On my vessel I have a problem with heavy wear of main engine bearing. We also observe high vibration on the bridge. Can you help?

In August 2015 we confront similar situation on a 38000 DWT bulk carrier.

 

Above are presented pictures we received from ship-owner of dismounted no. 4 and 6 main engine bearings during shipyard inspection. New one were put in their place.        

To fully analyze the problem we performed multichannel measurement on selected points of main engine, stern tube, top bracing for main engine, steering gear room and bridge to find the source of the problem. Additionally we performed tensiometric and torsional measurements of the main shaft.

 

After thorough analysis of collected vibration data and visual inspection of main bearings we came to a conclusion and made following remarks.

Measured torsional vibration level were within limits for continuous operation for whole range of RPM of main engine. Measured shaft bending stress values were in limits and no abnormalities were detected in full range of shaft angle.

As for main engine bearings that were showing highly dynamic interactions with main engine shaft, we recommended to perform jack-up test and confront the results with the one obtained in shipyard during building. Recalculate bearing reactions and deflection curve taking into account newly obtained jack-up test results.

Results from vibration measurement of the main engine at crankshaft level showed more rapid increase of acceleration after reaching 60 RPM.

Results for the top part of the engine and for main engine bracing indicated that frictional bracing that are installed on this particular vessel do not work properly and may be the source of high vibration on the bridge.

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