The varying wall thickness is interesting. Presumably they reduced the thickness the further they got from Russia, as the pressure drops. One of the methods used for clearing a stuck pig is reversing the flow.
I wonder how reversing flow works mechanically? Does Russia pump out of the pipe, reducing pressure, or would the receiving end increase pressure? Up to 220 bar, or would they have to stop lower?
I think the latter, since you can only reduce the pressure to the vapour pressure of the fluid. You get more bang for your buck pushing than pulling.
Also the pressure can generally be raised above the design pressure for short periods, pipes are generally hydro tested at 125 - 150% of the design pressure.
I wonder how reversing flow works mechanically? Does Russia pump out of the pipe, reducing pressure, or would the receiving end increase pressure? Up to 220 bar, or would they have to stop lower?