Water-lubricated sterntubes

An eco-friendly solution for cleaner oceans

With the introduction of the Polar Code and the continuous rise of polar cruising, more ship owners are turning to water-lubricated sterntubes. The harsh undersea environments can, however, lead to maintenance concerns. SKF’s Simplex BlueRun water-lubricated sterntube system has undergone vigorous testing to find an optimum balance between lubrication and wear.

Approximately 90% of the world’s shipping fleet are equipped with traditional, oil-lubricated sterntubes. However, vessels operating in Polar or also US waters must adhere to stricter regulations. The Polar Code prohibits any discharge of oil and under VGP2013 vessels must use environmentally acceptable lubricants (EALs) at all oil to sea interfaces, where technically feasible. Many ship operators therefore opt for sterntubes with a dedicated non-oil-to-sea interface, such as an air-seal or a completely water-lubricated sterntube.

Extensive testing, extreme durability

With over 70 years of market experience in shaft line solutions, SKF set high standards for themselves when developing a new water-lubricated sterntube to complete their range. “It sounds simple, but this type of sterntube is subject to higher wear and tear due to the lower lubrication properties of water,” explains Patrick Arand, Senior Product Manager at SKF Marine.

SKF chose a specially developed polymer bearing bush for Simplex BlueRun. The polyurethane it selected, a formulation developed in-house and tested against more than 100 alternatives, is harder than rubber but softer than composites – ideal for the levels of mechanical wear and tear in a harsh undersea environment. This material underwent more than 14,500 hours of vigorous testing under real-world conditions at SKF Marine’s testbed in Hamburg.

The very first SIMPLEX BlueRun installation was carried on a research vessel operating in coastal regions of the North and Baltic Seas. The vessel was further equipped with features such as a water quality system and a tail shaft monitoring system to provide even more fine-grained details on Simplex BlueRun’s performance.

In the meantime, SKF is looking forward to seeing more Simplex BlueRun installations as a means to help ship owners and operators go green. Whether in US waters or the arctic, SKF has a full range of solutions to help achieve VGP and Polar Code compliance.

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