Recently we were called by a Superintendent from Thome Ship Management,  to address a problem with the vessels BNWAS on board of the M.T.”Hafnia Lotte.”   The Bridge Navigation Watch Alarm System or BNWAS is designed to monitor bridge activity and alert the Captain (or other qualified personnel) if the bridge becomes unattended.

The watch system is composed of a main controller, reset button boxes, motion sensor boxes and alarm boxes.  When the system is activated the BNWS enters into the “dormant period.”  This period lies between 180 and 720 seconds.  This time span is adjustable by authorized personnel with a password.  If this dormant period expires without a crew member resetting the unit then the visual alarm will activate.  If the unit is then not reset then the internal buzzer turns on and the 1st stage alarm activates.  A period of 15 to 60 seconds will then activate the 2nd stage alarm, and if the unit is still not reset then a 3rd stage alarm will activate after a period of 90 to 180 seconds.

On the “Hafnia Lotte,”  the Captain and CO explained to our service engineers that they were having issues with resetting the unit and powering on issues with the system.  We started with the wiring, having traced the cables it became clear that it was not correct and therefore it was just going to be a matter of time before the unit failed.  Having re-wired the reset boxes correctly and double checked the junction boxes on the other decks.  We then checked the reset boxes that were located on the steering console, Portside wing and starboard wing.  These boxes were re-wired as they were not as per the wiring diagram.

The master unit itself was also not functioning correctly.  The unit was powering on but after a few seconds powered itself back off.  As we had a replacement master unit, we replaced and reset all the timers to what the vessel required.

Once completed we carried out a full test of the system and then signed it off as “in full working order.”

The “Hafnia Lotte” is a medium range oil product tanker that is currently managed by Thome Ship Management.  Thome Ship Management is one of the largest independent ship managers in the world and have their headquarters in Singapore.

Ravebo have been representing Marsen now since 2013.  Marsen are located in Busan, Korea  and specialize in the supply of measuring sensors, and also in the fields of level, pressure, temperature and gas measurement.

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