Internal and external hydrants are permanent fire extinguishing devices that are a very effective means of fighting fires thanks to immediate access to a continuous water supply. They are available in external (street) and internal variants in buildings. In this text, we provide the most important information about hydrants of the latter type. If you are involved in the installation of such devices, be sure to read our guide!
In this article you will learn:
- how do indoor hydrants work,
- what types of internal hydrants do we distinguish,
- what legal requirements apply to hydrants.
Hydrants - characteristics
Internal hydrants are fire extinguishing devices placed in the hydrant network and used to extinguish group A fires. They allow for the suppression of fire in the bud, before the fire spreads and before active fire protection is activated. The efficiency and effectiveness of operation depend, among other things, on a properly designed hydrant network, its capacity and pressure.
It is worth remembering, however, that according to the regulation, internal hydrants are used only in buildings where fire zones classified as a threat to people ZL are designated and in industrial and storage facilities PM. The presence of a hydrant will therefore depend on both the size of the building (mainly its height) and the function it performs.
Internal hydrants are housed in special cabinets, made and marked in accordance with the Polish and European Standards PN-EN 671-1 and 671-2. Depending on the type , they consist of a reel, valve, hose and nozzle. The equipment and performance depend on the type of hydrant, which must be adapted to the requirements of a specific building.
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Types of hydrants
The main division includes, of course, external and internal hydrants. However, the latter also come in several variants, differing primarily in the diameter of the hose, valve and nozzle. This in turn translates into differences in efficiency and the construction of reels or cabinets. This is because each type of internal hydrant has a slightly different application:
- Internal hydrant DN 25 - used in fire zones classified as ZL people hazard category, including public utility buildings such as schools, banks or large-scale stores. It is also installed in collective housing buildings, i.e. hotels and boarding houses. Its characteristic feature is a reel for a semi-rigid hose with a diameter of 25 mm and a length of 20 or 30 m. The supply installation on which DN 25 hydrants are installed should have a cross-section of at least 25 mm.
- Internal hydrant DN 33 - semi-rigid hose, must be used in a garage: single-storey closed with more than 10 parking spaces and in a multi-storey. They are characterized by a valve with a diameter of 52 mm with a funnel reduction or a DN32 ball valve. Their semi-rigid hoses have a diameter of 33 mm and a length of 20 or 30 m. Regardless of the valve used, the diameter of the supply system should be at least 50 mm.
- Internal hydrant DN 52 - are required in production and storage fire zones depending on the fire load density. They are used in production and storage buildings (PM). They are equipped with a flat-folded hose with a nominal diameter of 52 mm and a length of 15 or 20 m. The legislator allows it to be supplemented with an additional section of hose if the distance from the emergency exit in a given room exceeds 30 m. The diameter of the supply system on which DN 52 hydrants are mounted should be at least 50 mm.
In addition to the above-mentioned hydrants, protective cabinets for SWSP valves are also used. This is a cabinet equipped only with a 52 mm diameter valve, connected to the supply system, which in the event of a fire supplies water from fire trucks. This solution is used in high-rise and high-rise buildings according to the conditions specified in the Regulation of the Minister of Internal Affairs and Administration
Hydrants and legal requirements
The basic requirements for the installation of internal hydrants are specified in several documents. The most important seems to be the Regulation of the Minister of Internal Affairs and Administration of 7 June 2010 on fire protection of buildings, other construction objects and areas.
In order to properly understand these regulations, it is necessary to familiarize oneself with the definitions and types of fire zones described in the Regulation of the Minister of Infrastructure of 12 April 2002 on the technical conditions to be met by buildings and their location.
Thanks to all these regulations, you will learn about the division of buildings according to fire safety, the categories of risk to people ZL or the classification of buildings according to height groups. You will understand where and when to use individual types of hydrants and what efficiency they should have. In general, this knowledge is needed by sanitary system designers and fire experts for the purposes of reviewing and approving the project. However, it is good to have basic knowledge on this subject, because design errors occur, for which the installer often pays, because the Fire Department will not want to accept an installation that does not comply with the regulations.
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Hydrant efficiency
Each internal hydrant has its own capacity, which is measured at the nozzle outlet. Its minimum value depends of course on the type of device and its application:
- Fire hydrants DN 25 - minimum water collection capacity is 1.0 dm 3 /s.
- Fire hydrants DN 52 - minimum water collection capacity is 2.5 dm 3 /s.
- Fire hydrants DN 33 - minimum water collection capacity is 1.5 dm 3 /s.
The relevant Regulation of the Minister of Internal Affairs and Administration regulates the method of designing hydrants in buildings, ensuring their coverage by fire zones. Hydrants are placed primarily at entrances, in corridors and at evacuation exits from rooms, and in rooms at risk of explosion. Every building owner must remember that the designed fire protection device is to protect life and property. The design for the building and later permanent access to fire protection devices must be strictly observed. In order to use them freely in the event of a fire.
Internal hydrants recommended by Onninen
If you are looking for high-quality internal hydrants for the hydrant installation you perform at your customers', trust the devices of Przedsiębiorstwo Produkcyjno-Handlowe Gras. This is a Polish brand that has been designing, manufacturing and distributing fire protection devices, as well as equipment used in rescue and occupational health and safety since 1985. It specializes in the construction of internal hydrants with a semi-rigid and flat-folding hose.
In the Onninen wholesale offer you will find internal surface and recess hydrants DN 25. They are equipped with a semi-rigid hose DN 25 in a 30 or less frequently 20 meter version. The modular design of the hydrant allows its configuration according to the individual needs of the customer. It is used in the interiors of buildings that belong to the ZL category, such as schools, office buildings, hospitals, sports halls, hotels, cinemas, airports, shopping malls or conference centers.
Another example of a product in this category is a universal internal hydrant DN 33 used in garages, which can be connected to the supply from the right or left side. It is in accordance with the EN 671-1 standard and is equipped with a semi-rigid hose with a diameter of 33 mm in a 30 or 20 meter version.
The DN 52 internal hydrant with a flat hose , which is installed in industrial and storage halls (PM), will have a different application than the two above products. The hydrant design allows for surface and flush mounting, as well as the selection of the installation supply side through universal double-sided holes in the cabinet body. The hydrant cabinet is covered with polyester powder paint, thanks to which this device works perfectly in industrial conditions.
All hydrants are locked with a patent lock with a spare key placed on the door behind the glass pane. Other types of locks are also available as an optional design.
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