The sleeper is the part of the railway superstructure, which supports the rails and their loads transferred to the track substructure and distributed.
It is a further object of the threshold to fix the rail mounted thereon in position and thus ensure compliance with the gauge. End of 2003, the railway network of the Deutsche Bahn had a length of about 35,600 km; installed in it are around 54 million railway sleepers.
A distinction ( historically proven ) and sleepers (now predominant ) between longitudinal sleepers.
- 2.2.1 impregnating and use restrictions
- 2.3.1 Einblockschwellen
- 2.3.2 bi-block sleepers
Railway sleepers must be different requirements; they must withstand the weather, can distribute loads well be sufficient dimensional stability, and not least low in maintenance.
In the course of development of railway sleepers various materials have been used or are still used today. Among these materials:
- Steel ( sleeper )
- Steel (type Y)
- Softwood (pine and larch)
- Hardwood (beech and oak)
- Prestressed concrete
Before the advent of prestressed concrete sleepers and steel sleepers were in the construction of rail tracks often used. They are more durable than wooden sleepers and must not be impregnated with coal tar. The original trough-shaped steel sleepers - type is no longer used today because it can not be laid mechanized.
A special form of railway sleeper is the Y- steel sleeper, are assembled in pairs swinging formed steel profiles and thus yield a Y-shaped threshold. In track this threshold is each an attachment point shot at the one and two attachment points on the opposite rail and in the sequence of each alternately 180 ° placed with in the gravel bed.
Advantages of Y- steel sleeper are the low profile, high track resistance even in tight curves, the narrow gravel bed ( only 2.6 m at the top of the ballast bed, Vorkopfschotter counting ) and the substantial insensitivity derailment consequences in shunting. The Y-shaped steel sleeper has a high resistance to lateral displacement, and is more flexible than concrete sleepers. A disadvantage is the cost per individual threshold are due to high steel prices. The small footprint makes frequent consuming readjustment of the track required.
Meanwhile, these thresholds are suitable for all conversion technologies and allow the same speeds with the mechanical working through as in sleeper tracks. In their normal use route speeds of up to 120 km / h can be admitted. But there are already much faster trafficked routes with Y-sleepers went into operation.
It is often on routes that are equipped with Y-sleepers, an increased tendency for the fluting observed, which leads to increased noise levels. They are therefore not used when sound technical requirements must be met to avoid noise.
Y- steel sleepers are used in the network of Deutsche Bahn on seven sections. Due rusted Y- steel sleepers that have been tentatively postponed the mid-1990s on a solid track, had to be closed on 1 August 2012 for the running of trains a 14 km long stretch of the railway line between Berlin -Halle and Bitterfeld and hall. The damages arose because the rain water does not drain because of the impermeable subsoil and because of the track grates covered for noise reduction could not evaporate.
The wooden sleepers have a length of 2.6 m or more, and are based on cross-sectional dimension 26 cm width × 16 cm height. They are mainly on bridges and switches, but also fitted tight bends. As absorbing buffer between the rail and bridge structure lying, they reduce the engine noise by reducing vibrations and lower net mass (including mounting about 120 kg), the bridge load. As wood is easy to work with, it is possible to inexpensively produce individual threshold lengths and threshold holes to measure. Because of the expense of concrete sleepers lower height wooden sleepers are laid particular where the Bettungsstärke is limited. This includes bridges, tunnels and other Überwerfungsbauwerke.
At gelaschten rail joints and generally at the joints of railroad turnouts, even if they are welded, bolted together two wooden sleepers (" shock thresholds " or " dome sleepers " called ) installed. This should support the joints better and stabilize the effects of the tabs. But they may be worse stuff. If such shocks but are welded, then be at the top instead of the K-type and continuous ribs separate plates installed. Nevertheless, the aluminothermal welding on shock thresholds consuming and requires separate forms. In only rarely neuzuverlegenden Reichsbahn course they are only used to guarantee the fit of spare parts. Other forms of superstructure as K and Ks are no longer re-laid in Germany. Open sole plates, hook plates and rail anchors without shims there are only sporadically. Nailed superstructure decades was common in North America and Russia and the USSR and its successor states.
Hollows or cracks where water remains standing and promotes digestion, so reamed or broached that they can dry. Against the tendency of the timber to burst at the end faces of the thresholds, nail plates, or crown sheets are turned into the end grain.
Marking nails ( Nageno, Nagelschmiede Oberschona ) denote the mounting position of turnout sleepers. Years nails denote the manufacturer and the year of production of sleepers.
Wooden sleepers are made of hardwood in Europe beech and oak. In tropical countries, however, are used depending on the local availability the durable teak and other hard and resistant wood, such as muhuhu. Hardwood sleepers are installed both on the open road and in the field of bridges and switches. They have a lifespan of up to 35 years. Wooden sleepers transmit vibrations far less than other materials, so they are the preferred material for bridges in residential areas. Turnout sleepers have many different lengths, which has led to the fact that has been here a long time, even in otherwise equipped with concrete sleepers, rail facilities, maintained wood as a material. Another advantage of wooden sleepers is that they absorb derailments better than concrete and steel sleepers. Therefore, they are in particular continue to be used on marshalling yards and in the end systems.
For less polluted and tram tracks are also used softwood sleepers of pine and larch.
Directly without ballast bed on the road -makers of steel bridges laid out with an open timber sleepers lane bridge beams are called. Its cross section is significantly greater.
Impregnating and use restrictions
Wooden sleepers are impregnated with an impregnating ( Carbolineum ), to make them resistant to fungal, bacterial and insect infestation. This impregnation is also the cause of the typical dark appearance of wooden sleepers.
There is no effective substitute for Carbolineum. The impregnating agent and formed by evaporation from gaseous hydrocarbons, like copper, chromium, arsenic compounds health and environmentally hazardous substances. These substances and thus impregnated wooden sleepers subject in Germany since 1991 use restrictions that are set to 2002 in the Teerölverordnung, and since 2002 in the Chemicals Prohibition Ordinance.
The restrictions on carbolineumimprägnierte wooden sleepers are laid down in § 1 and in section 17 of the Annex to the Chemicals Prohibition Ordinance. For example, such thresholds may not be used indoors, in gardens, in agriculture or in places which tend to take place skin contact with the impregnated wood. The same applies to furniture, toys, playgrounds, or places where the thresholds come into contact with foodstuffs, livestock or crops. Previously found inexpensively acquired used wooden sleepers often in commercial landscaping and by individuals (such as in allotments ) as retaining walls, freestanding screen walls, seating areas and similar use.
For copper, chromium, arsenic impregnated wooden sleepers use limits are set out in section 10 of the Annex to the Chemicals Prohibition Ordinance. These prohibit, among other things, a use in residential buildings, in marine waters, in agriculture and in places where there is a risk of frequent skin contact or contact with food.
Wooden sleepers provide in addition to the impregnation also due to residues from the railway operation hazardous to health and the environment dar. These include waste oils ( from wheel bearings, wheel flange lubrication systems and other lubricated parts of rail vehicles ), easy on the oily surface -bound dust from partially asbestos-containing brake dust, introduced soot from exhaust gases and in the control of weeds in the track area pesticides.
Wooden sleepers must be considered as hazardous waste and disposed of accordingly, which in equipped with appropriate filters, flue gas cogeneration plants is easily possible today.
Well-preserved cars thresholds can be worked by the railway operators or service providers and used in other rail routes on.
Concrete sleepers are machine made of concrete, with the support of the rails with lateral cam against displacement and drill holes for the rail holders already be formed on the surface. In Spain, so concrete sleepers with preparation are installed for both the Iberian broad gauge as well as the UIC standard gauge also Traviesas poli -valent; so you can change the track width by simply converting the rail without having to replace the entire superstructure equal.
In early 2001 announced the Swedish Banverket to exchange 3.2 million delivered between 1992 and 1996 concrete sleepers for a total of at least 100 million DM. The thresholds weathered prematurely due to high curing temperature.
Significant advantages of prestressed concrete sleepers over wood and steel sleepers are a better position stability through greater weight and a long service life of about 40 years. With the control superstructure of the German railway prestressed concrete sleepers Type B 70 are used with a threshold distance of 60 cm.
In Germany, the testing of concrete sleepers in the 1920s began. Larger distribution they found after the preload allowed to take up large tensile forces. In the area of the German Railways were built on a large scale for the first time in 1949. By 1974, the network of the German Federal Railroad 25 million concrete sleepers were laid.
Prestressed concrete sleepers Type B 70 - named after the type of concrete and the introduction year used - have a length of 2.6 m at maximum cross -sectional dimensions of 0.30 m × 0.21 m and 300 kg per piece. The weight of the thresholds makes the use of machines for the installation required.
In France and in Switzerland ( was ) is the bi-block sleeper widespread. This consists of two concrete blocks connected by a guide arm of an L- or T -shaped steel profile. By dissolving the threshold into two blocks of the side sliding resistance is increased. The bi-block sleeper comes in Germany for fastening the rail at the slab track in use.
Art wooden sleepers
The Japan Railways (JR) noted in the 1970s that more than 70 % of the wooden sleepers used by it had a very short life expectancy due to weathering. She was looking for a company with a plastic threshold should be developed with properties similar to the wooden threshold. In 1978 FFU synthetic wood was developed in collaboration between the Japanese and the railroad company SEKISUI. In 1980, the first field tests took place on a bridge and a tunnel project. RTRI ( Railway Technical Research Institute ) tested in 1985 these thresholds and JR set based on the results FFU synthetic wood as a default threshold in the range of bridges, switches, special projects in any kind of a superstructure. In 2011, again sleepers of the field test were developed and tested in 1980 by RTRI. As a result RTRI informed the Japanese railway companies that these thresholds may remain in place for another 20 years.
FFU synthetic wood is mainly used in the field of railway bridges, turnouts, special projects, emerging with low overall height. By 2012, more than 1,200 km of track have been equipped with FFU synthetic wood. The processing takes place as for wood, but appropriate tool or tools with carbide tips will be recommended for machining steel. UV light has no influence on the technical quality of the threshold. FFU synthetic wood sleepers are recyclable at the end of your life expectancy to 100 %.
Holes on the project
Shinkansen in Tokyo on FFU
Crossover with FFU in slab track
Threshold soles denote an underside disposed on railway sleepers elastic layer, the so-called sleeper (English Undersleeperpad, abbreviation USP). This under -side coatings can be placed in the manufacturing process when concreting in the fresh concrete or subsequently glued to the undersides of railway sleepers.
In some technical parameters of the concrete sleeper has been unable to outweigh the advantages of the wooden sleeper. With under -side elastic plastic coatings of concrete sleepers, however, the wood threshold are reached in the contact area between threshold and gravel bearing qualities.
With all materials of the lower side threshold coating a surface strength of the materials is required, which prevents the penetration of dirt into the tips of these capping.
For sleeper internationally by different railway companies technical requirements are defined. In addition to these requirements of the fitness for use requirements for the system redundancy, the operational stability and acc. Asked KrW-/AbfG also to the recycling of the sole materials and the recyclability of the remaining body of the concrete sleepers.
Soled thresholds reduce due to the lower gravel stress the maintenance cycles of tracks and points to about 25 %, reduce the structure-borne noise emission of rail tracks, and allow a reduction in gravel thickness.
The rails were initially fixed with rail chairs and nails on the stone or wooden sleepers. Later, screws and then uses additional spring elements. These absorb the vibrations of the rail under load and their elongation at temperature fluctuation without canceling. The various systems of normalized total small parts that are used for rail mounting are referred to as types of superstructure; in Germany dominate on concrete sleepers, the superstructure and W on wooden sleepers, the superstructure K and KS with variants.
Alternatives to rail sleeper
Mid-1990s were developed several novel superstructure systems. The slab track comes from without ballasted and classic railway sleepers. Depending on the model, the thresholds are thereby reduced to small concrete plinths on which the rails are mounted, and the rails are mounted directly on the concrete pavement. Especially on high speed lines and in urban and metro tunnels in the slab track is used because of the more stable track position and the lower maintenance costs.
A compromise between sleeper superstructure and slab track is the frame -tie track.