Bilge Area Fire Fighting with Water Mist
In 2005 The International Maritime Organisation (IMO) published the revised guidelines IMO MSC/Circ. 1165 for equivalent water-based fire-extinguishing systems as referred to in SOLAS 74 for machinery spaces and cargo pump-rooms. By this amendment the existing MSC/Circ. 668, as amended by MSC/Circ. 728, was given a life time that expired in 2010. The new version for testing systems that are equivalent to that referred to in Solas Regulation II-2/12 has modification for the testing of systems in that tests specific for bilge area were implemented as mandatory.
Before 2005 virtually no manufacturers tested for bilge area protection, as bilges up to 750mm were normally not protected with separate bilge nozzles. However, in 2005 Danfoss Semco A/S conducted fire tests for bilge areas in accordance with the new test method described in IMO/MSC 1165. At that time the normal bilge height was 750mm, which was chosen for the test. Based on this Danfoss Semco was able to obtain formally approved bilge area protection with water mist nozzles. Besides this, the normal practice with bilges higher than 750mm, was to treat them as part of the engine room. Recently the new rules led to a change in practice that bilge area protection was required for all bilges and the manufacturer can only protect bilge areas up to the height for which they have an approval.
Danfoss Semco has recently finalised large scale fire test with water mist nozzles for bilge areas in accordance with these new guidelines and have obtained type approval from the maritime classes.
In order to get the optimal solution Danfoss Semco has developed a new nozzle that uses only water for extinguishing the three classification tests for fires in the bilge area. The classification tests comprise fire in pools located beneath an engine mock-up and consist of flammable liquid that is 0.5 square metres of heptane, 0.5 square metres of lubrication oil and 4 square metres of diesel.
All Danfoss Semco’s nozzles are drawn in 3D, which means that generating the production material is easier as this can be done directly from the 3D model. Even prototype nozzles are modelled in 3D. The spray pattern of the modelled nozzles is then implemented into a 3D model of the fire scenario of the enclosure and combustibles. By doing this the cost of developing new nozzles has been decreased as has the lead time from prototype to final approved nozzle. During the fire performance testing several parameters were recorded, such as temperature, damage due to the fire and time to extinguishment. These parameters serve as basis for developing of new nozzles and are used when modelling new nozzles.
The new nozzles can protect bilges that are up to 1.5 metres high, which currently is the highest on the market. This enables Danfoss Semco nozzles to be installed in bilges where the distance between the tank top and the bilge plates are up to 1.5 metres. The increase in height would meet the trend towards larger engine rooms, with bilge plates located above 0.75 metres that has previously been the benchmark.
Besides the new nozzles for water mist bilge areas Danfoss Semco can also protect bilges with the same height with nozzles using 1% AFFF foam additive. This means that the yard or owner can chose between water only or foam for the protection of bilge areas with height of up to 1.5 metres. In both cases the above mentioned classification fires were extinguished with very convincing results as, for example, the two oil test fires were extinguished faster than one minute after activation of the Sem Safe system.
With these new nozzles, Danfoss Semco can supply nozzles with type approvals in accordance with the current regulation, as well as machinery spaces with higher bilges. This is positive for all Danfoss Semco customers since they still can trust Danfoss Semco as a total solution provider of fixed firefighting equipment that is innovative in developing new products to meet tomorrows demand. The new type approvals could be a competitive solution for Danfoss Semco as no other manufacturers has yet invested in the new approvals for bilges at the same height for water mist nozzles without additives.
If the ship owner or the yard wants to have a solution with foam additives for bilge area protection, this can also be provided by Danfoss Semco. The approvals for the Sem-Foam system is also for bilges that is up to 1.5 metres in height. This gives the benefit that the yard does not have to remember all kinds of different heights for bilges as the two systems are approved for the same height.
Compared to competitors, the new Danfoss Semco nozzle uses approximately 14 percent less water than comparable nozzles on the market, while still extinguishing the fire with a reasonable margin. As a result of large spacing and low water consumption for the bilge area protection, the yard will experience lower cost for the installation. The installation cost are even reduced further since the nozzles are easy to mount as a normal pendent nozzle, so the installer does not have to install nozzles in a certain angle as most manufacturers have in their type approvals. The inclinations have been introduced in order to extinguish the fires where Danfoss Semco instead implemented this into our nozzle design resulting in nozzles that can provide water spraying almost horizontally. For other application such as parking garages we developed the first upright nozzle that sprays down wards, meaning that inside the nozzle the flow direction is reversed before it is distributed out of the nozzle.
One advantage of using water without additives is associated with the cost involved with a foam additive. Some maritime classification societies require full scale testing of the system after installation to see that the water mist can cover the entire machinery enclosure including the bilge area. For foam systems they require that the foam additive is part of this large scale testing. By adding the foam, the yard will add more costs for cleaning compared to if only water was used. Furthermore the owner has to monitor the shelf life of the foam concentrate and has to include the cost for regularly changing of foam concentrates during the operation of the ship.
In order to ensure the very best quality of all of our nozzles, we have chosen to make flow test of every single nozzle as part of internal quality management system. This means that we are certain that the delivered nozzle from our production all give the specified nominal flow which is the same flow as for the nozzles that passed the large scale fire testing. For other than the open bilge nozzles, for example, glass bulb operated nozzles, a leakage test is conducted on every glass bulb nozzle where all are subjected to a pressure test.
For more information, go to www.danfoss-semco.com