The purpose of this work is to present a simplified explicit model to assist the gas controllers during pig run operations. The model considers the mass balance to obtain an approximation of the transient flow profile and calculates the gas velocity using analytical equations to estimate pressure and temperature profiles, while the gas density is calculated by an explicit equation of state for real gas. The effect of seven different models for natural gas compressibility factor are verified on the Pig tracking model. Additionally, the influence of the temperature profile on the pig velocity is analyzed by varying of heat transfer coefficient. A total of five real test cases of pig run in two different section of the pipeline are used to test the model. The results revealed that the heat transfer coefficient slightly impacts the pig velocity. A maximum of 5.8% difference in the average pig velocity is found among the natural gas compressibility equations. As a general observation, the model was able to predict pig position within 8% of error.
It is well established the importance and benefits of pigging during the many phases of a pipeline life, from commissioning to operation and this includes cleaning, inspection and data acquisition as pointed out by McDonnell et al. (2004). Routinely, as required by the maintenance and integrity programs, is necessary to promote a Pig run to remove lubricants carried out from compression stations or dust and many other times to find corrosion points, dents or cracks. However, a significant amount of time is spent by operational staff during pigging operations. In remote control stations, operators must have adequate monitoring information about pig location to take the necessary actions in order to have safe and reliable pipeline operation.