Black out!

Black out!

You’re sitting happily in your cabin or dining in a restaurant on-board and all of a sudden without notice the lights go out, the AC goes quiet!  This might sound familiar to some readers as although not a regular occurrence it can happen from time to time.

We call this a blackout, which is when the electrical system on-board the vessel goes dead, and if the vessel is diesel electric drive, then no electricity means no propulsion.  Read about this here.  If the vessel is within the confines of a port or in heavy traffic this is of huge concern as we basically become sitting ducks and a huge navigational hazard, so what causes this and what protection do we have against a black out?

Electrical Generators on-board are fitted with shutdowns and alarms as protection against various scenarios which could cause damage or dangerous situations.  For example if the engine driving the generator lost lubricating oil pressure it would destroy itself in minutes resulting in an unsafe engine room plus the financial cost.  It is therefore fitted with an alarm if the pressure were to drop to warn the engineer on watch to take action, if the pressure falls further the engine will automatically shut down and the electrical breaker for the alternator would open thus it would stop producing electrical power.  This is just one example of a shutdown.  Modern systems are fitted with many shutdowns.

These include

  • Electrical Overload
  • Reverse Power
  • Low fuel oil Pressure
  • Low Voltage
  • High bearing temperature.


Ships generate their own power on-board by running diesel generators, now most modern cruise ships have at least 4 generators and are diesel electric drive which you can read about here.  Generally at sea we are running more than one generator which means a black out is less likely, but alongside in port with propulsion systems shutdown, the vessel will drop down to one generator.

If the running generator were to shut down for any reason there generally wouldn’t be enough time for the control system or the engineer to start another generator, this results on a complete loss of electrical power to the vessel.

All ships are fitted with an emergency generator which will automatically start and connect to the ships emergency switchboard within 45 seconds of the power loss.  The electrical switchboard provides power to various emergency systems, such as fire pumps, watertight doors, and steering gear.  It also provides power to certain main generator services such as fuel pumps and cooling pumps which facilitate the start of the main generators and restoration of power.

In the 45 seconds before the emergency generator starts certain safety and control systems are supplied by transitional batteries.  This includes fire detection, communication systems, control and monitoring systems and navigation systems.

Once Power has been restored then the engineers and electricians on-board have to restart and reset all the machinery.

How we protect against a black out?

During normal conditions, software is constantly monitoring the electrical generation and distribution system.  If an electrical generator comes in alarm due to a fault it can automatically start a standby generator or even slow the vessels drive motors down to reduce power consumption on-board.  Therefore if one of the electrical generators did shutdown the others would not be overloaded.

We call these power management systems and they are constantly improving which hopefully will reduce the chances of you experiencing a black out.  All marine engineers will have experienced a black out at some stage in there career and are trained in dealing with it and familiar with the sequence to restore power which I hope will give you some comfort

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