Crude, dirty or clean petroleum products, vegoils and easy chemicals! :speechls:
And how do they clean this sucker between loads?
There are cleaning chemicals these days that allow a ship to change straight from a dirty cargo like fueloil or crudeoil to something like jet fuel, especially when the ship has high quality coatings to its tanks (coatings are made of epoxy resin - like a non-stick pan, but on an industrial scale) or the tanks are stainless steel lined.
Generally a ship can change from dirty to clean by stages of trading in clean(er) cargoes, like taking a semi-clean cargo like Marine Diesel Oil, then three cargoes of clean Gasoil. The amount of cleaning between grades is comparatively negligible this way. This method is generally accepted as being sufficient to then trade very clean cargoes like Naphtha or Jet Fuel. A vessel that has traded the last two products mentioned would have little trouble then trading easy chemiclas - but the vessel would have to be specifically certified to carry easy chemicals first - there are different levels of certification and a vessel will generally be built to meet such specification.
Oh BTW all cargoes need to be lead-free to continue such trade - not so much of a problem these days, but it used to be.