Alignment of Large Marine Components with Laser Trackers

08 April 2024 · 5 min read

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Shipyard Laser Tracker Case Study

AW Laser, API-Partner, Measurement Service Provider, South Africa:
Alignment of Large Marine Components with Laser Tracker


Alignment with Laser (AW Laser) specializes in Alignment and laser trackers in South Africa. The measurement engineers of the AW Laser team are passionate users of mobile API laser measurement technology because it saves a lot of time and allows them to achieve more precise results. AW Laser is an API partner using API Laser Trackers to align machinery and equipment in a wide range of industries. AW Laser provides measurement services, especially for the shipyards, aluminum plants, steel mills, paper manufacturers, and sugar industries.

How it all started

Before using API 3D metrology, the AW Laser team still used Pruftechnik for their measurement services. Each task meant a new challenge and a different system was used for each solution and application. There was no measurement system that could solve the various measurement tasks in a fast and flexible way. – Only API’s Laser Trackers were able to change that.

The working environment in the docks

In the shipyard industry, ship repairs are part of the daily business. The working environment in the shipyards is dirty and rough because the ships are pulled into the dock directly from their last deployment without being cleaned. Accordingly, the API Laser Trackers are also exposed to this unclean environment.

A ship run aground

During the measurement work on the rudder of the grounded ship, the laser tracker was placed inside the rudder bores and the measurement was carried out from there. Here, measurements were actually taken from the lower bore to the upper bore to find out how much the bore alignment was out, and with API’s Laser Tracker, the AW Laser team was able to document a quick and accurate set of measurements of this existing calotte in relation to each other in a very short time.

Alignment of large ship parts

Another common measurement task is the alignment of the main diesel engine to the intermediate bearings and then to the tail shaft bearings. An important application here is checking the bore alignment of several bores in relation to the diesel crankshaft engine. Especially for these diesel bearings, an accuracy of almost 16 micrometers can be guaranteed. These values are well within the tolerance required by the ship owner.

Basically, these specific bearings do not need to be brought ashore – the original crank is simply brought into position on site through the use of the mobile Laser Tracker. This measurement task can be performed directly on the ship within a few hours – easily and quickly. The difficult thing about measuring on ships is the vibrations that sometimes occur. To ensure that the ship is almost vibration-free, no diesel engines should be running parallel to the measurement.

On site alignment of the rudders

In the rudder, the AW Laser team found some severe misalignments of the upper bore to the lower bore. These misalignments were not only offset, but also had a deviation in angle, e.g. due to a severe twist of the rudder.

AW Laser’s team was tasked with measuring the current situation and providing an assessment on the ship. After repairing the entire rudder, it was welded back into the ship. In the end, the rudder had an offset of only 0.497 millimeters – a very good value for a ship with mostly two to three millimeters of play in the bearings.

Rudder alignment

The AW Laser team used no additional tools, no jigs, no complex fixtures, no additional mounting techniques or anything like that for the measurement. They solved the measurement task and successfully readjusted the bearings.

Advantages of Laser Trackers

The speed and precision of the Laser Tracker are a perfect support for challenging measurement tasks. As with the vertical alignments, the AW Laser team was also able to check the horizontal alignment of the stern tube from the diesel through the bearing positions to the tail shaft. Again, the API Laser Tracker’s positioning, precision, speed and flexibility make it a perfect support.

Alignment of the stern tube

If these tasks were solved using traditional methods, special fixtures or optics would be required. Thanks to the invention of the Laser Tracker, there is no need to physically measure by hand. The use of the laser tracker saves significant time.

Horizontal alignment of the stern tube

Another alignment of the stern tube came up on a larger ship.

This tube shown is the actual drive shaft of the diesel engine. Modern large diesel engines have a hollow shaft so that measurements can actually be taken at the front of the diesel’s dome. Exactly where the flywheel is located and also at the rearmost part can actually be measured. The distance given is over six and a half meters. The AW Laser team obtained a very accurate cylinder projection during the measurement.

The flexible mounting options of the API Laser Trackers

One of the most complex measurement tasks that the AW Laser team mastered was checking the concentricity of a diesel engine.

Some diesel engines on large ships are two-stroke. For this measurement, the Laser Tracker had to be positioned horizontally. This is another special advantage of the API Laser Tracker, as it can be mounted vertically or horizontally. For this task, the team had to measure the top of the diesel cylinder and the bottom, to find the axis.

The team also had to measure the stuffing box to find if the cylinder was in line with the stuffing box. The greatest difficulty here was to mount the laser tracker optimally.

A specific mounting plan was developed for the particular situation and the laser tracker was finally attached to the cylinder head bolts. This was braced for stability as the ship was not in dry dock.

Elimination of the vibrations by two motors

During the measurement, an additional diesel generator had to be running to cancel out the vibration of the other diesel engine so that there would be no vibration to affect the measurement in this particular application. This allowed the AW Laser team to proceed with the alignment without any problems.

The right measurement strategy is crucial for accurate measurement

The selected measurement services for ship repairs show: There is always a special measurement strategy to successfully implement measurements even in applications with special requirements. The use of the Laser Trackers without leveling equipment perfectly helps with measurements on ships in water or in floating docks. The AW Laser team is convinced that the use of the API Laser Tracker significantly improves the solution of measurement tasks and makes our alignment and complex inspection tasks more efficient.

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