Tips from our expert: Stern tube seals for ferries

Passenger safety and planned maintenance intervals are the most important things for ferry companies. In order to achieve this, you can rely on Lagersmit Supreme® seals. Which seal fits your ferry best? In this blog our Supreme product specialist gives you tips about which sealing solutions are applicable on ferries. Keep reading to find out more!

Type 1: Supreme Ventus®

Zero emission is one of the topics that is getting more important in the maritime branch and is also relevant for ferries. The world’s focus on the environment is growing and environmental legislation is getting more stringent. Our Supreme Ventus ensures zero emissions of oil and thereby fulfils modern days requirements.

Is your ferry operating in US waters? Any leakage that is collected in the seal’s void chamber is drained into a monitoring tank in order to prevent an oil-to-water interface. This way the Supreme Ventus allows you to use mineral oils and still be VGP-compliant.

An important benefit of the Supreme Ventus is its ability to minimize wear and lengthen the seal’s lifetime, by creating a very low-pressure difference over the seal. The low-pressure difference is maintained at varying draughts, extending the seal’s lifetime. By monitoring the drained leakage, feedback is supplied about the condition of the seal. All data is stored and can be used for trouble shooting.

Type 2: Supreme SeaGuard Ventus®

Figure 1: Cross-section Supreme SeaGuard Ventus

For ferries it is very important that corrective actions can be taken, in the event of an unexpected failure, without the need of an immediate dry dock. The Supreme SeaGuard Ventus works the same as the Supreme Ventus, with one exception: instead of three there are four lip seals. The redundant oil repellent lip seal #3S and can take over lip seal #3 in case oil leakage is detected. This way dry dock can be averted. The Supreme SeaGuard Ventus gives optimum protection for ferries that are encountering harsh conditions.

Type 3: Supreme® Standard

As the name suggests, the Supreme Standard is the basic design of the Supreme range. The standard seal can be customized to your specific sealing needs with the aid of various options as described below. The Supreme Standard is commonly used for ferries that are sailing in moderate conditions.

Extra protection for the seal

The seal types discussed in this blog are most frequently applied on ferries and can be further customized by adding a few options to protect the seal even more.

Prevent seal damage caused by abrasive particles

Ferries often operate in coastal waters, containing sand and debris affecting the seal. Applying a Hard Metal Layer (HML) improves the wear resistance of the liner and decreases the docking time, because the liner doesn’t need machining for creating a virgin running surface. Damage to the seal caused by large abrasive particles can be avoided by adding a dirt barrier to the seal, that works as an axial lip seal preventing large abrasive particles from entering the seal. When operating in coastal waters it is advised to use NBR lip seals for their wear resistant properties.

Creating a new running surface after groove forming

Figure 2: Ferry

Our standard liner execution, made out of stainless steel, is not resistant to wear. Eventually the lip seals will create grooves in the liner. To expand the lifetime of the liner it is possible to add a Distance Ring from the beginning, which can be removed during maintenance once grooves are formed and shift the housing parts forward to create a fresh contact surface for the lip seals. In this case the liner can be reused without the need of shaft withdrawal and machining the liner.

No more fishing lines that harm the seal

Ferries also regularly sail in areas where fishing takes place and the fishing lines, nets or small ropes could damage the seal. To avoid this, net cutters can be welded to the rope guard. Lagersmit supplies stainless steel net cutters that severs fishing lines before entering the aft seal area. Another option to prevent harm from fishing lines is to install a wire winder to the propeller hub. And third, the dirt barrier also prevents small fishing lines from entering the seal.

Save time and money with split type seals

If you decide to retrofit your ferry to one of our Supreme seals, we also offer the possibility to install (fully) split seals. In this case, you don’t have to pull the shaft and this results in saving costs and docking time.

More info? Contact our seal expert!

About the author: Pepijn Swarte

Pepijn studied industrial design engineering at the Delft University of Technology and at The Hague University of Applied Sciences. He has been working for Lagersmit since 2013 and as Product Manager he is responsible for the research and development activities of the Supreme seals.