Introduction
A bridge watch alarm system is a device which triggers an alarm if an Officer on Watch (OOW) becomes incapable of performing the OOW’s duties. IMO had adopted the performance standard as MSC. 128 (75) and there are ships which have already installed the equipment on a voluntary basis. Currently, there are two types, i.e., one which requires the OOW to press a button in an interval (if he fails to do so, it triggers the alarm), or another, which detects movements of the OOW, using the motion sensor technology. (So far as the sensor finds movement of the OOW, the alarm will not go off).
The IMO Committee approved the draft amendments to the SOLAS Regulation that requires the mandatory carriage of a bridge navigational watch alarm system for the subsequent adoption at the MSC. 86. (Amendments to the SOLAS Reg. V/19 –Carriage requirements for a bridge navigational watch alarm system.)
Application: The draft amendments stipulate as follows:
1st July 2011 on or after all new builds of 150 gt or over (keel lay base)
Ships constructed prior to 1st July 2011 will have to fit the BNWAS by the 1st survey after:
1st July 212 for cargo ships of 3000 gt or over and all passenger ships
1st July 2013 for cargo ships of between 150 gt or over but less than 500gt
1st July 2014 for cargo ships of between 150 gt or over but less than 500gt
These requirements also apply to ships not engaged on international voyages.
Alarm Sequence
System Diagram
| 1st Stage Alert Reset Unit (RAP), 2nd & 3rd Stage Alert Units, Motion Reset Unit (MOT) |
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 RAP |
 WAP |
 MOT |
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1st Stage Alert Reset Unit (RAP) is used to give visible indication and audible alarms for all three stages, as well as acknowledge alarms of all three stages.
2nd & 3rd Stage Alert Units (WAP) is used to give visible and audible alarms for 2nd and 3rd stages, but has no control function.
Motion Reset Unit (MOT) detects movements and automatically resets the BNWAS accordingly.
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 Junction Box |
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Junction Box (JB04) has one input port and four output ports to simplify terminal connections among Control Box (X4300C), 1st Stage Alert Reset Unit (RAP), 2nd & 3rd Stage Alert Units (WAP), and Motion Reset Unit (MOT).
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