Pigging Dynamics in Two-Phase Flow Pipelines: Experiment and Modeling

Abstract

Summary Standard design procedures for two-phase pipelines subject to pigging operation still rely on steady-state methods. Because the flow behavior under a pigging operation is transient, more rigorous methods must be developed for a proper design of such operations. This paper presents an experimental and theoretical study on transient pigging operation. An extensive experimental program was carried out to acquire two-phase transient flow and pigging data on a 420-m- [1,378-ft-] long, 77.9-mm- [3.068-in.-] diameter horizontal pipeline. A computer-based data-acquisition system was used to obtain detailed information of the flow behavior during the experimental runs. The data include measurements of the time variation of the liquid slug size ahead of the pig, flow rates during the slug delivery, pig velocity, and pressure and liquid holdup distributions. The data were acquired at four measurement stations installed along the pipeline. A pigging model was developed for predicting the dynamics of a pigging operation. The model incorporates an improved simplified transient model that has been validated with the experimental data. A mixed Eulerean-Lagrangean approach was used to couple the transient model and the pigging model. The resulting computer simulator can predict the transient two-phase flow in a pipeline with or without pigging.