Characterization of bypass pig velocity in gas pipeline: An experimental and analytical study

For accurately characterizing bypass pig velocity, the paper firstly conducted a pigging experiment based on a newly developed bypass pig prototype in a gas pipeline, and a quasi-steady state bypass pig model was validated by the experiment. Moreover, an infrared ray-based pig velocity detection method was proposed. The results show that the entire average bypass pig velocity linearly changes with the rear driving gas flow rate and gas-to-pig velocity differences remain constant at the same bypass fraction. The existence of bypass fraction effectively reduces the pig velocity and alleviates the fluctuation of pig movement. Calculation results of the established model are in good agreement with the experimental data. The newly developed infrared ray-based pig velocity measurement results have the same accuracy as that measured by pressure sensors with deviations below 1%. The study sheds light on the promising prospect of bypass pigging technology in the application of natural gas field to safeguard energy transmission.