RE:RE:RE:RE:RE:Question for those who have worked with pipelines...A pig does work with the fluids in the pipeline....thats how it moves...the bigger question is....do you have to empty it?... I say....shut the valves....turn off the pump...pipelines are buried below the frost line...so temp shouldn't be a problem....not sure if oil freezes and expands like water does...if it did we'd have a lot of cracked engines across the country....I'm sure if you empty it...and release the pressure...you'd have to pressure test it again before starting it up again....better to leak water or air than oil..