TRIPPING OF LUBRICATING OIL PUMP LEADING TO BEARING FAILURE :
(manual was not clear, leading to diagnosis and fault repairing)
B Viswanath C/E (Superintendent)
The main engine was Pielstick 18 PC 2 V 400.On a summer day in the Port of Jeddah, a routine crankcase inspection of the main engine shown white metal flakes scattered inside. It was decided to open up all bearings and check for the damage. This was not an easy task. Unless the cylinder heads are out, there is no way, the bottom end bearings could be seen. Similarly until the connecting rods are out and crank counter weights opened, the adjacent main bearings can not be accessed. At random two units in Vee configuration were opened up first (where white metal flake concentration was more), the bottom end bearings checked up and found satisfactory.Random inspection will consume more time.
Hence it was decided to check systematically all the bearings. Two teams were formed, one to take care of aft 9 units and the other for the forward 9 units. At first all the bottom end bearings were opened up and found no damages, all bearings were ok. While planning to inspect the main bearings, on careful observation, No. 4 bearing shells were found displaced inside the housing, as the two halves have turned inside. The other bearings were checked and found their shells were in proper place.The focus then shifted to open up the main bearing No. 4 alone. To enable this, the adjacent counter weights on either side opened up and the main bearing opened up. The diagrams were not clear as the ship had only a translated manual. The engine was under slung engine. Chief engineer gave instructions for renewing the bearing shells. The top half was not going into the housing when helped with the tool provided.
The bearing got damaged when tried to force the shell inside.The company requested the class to assist the ship and as per the class surveyor, the bearing shell was forced and the bearing was boxed up. All other components which were opened up, were boxed back.At this time, Master informed that the cargo discharge is over and the vessel had to shift to anchorage. All engineers were reluctant to try the engine, but the complacency of C/E, the nothing will happen forced us to start the engine, the engine was started and taken to anchorage.At the anchorage, one more inspection was carried out, found the number 4 journal got damaged. The surveyor could not answer for this and he left the ship. The matter was referred to the manufacturers. The particular unit and its adjacent 4 units were opened up and their pistons removed, push rods removed as per the manufacturer’s advice.
The relevant LO passages were plugged and the ship limped to Singapore Port, where at the specialists came and did the crankshaft grinding insitu to suit an undersized bearing, with new bearing housing.The failure of the bearing was attributed to the LO pump failure due to high temperature during the previous voyage. Air ductings were modified, and more air was allowed to come to the LO pump motors. The line filter at the entry point to engine was also redesigned to necessitate proper cleaning and ease to changeover without stopping the engine.