Leakage Causes of Ground Pipeline Measurement Valve in a Gas Well

The pitting leakage of ground pipeline measurement valve in a gas well and its producing condition were investigated, and the failure reasons were analyzed by field research, metallographic structure, spectroscopy and chemical composition analyses. The results show that the microstructure and chemical composition of the valve and the chemical compositions of the inner surface plating, sealing ring and top cover meet the demands of the standards. There was serious erosion corrosion in the substrate and upstream of the valve.The ring ditch on the top cover of the valve ball resulted from the simultaneous action of erosion corrosion and crevice corrosion, which related to the structure defect of the ring crevice in the top cover. The finally formed ditch between the top cover and the ball resulted from erosion corrosion, gas corrosion and galvanic corrosion. The reason of the corrosion ditch on the inner surface of the valve was also the results of erosion corrosion, gas corrosion and galvanic corrosion on the coarse and uneven surface.