The present invention relates to a means for water supply to 5 a fire extinguishing installation on a helideck, preferably for use on offshore oil drilling or production platforms, of the type disclosed in the preamble of the independent claim 1 presented below.

¹ ° A helideck with a fire extinguishing installation of the type mentioned above is known from the applicant's own Norwegian patents 146.532 and 148.328 granted on October 20, 1982, and September 21, 1983, respectively. The objective of the helidecks according to said patents is to remove burning or i5 combustible fluid from the areas surrounding a crashed helicopter and to bring the fluid out to the peripheral areas of the helideck. To achieve this, water is fed in through water discharge orifices centrally positioned on the helideck and is allowed to flow out freely to all the edges and down

20 into a collection gutter arranged around the periphery of the helideck which gutter is provided with drain pipes.

When the water is supplied through said central orifices and flows freely to all edges or in all directions, the burning 5 or combustible fluid floating on the water will be carried with the water stream away from the central area of the deck and out into the gutter.

Experiments show that a propellant such as, e.g., jet fuel 0 that floats on the water and is still burning when it reaches the gutter is extinguished when it runs down through the drain pipes from the gutter together with the overflow water. This is due to a lack of oxygen.

5 Water having a low temperature could be used to prevent the occurrence of evaporation of fuel leaking from a helicopter. As long as the evaporation and therewith also the generation

of gas is prevented or held to a minimum by the low tempera¬ ture of the water, the possibility of ignition will be slight.

Water is an excellent extinguishing and cooling agent. By using it in excessive amounts in accordance with the above described system, any fire that may occur - burning fuel- will be driven away from the helicopter, thus preventing the helicopter from overheating.

10

In combination with the water stream on the helideck, water may also be used advantageously to cool down the helicopter itself with the aid of conventional water hose equipment having a jet nozzle or mist disperser, which will provide ■5 effective protection for the helicopter and the passengers therein.

Evacuation of passengers from the helicopter cabin is a critical factor in a disaster situation. Such evacuation may ° be performed with a greater degree of security on a helideck of the type mentioned above. With the proper hose equipment one would be able to approach the cabin with a high degree of safety and help the crew and passengers exit to safety. Water at a low temperature administered through a mist disperser will deter the development of flames and improve the atmosphere both inside and outside the cabin, thereby providing a basis for a safe evacuation.

By means of a fire extinguishing installation of the type 0 described above, it is also possible to realize a preventive effect in the event of a potential fire that could be caused by an accident on landing or take-off of a helicopter on the helideck, in that the water supply may be turned on and discharged onto the deck prior to a landing or take-off. 5 This means that the fire extinguishing installation would already be in operation and, in the initial phase of a fire

in connection with an accident, precious moments is gained in advance.

By flooding a sufficient stream of water over the deck, it is also possible to remove snow and ice on the helideck that can create problems for the traffic thereon, as the water melts the snow or ice. To enhance this process it is possible according to the present invention to heat the water.

It is apparent from the above that relatively large quanti¬ ties of water must be used to achieve the flooding of the surface of the helideck described above in order to obtain the above stated effects.

in order to avoid overloading the pressurized water system to which the fire extinguishing installation is connected, or if said pressurized water system lacks sufficient capacity to supply the necessary quantities of water, it is desirable to provide a means for water supply to the fire extinguishing installation that makes it possible to reduce substantially the supply capacity required for the pressurized water system.

This is achieved according to the invention with the aid of the characterizing features disclosed in the characterizing clause of the following independent claim 1, as well as in the characterizing clause of the subsequent dependent claims.

In connection with conversion of an existing helideck to a helideck of the type mentioned in the introduction above and provided with a fire extinguishing installation, there is discussed in the following figure descriptions the possibilty of introducing pressurized water to the water discharge orifices in the central area of the helideck without having to physically encroach on the existing deck surface of the helideck.

The invention will be described in more detail in the following, with reference to the embodiment examples schematically illustrated in the drawings, and wherein

Figure 1 is schematic side view of a helideck with an installation for feeding pressurized water to the water discharge orifices on the deck surface and recirculation of this water simultaneously with the removal of any fuel that may be floating on the water from the water to be recycled, and for supplying water from the pressurized water system in order to maintain the volume of the circulating water.

Figure 2 is a top plan view of a helideck, with arrows indicating the outflow of water from the water discharge orifices in the central area of the deck, in the direction toward the deck periphery with its gutter and drainage openings, and

Figure 3 shows an example of a grating sector unit with a water supply line mounted on the underside thereof for placement together with corresponding grating sector units on an existing helideck in connection with the conversion thereof.

Hence, Figure 1 presents a schematic side view of a helideck A, which is also shown from above in Figure 2 as an octagonal helideck where the actual deck surface 3 is covered by eight sector-shaped grating units a^-a that are supported by bars, beams or other spacing means lb, at a slight distance above deck 3; see also Figure 3. At the center of deck surface 3 are located water discharge orifices 2 connected to supply of pressurized water for flooding of the deck surface 3. At the periphery of deck surface 3 is arranged a gutter 5, preferably having a plurality of outlets 6 distributed around deck surface 3 to receive overflow water from said water discharge orifices 2.

The water supply to the fire extinguishing installation on helideck A comprises a tank 7 connected to a pressurized water system, preferably an existing pressurized water system B on the platform, via a control valve (float valve 9) for maintenance of a water level C in tank 7, preferably up to the lower end of drain pipes 6a from outlets 6 in gutter 5. Drain pipes 6a open out into the upper section 7a of tank 7, out from which runs an overflow pipe 7a'. The water discharge orifices 2 are connected to a water supply line 2a from the lower sector 7c of tank 7. In this water supply line 2a is a circulation pump 8 fitted for the supplying of water and thereby the provision of a stream of water through water supply line 2a, out of water discharge orifices 2, over deck surface 3 to gutter 5 and down outlets 6 to the upper sector 7a of tank 7. Fuel that descends onto helideck A and down onto deck surface 3 in the event of a helicopter accident is transported by the stream of water, possibly in a state of combustion, to gutter 5 and down outlets 6, where any existing flames are quenched due to lack of oxygen, and is conducted further to tank 7. Because the fuel is lighter than water, it floats on the surface of the water and therefore at the top of tank 7 and runs out, possibly together with some water, through overflow pipe 7a'. The major portion of the water remains in tank 7 and is recir- culated with the aid of circulation pump 8 in the cycle described above for reuse.

Any loss of water due to said overflow pipe 7a' will be replaced from the pressurized water system B via said control valve/float valve 9.

Because the water as a fire extinguishing agent is recycled in the manner described above, it may be served by pressur¬ ized water systems B having a relatively low capacity, as the pressurized water system B will merely serve to refill tank 7 in connection with the water loss taking place through overflow pipe 7a', or through possible evaporation.

The drain pipes 6a from outlets 6 may be connected to a header 6a' that opens out into tank 7.

Due to the fact that the propellant used for helicopters, so- called jet fuel, has a low flash point - namely around 38°C- it may be of importance to chill the circulating water so that it can hold the temperature of the fuel below its flash point and thereby prevent evaporation and ignition.

Under other circumstances it may be advisable to heat the circulating water in order to melt any snow and ice that may accumulate on the helideck and thereby dispose of the melt water through gutter 5 and outlets 6 and out through overflow pipe 7a' in tank 7. This melting of snow and ice is done through the maintenance of a desired water circulation at the desired water temperature.

Said cooling or heating, respectively, of the circulation water can be accomplished with the aid of a heat exchanger 9 provided in the water supply line 2a, preferably between the circulation pump 8 and water discharge orifices 2.

In the particular embodiment form of the float valve shown in Figure 1, the valve is disposed outside tank 7 in a vertical riser 9b connected at the lower end section thereof with tank 7, preferably at the mid-sector 7b thereof. The upper end section of riser 9b is connected to the pressurized water system B, optionally via a shut-off valve/cock 10. In this manner the amount of water supplied from the pressurized water system B may be regulated with the aid of cock 10, or the water supply may be shut off.

Float valve 9 comprises a float 9a which activates a shut-off means and is thereby capable of opening and closing the water supply from pressurized water system B, depending on the

water level C in tank 7 and in riser 9b communicating with tank 7.

In connection with the possible conversion of existing helidecks in order to adapt them to the above described fire extinguishing installation and its water circulation system, the grates 1 for helideck A, which are supported by be¬ ams/bars lb and are thereby spaced at a slight distance above deck surface 3 may, as mentioned above, be designed as

10 grate sector units a^ , a . etc.

In order to avoid physical encroachment or repair on the existing deck surface 3, e.g. by passing water supply lines 2b through deck surface 3 from the underside thereof, water

■5 supply lines 2a' may be disposed beneath the grates 1, and may run from the periphery of deck surface 3 to its central area. Said water supply line(s) 2a' is (are) connected at the inner end(s) thereof to water discharge orifice 2 and are provided at the outer end(ε) thereof with a coupling means for connection to pressurized water supply line 2a from tank 7.

Water supply line 2a' may advantageously be secured to the underside of the grate sector unit and thereby form a unit 5 which, together with other grate sector units a*^ , &2 , 3.3 , etc., composes the grate 1 on deck surface 3 of helideck A.

0

5