During sailing out from port found humming noise coming from main engine aft turbocharger. Checked externally and nothing abnormal was found. We first suspected that the exhaust side nozzle was choked and same was cleaned, still the sound persisted. After we arrived at the port the company arranged work shop to clean the blower side diffuser of both the turbochargers. After sailing out the noise was still found to be coming.

We made a round voyage and came back to Singapore. The company arranged workshop for the overhaul of both the turbochargers. Found the AFT turbocharger extensively damaged with the blower side impeller damaged and also the casing both were rubbing against each other. Also the rotor shaft had shifted due to the failure of the thrust collar and thrust pads.

It is suspected that the failure of the thrust pad and bearing took place due to the reduction of the lub. oil. Earlier the L.O flow orifice plate had been reduced to 10mm from the earlier 15mm, as it was suspected that the failure of the sister ship’s cross head bearing had taken place due to the reduction of the oil flow, which was also supplying the T/C system as shown below.

The possible failure of the aft turbo charger was due to the reduction of oil flow to the thrust bearing due to the reduction of the orifice plate diameter thus reducing the oil flow.

Lesson learnt:

Such dimensional changes should have manufacturer’s consent and also if possible the class can be consulted before effecting such changes. This may avoid major mishap at sea.

Batch - 45