Corrosion Cause Analyses And Mechanism Study Of Radiating Elbow Of A Weat Steamer

Steam genetrator is the key equipment of catalytic and cracking and heavy oil thermal recovery. As the enlargment of heavy oil thermal recovery scale, the corrosion of wet steamer and steam pipiline becomes more and more severe, even cause pipe cracking accident which have severe effect on usual production. Simutaneously, safe production is not guaranteed and the big loss is caused. The wet steamer is the key and exclusive equipment of heavy oil thermal recovery in oil field. It is composed of preheat section, convection section and radial section, of which temperature and pressure have obvious difference. Convection section and radial section often work under the condition of high temperature ans pressure, especially radial elbow which is heat pushing elbow. The quality of elbow is influenced by many factors. Additionally, the elbow section and straight pipe section have difference working condition and the corrosion of elbow exists inevitably.The thesis aims to the corrosion problem of wet steamer in one oil field. Local sample was taken from radial elbow. Macroscopic examination was conducted by naked eyes. Corroded product was observed by scanning electronic microscope and phase analysis was proceeded by X-Ray diffraction. Besided of the above, the mechanical properties of crack was estimated.Result shows that the tube is accord with standard. The corrosion cause of elbow results in vapor and water corrosion, oxygen corrosion, chlorine ion corrosion. So that acid environment produce on the bottom of the pit. Under the corroded substance, inner surface of elbow exists micro cracks from inside to outside along inter-granular which displays the characteristic of hydrogen corrosion. Because temperature facing flame is high, electrode potential is low and results corrosion more seriously. Three phase flow is consist of vapor, water and solid particle and as well as corroded substance which peels off corroded scale causing grain after hydrogen corroded detaching from substrate. Discovered new surface is broken through so as to make inner material to break away from elbow. So wall thickness of elbow decreases rapidly.On the basis of above analyses, several ways protected from corrosion were proposed as follows:(1) reasonable choose material;(2) strengthens the management, fulfils exactly the working instruction; (3) enhances PH suitably the value; (4) regular elimination pipe wall scaling and corrosion product; (5) sacrifice anode protection; (6) blowing-out protection method; (7)deaeration law.The investigation of corrosion of radial elbow based on practical condition has theoretical meaning. Simutaneously, proposing the prevention methods about corrosion of radial elbow has big actual meaning.Importantly, it has obvious economic and social meanings.