With requirements for all vessels to fit BNWAS being phased in from this year, Tom Henson-Webb,integrated bridge systems manager of UK company ANT, part of SAM Electronics, looks at some aspects of retrofitting systems to existing ships.
Bridge navigation watch alarm systems (BNWAS) have been around for many years for vessels classed for one man bridge operation but with the adoption of IMO resolution (MSC 282(86) BNWAS carriage is mandatory for most vessels.
Last year saw the regulation for mandatory installation come into force on all new cargo vessels above 150gt and all passenger ships regardless of size. This year all passenger ships and all cargo vessels of 3,000gt and above built before 1 July 2011 are required to have a BNWAS fitted prior to their next survey after 1 July 2012. The roll out then continues with cargo vessels between 500gt and 2,999gt in 2013 and vessels of 150–499gt in 2014.
Although this was an established product, originally with probably half a dozen manufactures, the number of companies now offering systems has expanded greatly and while some of the major navigation equipment suppliers have got in on the act, a number of small outfits have popped out of the woodwork offering ever cheaper solutions. Although newbuilds required the system from 1 July last year, it was only in October that BNWAS was added to Annexe A1 of the IMO Marine Equipment Directive and could therefore be ‘wheelmarked’. Prior to this systems could only be approved by classification societies and flag states which in theory meant each system would require a multitude of approvals from the various bodies. In practise most relied on the approval of one of the major organisations (Lloyds Register, DNV, MCA) as being sufficient (which in most cases it was). For these systems receiving a “wheelmark” (MED Mod B) certificate may be a formality, but for others, which relied on a less internationally recognised body, this may well not be the case.
Regardless of the various companies’ hype, a BNWAS is essentially rather simple, requiring the bridge operator to reset a timer every twelve minutes by pressing a button, which if not done, alerts other crew members to attend the bridge. Some navigation equipment include a BNWAS reset function (normally relay contacts) so that when this equipment is operated, a signal is transmitted to the BNWAS to automatically reset the timer. As BNWAS is now mandatory the number of systems with this capability is bound to increase so it will be the case that the operator will rarely have to manually reset the timer.
BNWAS will normally interface to other systems such as VDR, autopilot and GPS, but it is still a fairly small system. However on retrofits this will usually still necessitate the running of new cabling, not only to other systems within the bridge, but more crucially to remote alarm units in the captain and navigation officers’ cabins and communal crew areas. In many cases, running these cables will require a large amount of time and effort as deckhead and bulkhead panelling will need to be removed and transits opened. Essentially on any vessel where there is not easy access to cable runs or the cable runs are over a significant distance, the cost of installing the equipment is likely to be well in excess of the cost of the hardware.
A number of manufacturers have tried to play down the installation issue, claiming that theirs is the easiest to install (normally by minimising the number of separate units and cables), but the issue remains that running new cables from the bridge to accommodation areas will usually be necessary. To date the only exceptions to this have been two manufacturers in the Far East and one in the UK. The Far Eastern solution has been to use power line communication, which piggy-backs a standard computer network protocol onto the ship’s mains. This technology is normally used in large buildings to provide computer connections without running network cables. The suitability of this technology on vessels where different areas may not be powered from the same supply (different phases or different generators) is questionable and the MCA has indicated that its currently has a moratorium on the use of this technology. Both of these systems also only have approval within their own countries, so only time will tell if they will become wheelmarked. The UK alternative uses wireless technology (this is not computer wi-fi) to link all units with the only cabling being a local source of AC power. It is an RF mess technology which means that each unit acts as a repeater, retransmitting the signal so that all units are not required to be able to receive a signal from the bridge. Currently this system is unique in being the only system not requiring physical connections between the units and which has achieved wheelmark type approval.Share