What makes alignment onboard ships so complex?

Aligning the propulsion system

All the components of a ship’s driveline must work in harmony to transmit power from the engine to the propeller. Ideally, the centerlines of these components should be perfectly aligned – either in a straight line or along a calculated curve to compensate for expected hull flex. This ensures smooth rotation and reduces the forces and stresses acting on the components.

Even a small angular or offset misalignment can lead to serious issues over time. That’s why alignment checks are a core part of ship maintenance, particularly during dry-docking, after heavy repairs, or after a grounding or collision.

Let’s break down why this is so important:

•    Increased wear on components
Misalignment leads to uneven load on bearings, seals, and couplings. Bearings may experience edge loading, which wears them out much faster. Seals can deform or fail to maintain contact, allowing lubricants to leak and water to enter. Couplings may also suffer from uneven torque transmission, cracking, or overheating.

•    Vibrations and structural damage
When shafts aren’t aligned, the entire system can vibrate excessively. Over time, these vibrations propagate through the ship’s structure, damaging foundations, mounts, and even unrelated nearby systems. 

•    Higher fuel consumption
An aligned propulsion system is more efficient. Misalignment causes additional drag and resistance, which means the engine must work harder to deliver the same thrust. This inefficiency translates directly into higher fuel costs – something ship operators are under increasing pressure to control.

•    Catastrophic failure
In severe cases, misalignment can cause shafts to fracture, bearings to seize, or couplings to disintegrate. These failures are not only costly to repair but may endanger the safety of the crew and ship.

Getting the centerline straight

Before shaft alignment can deliver any real benefits, the supporting components must be in the correct position. This is where bore alignment comes into play.
Bore alignment ensures that stern tube and intermediate bearings are correctly positioned along a shared centerline. If these bearings are even slightly out of line, it introduces a misalignment that can’t be corrected by adjusting the shaft alone. Precise bore alignment is especially important when new bearings are installed, after foundation work, or during newbuild and retrofit projects. Using laser-based measurement tools, technicians can check the straightness and position of the bores quickly and with high accuracy.

Causes of Misalignment

Misalignment doesn’t usually occur overnight. It can creep in slowly or happen suddenly after an incident. Knowing what causes it – and what to watch out for – can help prevent bigger issues down the line.

Improper installation is one of the main culprits – if components aren’t correctly aligned during initial installation or after major service, problems can begin from day one. Hull flexure is another common factor, since a ship’s hull is not a rigid body. It can flex due to sea conditions, loading configurations, ballast, and even temperature, which may shift the position of driveline components. Over time, foundation settlement can also introduce misalignment, as the structural supports for machinery deform or shift, especially in older vessels.

How to recognize misalignment

Crews should be trained to look for warning signs during routine checks:

•    Excessive vibrations: This is often the first and most obvious sign. 

•    Noise: Rattling, whining, or grinding sounds from the driveline usually point to an underlying problem.

•    Hot spots: Abnormally high temperatures near bearings or couplings could indicate friction due to misalignment.

•    Premature component wear: If seals, bearings, or couplings are failing sooner than expected, alignment should be investigated.

•    Changes in fuel consumption: A steady increase in fuel use without a clear cause might be due to added resistance in the propulsion line.

Alignment is more than just another task

In the marine industry, safety, efficiency, and reliability are all non-negotiable. Precision alignment of your propulsion system may not be the most visible aspect of ship operations, but it is one of the most critical.

As vessels become larger, more complex, and increasingly automated, the importance of machinery running smoothly – and staying aligned – will only grow. The good news is that modern tools and methods make alignment easier to perform and verify than ever before.

Every operator, engineer, and crewmember should understand that proper shaft alignment isn’t just a maintenance task – it’s a key to safety, cost-efficiency, and operational success. Make it a priority in your maintenance routines, invest in the right tools and training, and you’ll keep sailing smoothly no matter what the sea throws at you.

How Easy-Laser® supports marine alignment

The Easy-Laser XT770 is a rugged shaft alignment system built for tough conditions. The system can measure with as little as 40° rotation of the shaft, which is useful if the shaft is difficult to rotate, or if pipe connections or other hull components are in the way. The system also supports bore alignment by verifying the straightness and centerline of stern tube and intermediate bearings. The dynamic measurement function allows measurement of thermal expansion, from cold to full operating temperature. 

In addition, Easy-Laser systems can be used to correctly position pods, rudder stocks, and water jet systems, as well as measure the flatness of crane slewing bearings. All measurements are automatically documented, streamlining communication and compliance. For the marine industry, precision laser alignment is key to reliability.