Analysis on adaptability of determination methods for pigging cycle of wet-gas pipeline

In actual operation, the pigging period of wet-gas pipeline should be determined by some methods to guarantee the efficiency of pipeline transportation. In order to study the adaptability of common determination methods for pigging cycle of wet-gas pipeline in China, the disadvantages of minimum gas transmission efficiency method, maximum allowable pressure drop method and maximum liquid inventory method were analyzed. Additionally, the variation rules of pipeline transportation efficiency and liquid inventory after pigging were emphatically studied based on two actual pipelines. The results show that the key factor to determine the pigging cycle is the volume of liquid slug as a result of pigging rather than the liquid inventory in pipeline when the maximum liquid inventory method is adopted, and it is limited to determine the pigging cycle by static liquid inventory. In the case of large throughput of pipeline, the minimum gas transmission efficiency method and the maximum allowable liquid inventory method are also limited for the pigging cycle obtained is infinite. For actual pipelines, the pigging cycle obtained by the minimum gas transmission efficiency method or the maximum liquid inventory method is too short, which cannot provide guidance for determination of field pigging cycle.