RE:RE:RE:Question for those who have worked with pipelines...SURE...reddeer and what is used to push the pig along???? Pipelines cannot be emptied with a pig....according to your own link. It takes "product in the pipeline" to push it along.
"This is accomplished by inserting the pig into a "pig launcher" (or "launching station")—an oversized section in the pipeline, reducing to the normal diameter. The launching station is then closed and the pressure-driven flow of the product in the pipeline is used to push the pig along the pipe until it reaches the receiving trap—the "pig catcher" (or "receiving station").