Smarter Choice: Composite Bearings for Modern Shipbuilders

why-composite-propeller-bearings-are-smart-choice-for-ship-makers

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Composite propeller bearings have been a real game-changer in the world of marine engineering.

Featuring a polymerised resin base and fibrous reinforcing material such as fibreglass or aramid (Kevlar), together with some clever design features, composite propeller bearings are considered a significant step up from the metal type.

Firstly, because the composite bearings aren’t fashioned from the ferrous-heavy materials you find in metal ones, they aren’t prone to rust or degradation in salty seawater.

Equally, the oil that is typically used to reduce friction with metal bearings isn’t needed with composites, as they have a clever way of harnessing the surrounding seawater to minimise friction as the propeller turns.

For many ship makers, this means composites are now by far the smarter choice for the bearings they use to help the propeller turn.

Below, we take a closer look at just why composite bearings are the go-to bearing for more marine engineers.

Biodegradable Materials

Because composite propeller bearings are made from inert, biodegradable materials and use seawater, not oil, as a lubricant, they are much more environmentally friendly than their metal counterparts.

This makes them a smarter choice for ship makers and fleet operators as governments around the world seek to encourage dirty marine-based companies to clean up their act.

For example, in the USA, the EPA Vessel General Permit (VGP) requires ships over 79 feet to use environmentally acceptable lubricants (EALs) in all oil-to-sea interfaces, where technically feasible.

On the other side of The Pond, the EU’s REACH Regulation looks to do something similar, encouraging shipbuilders to use materials with fewer hazardous chemicals, which makes self-lubricating, non-toxic composites appealing for modern shipbuilders.

Low Maintenance

Composite bearings also tend to need less aftercare and maintenance than other types.

Indeed, once installed, a composite bearing will enable the propeller to turn smoothly for many decades with minimal maintenance and repair.

Reduced Friction & Vibration

In some waterborne vessels, vibration and noise can be significant problems.

In pleasure boats and ferries, for example, ship operators try to provide guests with as noiseless a passage as possible.

Composite bearings help here, too.

The clever design of a composite bearing means they are fabricated with grooves that act to draw seawater between them.

This forms a pressurised film between the shaft and the bearing wall, creating a hydrodynamic film that allows seawater to pass through and provide a natural lubricant, thereby helping to reduce mechanical jarring and, consequently, noise and vibrations.

In addition, a composite bearing often contains graphite or is treated with a slick PTFE substance, which also helps reduce friction and vibrations in low-speed conditions when the seawater can’t counteract all the friction in the propeller shaft and needs help.

Lightweight Design

Bearings might be small, but they are used heavily throughout a ship, not just in propeller shafts – from rudders to pumps and winches.

In some vessels, every bit of extra weight counts – in racing vessels or light-weight sea-going ships, where speed is all-important, for example.

Here, it’s a smart decision to opt for composite bearings, as they offer a significant weight advantage over traditional bearings made from brass or other alloys.

Maritime Engineering’s Eco Boost for a Better Future

Composite bearings are the smart choice for a growing number of ship builders, and it’s not difficult to see why. They outperform competitors across the board – from reduced maintenance times to greater longevity and eco-friendliness.