Prague pneumatic tube
The Prague pneumatic tube is the only surviving urban pneumatic tube system in the world today . The devastating floods in 2002 put it out of service.
The system belongs to Telefónica , which is gradually repairing and conserving it, but the very limited inflow of funds made it impossible for the time being to at least partially put this globally unique technical rarity back into operation.
The Prague pneumatic tube network is 55 km long; the first publicly usable route was put into operation in 1899.
history
The first urban pneumatic tube was built in London in 1853 on the basis of inventions by Denis Papin (1647–1714). Other European cities followed, in the order Vienna , Berlin and Paris . The Prague pneumatic tube was opened to the public on March 4, 1899.
The first route was built in 1887, but initially it was only used for internal purposes. At that time it led from the main post office in Heinrichsgasse (Jindřišská ulice) to the post office on the Little Ring (Malé Náměstí) in the old town in one of the houses of the VJ Rott company (corner house Malé náměstí / Linhartská, next to what is now called "U Rotta") House. Later this route was extended to Prague Castle , so that it measured over 5 km. The system was used especially for sending telegrams .
However, the main development of the network did not begin until the years of economic boom 1927–1932. At that time, additional routes were built and during the boom, tens of thousands of containers were transported through the system every month.
After the occupation in March 1939, the Czech Republic became, as the so-called Protectorate of Bohemia and Moravia, in fact a part of the German Empire . The Prague pneumatic post continued to operate as a so-called Protectorate Post facility until the end of the war.
It was not until 1945 that special blue boxes were lowered, which since then have served the general public specifically for shipments sent with this system. During the Second World War , the pneumatic tube played an important role in supplying the beleaguered radio building .
In a trial in 1970, the transmission capacity of the pneumatic tube for the transmission of 50 telegrams between the Prague main post office and a post office in Prague Castle was compared with a messenger and a telex connection operated by the world champion in telex . The pneumatic tube took by far the shortest time at eight minutes.
In the 1990s the system was still being used to move around 9,000 containers per month. The operation gradually became weaker and the devastating floods in 2002 put its functioning at a temporary end.
The pneumatic tube network was completely flooded by the Vltava flood , similar to parts of the subway network . As a result, some routes were so badly damaged that repair was no longer an option.
Technology used
Pipelines
The pneumatic tube routes are made of steel pipes with a clearance height of 65 mm and a wall thickness of 2.5 to 3 mm. The tubes are connected by narrow 14 cm long pipe sockets, which ensure the exact equiaxedness of the connection and, after welding, also ensure that they are completely airtight. In order to avoid fault currents , which increase the corrosion of the material, ceramic insulators are also used at some points between the tubes. On the outside, the pipes laid in the ground are protected by an asphalt-glass fabric that is wrapped around them when they are warm and coated with hot asphalt . The pipeline is usually laid under the Prague sidewalks at a depth of 80 to 120 cm below the surface. Inside buildings and in the Prague collector network, the tubes have only been coated with anti-corrosion coatings.
The radii of the arches in the earth are at least 250 cm, but usually 300 cm is used. The minimum permitted radius inside the building is 200 cm. The arches are formed from special burned tubes using a cold bending machine specially designed for this purpose .
The signal cable, through which communication with the elements of the route is secured, is laid together with the pipeline.
Individual route sections are equipped with so-called inspection wells ( shafts ). In them it is possible to open a pipeline and determine the location of a fault or from there to remove a container that has got stuck on the route. This is made possible by pushing out a heavier container that has been sent to the location of the obstacle using a pressure of up to 30 atm .
Transport container
Aluminum containers are transported through the pipeline, which are made from short pieces of pipe 200 mm in length and an outside diameter of 48 mm. On the back of the pipe there is a plastic ring that prevents the aluminum from rubbing against the walls of the pipe. A fan made of elastic plastic is mounted on this plastic ring, which seals the container in the pipeline. A removable plastic cap is attached to the front. The diameter of the rear ring and the front cap is 57 mm each. The remaining 8 mm to the clear height of the pipeline are sealed against the inner wall of the pipeline by the elastic fan already mentioned, so that the pipeline system remains completely tight at this point and has very little friction during transport .
Drive units
Each section of the pneumatic tube system is equipped with its own drive unit, which is formed by a blower driven by an electric motor . One blower serves a section of the route with a maximum length of 3 km, so that several blowers have to be used on the longer routes. The blower must be able to reverse the run and thus generate either an overpressure or, conversely, a negative pressure in the pipeline. The fans are connected to the pipeline with T-connections . On both sides of the pipeline, a contact is attached at a suitable distance in front of a T-circuit , which is coupled to the container passing through.
The fan is first in suction mode so that the container is sucked in in the direction of the T-circuit. Before reaching them, the container closes a contact that reverses the fan. In the meantime, the container's inertia has passed the T-circuit. At the moment when he is behind her, the already reversed fan causes an overpressure on her.
Older fans were paddle fans (an off-center rotating blade in a cylinder 300 mm high). Newer blowers use a rotating piston.
broadcasts
Consignments with a diameter of up to 5 cm and a length of 30 cm can be stored in the containers. Their weight can be up to 3 kg. As a rule, the telegram forms were rolled up, but it was basically possible to transport any type of shipment up to the specified maximum dimensions and weight. Understandably, they could not contain any hazardous substances that could destroy the pipeline. On the other hand, the speed of the containers could be regulated so that, for example, a fragile shipment could be sent in a very gentle way.
Routes and stations
The Prague pneumatic tube network consists of five star-shaped main routes equipped with switches and concentrators and so-called subscriber connections. The total length of the routes is approx. 55 km. On some very frequented sections the pipeline is two-tube (separate directions), but the majority of the routes are only single-tube and the direction of the shipment is determined by the correct direction of travel of the compressors. The main routes connect the following post offices:
- Headquarters Jindřišská - Prague 2, Prague 3, Prague 10
- Headquarters Jindřišská - Prague 1, Prague 2
- Headquarters Jindřišská - Prague 5
- Headquarters Jindřišská - Prague 6
- Headquarters Jindřišská - Prague 7
There were 16 of the affiliate links, but only 7 have survived to date. In the whole of Prague, 24 pneumatic post stations have remained to this day.
The Prague pneumatic tube crosses the Vltava via three bridges ( Hlávkův most , Mánesův most and Most Legií ) .
Headquarters
The place where all the lines converged is in the main post office building on Jindřišská ulice ( 50 ° 5 ′ 0 ″ N , 14 ° 25 ′ 40.6 ″ E ). Here, on the one hand, precise evidence was provided for all shipments and, on the other hand, the entire system was controlled and monitored. This is also where the consignments were re-dispatched between the individual train paths. In such a case, the consignments were simply reloaded manually from their pockets by the operating personnel, from where they came to the entrance to another route for the following dispatch. Of course, this was accompanied by precise evidence.
The current condition of the route was indicated by signal lights on the associated head. Up to 10 consignments could be sent one after the other on the route at an interval of 30 seconds. In practice, however, this amount of mail was usually not used.
On routes with switches, the shipments had to be routed according to a predetermined sequence. The switch could only be set to the active state from the control center before the actual start of the container shipment. The first container was branched off by the relevant switch, but after its passage the switch returned to the neutral position so that further containers could pass through without a branch. That is why a container that was to branch off had to be placed first in the delivery.
swell
- ↑ a b Jakub Serých: Pneumatic Tube System in Prague. capsu.org, June 2004 (English) ( Memento of 19 July 2014 Internet Archive ).
Web links
- Pražská potrubní pošta. Čtrnáctka - Turistický akademický klub (Czech)
- Jakub Serých: Pneumatic Tube System in Prague. capsu.org, June 2004 (English) ( Memento of 19 July 2014 Internet Archive ).