The effect of longradius elbows on solid particle erosion

Abstract

Sand particles entrained in produced oil and gas can impact pipe materials and remove metallic materials during solid particles erosion. Erosion is a big issue for the oil and gas industry as many subsea pipelines exist in the world today and petroleum spill as a result of pipeline erosion is catastrophic. Solid particle erosion is an important subject when it comes to pipelines carrying solid particles in subsea mining and oil and gas operations. To predict erosion and maintain equipment integrity, the erosion phenomenon has been widely investigated over recent years. For pipelines carrying multiphase flows, solid particle erosion is affected by superficial gas and liquid velocities, particle size and shape, and flow regime. To alleviate erosion issues in elbows, longer-radius elbows could be used. Nevertheless, there is a limited experimental investigation in the literature, especially for multiphase flows. Therefore, long-radius elbows with different curvature radii were investigated for their effectiveness to reduce erosion. In this research, various elbows curvature with r/D=1.5 (r is the radius of curvature; r/D=1.5 is for standard elbow), 2.25, and 5 were examined in a 50.8 mm pipe diameter test section in a flow loop. They were examined under two-phase and multiphase flows. In liquid-solid and gas-solid (two-phase) flows, high and low mixture fluid density and viscosity were considered. Water (1cP viscosity) was used as the liquid phase. Moreover, multiphase flow cases were considered, such as slug/churn, dispersed-bubble and churn/annular flows with solid particles. In addition, in order to determine the effectiveness of other pipe fittings to reduce erosion, a triangular elbow was compared with a circular long-radius elbow in dispersed-bubble flow, where r/D=2.5. Furthermore, a standard elbow was examined with a 45º bend in dispersed-bubble and liquid flows. Moreover, three elbows with different orientations were conducted in gas flow with two particle sizes. Additionally, experimental data were collected with a standard elbow in various liquid and gas superficial velocities. Finally, the computational fluid dynamics (CFD) were validated with experimental data for (gas-solid and liquid-solid) two-phase and multiphase flows. Most importantly, a CFD based model for the correlation of long-radius elbows to the standard elbows that was developed previously to account for r/D was evaluated and improved specially for multiphase flow using the collected data.