<b>Mechanical Seal</b> In the course of time, mechanical seals were able to establish themselves as shaft seals in the shipping industry, mainly because of their comparatively low leakage and friction. The main components of the mechanical seal system are two rings sliding on top of one another (sliding ring and a counter ring), which are pressed against one another axially by a spring and between which a sealing gap with a gap size <1 µm is formed by hydrostatic and hydrodynamic effects. In this sealing gap there is a lubricating film made of the substance to be sealed (here water or oil), which significantly influences the function of the sliding direction. The distance between the two faces depends on several factors. These include, among other things, the nature of the mechanical seal significantly influenced. The distance between the two faces depends on several factors. These include the nature of the sliding surfaces, the pressure to be sealed and the sliding speed. The lubricating film leads to a reduction in friction, which practically prevents wear on the sliding surfaces. Possible wear of the sliding surfaces is automatically compensated for by moving up due to the spring pressure; Mechanical seals are therefore maintenance-free. One of the two rings sits rigidly in the stern tube, the other is attached to the shaft with anti-rotation pins. Sliding materials are usually made of carbon graphite materials, metal, ceramic, plastic or synthetic resin bonded carbon. Mechanical seals are designed in such a way that they can be serviced without being left in a dry dock.