Purpose of shaft grounding systems in marine engineering

It’s Science 101:

Electricity and water do not mix.

That maxim is no clearer than in marine engineering, where seawater mixed with a propeller’s electrical systems can cause corrosion, loss of efficiency and system failure.

To fully protect a ship, it is important to electrically ground the ship’s propeller to the hull. Propeller grounding limits corrosion and damage to the propeller shaft, bearings and gearbox.

All motor powered marine vessels must have some form of grounding system installed.

The axis is critical

One of the most critical parts in a marine vessel propulsion system is the shaft. Shafts that corrode over time lose their efficiency. An excessively corroded shaft can cause system failure.

A grounding system is important.

This is because as the electricity passes through the motor to the propeller, it mixes with water. The combination of the two, called an electrochemical reaction, causes corrosion on the shaft.

The shaft provides thrust to move the boat forward.

Shafts that corrode over time due to electrochemical reactions with seawater lose their efficiency. They are weakened by transferring power from the boat’s engine to its external propulsion system.

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

At the same time, unchecked corrosion can shorten the life of any boat. This can cause maintenance issues to occur sooner than otherwise as well.

How does it work?

The principle behind grounding the shaft is quite simple.

In most marine vessels, electrically driven propellers create charges along the exposed sections of the propeller. A grounding system ensures that as little charge as possible escapes. The system is designed to disconnect all electricity from the ship’s hull.

Grounding prevents free-flowing electrons from doing damage.

As a result, both the propeller and the engine can run longer and stronger due to less damage. In most cases, each propeller shaft must have a ground system.

One type of grounding system uses an off-axis metal layer. In this way, any electrochemical potential of the seawater will be attracted towards the outer shell instead of the axis itself.

Grounding Types Varies

The best type of grounding system to use depends on the boat.

There are different options and the owner can choose.

Some factors include the type of engine, the size of the boat, and the composition of the hull. Also, systems become more complicated depending on the amount of cargo being handled. At the same time, the number of propellers and motors a boat has also affects system choice.

Consult a Professional

It is not always possible to 100 percent prevent the corrosion of gold inside a marine vessel. But the importance of shaft grounding systems in marine engineering should not be overlooked.

Talk to a professional for the most up-to-date information on the purpose of grounding systems.