Additives for stern tubes

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 e.g. elastomers, paints and various metal types. 

Given that the stern tube is submerged beneath the seawater during its application, there is the potential for water to egress into the surrounding seawater, whether this be during normal use or as an accidental spillage. Lubricants lost in such a way can cause catastrophic effects to the aquatic ecosystem and so 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 regulatory requirements around protecting the environment. Using our technical expertise and in-depth application knowledge, we develop products with regulatory challenges in mind.  

Emkarox™ VG NS 

Our most recent product innovation is Emkarox VG NS, a range of innovative, non-sheening base fluids which allow the formulation of compliant lubricants without compromising on performance, even in the presence of water. 

Available in ISO 100 and ISO 150 grades, these base fluids and possess the properties of a conventional base oil, but also have the unique ability to partition into water.

Emkarox VG NS base fluids: 

• Have excellent inherent hydrolytic stability 
• Are non-emulsifiable 
• Readily disperse in sea water at low concentrations 
• Are non-sheening.