Study On Erosion-corrosion Behavior Of 90-degree Horizontal Elbow In Liquid-solid Flow

The transportation medium includes oil,gas,water and sand etc.,so gathering pipelines are facing a severe erosion-corrosion problem of multiphase flow,and erosion-corrosion seriously affects the safe operation of gathering and transportation system.Elbow is a weak link in the corrosion of the gathering and transportation system,but the understanding of erosion-corrosion of elbow is still limited,therefore,it is necessary to conduct further study on erosion-corrosion of elbow,which is important to ensure safe production of gathering and transportation system,and can provide guidance for design of pipelines under erosion-corrosion environment.In this paper,with the loop system designed independently,the erosion-corrosion behavior of 90-degree horizontal elbow was researched under the condition of liquid-solid flow by mean of combining test and numerical simulation.By specimens morphology observation,weight loss measurement and electrochemical test,the corrosion characteristics of different local area of elbow were determined,the contribution of corrosion,erosion and interaction to total weight loss was quantified.,the most severe location of erosion-corrosion was determined,the interaction mechanism of erosion and corrosion was analyzed.The erosion-corrosion behavior at different locations of 90-degree horizontal elbow was researched.The results showed that in the total erosion-corrosion rate,the percentage of pure corrosion rate and pure erosion rate is very small,the percentage of erosion-corrosion interaction rate is large,so erosion-corrosion interaction is the main cause in the damage of metal materials.In erosion-corrosion interaction rate,changed amount of corrosion rate caused by erosion and changed amount of erosion rate caused by corrosion are positive,and the former is obviously larger than the latter.So mechanical erosion process and electrochemical corrosion process can promote each other,and mechanical erosion playes a leading role in erosion-corrosion,and electrochemical corrosion also playes an important role.The most serious location of erosion-corrosion is at the bottom of the inner and outer part of test elbow that the axial angle θ between 75~90 degrees.The serious erosion location predicted by CFD numerical simulation is in good agreement with the serious erosion-corrosion location measured by test.The effect of sand concentration on 90-degree elbow erosion-corrosion behavior was also researched.The results showed that with the increase of sand concentration,the erosion-corrosion rate of specimens at different locations of 90-degree horizontal elbow increases.Sand concentration increases from 0% to 1.25%,the erosion-corrosion rate and pit depth of specimens at different locations of 90-degree elbow increases greatly.Sand concentration increases from 1.25% to 2.5%,the erosion-corrosion rate and pit depth of specimens at different locations of 90-degree elbow increases slightly.So the presence of sand particles in liquid-solid flow has greatly promoted the erosion-corrosion of metal materials.