Cunard Queen Mary 2 Electrical Failing Sparks Safety Concern

The Marine Accident Investigation Branch (MAIB) of the UK has issued a safety alert following the failure of a capacitor and explosion in the aft harmonic filter room aboard Cunard Line’s Queen Mary 2 back in September of this year

The QM2's alarm logs were found to have containted earlier warnings about the impending failure roughly 36 minutes before the accident took place. This is according to reports by MAIB. The vessel's alarm system regularly logged more than one alarm every minute, this information however was not seen therefore not acted on. A detection warning system was also found to be non-functional despite the ship having a long history of harmonic filter capacitor failures.

The safety alert made the following recommendations:

*Protection systems for critical equipment must be “fail safe” and should be thoroughly tested at regular intervals. In particular, the harmonic filters with current imbalance protection systems should be thoroughly checked by competent personnel.

*Awareness of the damaging effects of harmonic distortion needs to improve throughout the marine industry.

*Regular monitoring of electrical networks should be undertaken to provide early warning of deterioration.

*Procedures need to be established to manage distortion levels in the event that power conversion equipment and harmonic mitigation equipment fails.

*Machinery alarms should be regularly reviewed and prioritized so that the risk of the watch keeper being overloaded with too many alarms and not notice those from critical systems can be minimized.

Following the September 23rd explosion all four of the podded propulsion motors on the Queen Mary 2 shut down and a few seconds after the vessel experienced electrical blackout. Thick black smoke was also witnessed coming from the aft main switchboard room.

The MAIB said that subsequent inspection of the aft harmonic filter showed that one of its capacitors had failed catastrophically and another had developed a severe bulge.

Although the exact cause of the failure could not be determined, it was concluded that capacitor degradation was probably caused by a combination of transient high voltage spikes due to frequent switching operations and occasional network overvoltage fluctuations. The deterioration had not been detected because there were no internal fuses or pressure relief devices, and continued until it failed.