Physical Address
304 North Cardinal St.
Dorchester Center, MA 02124
IEC 62616:2010 — Bridge Navigational Watch Alarm System (BNWAS)
IEC 62616 is the international standard first published in 2010 by IEC Technical Committee 80 (Maritime navigation and radiocommunication equipment and systems) that specifies the performance requirements, functional characteristics, and test methods for Bridge Navigational Watch Alarm Systems (BNWAS).
A BNWAS is a critical shipboard safety system that monitors the alertness of the bridge watchkeeping officer (OOW) or pilot. If no operational activity is detected within a preset time interval, the system activates a graduated three-stage alarm sequence — local, remote, and general — ensuring that someone aboard is alerted if the watchkeeper becomes incapacitated due to illness, fatigue, or emergency.
💡 Regulatory Context: SOLAS Chapter V, Regulations 19 and 22 mandate that all cargo ships of 300 GT and above and all passenger ships engaged on international voyages must be fitted with a BNWAS. IEC 62616 provides the detailed technical specification for equipment compliance with these SOLAS requirements.
🎯 Alarm Sequence and Logic
IEC 62616 defines three escalating alarm stages for the BNWAS:
| Alarm Stage | Trigger Condition | Alarm Location | Timeout Duration |
|---|---|---|---|
| Stage 1 (Pre-alarm) | No operator activity detected | Bridge only (visual + audible) | 3–12 minutes (configurable) |
| Stage 2 | Stage 1 not reset | Officer quarters / crew cabins | 15 seconds after Stage 1 |
| Stage 3 | Stage 2 not reset | General crew areas + public spaces | 15 seconds after Stage 2 |
If the BNWAS is reset at any stage (via reset button or activity detection), the alarm sequence resets and the system returns to normal monitoring mode.
⚠️ Critical Requirement: The BNWAS must support three operating modes: automatic (auto-repeating alarm cycle), manual (manually enabled), and off (when at anchor or in port). System deactivation and reactivation must use a key-locked switch to prevent unauthorized disabling of the safety function.
💻 System Interfaces and Output Signals
Clause 6 of IEC 62616 defines the input/output interfaces in detail:
- Activity detection inputs: Can connect to heading control buttons, ECDIS operation, radar operation, navigation light controls, and other signal sources
- Reset inputs: Reset push-buttons must be installed at multiple key bridge positions (typically 3 or more)
- Alarm outputs: Drive local alarm indicators, remote alarm panels, and the general ship alarm system
- Data output: Serial interface outputs system status and alarm history with standardized message formatting
The standard specifies a serial data output format (RS-422/485) for integration with the Integrated Bridge System (IBS) and Voyage Data Recorder (VDR), enabling post-incident analysis of alarm events and operator responses.
✅ Engineering Design Insight: Activity detection is the most challenging aspect of BNWAS design. Over-sensitive detection causes nuisance alarms and reduces operator trust; under-sensitive detection fails to detect watchkeeper incapacitation. The optimal approach uses multi-source activity fusion — monitoring 6–8 signal sources including radar, ECDIS, autopilot, and dedicated activity sensors — with a reset timeout of 5–8 minutes for the best balance of safety and user acceptance.
🔨 Environmental Testing and Performance
IEC 62616 specifies the environmental conditions that BNWAS equipment must withstand:
- Operating temperature range: -15°C to +55°C
- Vibration resistance: Per IEC 60945 requirements for maritime equipment
- EMC compliance: Radiated emissions and immunity for shipboard environments
- Power supply variation: Normal operation at rated voltage ±10%
- Sound pressure level: Stage 1 alarm ≥ 75 dB(A) measured at 1 meter
🚨 Installation Considerations: Reset push-buttons must be installed at multiple locations on the bridge, including both bridge wings, the chart table, the central conning position, and any other location where the watchkeeper may be stationed. Each reset button location must be reachable without the operator leaving their watch station — even in emergency conditions. SOLAS specifically requires reset capability from both bridge wings.
📚 Frequently Asked Questions
💠 Engineering Practice Recommendations
BNWAS system design and installation involves careful consideration at both the hardware and software levels:
- Software safety architecture: The BNWAS firmware should implement a hardware watchdog timer (WDT) and power-on self-test (POST). If the microprocessor crashes, the watchdog must automatically trigger a Stage 3 alarm.
- System integration testing: As a component of the Integrated Bridge System (IBS), the BNWAS must be integration-tested with ECDIS, radar, autopilot, and VDR. Fault simulation testing should verify correct response to signal loss.
- Electromagnetic compatibility: The bridge environment hosts multiple radio transmitters. BNWAS equipment must demonstrate adequate EMI immunity through shielded enclosures and filtered connector interfaces.
Q1: How does the BNWAS interface with ECDIS?
The BNWAS receives activity signals from ECDIS via hardwired or serial connection (e.g., cursor movement, zoom operations, route modifications). When the watchkeeper interacts with the ECDIS, the BNWAS interprets this as operator presence and resets the inactivity timer.
Q2: Are there special considerations for restricted visibility conditions?
Yes. In restricted visibility or heavy traffic, the master may require a shorter Stage 1 timeout (reduced from 3–12 minutes to 1–2 minutes). BNWAS design should provide flexible timer configuration to accommodate different operational scenarios.
Q3: How does Stage 3 alarm notify the entire ship?
Stage 3 alarm must be connected to the general emergency alarm system, activating audible and visual alarms in all crew cabins, corridors, mess rooms, and public spaces. A voice announcement “Bridge unattended” or equivalent message should be included to clearly communicate the nature of the emergency.
Q4: Does BNWAS replace the traditional watchkeeper?
No. BNWAS is a supplementary safety device, not a replacement for qualified watchkeeping officers and lookouts. SOLAS explicitly requires that BNWAS shall not be used as a substitute for maintaining a proper navigational watch.
