Sand erosion measurements under multiphase annular flow conditions in a horizontal-horizontal elbow

Abstract

Gas-liquid annular flow is commonly observed in natural gas transmission and offshore horizontal pipelines. The presence of sand particles in such flows can cause severe equipment degradation of piping elements. The most vulnerable parts of pipeline systems tend to be components in which the flow direction changes suddenly such as elbows and tees. This paper presents the results of an experimental study on erosion in an elbow under gas-liquid-sand flow conditions. Firstly, erosion patterns and mass loss measurements were obtained in a test cell with paint erosion approach and aluminum elbow specimen. Secondly, a non-invasive Ultrasonic Technology (UT) device was employed to achieve erosion patterns in a 76.2mm ID stainless steel standard elbow. The wall-thickness loss was measured at 16 different locations on the elbow using dual element ultrasonic transducers. Experiments were performed with superficial gas velocities ranging from 27m/s to 49m/s at nearly atmospheric pressure. Superficial liquid velocities varied from 0.005m/s to 0.457m/s. In all cases examined, the orientation of the elbow was horizontal-horizontal. Three different sand sizes (20, 150 and 300μm sand) were used for performing the tests. Experimental results showed different erosion behaviors with variations of flow patterns in the horizontal-horizontal elbow (H-H). The data were also compared to some erosion data previously obtained in a vertical-horizontal elbow that shows erosion in H-H elbow is much smaller than V-H elbows for some of the multiphase flow conditions. In summary, the effects of different parameters such as sand size and liquid viscosity on measured erosion rates were investigated.