HK1108399B - Inerting method for preventing fires - Google Patents

Description

The present invention relates to an inertisation process to prevent fire or explosion in a confined space by lowering the oxygen content of the space in relation to the ambient air in the space.

Inertisation methods for fire prevention and extinguishing in closed spaces are known from fire-extinguishing technology. The extinguishing effect resulting from these methods is based on the principle of oxygen displacement. It is known that normal ambient air consists of 21% by volume of oxygen, 78% by volume of nitrogen and 1% by volume of other gases. For extinguishing or fire prevention, the introduction of, for example, pure or 90% nitrogen as an inert gas further increases the nitrogen concentration in the room concerned and thereby reduces the oxygen content. It is known that an extinguishing effect can occur when the oxygen content is less than 15 vol. Depending on the materials available in the room, a further burning of less than 12% of the oxygen content of the fuel may not be necessary.

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The patent DE 102 35 718 B3 describes a process for inerting one or more enclosed spaces to reduce the risk of fire and explosion by reducing the oxygen content in the enclosed space to a permissible level in relation to the ambient air. It also records a temperature value for a guest temperature in the enclosed space and determines the permissible level of oxygen content according to the temperature values, increasing the oxygen value with a higher temperature value. This method has the disadvantage, however, that the values depend greatly on the physical surface, the geometry, the special composition or the coverage by other safety materials.

Document US 4 846 410 describes a method for determining the net oxygen content, which depends on the oxygen content and the carbon monoxide equivalent of the inflammatory substances in the air of a coal-fired power plant.

However, it is known that temperatures in the range of -40°C to +60°C have no significant effect on the final ignition limit of solids and liquids. However, modern materials, both solids, especially small containers or packaging material, and liquids, can cause exhaust gases. These exhaust gases can, despite the reduced oxygen content, present an increased risk of fire or explosion.

Based on the problems described above concerning the safety requirements for an inert gas fire extinguishing system or an inertisation process, the present invention is intended to develop the inertisation process known from the state of the art and explained above so that it functions reliably regardless of the type of substances or goods stored in the protection area.

This problem is solved in the inerting process of the type described above by the features in the descriptive part of claim 1.

The advantages of the invention are in particular that an easy to implement and at the same time very effective inertisation process to reduce the risk of fire or explosion in a confined area can be achieved even when exhaust gases increase the concentration of the final ignition gases in the enclosure. The concentration of the final ignition gases is determined regularly by measurements. The disadvantages of inert gas concentration or oxygen concentration in the enclosure controlled by parameters are avoided and scattering of values of stored materials is avoided by timely measurement and reaction to increased concentrations of the final ignition gases due to gas balance.

Other embodiments of the invention are given in the subclaims.

The above problem is also solved by measuring the concentration of the final ignition gases in the enclosure at at least one point with one or more sensors, for example if the items or packaging stored in the enclosure are unevenly arranged.

Similarly, the oxygen concentration in the enclosure can be measured at several points and with one or more sensors, providing an additional safety feature in the case of uneven gas distributions in the enclosure.

The measurement of oxygen concentration can also be carried out with one or more sensors each, and the measurement with at least two sensors can increase the reliability.

In addition, the above-mentioned measurements of the concentration of the final ignition gases in the enclosure are fed to at least one control unit, as well as the concentration of oxygen in the enclosure. The multiple measurements fed to the control unit can be evaluated within the control unit based on a selectable algorithm. One or more control units can be provided. The advantage of a multiple design of the control unit is the increased safety of the overall system. This ensures that the entire control system remains functional even in the event of a failure of one control unit. If an increase in the concentration of the extinguishing gases is detected in the control unit by the extinguishing gases sensors, the oxygen concentration shall be further reduced to ensure that fires and explosions are safely prevented even in the presence of extinguishing gases (e.g. hydrocarbons).

Alternatively or additionally, it may be advantageously provided that the reference oxygen concentration is increased as the concentration of inflammatory gases decreases; this development of the invention may, for example, allow rapid passage of persons or other living creatures through the protected area.

The oxygen concentration can be conveniently controlled by a line drawn in the control unit, e.g. Fn = f(Kx).

In addition, the concentration of the final ignition gases produced by the exhaust gases of the goods stored in the storage room can be reduced by providing for a gas exchange or a fresh air supply in the shelter room, in order to prevent the concentration of the final ignition gases from continuously increasing through the exhaust gas and thus increasing the risk of fire or explosion.

In addition, if necessary, the signals from the sensors in the shelter can be transmitted wirelessly, allowing for changing storage material and/or goods geometries in the shelter.

The following illustration gives an example of the process of the invention.

It shows: Fig. 1A schematic arrangement of the shelter with its inert gas sources and valve, measuring and control devices.Fig.2An example of the change in oxygen concentration is influenced by the concentration of flammable substances in the shelter.

Figure 1 shows the basic function of the process, including the control and measuring instruments. The inert gas can be introduced from the inert gas source 2 through a valve 3 and one or more exhaust nozzles 7 into the chamber 1 by means of a control unit 4 which in turn affects the chamber 3. The control unit 4 is set so that a level of inertisation is achieved in the ground chamber 1. This basic inertisation level prevents fires in chamber 1 from occurring reliably under normal conditions. Under normal conditions, it is understood that there are no elevated concentrations of fire-promoting substances in chamber 1.The control unit 4 measures the oxygen concentration in the chamber 1 by means of an oxygen sensor 5 and controls the flow of inert gas accordingly. At least one other sensor 6 detects the presence and concentration of gases from material emissions. If the concentration of flammable or explosive gases in the air surrounding the chamber 1 increases (for example by an increased concentration of hydrocarbons), this is measured by means of the sensor 6. This measurement is fed to the control unit 4. The corresponding field function in the control unit 4 and the valve 3 increases the concentration of the gas in the chamber 1. The intake gas is then continuously increased.until the desired lower oxygen concentration in the enclosure, measured by the oxygen sensor 5, is reached and reliable fire protection is provided even under these harsh conditions.

Figure 2 shows an example of a possible evolution of oxygen concentration in chamber 1 depending on the concentration of flammable gases Kx in the chamber 1. The basic inertisation level of oxygen concentration indicates the level of inert gas required to reduce the risk of fire or explosion under normal conditions. The test chemical is used to determine the concentration of the inert gas.

List of reference marks

1 Protection area2 Inert gas source3 Valve4 Control unit5 Oxygen sensor6 Hydrocarbon sensor7 Inert gas entry

Claims (8)

1. An inerting method for preventing fire or explosion in a closed protected room (1), wherein the oxygen content in the protected room (1) is reduced to a base inerting level which corresponds to a reduced oxygen content compared to the ambient air, characterized in that the reduced oxygen content in the protected room (1) corresponding to the base inerting level is set as a function of the concentration of inflammatory gases in said protected room (1).
2. The method according to claim 1, characterized in that the concentration of inflammatory gases in the protected room is measured at one or a plurality of locations by means of one or a plurality of sensors (6) respectively.
3. The method according to claim 1 or 2, characterized in that the concentration of oxygen in the protected room is measured at one or a plurality of locations by means of one or a plurality of sensors (5) respectively.
4. The method according to claim 3, characterized in that the measured values for the concentrations of inflammatory gases and/or oxygen are relayed to at least one control unit (4).
5. The method according to claim 4, characterized in that the set value for the oxygen concentration decreases with increasing concentration of inflammatory gases.
6. The method according to claim 4 or 5, characterized in that the set value for the oxygen concentration increases with decreasing concentration of inflammatory gases.
7. The method according to any one of claims 3 to 6, characterized in that the control unit (4) regulates the set value for the oxygen concentration in accordance with a characteristic stored in said control unit (4).
8. The method according to any one of the preceding claims, characterized in that the concentration of inflammatory gases is reduced by a gaseous exchange and/or fresh air supply into the protected room (1).