The purpose of BNWAS (Bridge Navigational Watch Alarm System) is to monitor bridge activity and detect operator disability which could lead to marine accidents.
BNWAS monitors the watch officer’s presence through watch safety system functions.
A watch officer is required to press the button on a Timer Reset Panel or to operate navigation equipment (e.g. ECDIS, Radar, etc.) at certain intervals.
When the officer fails to press the button within pre-set intervals, visual and audible alarms will be generated in the wheelhouse.
If the officer doesn’t respond to the alarm, the system transfers the alarm to the Cabin Panels installed in other sections of the vessel in order to inform backup officers of the watch officer’s incapacity.
Timer reset function and Visual indication
The timer reset may be facilitated by one of following means:
- Pressing the reset button on the Main Panel/Timer Reset Panel
- Provoking the motion sensor
- Initiate operation of various navigation equipment
It is important to keep in mind when planning a BNWAS installation that the external devises, which can act as reset devises, need to be located in position where proper lookout can be done by the watch officer.
For the motion sensor, it is critical to locate it in such a way that it cannot be activated by the ships movements. Thus, any curtains present on the bridge deck should not come in the way of the sensor.
For first line of alert, in accordance with IMO Res. MSC.128(75), sufficient number of visual indications (flashing lights) are to be installed and connected.
The visual indications should be visible from all operational positions within the bridge where the OOW (Officer of the Watch) may be stationed to perform his duties.
These positions are made up by, but not limited to, Conning work station, Navigation support work station, steering work station and 2 x docking work stations.
BNWAS should incorporate the following 3 operational modes:
- Automatic: The BNWAS is automatically activated when the vessel is navigating by means of heading or track control system (autopilot/trackpilot), and inhibited as the heading/track control system is deactivated.
- Manual ON: The BNWAS is always in operation
- Manual OFF: The BNWAS is turned off completely