Design of an elbow for integrated gravimetric, electrochemical and acoustic emission measurements in erosion-corrosion pipe flow environments

Erosion-corrosion degradation in oil and gas pipelines is a significant problem, and a change in flow geometry can significantly enhance rates of degradation. In this study, a 3D printed 90 degrees elbow, integrated into a flow loop, was developed to evaluate erosion-corrosion of X65 carbon steel along both the inner and outer internal portions of the bend in an aqueous carbon dioxide (CO2)-saturated environment containing sand particles. Designing representative geometries capable of measuring rates of corrosion, erosion and their synergistic interactions, can be challenging and currently no designs have been reported in literature that effectively integrate the required measuring techniques to determine local degradation rates throughout the component. To elucidate the individual contributions to overall erosion-corrosion degradation rates, gravimetric and electrochemical measurement techniques were used to quantify degradation rates at multiple locations in the flow geometry, with the specimen design also enabling the possibility of completing acoustic emission measurements to detect particle impacts. The design of the elbow is presented and erosion-corrosion tests were conducted to determine the magnitude and individual contributions of erosion, corrosion and erosion-corrosion interactions at a flow velocity of 6 m/s in a CO2-saturated, pH 4, 60 degrees C, 2 wt% NaCl solution containing 1000 mg/L of sand particles.