Prague pneumatic post
Encyclopedia
The Prague pneumatic post (Czech: Pražská potrubní pošta) is the world's last preserved municipal
pneumatic post
system. It is an underground system of metal tubes under the wider centre of Prague
, totalling about 55 kilometres (34.2 mi) in length. Known as the Old Lady of Czech telecommunications, the system started service in 1889 and remained in use by the government, banks and the media until it was rendered inoperative by the August 2002 European floods
. The current owner, Telefónica O2 Czech Republic gradually is repairing and conserving the system; due to limited funding the system remained inoperative as of March 2007.
pneumatic post entered public service on March 4, 1889. The first lane had been constructed as early as 1887, but at first it only served internal purposes. It ran from the main post office
in Jindřišská st. (next to the Wenceslas Square
) to the post bureau at Malé náměstí square (next to the Old Town Square) in the Old Town. (This bureau was situated in a corner house with Linhartská st., belonging to the V. J. Rott company, next to a house that is called 'U Rotta' today.) The first lane was later extended as far as the Prague Castle
, making it over 5 km long. Prague was the fifth city in the world to receive a pneumatic post system after London
, Vienna
, Berlin
, and Paris
, which was considered a major achievement for Prague.
The system initially was employed mainly for sending telegrams
. Only three stations had been connected between the Prague post
and the telegraph office as of 1901.
The system was established for those desiring to send a document fast. The document would be taken to the post office and rolled up into a metal capsule. The clerk would then drop the metal capsule down a hatch leading to a predestined location. After the clerk pressed a button, the capsule would be moved by compressed air along a network of tubes beneath the pavement.
The main growth of the network dates to the economically prosperous era of 1927–1932. In those years, new lanes were constructed and tens of thousands of capsules transported per month. During the Prague Uprising
the pneumatic post played a role in supplying the besieged building of the Czech radio
.
In the late 1990s, the system was used by over 20 subscribers and operating at a loss, so kept rather for prestigious reasons. The traffic weakened gradually and the 2002 floods seriously damaged it, flooding 5 of the 11 underground engine rooms.
pipes of 65 mm bore
and wall thickness of 2.5–3 mm. The pipes are connected with tight couplers 14 cm long to ensure perfect coaxial alignment and then welded together, ensuring air-tightness. To prevent dispersion
current
from causing excess corrosion, ceramic insulators are inserted between the pipe segments at some places. Pipes buried underground are protected from the outside by a layer of fiberglass
, wound around at increased temperature and coated with hot asphalt
. The pipeline is typically buried under the Prague sidewalk
s 80–120 cm deep. Inside buildings and in the Prague trunk conduit network the pipes simply are coated with anti-corrosive paint.
The minimum bend radius
is 250 cm for underground pipes, but 300 cm is the most commonly used radius. Inside buildings a bend radius as low as 200 cm is allowed. The bends are made of special annealed
pipes at normal temperature, using a custom-made bender.
A signaling cable is laid along with the pipe, enabling communication with the track components.
The lane segments are equipped with dumb wells, where the pipeline can be opened and inspected, or a stuck capsule removed. For this purpose a heavier capsule can be sent at a pressure of up to 30 atm
, knocking the stuck capsule out.
capsules measuring 48 mm in outer-diameter and 200 mm in length. On the rear end they are fitted with a plastic circlet, preventing friction
against walls of the pipe and a soft plastic skirt, sealing air behind the capsule. The diameter of the rear circlet is 57 mm. The remaining 8 millimeters of the bore are sealed just by the skirt, allowing for excellent airtightness and low friction at the same time.
-powered air pump
. One pump can service at most 3 kilometers of pipeline, so it's necessary to use several pumps on longer lanes.
The pumps must be reversible
, creating either pressure
or vacuum
. The pumps are connected to the pipes with tee-fittings. On both sides of the tee the pipe is equipped with switches activated by a passing capsule.
At first the pump is set to intake mode, pulling the capsule towards the tee. Before reaching it, the capsule hits the first switch, causing the pump to start reversing. Meanwhile the capsule reaches the tee-fitting. As it passes the tee, the pump is already fully reversed and starts to push the capsule away.
The older pumps were bladed, having a single blade
, mounted eccentrically inside a 300 mm high cylinder. More recent pumps employ a rotating piston
instead.
For obvious reasons, dangerous and corrosive substances, which could damage the pipeline, were banned. On the other hand, the travel speed could be adjusted, allowing for transporting fragile packages.
, fitted with switches
and concentrator
s, and of subscriber's lines. The total length of the lanes is about 55 kilometers. Some of the most frequented segments have two pipes (one for each direction), but the majority of the lanes use a single pipe and the direction is determined by setting up the pumps to run in the desired direction. The main lanes connect the following post offices and bureaus:
Originally there were 16 subscriber's lines, but only 7 have been preserved up till today. A total of 24 pneumatic post stations remain today.
The network crosses the river Vltava
in three spots making use of bridges (Hlávkův most, Mánesův most, most Legií).
The current lane state was indicated by indicator lights on the lane's controller. Up to 10 packages in 30-second intervals could be sent on the same lane at once, although this was rarely used in practice.
When sending capsules to switched lanes, the capsules had to be sent out in a predefined order, as the switches could only be activated before commencing the transfer. The first capsule would be diverted, after which the switch would automatically slide back to its neutral position, sending the remaining capsules in the straight direction. Therefore, the capsule that was meant to branch off had to be sent first.
City
A city is a relatively large and permanent settlement. Although there is no agreement on how a city is distinguished from a town within general English language meanings, many cities have a particular administrative, legal, or historical status based on local law.For example, in the U.S...
pneumatic post
Pneumatic tube
Pneumatic tubes are systems in which cylindrical containers are propelled through a network of tubes by compressed air or by partial vacuum...
system. It is an underground system of metal tubes under the wider centre of Prague
Prague
Prague is the capital and largest city of the Czech Republic. Situated in the north-west of the country on the Vltava river, the city is home to about 1.3 million people, while its metropolitan area is estimated to have a population of over 2.3 million...
, totalling about 55 kilometres (34.2 mi) in length. Known as the Old Lady of Czech telecommunications, the system started service in 1889 and remained in use by the government, banks and the media until it was rendered inoperative by the August 2002 European floods
2002 European floods
In August 2002 a 100-year flood caused by over a week of continuous heavy rains ravaged Europe, killing dozens, dispossessing thousands, and causing damage of billions of euros in the Czech Republic, Austria, Germany, Slovakia, Poland, Hungary, Romania and Croatia....
. The current owner, Telefónica O2 Czech Republic gradually is repairing and conserving the system; due to limited funding the system remained inoperative as of March 2007.
History
The PraguePrague
Prague is the capital and largest city of the Czech Republic. Situated in the north-west of the country on the Vltava river, the city is home to about 1.3 million people, while its metropolitan area is estimated to have a population of over 2.3 million...
pneumatic post entered public service on March 4, 1889. The first lane had been constructed as early as 1887, but at first it only served internal purposes. It ran from the main post office
Post office
A post office is a facility forming part of a postal system for the posting, receipt, sorting, handling, transmission or delivery of mail.Post offices offer mail-related services such as post office boxes, postage and packaging supplies...
in Jindřišská st. (next to the Wenceslas Square
Wenceslas Square
Wenceslas Square is one of the main city squares and the centre of the business and cultural communities in the New Town of Prague, Czech Republic. Many historical events occurred there, and it is a traditional setting for demonstrations, celebrations, and other public gatherings...
) to the post bureau at Malé náměstí square (next to the Old Town Square) in the Old Town. (This bureau was situated in a corner house with Linhartská st., belonging to the V. J. Rott company, next to a house that is called 'U Rotta' today.) The first lane was later extended as far as the Prague Castle
Prague Castle
Prague Castle is a castle in Prague where the Kings of Bohemia, Holy Roman Emperors and presidents of Czechoslovakia and the Czech Republic have had their offices. The Czech Crown Jewels are kept here...
, making it over 5 km long. Prague was the fifth city in the world to receive a pneumatic post system after London
London Pneumatic Despatch Company
The London Pneumatic Despatch Company was formed on 30 June 1859, to design, build and operate an underground railway system for the carrying of mail, parcels and light freight between locations in London...
, Vienna
Vienna
Vienna is the capital and largest city of the Republic of Austria and one of the nine states of Austria. Vienna is Austria's primary city, with a population of about 1.723 million , and is by far the largest city in Austria, as well as its cultural, economic, and political centre...
, Berlin
Berlin
Berlin is the capital city of Germany and is one of the 16 states of Germany. With a population of 3.45 million people, Berlin is Germany's largest city. It is the second most populous city proper and the seventh most populous urban area in the European Union...
, and Paris
Paris
Paris is the capital and largest city in France, situated on the river Seine, in northern France, at the heart of the Île-de-France region...
, which was considered a major achievement for Prague.
The system initially was employed mainly for sending telegrams
Telegraphy
Telegraphy is the long-distance transmission of messages via some form of signalling technology. Telegraphy requires messages to be converted to a code which is known to both sender and receiver...
. Only three stations had been connected between the Prague post
Mail
Mail, or post, is a system for transporting letters and other tangible objects: written documents, typically enclosed in envelopes, and also small packages are delivered to destinations around the world. Anything sent through the postal system is called mail or post.In principle, a postal service...
and the telegraph office as of 1901.
The system was established for those desiring to send a document fast. The document would be taken to the post office and rolled up into a metal capsule. The clerk would then drop the metal capsule down a hatch leading to a predestined location. After the clerk pressed a button, the capsule would be moved by compressed air along a network of tubes beneath the pavement.
The main growth of the network dates to the economically prosperous era of 1927–1932. In those years, new lanes were constructed and tens of thousands of capsules transported per month. During the Prague Uprising
Prague uprising
The Prague uprising was an attempt by the Czech resistance to liberate the city of Prague from German occupation during World War II. Events began on May 5, 1945, in the last moments of the war in Europe...
the pneumatic post played a role in supplying the besieged building of the Czech radio
Ceský rozhlas
Český rozhlas is the Czech Republic's publicly funded radio broadcasting organization.It offers the following radio channels:*ČRo 1 – Radiožurnál: news and information*ČRo 2 – Praha: talk and family programmes...
.
In the late 1990s, the system was used by over 20 subscribers and operating at a loss, so kept rather for prestigious reasons. The traffic weakened gradually and the 2002 floods seriously damaged it, flooding 5 of the 11 underground engine rooms.
Pipes
The lanes consist of steelSteel
Steel is an alloy that consists mostly of iron and has a carbon content between 0.2% and 2.1% by weight, depending on the grade. Carbon is the most common alloying material for iron, but various other alloying elements are used, such as manganese, chromium, vanadium, and tungsten...
pipes of 65 mm bore
Caliber
In guns including firearms, caliber or calibre is the approximate internal diameter of the barrel in relation to the diameter of the projectile used in it....
and wall thickness of 2.5–3 mm. The pipes are connected with tight couplers 14 cm long to ensure perfect coaxial alignment and then welded together, ensuring air-tightness. To prevent dispersion
Dispersion
Dispersion may refer to:In physics:*The dependence of wave velocity on frequency or wavelength:**Dispersion , for light waves**Dispersion **Acoustic dispersion, for sound waves...
current
Electric current
Electric current is a flow of electric charge through a medium.This charge is typically carried by moving electrons in a conductor such as wire...
from causing excess corrosion, ceramic insulators are inserted between the pipe segments at some places. Pipes buried underground are protected from the outside by a layer of fiberglass
Fiberglass
Glass fiber is a material consisting of numerous extremely fine fibers of glass.Glassmakers throughout history have experimented with glass fibers, but mass manufacture of glass fiber was only made possible with the invention of finer machine tooling...
, wound around at increased temperature and coated with hot asphalt
Asphalt
Asphalt or , also known as bitumen, is a sticky, black and highly viscous liquid or semi-solid that is present in most crude petroleums and in some natural deposits, it is a substance classed as a pitch...
. The pipeline is typically buried under the Prague sidewalk
Sidewalk
A sidewalk, or pavement, footpath, footway, and sometimes platform, is a path along the side of a road. A sidewalk may accommodate moderate changes in grade and is normally separated from the vehicular section by a curb...
s 80–120 cm deep. Inside buildings and in the Prague trunk conduit network the pipes simply are coated with anti-corrosive paint.
The minimum bend radius
Bend radius
Bend radius, which is measured to the inside curvature, is the minimum radius one can bend a pipe, tube, sheet, cable or hose without kinking it, damaging it, or shortening its life. The smaller the bend radius, the greater is the material flexibility...
is 250 cm for underground pipes, but 300 cm is the most commonly used radius. Inside buildings a bend radius as low as 200 cm is allowed. The bends are made of special annealed
Annealing (metallurgy)
Annealing, in metallurgy and materials science, is a heat treatment wherein a material is altered, causing changes in its properties such as strength and hardness. It is a process that produces conditions by heating to above the recrystallization temperature, maintaining a suitable temperature, and...
pipes at normal temperature, using a custom-made bender.
A signaling cable is laid along with the pipe, enabling communication with the track components.
The lane segments are equipped with dumb wells, where the pipeline can be opened and inspected, or a stuck capsule removed. For this purpose a heavier capsule can be sent at a pressure of up to 30 atm
Atmosphere (unit)
The standard atmosphere is an international reference pressure defined as 101325 Pa and formerly used as unit of pressure. For practical purposes it has been replaced by the bar which is 105 Pa...
, knocking the stuck capsule out.
Transport capsule
The system uses aluminiumAluminium
Aluminium or aluminum is a silvery white member of the boron group of chemical elements. It has the symbol Al, and its atomic number is 13. It is not soluble in water under normal circumstances....
capsules measuring 48 mm in outer-diameter and 200 mm in length. On the rear end they are fitted with a plastic circlet, preventing friction
Friction
Friction is the force resisting the relative motion of solid surfaces, fluid layers, and/or material elements sliding against each other. There are several types of friction:...
against walls of the pipe and a soft plastic skirt, sealing air behind the capsule. The diameter of the rear circlet is 57 mm. The remaining 8 millimeters of the bore are sealed just by the skirt, allowing for excellent airtightness and low friction at the same time.
Propulsion units
Each lane is equipped with a dedicated propulsion unit, consisting of an electricallyElectric motor
An electric motor converts electrical energy into mechanical energy.Most electric motors operate through the interaction of magnetic fields and current-carrying conductors to generate force...
-powered air pump
Pump
A pump is a device used to move fluids, such as liquids, gases or slurries.A pump displaces a volume by physical or mechanical action. Pumps fall into three major groups: direct lift, displacement, and gravity pumps...
. One pump can service at most 3 kilometers of pipeline, so it's necessary to use several pumps on longer lanes.
The pumps must be reversible
Reversing (Vehicle maneuver)
Reversing is the process of driving a vehicle in the reverse direction in order to maneuver. Rear view mirrors are standard equipment for this endeavor. Extremely large or luxury vehicles may have in addition technical aids such as backup cameras...
, creating either pressure
Pressure
Pressure is the force per unit area applied in a direction perpendicular to the surface of an object. Gauge pressure is the pressure relative to the local atmospheric or ambient pressure.- Definition :...
or vacuum
Vacuum
In everyday usage, vacuum is a volume of space that is essentially empty of matter, such that its gaseous pressure is much less than atmospheric pressure. The word comes from the Latin term for "empty". A perfect vacuum would be one with no particles in it at all, which is impossible to achieve in...
. The pumps are connected to the pipes with tee-fittings. On both sides of the tee the pipe is equipped with switches activated by a passing capsule.
At first the pump is set to intake mode, pulling the capsule towards the tee. Before reaching it, the capsule hits the first switch, causing the pump to start reversing. Meanwhile the capsule reaches the tee-fitting. As it passes the tee, the pump is already fully reversed and starts to push the capsule away.
The older pumps were bladed, having a single blade
Blade
A blade is that portion of a tool, weapon, or machine with a cutting edge and/or a pointed tip that is designed to cut and/or puncture, stab, slash, chop, slice, thrust, or scrape animate or inanimate surfaces or materials...
, mounted eccentrically inside a 300 mm high cylinder. More recent pumps employ a rotating piston
Piston
A piston is a component of reciprocating engines, reciprocating pumps, gas compressors and pneumatic cylinders, among other similar mechanisms. It is the moving component that is contained by a cylinder and is made gas-tight by piston rings. In an engine, its purpose is to transfer force from...
instead.
Packages
The capsules can be loaded with packages up to 5 cm in diameter and 30 cm in length. Their weight can be up to 3 kg. Generally these were rolled-up telegrams, but any package within the set limits could be transported.For obvious reasons, dangerous and corrosive substances, which could damage the pipeline, were banned. On the other hand, the travel speed could be adjusted, allowing for transporting fragile packages.
Lanes and stations
The Prague pneumatic post network consists of five main lanes arranged in a star topologyStar network
Star networks are one of the most common computer network topologies. In its simplest form, a star network consists of one central switch, hub or computer, which acts as a conduit to transmit messages...
, fitted with switches
Railroad switch
A railroad switch, turnout or [set of] points is a mechanical installation enabling railway trains to be guided from one track to another at a railway junction....
and concentrator
Concentrator
In telecommunication, the term concentrator has the following meanings:# In data transmission, a functional unit that permits a common path to handle more data sources than there are channels currently available within the path...
s, and of subscriber's lines. The total length of the lanes is about 55 kilometers. Some of the most frequented segments have two pipes (one for each direction), but the majority of the lanes use a single pipe and the direction is determined by setting up the pumps to run in the desired direction. The main lanes connect the following post offices and bureaus:
- Jindřišská st. – Prague 2, Prague 3, Prague 10
- Jindřišská st. – Prague 1, Prague 2
- Jindřišská st. – Prague 5
- Jindřišská st. – Prague 6
- Jindřišská st. – Prague 7
Originally there were 16 subscriber's lines, but only 7 have been preserved up till today. A total of 24 pneumatic post stations remain today.
The network crosses the river Vltava
Vltava
The Vltava is the longest river in the Czech Republic, running north from its source in Šumava through Český Krumlov, České Budějovice, and Prague, merging with the Elbe at Mělník...
in three spots making use of bridges (Hlávkův most, Mánesův most, most Legií).
The headquarters/switchboard
All the lanes converge to the main post office in Jindřišská St. Here all the packages were carefully recorded and from here the network was controlled and monitored. This is also the place where the packages were forwarded from one lane to another. The capsule was picked up from a receiving pocket by a member of the staff, recorded and inserted into the inlet of another lane.The current lane state was indicated by indicator lights on the lane's controller. Up to 10 packages in 30-second intervals could be sent on the same lane at once, although this was rarely used in practice.
When sending capsules to switched lanes, the capsules had to be sent out in a predefined order, as the switches could only be activated before commencing the transfer. The first capsule would be diverted, after which the switch would automatically slide back to its neutral position, sending the remaining capsules in the straight direction. Therefore, the capsule that was meant to branch off had to be sent first.
External links
- Pneumatic Tube System in Prague
- "I Got Root on the Prague Pneumatic Post", 1999
- A Relic That Hasn't Gone Down the Tubes , Business Week 8 Oct 2001