Bottom End Bolt Failure – Auxiliary Engine Break Down

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.