Erosion hot spots of drain valve under higher particle flow rates

Abstract

Drain valves mounted onto the blow-off pipelines of natural gas gathering plants are often used to discharge deposited particles in separators. Particle flows (greater than 0.01 kg/s) always lead to inner and even outer leakage owing to erosion hot spots in the valve body and valve core. In this study, various approaches, including online particle monitoring experiments, ultrasonic wall thickness measurements, and flow control methods were used to investigate valve erosion hot spots in field experiments. Numerical simulations with a large-scale moving grid method were conducted to demonstrate the dynamic erosion in a compressible gas flow. The results reveal that the erosion hot spots continuously shifted to nearby areas during the surface evolution. The local erosion rate of the original erosion hot spots always exhibited a decreasing trend, while the erosion rates of the nearby hot zones exhibited an increasing–decreasing trend. The erosion rate of the erosion-deformed zones that suffered delayed particle impacts always exhibited an increasing trend. When the pressure increased from 0.5 MPa to 3.5 MPa, the erosion hot spots shifted to Point_B 3. The velocity contour considering the gas compressibility was also determined for this process, and the gas velocity spraying to the facing wall was successfully created. The Oka erosion model was combined with the moving grid method and validated as the most appropriate method for predicting erosion hot spots. As time evolved, the operational flow rate of a 10% valve opening at 46,080 s was equal to the flow rate of a 40% opening at 0 s. On the basis of this relationship, the entire failure process of the valve was accurately obtained using a semi-empirical method. Finally, two novel valve structures are proposed to create a strong erosion–absorbing effect and thereby weaken the erosion hot spot of the valve.