Hi expertise In our refinery we have preheat trains (heat exchangers) and their tubes made of 12% Cr and %BD Mo but unfortunately there were many leaks at some of these tubes . The samples was collected before and found the following 89% iron sulfide and 11% Nacl . in regard to that any help to figure out the main reason lets the tubes fail . Thanks

Following facts need to be known before any attempt can be made to reply. These are 1) %age S (2) % Cl- (3) naphthanic acid (TAN) (4) operating temp of HE (5) Type of failure (ptting/grooving or any particular pattern) (6) caustic addition (y/n) You must be having periodic test data of Crude ex desalter. Pl. go thru' it. It will give you some indication about the performance of Desalter. Also please let us know about the performance of your distillation colum top, pH ex reflux drum boot water. Also whether colum top dome is monel lined or not. Without getting a proper picture, it will be difficult to comment. Regards Chakra

Hi again This failure happened at the heat exchangers (preheat trains) frequently at the tubes (12% cr %BD mo) floating sheet and its cover (5 cr %BD mo) . Caustic is injected to the crude before it enters the preheat to control the chloride at the over head when the chloride is high the normal practice the amount of caustic increased. Crude enters at 165°C where it is heated to 177°C. the amount of chloride at the over head top was measured to be 25 ppm and it changes some time to reach 35 ppm and there was no naphthanic acid at our crude. The failure is pitting at the tube sheet and tubes and erosion at the floating head sheet gasket. Distillation colum Amine filmer and netreulzer injected at the top of the distillation column and the ph of the bot about 6.6 and it not fixed number . The column top is cladded with Hastelloy and it was replaced before 3 years due to pitting corrosion and localized corrosion . Thanks