Optimization of receiving process in pigging operation of long-distance gas pipeline

As a bottleneck in pigging operations, control over pig running rate may frequently present hazards to pig-receiving operations. To protect the pig receiver and accessories against damages induced by high pig running rate, and thereby enhance safety and reliability of pig-receiving operation, the indirect pig-receiving process is proposed on the basis of direct pig-receiving process. In particular, branch pipeline at the inlet T-joint and the pig-pilot pipe of the pig receiver are used jointly to establish communication before and after the pig to counteract the ball-driving pressure difference and so reduce the velocity of the pig entering the pig receiver. Then, openness of valves on the branch feeding lines is adjusted to re-establish the differential pressure, so that the pig can enter the pig receiver slowly. Through HAZOP of the new process, some suggestions are proposed to ensure its smooth implementation. For example, the new processes is included in the pipeline SCADA system to ensure real-time monitoring; monitoring over key nodes is strengthened, more gas detectors and more frequent detection are used. Field applications show that the new process can effectively control the speed of the pig entering the pig receiver, so as to avoid potential damages and achieve proper buffering effects.