WO2003024531A1

WO2003024531A1 - Method for fire fighting and extinguishing equipment system for fire prevention

Info

Publication number: WO2003024531A1
Application number: PCT/FI2002/000740
Authority: WO
Inventors: Kari Lounatmaa; Immo Rantala
Original assignee: Kari Lounatmaa; Immo Rantala
Priority date: 2001-09-17
Filing date: 2002-09-17
Publication date: 2003-03-27
Also published as: FI112036B; FI20011831A; EP1427483A1; FI20011831A0

Abstract

In a method for fire fighting by using nitrogen as extinguishing agent, especially in building fires or other fires in closed spaces, liquid nitrogen is stored at the fire station (S) in a storage tank (1), wherefrom extinction containers (3) used for fire fighting are filled in, and the extinction containers (3) are kept in state of readiness in an intermediate storage (2), and in case of fire the extinction containers (3) are used at the fire scene as breakable fire extinction means throwable or deliverable in another manner to the burning target that cause upon breaking the nitrogen gasified from the liquid nitrogen to spread in the burning target and a considerable decrease in the target's temperature. The extinction containers (3) are also used to distribute liquid nitrogen to selected burning spots at the fire scene.

Description

Method for fire fighting and extinguishing equipment system for fire prevention

The invention concerns a method for fire fighting, especially in building fires, where there are seats of fire in inside rooms. The invention further concerns an extinguishing equipment system for fire prevention by means of which the said method can be carried out.

In fire fighting different sprayable substances have been used that are directed to the burning target. A typical example of these are different extinguishing foams, carbon dioxide and traditional water that is largely applied as extinguishing agent by the fire brigades in building fires.

A method is presented in the European patent application 302 797 for fire fighting based on use of a tank truck whose tank contains liquid nitrogen that can be sprayed directly to the target or led from the tank as gaseous wide front with the wind. The method is intended to be used in the open.

Similarly for fighting fires in the open, for example forest fires, "bombs" containing liquid nitrogen have been suggested ,as presented in the French patent application 75 19507 (publication 2 315 290). Here it has been presented to drop e.g. tanks containing liquid nitrogen from a helicopter to the burning target. The liquid nitrogen when gasified on the one hand cools down effectively the burning target and on the other hand creates an oxygen-free environment that suppresses the flames. This method of application is theoretically suitable for objects that are difficult to reach due to high temperature and where there are with certainty no people. Tanks containing liquid nitrogen that could be dropped as "bombs" or shot as ""projectiles" to the target have been presented also in the French patent application 86 12370 (publication 2 603 193). These tanks may be equipped with a fuse to ensure breakage of the tank anoUspreading of the contents, for example, at a certain altitude. For this purpose the fuse may be a time fuse, remote con- trolled, or detecting the approach to target. A drop bomb containing extinguishing agent in form of liquid carbon dioxide is presented in the international publication WO 94/20169. About the use of liquid nitrogen for fighting building fires there is a literature survey in an article J.H. McGuire, Fighting Building Fires with Liquid Nitrogen: A Literature Survey", Fire Safety Journal, 4 (1981) 15-19.

In building fires where the fire mostly spreads in closed spaces until today no such method or system based on liquid nitrogen has been presented that would be adaptable in practice to the work of fire bri- gades or similar fire fighting organizations and would be suitable for the extinguishing equipment that they use. The invention is intended to present a method that can be applied for extinction of many types of building fires to prevent fire from spreading in inner rooms, for example, as a supplement to conventional fire fighting methods, or, in many cases, to replace them. The purpose of the invention is also to present a system that is suitable for use by fire prevention organizations as a part of their extinguishing equipment.

To achieve these objects the main characteristics of the method according to the invention is that liquid nitrogen is stocked in a store tank at the fire station, and from the tank extinction containers used for fire fighting are filled in and kept in state of readiness in an intermediate storage, and in case of fire the extinction containers are used as breakable fire extinction means throwable or deliverable in another manner to the burning target, that cause upon breaking the nitrogen gasified from the liquid nitrogen to spread in the burning target and a considerable decrease in the target's temperature, or the extinction containers are used to distribute liquid nitrogen to selected burning spots at the fire scene.

The intermediate storage where the extinction containers are kept can be a thermally insulated box-type space similar to a cool box where there are several extinction containers. Alternatively the extinction containers can also be surrounded by liquid nitrogen in the intermedi- ate storage where the filling of the intermediate storage from the storage tank can be carried out so that when filling the extinction containers also the space around them in the intermediate storage is filled acting as an effective insulation.

The intermediate storage can be at the fire station in a place reserved for it or ready in a vehicle, for example in a tank truck or another car driven to the fire place, or in a separate unit moved by a vehicle such as a trailer.

The extinction containers can be in the intermediate storage in closed condition but equipped with safety valves i.e. pressure relief valves to prevent the pressure from increasing in the containers during storage. When an extinction container is taken to be carried, that is, it will be launched by throwing, rolling or other means to the burning target within a short period of time the safety valve is permanently closed. The safety valve is closed at the latest when the carrier aims the extinction container at the target, eg. just before throwing, rolling and so forth. The safety valve may be situated in the sealing member of the filling hole like in a cap. At the same time when the safety valve is closed, a part acting as a kind of "fuse" that produces the increase of gas pressure in the container is activated. In this way the breakage of the container and spreading of nitrogen in the environment is supported when the extinction container reaches its target.

A storage tank for liquid nitrogen and an intermediate storage of extinction containers containing liquid nitrogen in state of readiness at the fire station, which extinction containers are used as actual extinction equipment, belong in turn to the system according to the invention. This intermediate storage is easy to take with to the fire scene when a fire alarm is received and it can already be situated in a vehicle or separate transport unit that can be coupled thereto, such as a trailer. From the liquid nitrogen storage tank new extinction containers can be filled to be kept in the intermediate storage when old extinction containers have been used.

In the following the invention is explained in more details by referring to enclosed figures where Figure 1 presents diagrammatically the system according to the invention,

Figure 2 presents one solution for intermediate storing of extinction containers,

Figure 3 presents the construction of an individual extinction container, and

Figures 4 and 5 present one solution for situation of the different elements of the system at the fire station.

Figure 1 presents as sectional diagram the system according to the invention. Arrow N₂ indicates the flow of nitrogen in the system. At a fire station S or similar station where the fire extinction equipment is in state of readiness, there is a storage tank 1 from which liquid nitrogen is filled into extinction containers 3 that are kept in an intermediate storage 2. The storage tank can be supplied with nitrogen from the factory, or a new storage tank in replacement of the old one can be delivered from the factory. The intermediate storage is located at the fire station in such a place from which it can be easily taken with to the fire scene. The intermediate storage 2 can be situated in a place foreseen for it and separated from the vehicles or it can be mounted in readiness in such a vehicle or transport unit (trailer) transportable by a vehicle that is driven to the fire scene when an alarm is received. Arrow A indicates the transfer of such an intermediate storage 2 to the fire scene F from the station S that is indicated by dot-and-dash lines. At the fire scene F the extinction containers 3 are taken away from the intermediate storage 2, set in ready for operation state, and launched to the burning target by throwing or another appropriate way (containers used this way are indicated by crosses). Unused extinction containers are returned to the intermediate storage. The used containers are replaced by new ones at the fire station. Extinction containers can also be emptied without having to break them, thus liquid nitrogen can be distributed in the fire place to selected burning spots by pouring, especially to difficult places where there is no room for a extinction container but that can be safely approached. Such containers can be refilled after use.

Figure 2 presents, a sidewall extracted, a removable intermediate stor- age 2 or storage box belonging to the system. The intermediate storage is equipped with thermally insulated wall panels 2a inside of which there is a storing space 2b for the extinction containers 3. Also the extinction containers 3 can be isolated from each others by partition walls. The storing space is closed on the top by a cover 2c that is detachable allowing thus an easy access to the extinction containers 3. The intermediate storage can function like a cool box thermally insulating the liquid nitrogen containing extinction containers 3 inside. The liquid nitrogen to be filled from the storage tank can be led through a special construction chute that directs the liquid nitrogen both into the open mouths of the extinction containers and outside the extinction containers. This kind of a box must naturally be liquid-proof. Thus the extinction containers are surrounded by liquid nitrogen that acts as an effective insulation for them (in addition to the partition walls inside the box if used). In the covέr 2c o elsewhere in the storage box a safety valve can be installed through which the gasified nitrogen inside the intermediate storage can escape.

It is clear that the filling with liquid nitrogen from the storage tank can take place by letting a certain amount of liquid nitrogen flow from the storage tank into a special carrying receptacle by means of which the extinction containers 3 in the intermediate storage are filled. Furthermore, it is possible to fill the extinction containers 3 separately from the intermediate storage 2 and place them in the intermediate storage 2 only after filling. In this case it is recommended to use in the intermediate storage partition walls isolating the extinction containers from one another.

Figure 3 presents the construction of an individual extinction container as vertical sectional view. The extinction container can be a vessel nar- rowing upwards to the filling hole that can be fully closed. For easy handling the vessel is equipped with a carrying handle 4. The vessel can be of upwards narrowing type in order to minimize the free surface of liquid nitrogen in the upper part of the vessel. The filling hole 5 can be closed by a cap 6 or similar sealing member. In the intermediate storage 2 the extinction containers 3 are closed by caps 6. In the container there is also a safety valve 7 connected to the gas space inside the extinction container, the purpose of which is to discharge gas from the container when the pressure increases too much. The safety valve can be of a type that stays in open state after the pressure has risen above a certain limit and nitrogen gas has escaped, or of type that closes by a predetermined return force, e.g. spring-loaded, after nitro- gen gas has escaped and the pressure in the extinction container has decreased below a certain limit. The safety valve 7 of either type can be fully closed, in which case it does not allow the gas to escape from the extinction container even if the pressure would rise above the relief pressure, thus helping to increase the gas pressure in an operation situation. The closing means in its closure position can block permanently an opening through which the gas normally exits after the safety valve or it can retain a moving part of the safety valve permanently in the closure position where the part prevents the passage of the gas.

The safety valve 7 can be situated in the upper part of the extinction container separately from the cap 6 or similar sealing member of the filling hole 5, but it can as well be integrated to it as shown in Figure 3.

When an extinction container is taken to be carried with the intention to launch it by throwing or in another manner to the burning target, the safety valve 7 can still be in condition where it opens if too much pressure is developed in the extinction container 3 during the time it is carried. When the extinction container is activated or "tuned" to an operational state the safety valve 7 is permanently closed whereupon the nitrogen pressure in the container is capable of increasing to a suitably high level to ensure the wall of the container 3 to break due to an impact when it hits the burning target and/or the prevailing temperature in the burning target increases the nitrogen pressure in the extinction container.

The extinction container 3 can also be equipped with a kind of a fuse 8 that actively causes the pressure increase in the container. This fuse can be based, for example, on a cartridge that releases pressurized auxiliary gas, for example carbon dioxide, that increases the gas pressure within the extinction container 3. The fuse 8 can be activated by means of a pushing member or similar trigger located outside the con- tainer. Just before the carrier of the container releases his/her hold from the extinction container, the safety valve 7 is permanently closed and the fuse 8 is at the same time activated. It is possible to organize both functions to take place simultaneously by integrating the safety valve 7 and the fuse 8 operationally together so that the movement of the pushing member or similar trigger at the same time closes the safety valve 7 permanently and activates the fuse 8. The movement can break, for example, a capsule containing carbon dioxide or similar at the same time when it closes the safety valve. Figure 3 presents, nevertheless, a separated safety valve 7 and fuse 8 where there is a capsule that breaks when it is pressed down by a pushing member against e.g. a sharp part and develops gas when breaking. In addition to the safety valve 7 the container can be equipped with a further safety valve 9 that is a cap placed in a hole in the wall that bounces out when the gas pressure increases but that is anchored to the container so that it always stays with the container. This kind of a safety valve 9 can also be the only safety valve of the container.

The safety valve 7 and fuse 8 can be integrated to the cap 6 or similar sealing member whereupon the walls of the extinction container 3 do not have to be equipped with different functional members at different places. It is possible, for example, that a sealing member including all these components is turned by means of a screw-type coupling down into the filling hole 5 and it has a part moving in the axial direction of the sealing member. If the pressure increases in the gas space beneath the filling hole 5, the part bounches up when a predetermined force dependent on the gas pressure is exceeded, releasing one or more outlets in the sealing member through which the gas can escape. By pushing slightly the part can be returned in position where it again functions as safety valve. If the part is pushed with more force deaper it locks in the sealing member such as the cap 6 so that no pressure from inside can open it (safety valve permanently closed), and at the same time it activates the fuse 8 by breaking the capsule or a similar closed space containing pressurized gas, also arranged in the sealing member. The different positions are clearly indicated on the sealing member. In the sealing member, also another part can be used that moves independently from the first part acting as the safety valve. By moving of the other part the first part can be locked (safety valve 7 permanently closed) and the fuse 8 activated (the movement breaks at the same time the capsule or similar). All the above mentioned movements can still be arranged in such a manner that the movement of the part that locks the safety valve 7 does not yet activate the fuse 8 but only the movement that is carried out as an extension of this first movement breaks the capsule or similar. In this stage the extinction container has to be ejected.

The fuse 8 can also be arranged to work by remote control. Here it does not have to be activated before the extinction container 3 is ejected or got rid of in another manner.

The actual extinction container 3 can be made of such material that breaks when getting near a seat of fire through an impact and/or increase of internal pressure, e.g. of liquid nitrogen proof plastic. Its volumetric capacity can vary according to the size of the inside room to be extinguished. It is optimally of a size that it can still be easily carried and its capacity can vary in the range of 1 litre - 15 litres, optimally 3 to 12 litres. Already a small volume of liquid nitrogen is very effective in inside rooms. The shape can vary from cylindrical to prism-shaped. The shape of the container can also be flat or round.

In Figure 3 is further shown a weakening 10 made into the wall of container 3 due to which the container breaks more easily through an impact and/or internal pressure at the burning target. The deterioration can be made e.g. by grooves made in the wall.

If the extinction container 3 is used to distribute liquid nitrogen to selected points in the fire scene it can be equipped with a spout or a suitable hose. This kind of a spout or hose can be attached to the previously described container as an accessory, for example it can be fastenable on the hole 5 after the cap 6 has been detached if the con- tainer is desired to be used to pour liquid nitrogen instead of throwing. The container can also be designed merely for pouring liquid nitrogen, and in this case it does not have to be easily breakable, and this kind of a container does not have to be equipped with a fuse 8 or weakening 10 but it is recommended to have another openable hole in addition to the hole 5 in order to allow air to flow into the container during pouring.

Figures 4 and 5 present as top and side views the storage tank 1 , intermediate storage 2 and location of the extinction containers 3 at the fire station during filling. The storage tank and intermediate storage including the extinction containers can be surrounded by a fence A. A filling pipe 12 equipped with a manually operated cut-off valve 11 has been led from the storage tank 1 to the vicinity of the intermediary storage 2. The separate extinction containers 3 can be filled by leading nitrogen into the box forming the intermediate storage 2 where there is a chute or another construction that leads the nitrogen into the containers 3, or the mouth of the filling pipe 12 can be movable to different the containers 3 so that they can be filled individually. In Figure 4 can be further seen that the containers are curved in their horizontal section like a "pocket flask" in order to be better adapted to the human body. When the intermediate storage has been filled it can be transferred to a standby station, e.g. to a vehicle or unit driven by a vehicle (trailer) or to another place reserved for it at the fire station.

When using liquid nitrogen in building fires or other fires in essentially closed spaces to suppress seats of fire it has to be taken into account that the nitrogen must not cause damage to people near the fire. The extinction devices are especially suited for fighting serious seats of fire quickly, thus enabling to prevent the fire from spreading in areas where it can cause danger to people. If final extinguishing is needed it can be done by traditional means, e.g. with water.

The advantages of liquid nitrogen as extinction agent are obvious: A small volume of it can produce a large volume of nitrogen gas (700:1) that quickly replaces the oxygen and at the same time, while gasifying at a low temperature, absorbs a big amount of heat. The nitrogen gas does not stay at the fire scene (compared to water causing water damages) but is released into the atmosphere as its natural component being non-poisonous. The advantages of fire fighting with nitrogen as compared to fighting with water are the following:

— nitrogen does not conduct electricity (safety at work), — nitrogen does not cause moisture damages,

— liquid nitrogen has a low temperature,

— nitrogen causes an effective oxygen depletion in the burning object,

— nitrogen effectively prevents combustion gases from flashing, i.e. exploding, and

— nitrogen requires a smaller volume for the same extinction capacity.

Claims

Claims:

1. Method for fire fighting by using nitrogen as extinguishing agent, especially in building fires or other fires in closed spaces, character- ized in that liquid nitrogen is stored at the fire station (S) in a storage tank (1), wherefrom extinction containers (3) used for fire fighting are filled in, and the extinction containers (3) are kept in state of readiness in an intermediate storage (2), and in case of fire the extinction containers (3) are used at the fire scene as breakable fire extinction means throwable or deliverable in another manner to the burning target that cause upon breaking the nitrogen gasified from the liquid nitrogen to spread in the burning target and a considerable decrease in the target's temperature, or the extinction containers (3) are used to distribute liquid nitrogen to selected burning spots at the fire scene.

2. Method according to claim 1 , characterized in that the extinction containers (3) are transported to the fire scene in the intermediate storage (2).

3. Method according to claim 2, characterized in that the intermediate storage (2) of the extinction containers (3) is kept at the fire station (S) in a vehicle or in a separate unit that can be connected to and transported by a vehicle.

4. Extinguishing equipment system for fire prevention that includes liquid nitrogen as extinction agent, characterized in that the system includes a storage tank of liquid nitrogen (1) situated at the fire station (S) and in state of readiness an intermediate storage (2) of extinction containers (3) containing liquid nitrogen.

5. Extinguishing equipment system according to claim 4, characterized in that the intermediate storage (2) is a heat insulated closed space.

6. Extinguishing equipment system according to claim 4 or 5, characterized in that the intermediate storage (2) is situated in a vehicle or separate unit that can be connected to and transported by a vehicle.

7. Extinguishing equipment system according to any of the preceding claims, characterized in that the extinction containers (3) are equipped with a safety valve (7, 9) that is arranged to let gas escape from the extinction container in order to prevent excessive pressure development inside the container.

8. Extinguishing equipment system according to any of the preceding claims, characterized in that the extinction containers are equipped with an activating element, such as a closing means that closes the safety valve completely or a fuse (8) causing the pressure to increase inside the container.

9. Extinguishing equipment system according to any of the preceding claims 4 to 7, characterized in that the extinction containers (3) are equipped with pouring element, such as a spout or hose, to distribute liquid nitrogen from inside the container to selected burning spots at the fire scene.