Stern Tubes

We are world leading in the development of synthetic base oils for use in environments where oil release or spillage may occur and have developed an industry leading range of Priolube™ ester base oils. Many of our products designed for environmentally sensitive areas and almost all have low toxicity towards acquatic organisms.

The stern tube is vital for marine propulsion and pollution prevention. Global shipping fleets operate with oil-lubricated stern tubes, which are submerged below deck and have a direct interface with seawater. Oil leakage from stern tubes is now considered to be an issue of concern and can have substantial effects on the aquatic ecosystem.

What makes a good stern tube oil?

Marine vessels are driven through the ocean by means of a propeller, connected to the diesel engine via a propeller shaft. Housing this assembly is the stern tube, which contains many bearings and seals as well as oil and water sealing "glands", which aid the expulsion of seawater and maintain lubricating oil integrity. 

A stern tube oil is necessary to provide lubrication to stern tube bearings and propeller shaft seals, deliver excellent hydrolytic stability and maintain oil integrity should water ingress occur. The oil itself must also be compatible with the range of materials found inside the stern tube. 

As a stern tube is submerged beneath seawater during use, there is the potential for lubricant to egress into the surrounding seawater, either during normal use or as an accidental spillage. Lubricants lost in such a way can cause catastrophic effects to the aquatic ecosystem. There is now a drive to use environmentally acceptable lubricants (EALs) on board vessels to protect the environment should oil leakage occur. 

We understand it can be difficult to formulate and meet regulator requirements around protecting the environment. Using our technical expertise and in-depth application knowledge, we develop products with regulatory challenges in mind. 

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