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Feature 2 | RO-RO TECHNOLOGY Fire tests for ro-pax composites


Large-scale fire tests have been conducted focusing on alternative lightweight materials for ro-pax cabin and corridor construction. Tommy Hertzberg, Jesper Axelsson, and Magnus Arvidson, all of the Department of Fire Technology at SP Technical Research Institute of Sweden, report.


STENA Rederi AB, Kockums AB, DIAB AB, Callenberg Fläkt Marine AB, Ultra Fog AB, Thermal Ceramics Europe., Consilium Fire & Gas AB, Isolamin AB, Hellbergs International AB, ScanMarine AB, TYCO Building Services Products (Sweden).


Involved in the project was also a DNV-led subgroup of the EU project SAFEDOR, that included also the two Norwegian companies Brødrene Aa AS and Fireco AS. The assistance of DNV-SAFEDOR and other project partners is greatly acknowledged.


I


nterest is growing in the use of lightweight construction materials for shipbuilding. Combustible


lightweight materials for shipbuilding, previously prohibited by the SOLAS requirement for ‘steel or equivalent’ construction material, are now permissible through the new (2002) Regulation 17 on ‘Alternative design and arrangements’. However, the (equivalent) safety level


has to be demonstrated and the below described fire experiment involving combustible composites should be seen in this light. Two Swedish research projects focused


on lightweight shipbuilding - LASS (Lightweight construction applications at sea, www.lass.nu) and DIBS (Design basis for fires at sea) - jointly conducted large- scale fire tests recently. For this purpose, a two bed cabin and corridor ‘ro-pax replicate’, surrounded by a properly insulated FRP (Fibre Reinforced Plastic) composite superstructure, were built in the SP fire lab in Borås, Sweden. All materials used (bedding materials,


flooring materials, etc), except the composite, were materials one would expect to find on a standard ro-pax vessel. Furthermore, a realistic amount of luggage was placed in the cabin. Fire was initiated by igniting a small wooden crib placed in the lower, leſt hand side cabin bed (see Figure 1). Te intensity and duration of the fire that developed when the cabin door was leſt open and the sprinkler was disconnected was somewhat surprising.


Composite conditions The main idea of the project was to design experiments to resemble possible fires in a ro-pax cabin. The objectives were to study design fires, eg fire development and the


32 Figure 1:Figure 1: The cabin interior. The cabin interior.


influence of sprinklers, ventilation, etc, and to evaluate the behaviour of a composite structure under realistic fire conditions. The test set up consisted of two B-


15 passenger cabins connected to a corridor, built inside a fire insulated plastic composite superstructure. Each of the cabins had a window opening. An open deluge (drencher) sprinkler system was installed on the outside of the superstructure in order to evaluate fire protection of the composite ‘hull’. The outer construction consisted


of a composite front with two window openings and one bulkhead at the right hand side, as viewed in Figure 2. The composite ‘decks’ were situated


above and below the two cabins and the corridor. All composite materials except the below deck were insulated using certified FRD 60 (Fire Restricting Division) insulation. A floating floor system was used on the bottom deck.


Four cabin fire experiments were


conducted where either the (water mist) sprinkler system activated as expected, thereby efficiently controlling the fire, or where the door and window openings were sealed closed and the limited amount of oxygen made the fire self- extinguish. These tests will be described in detail in a forthcoming SP report. Discussed here are the experiments made with particular importance for the composite construction only: the flashover fire test and the tests where the drencher system on the outside of the superstructure was activated.


Flashover fire test In the fifth fire test several simultaneous fault functions were simulated: the sprinkler system was disconnected and the door of the cabin was left open. However, the window was closed and mounted with fireproof glass. This resulted in a very intense flashover fire, a 2MW-3MW fire that lasted 35-40 minutes in the cabin ignited. The other cabin was closed and not furnished. The fire involved all combustible


interior materials and the floor covering inside the cabin (denoted ‘Cabin A’) and the corridor. After the fire, it was observed that all cabin panels were more or less deformed and that two ceiling panels had fallen to the floor. The cabin’s aluminium floor plates had melted over a large area and were completely consumed in an area between the bunk beds. The underlying floating floor insulation and part of the composite deck were also severely damaged in a limited area. The fire insulation under the upper


deck and on the bulkheads was almost unaffected, except for a small spot centred approximately below the cabin, where the insulation seemed to be


The Naval Architect April 2008


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