Experimental investigation of sand particle erosion in a 90° elbow in annular two-phase flows

Upward gas-liquid-solid flows are often observed in oil and gas transmission pipelines. The presence of solids in such flows is a concern, as it can cause serious damage to pipe fittings, which are prone to erosion. These are normally components such as elbows and tees that can change the flow direction. The current work presents the results of an experimental erosion campaign including 56 tests in a 101.6-mm standard elbow (radius of curvature of 1.5) under gas-sand and gas-liquid-sand flow conditions. The latter included 38 tests (30 distinct conditions) mostly in the range of annular and unstable annular flows. Thickness loss measurements were made using a non-invasive ultrasonic technology instrument at 8 different points along the outer bend of the elbow to investigate effects of various factors on erosion. Additionally, flow visualization and paint erosion studies were performed to examine liquid distribution as well as the particulate phase behavior. Generally, when superficial liquid velocity increased, erosion ratio decreased for low liquid rate conditions. This trend, however, reversed for higher liquid rates. Also, the paint erosion experiments revealed that the location of the maximum erosion was around 40 degrees-50 degrees on the middle outer bend, for all cases examined.