Railway sleeper
In the sleeper is the part of the railway superstructure , the rail carries and their loads on the track - substructure transmits and distributes.
It is also the task of the sleeper to fix the rail attached to it in its position and thus to ensure that the gauge is maintained . At the end of 2003, the Deutsche Bahn route network was around 35,600 km long; Around 54 million railway sleepers are built into it.
A distinction is made between long sleepers (historically documented) and cross sleepers (predominant today).
conditions
Railway sleepers have to meet various requirements; they must be able to withstand the weather, be able to distribute loads well, be sufficiently dimensionally stable and, last but not least, be inexpensive to maintain.
material
Various materials have been used in the course of the development of railroad ties, or are still used today. These materials include:
- Steel (cross sleeper)
- Steel (type Y)
- Softwood (pine and larch)
- Hardwood (beech and oak)
- prestressed concrete
- plastic
Steel sleeper
Before prestressed concrete sleepers appeared, steel sleepers were also often used. With a service life of approx. 70 to 100 years, they are significantly more durable than wooden sleepers and do not need to be impregnated with coal tar oil . Due to the trough (filled with gravel), they offer better track stability despite their lower mass. There were and are different rail fastenings adapted to the steel sleepers, but since the 1930s, at least in German-speaking countries, the superstructure type K and, most recently, Ks with ribbed plates welded onto the trough sleeper has established itself . In the event of derailments, steel sleepers tend to bend and, as a result, to narrow the track. Another disadvantage is the poor insulation properties. The use of track circuits is just as difficult as the possibility of keeping the drive return current in the track. The latter is necessary for direct current railways in order to avoid undesirable electrochemical corrosion near the track.
The conventional, trough-shaped steel sleeper design is hardly used today, as it is difficult to install with quick-change machines. In addition, the mechanized tamping is made more difficult because the troughs have to be filled with gravel from below. Before the mechanization, the filling mold process was used, in which filling molds (frames with dimensions like the sleepers to be laid out afterwards) placed on side rails were filled with gravel and compacted. The tracks laid in this way are very stable, but the personnel expenditure and the slow work progress are no longer acceptable. Due to their low overall height, however, they are still laid on and under bridges, for example, since sufficient bedding strength can be achieved even with limited space.
Y threshold
A special form of the railway sleeper is the Y-steel sleeper, in which pairs of curved double-T steel profiles are joined together to form a Y-shaped sleeper. In the track, this sleeper is placed in the ballast bed with one fastening point on one rail and two fastening points on the opposite rail and rotated alternately by 180 ° in the sequence. Special end sleepers are installed at the transition to other sleeper shapes.
This type of sleeper was developed by Jürgen Frenzel and Günter Fasterding, whereupon the first operational tests were carried out in 1984 in the Peine-Salzgitter steelworks. In 1986 an operational test followed on the Hanover – Braunschweig railway line , and in 1987 the OHE tracks and one track in the Linderhauser tunnel were equipped .
The advantages of the Y-steel sleepers are the low overall height, the high track stability even with tight curve radii , the narrow ballast bed (only 2.6 m on the ballast bed top edge, including the head ballast) and the extensive insensitivity to derailment in shunting operations. Y-steel sleepers have a high lateral displacement resistance and are more elastic than concrete sleepers. Disadvantages are the costs for each individual threshold and their dependence on steel prices. The small footprint also makes frequent, complex readjustments of the track necessary.
These sleepers are now suitable for all conversion technologies and they allow the same speeds for machine processing as in cross sleeper tracks . In their normal use, maximum line speeds of up to 120 km / h are permitted. However, routes with Y-sleepers traveled much faster have already gone into operation. Track construction machines , in particular track tamping machines, must, however, be set up to offset the rail supports.
In many cases, on routes equipped with Y sleepers, an increased tendency to ripple formation is observed, which leads to increased noise emissions . They are therefore not used if there are acoustic requirements to avoid noise .
A 14 km long section of the Berlin – Halle railway line between Bitterfeld and Halle had to be closed on August 1, 2012 due to rusted Y-steel sleepers that were experimentally relocated on slab tracks in the mid-1990s . The damage was caused because the rainwater did not run off because of the impermeable subsoil and because the track gratings were covered for sound insulation, it could not evaporate.
Wooden sleeper
Wooden sleepers for standard gauge usually have a length of 2.4 to 2.7 m and are based on the cross-sectional dimension of 26 cm wide × 16 cm high. They are mainly installed on bridges and in points, but also in tight arches. Lying as a damping buffer between the rail and the bridge structure, they reduce the driving noise due to lower vibrations and lower weight (including fastening around 120 kg) and the load on the bridge. Since wood is easy to work with, it is possible to manufacture individual sleeper lengths and custom-made sleeper bores at low cost. Due to the lower height compared to concrete sleepers, wooden sleepers are laid in particular where the bedding thickness is limited. This applies to bridges, tunnels and other overpass structures .
Two wooden sleepers screwed together (called "shock sleepers" or "coupling sleepers" ) are installed on lashed rail joints and generally on the joints of Reichsbahn turnouts, even if these are welded . These should better support the impact and stabilize the effect of the tabs. However, they are more difficult to stuff. If such joints are to be welded, separate ribbed plates are installed in the superstructure type K instead of the continuous ribbed plates . In spite of this, aluminothermic welding is more complex and requires special shapes. In Reichsbahn turnouts that are seldom re-installed, they are only used to ensure that replacement parts fit. Other types of superstructure than K and Ks are no longer being relocated in German-speaking countries. Open pallets, hook plates, spring nail superstructures and rail fastenings without pallets are only found in isolated cases. Nailed superstructures were common for decades in North America and Russia or the USSR and their successor states.
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Holes or cracks in which water remains and promotes digestion are drilled or cut so that they can dry out. To counteract the tendency of the wood to burst open on the front sides of the sleepers, nail or crown plates are hammered into the end grain .
Marking nails (Nageno, Nagelschmiede Oberschöna) indicate the installation position of turnout sleepers. Annual nails designate the manufacturer and the year of production of sleepers.
Wooden sleepers are made of hardwood , in Europe beech and oak . In tropical countries, on the other hand, depending on local availability, resistant teak and other hard and resistant woods, such as B. Muhuhu and in South America Quebracho. Hardwood sleepers are installed both on the open road and in the area of bridges and switches . They achieve a service life of up to 35 years. Wooden sleepers transmit vibrations far less than other materials, making them the preferred material for bridges in residential areas. Turnout sleepers have many different lengths, which has resulted in wood being used as a material for a long time, even in railway systems that are otherwise equipped with concrete sleepers. Another advantage of wooden sleepers is that they can cope with derailments better than concrete and steel sleepers. That is why they are still used in marshalling yards and in drainage systems in particular .
Softwood sleepers made of pine and larch wood are also used for lightly loaded and tram tracks .
Wooden sleepers laid directly, i.e. without a ballast bed, on the girders of steel bridges with an open roadway are called bridge girders. Their cross-section is significantly larger.
Impregnating agents and restrictions on use
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Wooden sleepers are impregnated with impregnation oil ( carbolineum ) to make them resistant to fungal and insect attack. This impregnation is also the reason for the typical dark appearance of wooden sleepers.
There is no effective substitute for carbolineum. The impregnating agent and the gaseous hydrocarbons resulting from evaporation are just like copper - chromium - arsenic compounds hazardous to health and the environment . These materials and wooden sleepers impregnated with them have been subject to restrictions on use in Germany since 1991, which were laid down in the Tar Oil Ordinance until 2002 and in the Chemicals Prohibition Ordinance since 2002 .
The restrictions for carbolineum-impregnated wooden sleepers are set out in Section 1 and Section 17 of the Annex to the Chemicals Prohibition Ordinance. For example, such sleepers must not be used indoors , in gardens , in agriculture or in places where there is frequent skin contact with the impregnated wood. The same applies to furniture , toys , in playgrounds or in places where the sleepers come into contact with food , farm animals or crops .
In the past, used wooden sleepers bought cheaply were often used in commercial landscaping and by private individuals (e.g. in allotments ) as retaining walls, free-standing privacy screens, seating and the like. Since there was not yet sufficient awareness of the toxicity of the wood preservatives used, they were even used in children's playgrounds, at most the sticky tar and the strong smell were considered unpleasant. While they have mostly been removed from public green spaces, reused railway sleepers can still be found in private gardens, especially from single-family homes from the 1970s and 1980s.
For wooden sleepers impregnated with copper-chromium-arsenic, usage restrictions are specified in Section 10 of the Annex to the Chemicals Prohibition Ordinance. These prohibit 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 train operation, a risk to health and the environment . Among these, among others, used oil (from Achsgleitlagern , wheel flange lubrication systems and other lubricated parts of rail vehicles ) to the oily surface of weakly bound dust from partially asbestos brake dust, soot from exhaust gases and for weed control in the track area introduced pesticides .
Wooden sleepers must be regarded as hazardous waste and disposed of accordingly, which is now possible without any problems in waste incineration plants equipped with appropriate flue gas filters .
Well-preserved, used sleepers can be refurbished by the railway operators or service providers and used on other railway lines.
Concrete sleeper
Concrete sleepers are poured from concrete by machine, whereby, in contrast to wooden sleepers, the holes for the sleeper screws are cast in from the start with dowels. In the case of newer designs, the rail mounts are also molded onto the surface. In Spain since 1990 traviesas polivalentes , ie concrete sleepers with rail mounts according to the superstructure W for Iberian wide and UIC standard gauge, have been installed; This allows you to change the track width by simply moving the rail and angled guide plates without having to change the track grid.
At the beginning of 2001 the Swedish Banverket announced that it would exchange 3.2 million concrete sleepers delivered between 1992 and 1996 for a total of at least 100 million DM. The sleepers weathered prematurely due to an excessively high curing temperature.
Single-block threshold
Significant advantages of sleepers made of prestressed concrete compared to wooden and steel sleepers are better positional stability due to the larger mass and a long service life of around 70 years. In the standard superstructure of Deutsche Bahn , prestressed concrete sleepers of type B 70 with a sleeper spacing of 60 cm are used.
In Germany, concrete sleepers began to be tested in the 1920s. They became more widespread after the prestressing of the reinforcement ("prestressed concrete sleepers") made it possible to absorb greater tensile forces. In the area of the Deutsche Bundesbahn they were first installed on a larger scale in 1949. By 1974, 25 million concrete sleepers had been laid in the network of the Deutsche Bundesbahn . After the rail fastenings had been taken over by the usual wooden sleepers in the first decades, the rail inclination was first incorporated into the sleepers, in the 1970s one could switch to simplified designs such as the superstructure W , which dispensed with ribbed or base plates for the Use with concrete sleepers have been optimized.
Prestressed concrete sleepers of type B 70 - named after the concrete type used and the year of introduction - have a length of 2.6 m with maximum cross-sectional dimensions of 0.30 × 0.21 m and a weight of approx. 300 kg. This mass of sleepers makes the use of machines for the installation absolutely necessary.
Two-block threshold
In France and Switzerland (was) two-block sleepers are widespread. These consist of two concrete blocks that are connected to one another with a track holder made of an L- or T-shaped steel profile. By dividing the threshold into two blocks, the lateral displacement resistance is increased. Two-block sleepers are used in Germany to fasten the rails to the slab track , but only in order to be able to pre-produce the rail fastenings with a defined gauge under factory conditions
Plastic threshold
In 1961 magazines reported that stress tests for plastic sleepers that had been developed by a Mr. Ostermann had taken place successfully in Hamburg. These were metal sleepers resembling metal sleepers, hollow-form sleepers open at the bottom and over 2 m in length. Modern full-form plastic sleepers could be an alternative to wooden sleepers, as they are considered to be less sensitive to the weather, rot and insect infestation due to the material used. Due to the elastic properties of some plastics, some of these sleepers are said to have increased vibration and sound-absorbing properties compared to wood.
In contrast to wooden sleepers, plastic sleepers do not release any pollutants into the environment. While the impregnated wooden sleepers are to be treated as hazardous waste according to the law at the end of their service life, plastic sleepers can be recycled.
In Germany, plastic sleepers are currently used as a replacement for wooden sleepers in switch areas, in track tracks and as a replacement for wooden bridge beams on bridges with an open roadway. Their resistance to temperature influences and the effects of chemicals also allows them to be installed in industrial tracks, for example in bottling plants.
Glass fiber reinforced plastic recyclate sleeper
Glass fiber reinforced plastic recyclate sleepers are made from recycled plastic granules.
Plastic bridge girders on the Pritzerbe railway bridge
Plastic bridge beam (Pritzerbe)
Plastic turnout sleepers, Hamburger Hochbahn
Long glass fiber reinforced polyurethane threshold
The Japanese Railways (JNR) found in the 1970s that more than 70% of the wooden sleepers it used had a very short life expectancy due to weathering. They were looking for a company to develop a plastic sleeper with similar properties to the wooden sleeper. In 1978, FFU synthetic wood was developed in cooperation between the Japanese railways and the SEKISUI company. The first field tests on a bridge and a tunnel project took place in 1980. RTRI (Railway Technical Research Institute) tested these sleepers in 1985 and, based on the results of the research, JR used FFU synthetic wood as the standard sleeper in the area of bridges, switches, special projects in every type of superstructure. In 2011, sleepers from the field test from 1980 were again expanded and tested by the RTRI. As a result, RTRI informed the Japanese railway company that these sleepers could remain in use for another 20 years.
FFU synthetic wood is mainly used in the area of railway bridges, switch systems, special projects, sleepers with a low overall height. By 2012, more than 1200 km of track had been equipped with FFU synthetic wood. The processing is carried out in the same way as for wood, but suitable tools or tools with hard metal cutting edges are recommended for processing steel . UV light has no influence on the technical quality of the threshold. FFU synthetic wood sleepers are 100% recyclable at the end of their life expectancy.
FFU bridge beams on a Deutsche Bahn bridge
Holes in synthetic wood
Shinkansen in Tokyo on FFU sleepers
Turnout with FFU sleepers in slab tracks
Soling
Sleeper pads refer to an elastic layer on the underside of railway sleepers, the so-called sleeper pad (USP). These underside coatings can be applied in the production process during concreting in fresh concrete or subsequently glued to the underside of railway sleepers.
In some technical parameters, the concrete sleeper has so far not been able to outweigh the advantages of the wooden sleeper. With elastic plastic coatings on the underside of concrete sleepers, however, storage qualities of the wooden sleeper can be achieved in the contact area between sleeper and ballast.
For all materials of the underside sleeper coatings, a surface strength of the materials is required that prevents the gravel tips from penetrating into this sole.
International railway companies define different technical requirements for sleeper pads. In addition to these specifications of usability, requirements for system redundancy, operational stability and acc. KrW- / AbfG also applies to the recycling of the sole materials and the recyclability of the remaining concrete body of the sleepers.
As a result of the lower ballast stress, padded sleepers extend the maintenance cycles of tracks and points up to around four times, reduce the structure-borne noise emissions from track systems and enable the ballast thickness to be reduced .
Rail fastening
The rails were initially fixed to the stone or wooden sleepers with nails and, especially in Great Britain and France, a little later in rail chairs with wooden or spring steel wedges. Screws and then additional spring elements were used later. These absorb the vibrations of the rail under load as well as its expansion with temperature fluctuations without breaking. In continental Europe, production boards established themselves between sleepers and rails, initially as open production boards or strip boards, later developed into hook boards and the ribbed boards that are still common today. The various overall systems of standardized small parts that are used to fasten the rails are called superstructures; In Germany, superstructure W dominates on concrete sleepers and superstructure K and Ks with variants on wooden sleepers .
Alternatives to the railway sleeper
In the mid-1990s, various new types of superstructure systems were developed. The slab track works without a ballast superstructure and classic railway sleepers. Depending on the design, the sleepers are reduced to small concrete bases on which the rails are mounted, or the rails are mounted directly on the concrete roadway. The slab track is used in particular on high-speed lines and on urban and underground trains in tunnels because of the more stable track position and lower maintenance costs.
The frame sleeper track is a compromise between sleeper superstructure and slab track .
handling
On construction sites, the lighter wooden sleepers in particular were traditionally carried by at least two or more strong people by grasping them on both sides with sleeper pliers. These are so long that they allow wide-legged, straddled over the threshold, largely upright standing to lift the same.
When these pliers are folded over the shoulder for transport, the rectangular handle rings butt against each other. If the ends of the tong gripper arms, which are bent inwards at right angles, are held under the underside of the sleeper or if they - penetrating a little into the wood - clamp the cross-section of the sleeper laterally, the handles are 50-100 cm apart. Even pulling or lifting with the human arms, which are hinged shoulder-width apart, usually creates a sufficient gripping torque on the pincer joint to clamp the sleeper well with the shorter gripping legs.
In order to replace a damaged sleeper, it was exposed from the surrounding track ballast with staples and ballast forks, the rail fastenings loosened and pulled out of the track bed from the side. The newly inserted ones were positioned by striking the face with a hammer and levering backwards. After installation and backfilling, new sleepers must be tamped. The creation of a track breakthrough for a cable crossing underneath the work area to be kept free for the use of construction machines can also make sleeper expansion necessary, trains could still pass with speed limits and interception in the work pit.
In the meantime, manual work for changing sleepers has become rare and, at least in industrialized countries, only common when space is limited. Increased loads and speeds no longer permit work on the track that is not closed, and the stability of the track is impaired. The most frequently used, because they are most versatile, tools are road- rail excavators . Concrete sleepers cannot be handled without lifting equipment because of their mass and for reasons of health and safety.
literature
- August Haarmann: The Railway Track. Historical part , Engelmann, Leipzig 1891. XL, 852 S. The standard work on the subject
- Herbert Lachmayer , Peter Plica (Ed.): Over the threshold , Böhlau, Vienna 2003, ISBN 3-205-77090-0 . 333 p.m. numerous Fig. Magnificently furnished volume on the technical and cultural history of the railway sleeper.
- Gerhard Hempel: Prestressed concrete sleepers - a constant problem? Ernst & Sohn, Berlin 2001, Bautechnik 78, pp. 421–429
- Railway Technical Research Institute, Follow-up Survey on FFU Synthetic Sleeper after 30 years in Service; Report June, 2011
Web links
- Studiengesellschaft Holzschwellenoberbau eV
- https://www.gleisbau-welt.de/lexikon/fahrweg/oberbau/schwellen/
Individual evidence
- ↑ https://www.hyperion-ip.eu/tag/y-stahlschwelle-2/
- ↑ Alexander Schierholz, Kai Gauselmann: Rust eats up sleepers . In: Mitteldeutsche Zeitung , August 3, 2012, pp. 2, 4.
- ↑ News update shortly . In: Eisenbahn-Revue International , issue 5/2001, ISSN 1421-2811 , p. 224
- ↑ a b Report 25 million concrete sleepers laid in 25 years . In: Railway technical review . August 1974, p. 533
- ↑ a b Heins Schultheiß: Thirty years of concrete sleepers with the Deutsche Bundesbahn . In: The Federal Railroad . Vol. 57, No. 10, 1981, ISSN 0007-5876 , pp. 841-846
- ^ Günther Leykauf, Walter Stahl: Investigations and experiences with padded sleepers. ( Page no longer available , search in web archives ) Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice. In: EI - Eisenbahningenieur (55) 6/2004, pp. 8-16
- ↑ Frank H. Müller-Borrutau: concrete sleepers with elastic sole. Experience and knowledge with a new component. (PDF; 351 kB) Accessed July 9, 2010 .
