Point heating
A point heater is a device that is intended to ensure the function of railway points in cold weather . In particular, the points are to be prevented from freezing. They should keep moving parts of points free of snow and ice in order to keep the points adjustable.
At the end of 2014, around 49,000 of around 70,000 points in the Deutsche Bahn network were equipped with point heating. According to the company, their operation costs 44 million euros each winter.
functionality
Are heated in principle stock rails and lock compartment (Umstellgestänge and closure parts), if present also movable frogs and increasingly also tongues . On high-speed routes in the Deutsche Bahn network, turnouts located up to 300 meters deep in tunnels must be heated. Point heating systems must provide sufficient heating power to enable the points to be changed over even in snow and ice. On the other hand, the lubricants used on the sliding chairs must not be influenced (especially evaporated).
According to the company, points are not heated in areas with low operating performance or in certain shunting areas, as this does not work logistically and is also too expensive.
In the case of switches in road space , especially in tram networks, snow that has been pressed in by motor vehicle traffic must also be melted in order to ensure that the switches function properly. The correct dimensioning of the heating is difficult here, because on the one hand the greatest possible heating power is necessary in the case of high traffic volumes in order to keep the tongues ( tongue heating ) freely movable, on the other hand, however, excessive heating can impair the effectiveness of the lubricants used.
Heating devices of several neighboring points are combined into one point heating system .
Energy source
Point heating systems are mostly operated electrically. Operation with natural gas , propane gas , geothermal energy , coal or district heating is also possible.
The heat is transferred via thermal radiation , partly also by conduction , by means of heating rods. Up to 14 such bars, which are up to 5 m long and have a temperature of 65 to 75 ° C, are used per switch. Power can be supplied via the (public or railway-owned) 50 Hz network as well as from the contact line network (15 kV, 16.7 Hz) via a transformer . In the past, switchable mast transformers were used at Deutsche Bahn , now the transformers are enclosed in a concrete station on the ground and connected to the catenary via a mast switch. The heating output of electrical point heating systems ( EWHA ) ranges from around five kilowatts (for small track radii) to around 50 kilowatts (high-speed points).
Gas from public energy providers is used for natural gas heating . The propane gas heater is operated either from transportable 300 kg tanks or stationary large tanks up to 43 t. Gas heaters are usually designed as infrared heaters . Geothermal heating systems usually require a connection to the public power grid and heat the switch with hot water using a heat exchanger.
Which energy source is used depends, on the one hand, on the possibility of using public energy sources and, on the other hand, on the weather conditions to be expected. In the area of Deutsche Bahn , gas heating is preferred in areas of extreme weather, as it has an output that is up to three times higher than that of electrical point heating.
On January 24, 2007, the first geothermal point heating system was put into operation as a pilot system in the Deutsche Bahn network at Holzminden station .
According to the company, heating a normal switch over three months costs as much as heating a home over a year.
Control engineering
In older designs, the point heating is switched on by the signal box , newer designs work fully automatically. With a weather-dependent control, moisture, precipitation, outside temperature, snowfall and ice formation are recorded at a sensor station (usually on a main track with heavy traffic). In addition, the rail temperature is determined at the most unfavorable switch (reference switch). As a rule, the lock compartments are heated at temperatures below 0 ° C, the stock rails and tongues only when it is precipitation at the same time. In addition, the lock compartments have covers that reduce the entry of snow. In the case of points that are used at higher speeds, the tongues are effectively kept free by the airflow.
history
In the early days of the railway, points were kept free in winter by local staff, economic considerations and the lack of sufficient staff led to the development of point heating. The increasing train density also stood in the way of manual cleaning of the switches. First, steam and oven heating were developed. Steam heaters used the train preheating systems and building heating systems available in all stations . Ovens installed under or next to the switches must be checked for operability at regular intervals and fuel added.
At the beginning of the 1950s, the first experiments with electrically heated points were made in the foothills of the Alps. At the end of the 1970s, turnouts that were important to the operation were preferably heated electrically, while gas and circulating point heating dominated the rest of the network.
alternative
The installation of a point heater can be uneconomical for points with little traffic. These points can be made less sensitive to snow and frost by partially removing the ballast. Part of the ballast is removed in the sleeper compartments under the tongues. The tongues can therefore no longer be hindered or blocked in the adjusting movement so quickly by the snow. The snow holes also make it easier to remove the snow in the tongue area.
Web links
Individual evidence
- ↑ a b c Deutsche Bahn AG (Ed.): Electrical switch heating systems. Directive 954, module 9101, valid from October 1, 20161
- ↑ Peter Thomas: Air conditioning against winter weather . In: Frankfurter Allgemeine Sonntagszeitung . No. 48 , November 30, 2014, p. V10 (similar version online ).
- ↑ a b c d Point heating systems at Deutsche Bahn AG. In: Deine Bahn, Issue 1/2010, pp. 51–56, ISSN 0948-7263 .
- ↑ a b Morten Freidel: "We all have to readjust the points" . In: Frankfurter Allgemeine Zeitung . No. 201 , August 30, 2014, ISSN 0174-4909 , p. 7 ( online ).
- ↑ Without a source
- ↑ Pilot installation of a geothermal point heating system ( Memento from March 4, 2016 in the Internet Archive )
- ↑ a b Karl Scheideler: Point heating systems - a contribution to the safety of rail traffic in ice and snow . In: The Federal Railroad . No. 12 , 1979, ISSN 0007-5876 , pp. 913-918 .