How does an overpressure fire extinguisher work
|Niederlungwitz volunteer fire brigade|
- Classification of fire classes
- Differentiation according to type
- Differentiation according to extinguishing agent
- Information on the label on the fire extinguisher
- Hazard warnings and limits of use for fire extinguishers
- Construction and operation of a powder extinguisher
- Instructions for handling the portable fire extinguishers
- Environmental protection during fire fighting exercises
Classification of fire classes
There are five fire classes across Europe:
|Fire class||short explanation||symbol|
|Fire class A:||Fires of solid, glowing substances. |
e.g .: Wood, paper, plastics, coal
|Fire class B:||Fires of liquid or liquefying substances. |
e.g .: Varnishes, paints, alcohols, petrol, waxes
|Fire class C:||Fires involving gaseous substances. |
e.g .: Methane, acetylene, natural gas
|Fire class D:||Metal fires. |
e.g .: Aluminum, sodium, potassium
|Fire class F:||Edible oils and fats fires. |
e.g .: Frying devices and kitchen equipment
Differentiation according to type
Fire extinguishers are divided into 4 types. These are:
- Permanent pressure extinguisher
- Charging extinguisher
- Gas extinguisher
- Fire extinguishers with chemical pressure generation
Permanent pressure extinguisher are hand-held fire extinguishers that are constantly under pressure, nitrogen is used as a propellant. The extinguishing agent and the propellant gas are in an extinguishing agent container. The propellant exerts constant pressure (permanent pressure) on the extinguishing agent. If the triggering device is actuated, the extinguishing agent is conveyed to the outside through the riser pipe and the spray nozzle.
Charging extinguisher are hand-held fire extinguishers that are only pressurized when necessary. A distinction is made between charging extinguishers with an internal propellant cartridge and charging extinguishers with an external propellant cartridge. Carbon dioxide is used as the propellant. If a connection is established between these two containers, the propellant gas flows from the propellant container into the extinguishing agent container and the fire extinguisher is ready for use.
Gas extinguisher are fire extinguishers with an extinguishing agent container that holds the extinguishing agent, which is a compressed gas. The gas extinguishers can contain an additional propellant gas in addition to the extinguishing agent.
Fire extinguishers with chemical pressure generation generate the necessary overpressure in the extinguishing agent container by means of a chemical reaction that generates the propellant gas (e.g. CO2). The chemical reaction is started when the fire extinguisher is started.
Differentiation according to extinguishing agent
Furthermore, fire extinguishers are divided according to extinguishing agent. These are:
- Water extinguisher
- Foam extinguisher
- Powder extinguisher
- Carbon dioxide extinguisher (CO2 extinguisher)
- Halon extinguisher (prohibited since 01/01/1994)
Water extinguisher can only be used in fire class A (embers forming solid substances). With a maximum of 9 liters of water, they cause minor water damage and have a cooling extinguishing effect.
According to VDE, when using water extinguishers in electrical systems with low voltage (below 1000 V), a safety distance of at least 1 m must be maintained. Use at high voltage (over 1000 V) is not permitted.
They are available with the following nominal capacities: 2l; 3l; 6l and 9l.
Foam extinguisher can be used in fire class A (embers forming solid substances) and fire class B (flammable, liquid substances). The foam compound in the extinguishing water reduces the surface tension of the water and can therefore penetrate densely compressed substances better than water. With a maximum of 9 liters of water, they cause minor water damage and have a cooling extinguishing effect. In the case of liquids, the vapor pressure is reduced to such an extent that the flammable liquid can no longer produce a sufficient amount of flammable vapors. Furthermore, the foam compound forms an oxygen-impermeable foam carpet.
According to VDE, when using foam extinguishers in electrical systems with low voltage (less than 1000 V), a safety distance of at least 1 m must be maintained. Use at high voltage (over 1000 V) is not permitted.
They are available with the following nominal capacities: 2l; 3l; 6l and 9l.
Powder extinguisher have a great extinguishing effect in the fire classes indicated on the fire extinguisher. A disadvantage, however, is the pollution of the environment by the extinguishing powder.
According to VDE, when using powder extinguishers in electrical systems with low voltage (below 1000 V), a safety distance of 1 m must be maintained. The extinguishing powder (and thus also the fire extinguisher) is offered for the following combinations of fire classes:
ABC powder extinguisher have a cooling, suffocating and anti-catalytic extinguishing effect. When the ABC powder melts, it removes heat energy from the seat of the fire, which has a cooling effect. As it melts, the ABC powder forms a layer of salt and prevents the supply of oxygen. Due to this salt layer, ABC powder extinguishers must not be used at high voltage (over 1000 V).
BC powder extinguisher have a mechanical, asphyxiating and anti-catalytic extinguishing effect. In the case of high voltage (over 1000 V), a safety distance of 3 - 5 m must be maintained
Powder extinguisher "D" with metal fire powder have a cooling, suffocating and anti-catalytic extinguishing effect and hardly play a role in preventive fire protection. The same safety distances as for the ABC powder extinguisher are to be used here.
Powder extinguishers are available with the following nominal capacities: 1kg, 2kg, 3kg, 4kg, 6kg, 9kg and 12 kg
Carbon dioxide extinguisher (CO2 extinguisher) are used in fire class B (flammable, liquid substances) and fire class C (flammable gases) e.g. in kitchens, laboratories and data centers. Carbon dioxide is a residue-free extinguishing agent. Carbon dioxide extinguishers have a cooling and suffocating extinguishing effect.
According to the VDE, they must maintain a safety distance of at least 1 m when in use in electrical systems with low voltage (below 1000 V). In the case of high voltage (over 1000 V), a safety distance of 3 - 5 m must be maintained
Carbon dioxide extinguishers are available with the following nominal capacities: 2kg and 5 kg.
The minimum extinguishing time with an open interruption unit and continuous discharge of extinguishing agent, depending on the filling quantity, is 6-15 seconds.
Information on the label on the fire extinguisher
The entire title block of a fire extinguisher is divided into 5 parts.
|Title block 1 contains:|
|Title block 2 contains:|
|Title block 3 contains:|
|Title block 4 contains:|
|Title block 5 contains:|
Hazard warnings and limits of use for fire extinguishers
Fire extinguishers are in compliance with the Fire classes And the Warning notices to use. The warning notices printed on the label of the fire extinguisher must be observed!
When fire extinguishers are used in the area of electrical systems, due to the dangers of the conductivity of the extinguishing agent or due to the inadmissible approach to the electrical system, certain Safety distances to be observed.
The safety distances specified on the fire extinguisher or the safety distances in the following table must be observed:
|Fire extinguisher with the extinguishing agent ...||Tensions up to ...|
|1000 V||110 kV||220 kV||380 kV|
|Water (with spray nozzle)||1 m||Instructions for use on the fire extinguisher must be observed|
|Water (with full jet nozzle)||3 m|
|foam||3 m||commitment just in voltage-free system parts|
|ABC powder||1 m|
|BC - powder||1 m||3 m||4 m||5 m|
|Carbon dioxide||1 m||3 m||4 m||5 m|
In the case of portable fire extinguishers with carbon dioxide, it should also be noted that the carbon dioxide not only displaces the oxygen from the combustion zone, but also the oxygen required for breathing. Therefore, special protective measures (e.g. breathing apparatus) are required in narrow, poorly ventilated rooms.
Construction and operation of a powder extinguisher
... the device with which you are most likely to be confronted
|1||Securing tab or pin: This is usually yellow and placed in such a way that it is easy to find.||Tear By the tab or pull out the pen.|
|2||Strike or release button: mostly red, can also be integrated into the handle.||Beat Firmly press the button until you have overcome the resistance. It takes about 5-10 seconds for the pressure to fully unfold !!|
|3||Propellant cartridge: it is closed with a thin membrane, which you pierce with the thorn of the strike button.|
|4||Blowpipe: this leads the propellant gas into the extinguishing agent container.|
|5||Signal pin: is rarely present.|
|6||Riser pipe: this will lead the propellant to the hose.|
|7||Extinguishing pistol with locking mechanism: for the dosed delivery of the extinguishing agent.||Now apply the extinguishing powder in spurts to the source of the fire.|
Instructions for handling the portable fire extinguishers
Environmental protection during fire fighting exercises
If the following rules are observed, there are no concerns about practicing with fire extinguishers.
- Exercises may only be carried out in such a way that there is no avoidable impairment of waters.
- Extinguishing exercises must not be carried out in water protection and groundwater catchment areas of drinking water extraction systems.
- Exercises with foam fire extinguishers must not be carried out in the inflow area of and on surface waters, in areas reserved for public water supply, in karst areas and wet biotopes.
- The use of foam fire extinguishers or powder fire extinguishers for extinguishing demonstrations without exercise and trial character must be avoided.
- Foam fire extinguishers should be used on paved surfaces with a drain to biological sewage treatment plants.
- Powder fire extinguisher exercises must be performed on paved surfaces. After completion, powder residues must be swept up and properly disposed of
- For exercises, unleaded carburetor fuel should be used in a liquid-tight drip tray for the liquid fire objects and untreated, seasoned and dry wood for solid fire objects.
Sources: www.minimax.de; www.jockel.de; www.gloria.de; www.einhell.de
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