Purpose of Shaft Grounding Systems in Marine Engineering

Posted on

Purpose of Shaft Grounding Systems in Marine Engineering

It’s Science 101:

Electricity and water don’t mix.


To completely protect a ship it’s important to electrically ground the ship’s propeller to the hull. Grounding the propeller limits corrosion and damage to the propeller’s shaft, bearings, and gear box.

Every motor-powered marine vessel should have some sort of shaft grounding system installed.

Shaft is Critical

One of the most critical parts in a marine vessel’s propulsion system is the shaft. Shafts that become corroded over time lose their efficiency. An overly corroded shaft can lead to system failure.

A grounding system is important.

That’s because as electricity runs through the engine to the propeller it mixes with water. The combination of the two – called an electro-chemical reaction – causes corrosion to the shaft.

The shaft provides thrust to move the vessel forward.

Shafts that become corroded over time due to electrochemical reactions with seawater lose their efficiency. They become weaker at transferring energy from the vessel’s engine to its exterior propulsion system.

A grounding system is also necessary to protect the drive-motors bearings from electrical damage. Excessive capacitive discharge can lead to electrical bearing failure.

At the same time, corrosion left unchecked can shorten any ship’s lifespan. This may cause maintenance problems too occur sooner than otherwise.

How Does It Work?

The principle behind shaft grounding is fairly simple.

In most marine vessels, propellers driven by electric current create charges along the exposed sections of the prop. A grounding system insures that as small a charge as possible escapes. The system is designed to ground out all electricity in the ship’s hull.

The grounding prevents free-flowing electrons from doing their damage.

As a result, both the propeller and engine are able to run longer and stronger due to less damage. In most cases, each propeller shaft should hold a ground system.

One type of a grounding system uses a layer of metal outside the shaft. This way, any electrochemical potential from seawater will be attracted to the outer layer as opposed to the shaft itself.

Types of Grounding Varies

The best kind of grounding system to use depends on the vessel.

There are different choices and owner can choose.

Some factors include the type of engine, size of the ship and composition of the hull. Also, systems get more complicated depending on the amount of charge handled. At the same time, the number of propellers and engines a vessel has also affects the choice of system.

Consult a Professional

It’s not always possible to prevent 100 percent corrosion on or within a marine vessel. But the importance of shaft grounding systems in marine engineering should not be overlooked.

Talk to a professional for the most current information on the purpose of grounding systems.