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Part of Report - The cutting extinguisher as a clearance and fire extinguishing
tool on carbon fibre composite ships
Tomas Carlsén, Bi97
Henrik Winkler, Bi97
Report 5069
ISSN:1402-3504
ISRN:LUTVDG/TVBB —5069 –SE
Summary
Kockums Shipyard Ltd in Karlskrona has been assigned by
the Swedish DMA to start building Visby-class corvettes. These corvettes
are made of a sand-wich construction with carbon fibre laminate on each
side of a core,Divinycell. This report evaluates the suitability of the
cutting extinguisher as a cutting and fire extinguishing tool on board
the ship. Furthermore, by using a cone calorimeter,the fire qualities
of the construction have been examined.
The cone calorimet r tests showed that the material, when
exposed to a radiation level of 35 kW/m 2, ignites at approximately 530
°C with the use of a pilot flame. When burning, the material generates
approximately 100-200 kW/m 2, depending on the thickness of the carbon
fibre layer. This is about the same amount as is generated by burning
wooden panels. The sandwich construction is an excellent heat isolator,
but on the other hand it loses all of its structural integrity after only
about a minute of fire exposure. This is due to the fact that the core
shrinks at a temperature of approximately 90 °C and lose the adhesion
to the carbon fibre laminate.
The cutting extinguisher, which has been developed by Cold
Cut System Ltd in Kungsbacka, was made with the purpose of facilitating
the fire brigade making holes in roofs. At tests it turned out that it
had the side effect of extinguishing fires once it had cut through the
roof material.
The cutting tests were performed on three different types
of sandwich construction. The constructions were chosen to correspond
to a minimum, medium and maximum laminate layer thickness as used on the
ship. The cutting extinguisher tests proved that it is a very capabel
cutting tool indeed. It cut through the various constructions without
any problems what so ever. Operators unaccustomed to the equipment will
experience difficulties only with the maximum laminate layer thickness,
when the need of an optimum cutting speed is essential to perform a fast
and even cutting.
The extinguishing capacity of the cutting extinguisher was
tested in a container at the Navy rescue school in Karlskrona. Four tests
were performed and for each test a mock wall was made, containing three
sandwich panels, and mounted in front of a container opening. The mock
wall was exposed to the radiation from a fire of 3,6 MW in which the temperature
was approximately 500 °C. In two tests the fire was burning for five
minutes and in two tests ten minutes before the cutting through one of
the sandwich panels were initiated. The cutting turned to fire extinguishing
once the sandwich panel was penetrated and water was sprayed for 30 seconds
in two tests (5 and 10 minutes pre-burning) and for 60 seconds in the
remaining two tests. Once the sandwich panel was penetrated the fire was
put out in approximately 10 seconds. The quipment that was tested delivered
a water flow of 28 litres per minute, which equals a theoretical extinguishing
yield of 6,5 MW.
To sum it up, the cutting extinguisher would be an excellent
complement in addition to conventional fire tools on board the Visby-class
corvettes. By using the cutting extinguisher initially on a fire in a
contained compartment and when a passage is made continue the remaining
fire fighting with conventional nozzles, the damage would be reduced and
time would be saved.
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