Stern tube bearings have an important role to play in supporting a ship’s propeller shaft as it passes through the hull via the stern tube.
Among other things, the bearings help keep the shaft aligned and allow it to rotate smoothly while preventing water from leaking into the hull of the ship.
In the past, the bearings used to do this job required lots of maintenance and checks, as they were often fashioned from rust-prone ferrous-heavy materials that required plenty of lubrication.
This meant wear and corrosion were a big problem, and oil changes had to be carried out regularly.
The advent of new types of composite bearings fabricated from non-ferrous composite materials has changed all that.
Here’s how.
Corrosion
In saltwater marine environments, it’s inevitable that metallic elements like bearings take a battering and corrode after prolonged use.
This means that regular checks for pitting and rust need to be performed by the ship’s engineers, and frequent oil checks and changes are also necessary with this type of bearing.
Composite bearings have been a game-changer in terms of bearing longevity and maintenance overheads.
Polymer-based materials that make up modern bearings are super resistant to saltwater corrosion and general wear.
That’s because polymers don’t undergo the electrochemical corrosion that occurs when metal meets saltwater.
Low Maintenance
Less corrosion and zero rusting mean that polymer-based bearings are naturally much more low-maintenance than the metal versions.
This means that newer composite-based bearings have significantly cut down the amount of maintenance a ship’s engineers need to dedicate to maintenance.
At the same time, the new type of bearing can also use the surrounding seawater to provide the lubrication, eliminating the need for oil checks and changes.
This simplifies maintenance regimes and removes the risk of oil leaks or harmful chemicals leaching into the seawater and harming marine wildlife.
Eco-Friendly
Not only do self-lubricating bearing systems take the hassle out of maintaining them, but they also allow ship operators to steer clear of penalties from environmental agencies, which are increasingly turning their attention to polluters of marine environments.
By avoiding the use of heavy oils and greases, composite bearings make it easier for the operators of ships and boats to meet marine environmental standards.
And because there is no need to keep large amounts of oil or grease on board, a ship’s fuel efficiency also gets a boost.
Dirty Water Systems
Some bearing systems require a clean water feed to regulate heat and reduce friction.
This adds to the hassle and cost of maintaining a bearing system as a clean-water feed requires the installation of a clean-water filtration system and the ready supply of freshwater, which needs to be stored on board.
The latest low-maintenance stern tube solutions do away with the need for the clean-water feeds and can instead use the abundantly available dirty seawater, even when it’s turbid and contains abrasives, to feed the bearings and keep them frictionless.
Conclusion
The latest polymer-based stern bearings have revolutionised the shipping industry in many ways.
Their clever design and advanced material composition have taken the hassle out of maintenance and servicing the bearings that play a small but vital role in a ship’s operation.
