Stern Tube Oil

Buying Quality Stern Oil for the Ship

It is important to lubricate the propeller shaft bearings of the ship to enhance its efficiency. Bearings support the shaft and propeller. They also count towards the alignment of the shaft. If not well lubricated, much of the energy generated around the shaft ends up being lost to friction. Quality stern tube oils reduce high fuel consumption and the possibility of damage.

Your choice of lubricants is dependent on the sealing and bearing arrangements, along with the local legislation. Most jurisdictions, including the USA, have introduced permits that cover permissible pollutants in their waters.

A History of Propellers

The material that has been used by propeller-driven ships until recently is Lignum Vitae. With this type, the bearings are made of wood staves that are inserted longitudinally into a bronze sleeve, which surrounds the propeller shaft. It did not require much lubrication as it worked well with seawater. However, it had a few shortcomings, which made it ineffective.

These bearings were replaced with white metal bearings that required some lubrication. These bearings still make the largest portion of bearings and use mineral oil based lubricants. Unlike the former that used stuffing boxes, these systems use seals at the end of the stern tube to prevent seawater ingress and oil loss.

New Types of Lubricants for Stern Tubes

Several stern tube oil varieties are available for different ships and conditions. Until 2002, all the oils were mineral-based. However, there are biodegradable oils that can be used in areas with strict environmental regulations. The oil you choose should offer excellent emulsification properties, prevent corrosion to parts exposed to seawater and provide effective lubrication to critical components of the stern tube. SAE 30 lubricants are commonly used for regular running of the shaft, which SAE 40 is recommended where bearings are leaking small amounts of oil as it has higher viscosity.