hydrant
A hydrant (from ancient Greek ὕδωρ hydōr "water") is a fitting for drawing water from a water distribution system .
Water suppliers use hydrants at regular intervals (in residential areas usually 100 to 150 meters) as part of the central fire water supply for cities and municipalities. They enable the fire brigade , but also public (e.g. road maintenance service, municipal companies) and private (e.g. street cleaning companies, tent festival organizers) users to draw water from the public water supply network (collective water supply ). In addition, hydrants are used for the maintenance of pipelines: for flushing, for venting or for relaxing (releasing pressure). If a line section fails, they are intended to make emergency connections with hoses. Special signs point out underground hydrants in public spaces.
The term is also common for withdrawal points for other liquids, for example kerosene from a pipeline .
history
Before water pipes were built, wells and bodies of water were often the only source of drinking water and were also used to fight fires . However, it took a lot of buckets and people. The administrations responsible for the safety of the citizens in villages and towns had laid down the behavior in the event of fire in fire regulations early on . For example, in the "Fire Regulations of the High Princely Anhalt City of Dessau " published in 1764 :
“(6.) So that there should not be a lack of the buckets needed for extinguishing, every brewery ought to have six and every stall three fire buckets [...] in good condition. But if a homeowner does not have this appropriate number, the council should ensure that they can get the buckets at a cheaper price. "
In order to convey water to inhabited settlements, wooden pipes, known as piping , were laid sunk in the ground at an early stage . Such an early system has come down to us from Augsburg from 1460. The tree trunks, pierced lengthways, transported the water without pressure using a gradient. The accessible places of the pipes were unsuitable for fire fighting. If these spots were created by drilling from above, they were closed again after use with a longer wooden stopper that was visible from the pavement. This method is considered to be the forerunner of the "hydrant pipes" used today.
The development of fire engines , i.e. hand-operated water pumps, slowly replaced the bucket chain. Since the possibilities for drawing off water were not available everywhere in inhabited places, storm barrels were developed for the temporary storage of water. Councilors offered bonuses for those horse owners who, in the event of a fire, were the first to arrive at the location of the storm barrels in their wagon and then transported them to the source of the fire. Also were rainwater tanks used for storage of water or artificial extinguishing water ponds applied, whose position has been marked on the roadside. In some cases elevated tanks were built if they could be filled by pumps.
The first permanently laid metal water pipes with constantly available tapping points brought great relief. These were given the designation hydrant . Water towers filled with steam pumps or later electric pumps or reservoirs located at a higher level maintain the necessary water pressure hydrostatically . The first hydrants, known as fire exchanges , were set up in Vienna around 1850 . This means that water can be made available more quickly and with less effort.
A similar device for easier water extraction was the water tank according to Lambert from 1849, today this would be called an underground hydrant.
The water supply and water supply are just as much part of the water supply of hydrants as the protection of the water. Technical measures must be taken to prevent withdrawn water from flowing back into the drinking water network. This has happened now and then, but for the last few years there has been a great deal of emphasis on preventing it. This was also reflected in the 2001 amended drinking water ordinance.
Post hydrant
overview
The pillar hydrant (in Austria pillar hydrant) is permanently installed above ground and has several outlets with standardized couplings , usually in the nominal size B or C and more rarely also A. This also depends on the inner diameter of the supply line. The A outlet is mostly used in industry and in larger residential complexes in order to be able to draw larger amounts of water from the network. A suction hoses must not be connected to this A-outlet , since under unfavorable circumstances a negative pressure could arise in the pipe network and this could lead to damage in the pipe network. The delivery rate of the hydrant is important for the fire brigade. As a rule of thumb, the delivery rate in liters / minute for the post hydrant is 12 to 15 times the nominal diameter (for example H100: min. 1200 l / min to max. 1500 l / min).
Fall jacket hydrant
The fall jacket hydrant is a subspecies of the post hydrant . The B outlets, which each have their own shut-off device, are covered with a fall jacket that protects them from dirt and damage. The outlet with the nominal size A is mostly used for particularly endangered objects such as airports or industrial plants.
To start up the hydrant is connected to the inner triangular at the hydrant key a holder dissolved in the hydrant head slides down so that the case shell and releasing the upper unloading valves. By turning the entire head, the valve cone is opened, the air contained in the column escapes through the inflowing water via a vent valve, also known as a pin . The notice bolt also prevents the drop jacket from closing before the hydrant has not been closed and the water column has been reduced via the automatic drainage. This prevents freezing.
Kippmantel hydrant or "Alter Münchner"
There are tilting jacket hydrants in Munich that were installed at the beginning of the 19th century. In the 21st century there are only a few functional fittings left. These hydrants require a special hydrant key to operate. The left-closing valves are another special feature.
Underground hydrant
overview
DIN hydrant
Sign to an underfloor H ydranten DN 300 (diameter 300 mm) 1.1 meters to the left and 8.4 meters in front of the shield
Fountain of a defective underground hydrant
DN80 pipe with heavy rust
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The underground hydrants are located below a hydrant cap, which is installed flat in the street. The lid of the hydrant cap is lifted out with the slide key and swiveled to the side, whereby the hydrant base becomes accessible.
The underground hydrant enables a standpipe to be connected. Underground hydrants have the disadvantage that they can be parked by motor vehicles or frozen by snow or ice and are therefore often unusable. The freezing of the lid in the hydrant cap can largely be avoided by greasing both parts or by inserting a plastic film, but requires regular maintenance. Wuerttemberg shaft hydrants are common in parts of Wuerttemberg. They were preferred because they are about one meter deeper than the normal underground hydrants, thus reducing the risk of freezing over in cold winters. However, snow is a problem for all underground hydrants insofar as the shafts disappear under the snow cover and must first be searched for. This means that it is necessary to have a precise designation using signs indicating the exact location of the hydrant. The signs indicate the lateral and forward distance of the hydrant from the sign in meters. The delivery rate (in liters / minute) of an underground hydrant can be estimated from 7 to 10 times the nominal diameter using a rule of thumb (for example: H80 results in min. 560 l / min to max. 800 l / min). The factor range results from the degree of utilization of the line to which the hydrant is connected. The maximum delivery rate is achieved with a clean pipe. Sediments and encrustations are deposited in old and rarely used pipes, which minimize the usable cross-section of the pipe.
Marking in public spaces
Special hydrant signs indicate underground hydrants in public spaces.
Standpipe
The standpipe is a water-bearing fitting for drawing water from the public supply network via underground hydrants. It consists of a long lower part of the standpipe with a handle, a claw nut at the foot of the pipe with a sealing ring and a short upper part of the standpipe with a stuffing box and gland follower . Above this there are two screw-down valves with one or two fixed couplings . In newer standpipes, non-return valves are also being installed more and more frequently to prevent water from flowing back out of the connected hose, as this can contaminate the drinking water network.
The standpipe is attached to the handle by turning it clockwise on the hydrant seat, the claw nut being held in the claw of the underground hydrant and screwed up; as a result, the sealing ring is pressed firmly onto the underground hydrant and seals it tightly even at higher pressures.
The stuffing box gland is connected to the handle with two screws, so the upper part of the upright pipe can be turned into a more favorable position through the stuffing box; This should always be done by turning it clockwise to prevent the claw nut from turning out of the claw and the standpipe shooting up under pressure.
The fixed couplings enable two hose lines to be connected to the standpipe at the same time. In front of them are the screw-down valves which, when open, must release the entire flow cross-section. Any leaks must be easy to repair through the design of the valves. The valve disks are rotatable and secured against loosening by themselves.
Standpipes for the fire brigade are standardized with two B-fixed couplings according to DIN 14375. They weigh no more than 7.5 kg and are tested for leaks at 25 bar , the shut-off devices at 16 bar each. Standpipes with two C-fixed couplings are no longer standardized.
In order to be able to use a standpipe, a slide key is required with which the hydrant shaft and the hydrant itself can be opened. Before the hose line is connected to the hydrant, it must be flushed through the standpipe so that stones and dirt from the line can not damage the fire pump . In addition, the standpipe must be secured against traffic.
In addition to the standpipe standardized by DIN 14375, the 1.95 m long standpipes are occasionally used for Württemberger shaft hydrants .
All hydrant types have a foot valve, which is also used for emptying. This valve is moved from above by means of a linkage with the hydrant or slide key at the underground hydrant. Normally the hydrant is water-free and therefore cannot freeze. It is emptied either via a ballast bed or the rainwater sewer system .
Standpipes are also used by the water suppliers for the drinking water supply at festivals, trade fairs and similar events. Often they are then equipped with a water meter .
Fire hydrant directory
A hydrant directory or hydrant map is a street map in which all hydrants, open bodies of water and underground fire-fighting water tanks are entered. The card is maintained by the responsible water supplier or municipal office. In many cases, these plans can also be accessed digitally.
Some fire brigades now keep hydrants lists ready in the fire engine or in the crew room so that the location of hydrants can be explored when approaching the scene and the vehicle placement can be determined accordingly. Hydrant locations can also often be called up using a smartphone.
A special map is being set up within the OpenStreetMap project . This shows the location and further information on fire stations, hydrants and medical emergency rooms.
Relevant standards / regulations
In Germany and Austria, most of the relevant standards are harmonized with the European standard . In addition, there is still scope within the standards for both application and design, which is not described in detail here.
- DIN EN 14339 "underground hydrants" (replacement for DIN 3221)
- DIN EN 14384 "Post hydrants" (replacement for DIN 3222)
- DIN 3321 "Requirements and approval tests for hydrants"
- ÖNORM F 2010
- EN 1074-6 "Valves for water supply - Requirements for usability and their testing - Part 6: Hydrants"
- DVGW e. V .: Technical information, leaflet W 331, selection, installation and operation of hydrants . DVGW German Association of the Gas and Water Industry e. V., Bonn 2006, ISSN 0176-3504 .
- DVGW e. V .: Technical rule, worksheet W 405, provision of extinguishing water through the public drinking water supply . DVGW German Association of the Gas and Water Industry e. V., Bonn 2008, ISSN 0176-3504 .
International differences
The public water supply network in Central Europe is laid in the ground below the frost line. Hydrants have a shut-off element (slide), which is also attached at the corresponding depth of the earth. After the shut-off element is closed, the pipeline between the shut-off element and the hydrant (riser) is emptied by means of a valve, so that frost protection is restored. In international parlance, this is referred to as a "dry barrel" hydrant.
This arrangement is not necessary in areas where there is no risk of frost. The riser remains filled with water. Barrier elements are only available above ground or directly below ground level. This type is called a “wet barrel” hydrant.
See also
literature
- Lutz Rieck: Die Rote Hefte, booklet 06 - fire extinguishing fittings . Kohlhammer, Stuttgart 2000, ISBN 978-3-17-015171-0 , pp. 44-46 .
- Lothar Schott, Manfred Ritter: Fire Brigade Basic Course FwDV 2 . 20th edition. Wenzel-Verlag, Marburg 2018, ISBN 978-3-88293-220-1 .
- Ulrich Kortt (arr.): Hamilton. Fire Service Manual . Boorberg, Stuttgart 2012, ISBN 978-3-415-04560-6 .
Web links
- How a hydrant works - pictures of underground and pillar hydrants
- Extinguishing water supply calculation program on the deployment wiki
- Development of the Württemberger shaft system (PDF; 534 kB)
Individual references / comments
- ↑ Renate Wahrig-Burfeind (Ed.): True. Illustrated dictionary of the German language . ADAC-Verlag, Munich 2004, ISBN 3-577-10051-6 , pp. 402 .
- ↑ Technical recommendation - fire water supply from hydrants in public traffic areas. (PDF; 185 kB) German Fire Brigade Association - AGBF / DVGW, December 21, 2018, accessed on December 21, 2018 .
- ↑ a b c The history of water supply in Saxony-Anhalt , accessed on February 15, 2018.
- ↑ The History of the Vienna Fire Brigade , accessed on February 15, 2018.
- ^ Franz-Josef Sehr : The construction of the first aqueduct for Obertiefenbach . In: Yearbook for the Limburg-Weilburg district 1999 . The district committee of the district of Limburg-Weilburg, Limburg-Weilburg 1998, p. 274-276 .
- ↑ Anonymous: Lambert's water tank, which is embedded in the pavement, in order to be able to drain water from the main water pipes in the event of a fire, etc. In: Polytechnisches Journal . tape 113 , 1849, pp. 190–191 ( [1] [accessed March 7, 2019]).
- ^ Hydrant science ( Memento of December 2, 2012 in the Internet Archive ) (PDF; 287 kB), Sendling youth fire department
- ↑ Office for fire water supply of the city of Essen ( Memento from September 21, 2007 in the Internet Archive )
- ↑ Digital hydrant directory on http://www.baufachinformation.de/ as PDF
- ↑ List of hydrants in Germany as part of the loading of an HLF (D)
- ↑ Act faster with the hydrant app on the website of the Austrian Association of Municipalities from November 3, 2016, accessed on February 15, 2018.
- ↑ OpenFireMap
- ↑ Kohlhammer Die Roten Hefte 27a The extinguishing water supply Part I The central water supply page 61; second paragraph; 4th edition of 2000; ISBN 3-17-015011-1