Bottom end bold failure – auxiliary engine break down
R. Muthamizh Selvan, 3/E
The ship was a bulk carrier. It had 3 YANMAR auxiliary engines driving 3 alternators. No.3 A/E was decarbonised and all the bottom end bolts were renewed with modified new ones as per the manufacturer’s instructions. The auxiliary engine ran normally for nearly 600 hrs. The incident took place when the ship was in port, and the AE3 was running on load. Suddenly an abnormal noise heard, found unit 3 crankcase door cracked and oil was splashing out. Standby generator came on load and AE3 was stopped. On inspection found, the piston, connecting rod were broken and lying inside the crank case. The crank case door and the frame forming a part of unit 3 were heavily damaged, other units remained normal. The lock plates for bottom end bolts were in place.
The cause could not be found and took it for granted that material failure had taken place.(Remarks by a Chief Engineer: Since the failure has taken place after 600 hrs and other bolts remaining alright, just attributing to material failure may not be accepted. There might be a failure of Lub oil, as the trip has not taken place and the personnel had stropped the auxiliary engine manually. Even after the break down, definitely the lub oil pressure will drop and AE should have tripped off on low lub oil pressure. The trips have not been checked on regular basis or they were not functioning)