When I started writing under the pseudonym ‘hawsepiper,’ that’s what I was doing with my time. I worked on steam tankers for 8 years before switching over to barges. I got my license a while back, but it never seemed to make sense to bother changing the name. I AM a hawsepiper, after all. I’m licensed, but never went to an academy. I started out as a marine scientist an policy analyst, but went to sea when I realized I hated what I was doing and the people I was working for. As Steamer said, though, I do tend to rant. You spend well over 100k on an education in the humanities, hard sciences AND international policy and then realize you were happier working on little fishing boats, and see what it does for your temper.
As far as the original question, jackson, most ship-to-barge lightering is done (in the US) with non self-propelled barges. There are a FEW self-propelled barges around, I think, but I haven’t seen them in the US. There used to be a fleet of them for bunkering around the anchorages at the Panama Canal, and northern Europe was rotten with them. The peculiarities of our maritime commerce, legal environment and infrastructure make ship-to-barge lightering reasonably efficient given the high cost of manning and terminals geared towards smaller parcels and docks. Non-self propelled barges may be manned full time (rather than having the crew live on a tug) or not, have decent living quarters, a cargo office, generators, or just a folding chair on deck, and dedicated pumping systems (usually diesel engines running to a geared screw-type impeller pump connected to a pipeline that feeds all the tanks on board) for discharging the oil. The type and complexity is based on the needs of the folks involved.
Self-propelled barges were an end-run around expensive manning and restrictive regulations affecting ships. They truly have no prime movers dedicated to propulsion- rather, they rely on a low-geared PTO-drive or hydraulic pump on both sides of their pump engines- The forward PTO would run to the cargo pump drive, and the after PTO would run to a z-drive unit or v-drive to power a gearbox in front of a short prop shaft underdeck, running to a propeller. Like the old ITB units, they are not a great substitute, but they get you around construction and manning regs… that being said, the whole idea is to have a small crew and a cheap-to-build,maintain and keep in compliance vessel to save money. Work hour restrictions then become an issue, as does the cost of lay time and lost time… the few self-propelled bunker barges I saw were not very good at seakeeping, maneuvered horribly, and were not very big… I believe that there is an economy of scale issue, as well with the need to have the cargo pump engine also be the prime mover. You would have to use the same engine to power both units, otherwise it WOULD be a prime mover, and then become a ship.
Hope this helps.