The complete stern tube and sealing system (2): Stern tubes

Vincent van der Heiden

The slogan ‘The Origin of Sealing Solutions’ suggests that Lagersmit only offers seals. But did you know we also supply the complete stern tube and sealing system including stern tubes and bearings? In a previous blog we gave an introduction to Lagersmit’s bearings, but this blog focuses on complete stern tube systems. Keep reading to find out more about the working principles and how our stern tube system delivers you Peace of Mind.


The stern tube is installed at the stern of the ship and carries the sliding bearings that are used to support the propeller shaft. The stern tube is filled with a lubrication medium and provides room for needed piping for example oil lines, temperature sensors and the Supreme Ventus® system. Seals are installed at the aft and forward end of the stern tube.


Every stern tube design is customised according to the customer’s requirements. Because the stern tube can be fully equipped with piping, bearings and seals, the installation can be done within a day. There are various types of stern tube systems available and when making the selection you have to take several factors into consideration.


Factor 1
First, an important factor is the intended lubrication medium. Oil-lubricated stern tube systems are the most common and occasionally ship owners require a water-lubricated or grease-lubricated stern tube system.
Factor 2
Second, depending on the ship design, the stern tube can be supported with struts or can be positioned within the ship’s hull. Often the surrounding sea water will suffice for dissipating the heat from the stern tube oil. The heat generated by bearing friction is then transferred through the shaft and the stern tube inner surfaces towards the outer surfaces of the stern tube, adjacent to the sea water. If the natural heat dissipation doesn’t suffice and the oil temperature needs to be controlled, an external lube oil unit can be acquired for circulating and cooling the stern tube lube oil. Circulating the oil also provides the means to separate water from the oil, in case of water ingress.
Factor 3
Third, it is inevitable that stresses occur in the stern tube during installation and operation due to thermal growth. To prevent internal stresses, the forward end of the Lagersmit stern tube is free to extend in an axial direction, without compromising the strength and stiffness, or the attachment to the hull.


We offer complete stern tube systems with the bearings, piping and seals already in place. This will make the installation much easier and saves you valuable time and money. The design of the stern tube system can be customised according to your needs with a broad range of options.


Other advantages of our stern tube system: they are


  • delivered fully assembled on site
  • compatible with Lagersmit’s Supreme Ventus sealing system
  • ready-machined in a controlled environment
  • easily installed by means of a resin casting
  • interfaced with Lagersmit-type seals

In addition to stern tube bearings, we also deliver intermediate shaft bearings to support longer shafts in a driveline. If an open or closed water stern tube system is required, please call us for further information.

This was part two of the blog, ‘The complete stern tube and sealing system’. In a previous blog we focused on the bearings and gave you more information about the working principles, how our bearings deliver you Peace of Mind and what are the advantages of using a white metal lining.

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