MAN ENERGY SOLUTIONS SERVICE LETTER SL-2022-721

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Figure 2. Axial thrust bearing with undamaged locking key
Figure 3. Inspection of locking key, wear is clearly visible

Inspection results:

• Wear below 25% of the locking key width

Operation can be continued, but the next inspection must be scheduled according to the actual running hours and the observed wear rate (mm/1000 running hours).

• Wear below 50% of the locking key width

Prepare for a replacement and upgrade to the new design.

• Wear beyond 50% of the locking key width

Replace or upgrade the axial bearing immediately.

Observation

As the present design of the thrust bearing assembly allows some free movement of the thrust bearing rings during operation, variation in engine installations and propeller designs etc. may lead to difference in the vibration/resonance level in service; causing the excessive wear.

Design and installation

The bearing design and load conditions have been verified and are found well within the requirements and meet the expected load conditions under even heavy sea conditions. The alignment of the engines has been checked in the reported issues, and so far there is no indication that the wear issue on the thrust bearing is related to the engine alignment.

Countermeasure

In order to reduce possible influence of vibrations/resonance on the thrust bearing system, a stronger fixation of these has been introduced as the standard for all newbuildings and is also available as a retrofit for engines in service. The new design adds two 12 mm guide pins to the bearing cap, and 12 mm holes for fixation of the guide pins have been added to the thrust bearings.

In case wear is observed on the axial bearings, a service kit for introduction of the new fixation is available throughout our PrimeServ organisation.

Source – MAN Energy Solutions