DIN 87721-1:2014-04

The document specifies drain screws for water and oil tanks, where the shell plating forms the tank bottom. The whole screw joint consists of a weld-in plate and a drain screw of metric thread which is installed with a suitable sealing. The height of the recess at the weld-in plates is rated in accordance with the shell plating thickness, thus avoiding any projection at the ship's shell.