Pigging operation of the Sichuan-East Gas Transmission Pipeline

Currently, there are no consistent standards and regulations for pigging operations of long-distance gas pipelines, for example, in relation to selection of pig, definition of pig parameters and velocity control. The pigging operations of the Sichuan-East Gas Pipeline have been analyzed mainly for equipment selection, parameter definition, adjustment of pig retrieval process, monitoring of pig as well as velocity prediction, so as to identify the pigging practices of large-diameter pipelines. In this study, both polyurethane (PU) pig and cup pig are utilized. The wring of cup pig is 3% of wall thickness of main pipeline section and that of PU pig is 5%. Through adjusting the process of pig recovery, the recovery velocity is controlled. Pigs are monitored in the valve chamber or at the inlet or outlet terminals. Before operation, the velocity of pig was simulated with SPS, showing 5% less than the actual velocity. Except during the stages of pig launching and retrieval, both pigs didn't differ so much in velocity. Through the identification of features inside the pipeline, contaminants in pipelines can be removed so as to improve the operation efficiency of pipeline. Accessibility of pipeline is inspected to lay a basis for the further internal inspection. This paper presents relevant experience and put forward suggestions on improvements, which can serve as a reference for the pigging operations of large-diameter pipelines.