed. Rather, the oxide is dissolved or prevented from forming, allowing corrosion of the unprotected surface.

5. There is a cleared difference b/w single and double phase FAC. Single-phase FAC produces a scalloped appearance, similar to an orange peel while Two-phase FAC produces a “tiger striped” or streaked appearance. Single-phase FAC case Two-phase FAC case

6. FAC rate is peaked in 130-150 oC and is due to fact that at higher temperature magnetite layer becomes denser and solubility of Fe3O4 reduces in water.

7. FAC rate increases with increase in pH of working fluid however temperature contribution should must keep in mind as it considered a sort of pH control agent.

8. FAC: transfer of Fe(OH)+ and Fe(OH)2 is accelerated by not only average velocity but also turbulence factor which can described on shape factor bases, higher the Kc higher will be the FAC.

9. FAC rate also depend on material used, in carbon steel FAC is maximum while it suddenly decreases according to Cr(+Mo) contents thus FAC in carbon steel can mitigated with high Cr contents.

10. FAC rate decreases with increasing Dissolved Oxygen (DO) and it is due to the hematite formation which prevent FAC more than magnetite layer that form in common.

11. Process piping isometric drawing and detail description is used to make its geometry, meshing, CFD analysis etc.

12. Geometry is developed by using Pro/Engineer and then is saved in IGS format.

13. GAMBIT is used for meshing. Hex core mesh is used in order to lower cell counts and improve the quality, this type is generally used for flow volumes with complexity near the walls.

14. Meshed file that has generated is solved in segregated solver, 3D space, implicit formulation, cell based gradient option and absolute velocity formulation at steady state condition is set for analysis.

15. In order to check grid independency (GIT) two grids with different counts are made and solved to get velocity contours when these give very less remarkable difference grid independency proved. Grid Cells = 450,000 Time for solution = 1.25 hrs Grid Cells = 550,000 Time for solution = 1.75 hrs

16. Velocity contours and velocity vector are determined.

17. Contours of wall sheer stress and absolute pressure also give an idea to predict the location of high corrosion attack.

18. Discrete phase model enhancement feature can be used to calculate erosion rate at walls result shows in unit less quantity which in actual heaving units of length/time.

19. Further description of model provide more deep analysis of Erosion Rate, from velocity contours corresponding to maximum velocity erosion rate of 1.1 mm per year calculated Here B = 495 (for 2.75mm diameter particles) V = 7.64 m/sec So Maximum Erosion Rate is ERmax = 1.1 mm/year

20. Layout of experimental setup for determination of Flow Accelerated Corrosion is shown. Open system design is selected in order to examine phenomena at low temperature.

21. Centrifugal Pump, water storage tank, pipeline and fitting that used in setup are shown. Pipe lines of UPVC are used in order to retain integrity above 90oC. Water tank Pump Pipe lines and Fittings

22. Specimens Holder different views and coupon used in experiment are shown, specimens holder is also made of thermal resistance plastic material.

23. Assembled setup in operating and non operating condition is shown while proceeding experimental clip provide better visual aid of completed experiment. video.mp4

24. Main objective of experiment is to determine FAC at low temp which may further explained as determination of threshold temperature for FAC, Experimental working conditions are given in table.

25. During experiment water chemistry is maintained as of chemistry of secondary side of KANUPP or as chemistry of water used in CIAL experimental rig.

26. Observations and calculations at end of experiment give the idea of corrosion rate in coupons maintained at specific conditions, in coupon 2 maximum corrosion rate is observed 1 2 3 4

27. pH and conductivity trend of working fluid during experiment w.r.t time shows almost constant pH and increasing trend of conductivity; increase in conductivity is due to addition of crud from old pump.

28. RESULTS AND DISCUSSION CFD analysis of give the maximum wall thinning rate of 1.1 mm per year, while in the plant the data maximum thinning rate of feeder is given 0.1084 mm per EFPY. A great difference in thinning rate is due to neglecting the welding points in feeder geometry development, Ignoring chemical addition effect in primary stream etc.

29. RESULTS AND DISCUSSION (Contd....) From experiment maximum corrosion rate found in coupon no 2 because of maximum eddies formation due to flow pattern. No evidence of FAC observed on coupons (orange peel appearance) surface and not remarkable wall thinning measured. At 90oC no FAC occurred so there is no need to do experiment below this temperature.