Pipe tunnel
The pipe tunnel ( engl. Duct keel or pipe duct ) on a ship is a walk-in tunnel height of the double bottom in the longitudinal center of the vessel, usually continuously from the machine room up to the bow .
In the pipe tunnel, sections of the pipelines for ballast water and fuel lines as well as the associated shut-off valves are installed. The purpose of this is to run the pipes and shut-off valves dry through the ship, i.e. not to have to run through any filled ballast water or fuel tanks.
For maintenance purposes, the pipe tunnel can be entered from the engine room, from the cargo hold and from the forecastle via manholes . Because of the usually very cramped space conditions - a pipe tunnel often only has a total cross-section of 1.5 × 1.5 meters, and frames and longitudinal beams also run through it - and the relatively long length - between 80 and 250 meters depending on the type of ship Pipe tunnels are usually equipped with a track system so that a carriage can be used for transport during maintenance and control work.