Study of accelerated erosion of elbow-shaped connections with corrosion defects

Abstract

In the later stages of gas field development, corrosion and erosion wear often occur in elbow-shaped connections used for gas transportation. Combined with laboratory corrosion experiments, the paper is based on CFD to study the distribution characteristics of pressure and velocity in the flow field for the elbow with pre-set corrosion defects. Simultaneously, the specific procedure is designed to track the formation of Dean vortices, thereby revealing the impact patterns of different corrosion defect features on the erosion outcomes of the elbow. Accordingly, the effect of different arrangement, number and form of corrosion defects on erosion wear was systematically analyzed. The results show that: (1) A comparative analysis of the three different defect distribution forms indicates that erosion occurs mainly at the bend near the outlet Section (45° ~ 60°). Double corrosion defects in the radial distribution will significantly accelerate the rate of pipe erosion, changing the location of maximum erosion rate. (2) By controlling the number of corrosion defects to represent the size of the corroded area, the study reveals as the number of defects increases, the rate and area of erosion in surface of the target material increases significantly. Thus, the area of the corrosion will explicitly change the effect of erosion. (3) As the depth of the defects (corrosion rate) increase, the erosion rate around the radial and axial defects increases exponentially compared to the absence of corrosion, reaching a maximum of 7.8 × 10−6 kg/(m2·s). Corrosion and erosion are two complementary forms of damage to pipe in the production process. The presence of corrosion defects leads to faster erosion rates and changes in the overflow area, reducing service life. Hence, only a reasonable control of both types of wear can ensure the longevity of gas production and transportation.