Erosion is a complex process, especially with the presence of small particles and in complex geometries such as elbows in series. Erosion due to the solid particle is affected by different parameters such as material properties, particle material, shape and size, superficial gas and liquid velocities, flow regime and geometry. The main objective of this work is to investigate the effect of particle size in two 3-inch (76.2 mm) diameter elbows in series with curvature radius to pipe diameter ratio (r/D) equal to 1.5. A test section was constructed in a flow loop with a distance between the elbows equal to 12D. Paint removal experiments were conducted to determine the erosion patterns and hot spots of erosion using acrylic elbows. Additionally, erosion experiments were conducted with 300, 75, and 25 μm particle sizes in gas-liquid-sand annular flow in stainless steel elbows. The wall thickness loss of the elbows has been measured using state of the art non-destructive fix-mounted, temperature compensated, ultrasonic transducers. Experimental results showed that higher erosion was obtained with 300 μm particle size where the erosion in the second elbow is lower than the first elbow with the 12D distance. With respect to the maximum erosion ratio of the second elbow to the first elbow, the results showed that the ratio of erosion rates in two elbows (second to first) decreases with increasing the particle size. A higher ratio of the two elbows was obtained with 25 μm compared to 300 and 75 μm particle sizes. However, in the first elbow, the erosion rates decrease with decreasing particle sizes.