An oil/chemical tanker was underway. In the early morning hours a main engine lube oil separator alarm sounded on the bridge and, due to the vessel being UMS [having an unmanned machinery space], in the chief engineer’s cabin. The chief engineer called the bridge and informed the OOW that he was entering the engine room. He went to the purifier room and noticed the lube oil separator’s discharge pressure was low. He adjusted the discharge pressure but immediately the separator’s alarm activated again. On his way to the engine control room to acknowledge the alarm, the chief engineer saw there was now smoke in the engine room. He also noticed that the main engine turbocharger was surging and the main engine was hunting.
He called the bridge and told the OOW to put the engine pitch to zero. He then stopped the main engine by emergency stop. The vessel was blacked out for a short time before a diesel generator came on line. The chief engineer now saw that all the crank case relief valves of the main engine were opened.
Meanwhile, the Master had come on the bridge and the vessel’s position, set and drift were verified and the anchors prepared for use. After about 10 hours drifting the vessel reached favourable depths for anchoring, and was anchored. Meanwhile, it was found that the main engine crankshaft had seized, so repair by ship’s crew was not feasible. Shortly thereafter the vessel started to slowly drag anchor. The Master and company emergency response team agreed to use tug assistance to proceed to a repair facility. Later that day the tow operation was begun and the vessel brought to a port of refuge.
The company investigation found that a crankpin bearing had turned in place, thereby clogging the oil cooling hole and causing the subsequent cascading sequence of damage that culminated in the crankshaft seizure. The company had always followed engine manufacturer’s maintenance recommendations and was using manufacturer’s spare parts.
Due to size of the engine (less than 2250 kW), and in compliance with SOLAS, it was not fitted with a crankcase oil mist detector or engine bearing temperature monitors.
- Crankcase oil mist detectors or engine bearing temperature monitors are a very good investment even for smaller ships that are exempt from having them by international regulations; they can give an early warning of engine anomalies that, otherwise undetected, can cause serious damage.
- Planned maintenance should be at least as rigorous as manufacturer’s recommendations. Consideration should be given to exceeding those recommendations in order to further reduce risks.