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A barge is lifted into the Neckarzimmern lock
Computer animation that simplifies passing through a lock

A lock or ship lock (n system) is an engineering structure that enables watercraft to overcome differences in level between two sections of a waterway .

The lock is a form of descent structure .

They are characterized by an attached between the two sections chamber that each with a floodgate both upward ( upstream water ) and down ( underwater ) waterproof can be closed. While the smuggling of a vessel are closed both doors, and the chamber is usually by so-called Torumläufe filled (for small locks also provided with sliders openings in the gates) for the lifting or lowering on the upper level and lower the Level emptied. The gates are alternately closed and opened:

  • Ascent : drive in - close at the bottom - fill - open at the top - extend,
  • Descent: drive in - close at the top - empty - open at the bottom - extend.

Lock types are:

According to location and waterway, a distinction is made between:

  • Inland lock,
  • Sea lock,
  • Harbor lock,
  • River lock,
  • Canal lock.

A sea lock connects an inland waterway, which usually also has an inland port, with the sea (e.g. Wilhelmshaven sea lock ). In seas with tides (e.g. the North Sea ), their sides alternate between upstream and downstream water. A canal or river lock that leads to an (inland) port (e.g. Linden port lock ) is usually referred to as a port lock . Sometimes it is just in the vicinity of a port.

Locks, rolling mountains and ship lifts are grouped under the collective term descent structures.

Construction methods and principle of operation

Single-chamber lock, functional principle
1 to 7: ascent of a ship
8 to 14: descent of a ship
Time-lapse illustration of a lock passage in the Anderten lock

A lock consists of one lock chamber, with a double lock of two lock chambers that are structurally connected in a building, and for each chamber of two or more lock heads with lock gates, of which generally never more than one is open at the same time. There are locks with more than two gates, for example, at crossings of canal systems, such as the boiler lock in Emden and the round lock in Agde , or to subdivide a long lock chamber with a central gate, as on the Main. When the lock gates are closed, the water level in the lock chamber, and with it the ships floating in the lock chamber, can be raised to the level of the upper water by water inflow from the upper water or lowered to that of the lower water by draining. Once the respective water level has been reached, the delimiting lock gate is opened and the ships can exit the lock chamber into the adjacent water section or enter the lock from there. No pumps are required for the inflow and outflow of running waters; the water flows from the upper water into the lock chamber and when it is lowered it flows out of the lock chamber into the lower water . In the case of shipping canals, water is lost from the upper section to the lower section during locks. To compensate for this, water is pumped back or, in the case of economy sluices , part of the sluice water when emptying the sluice chamber is directed into the side economy basin and used again for the next filling. Examples of this are the Anderten double sluice on the Mittelland Canal and the Henrichenburg sluice on the Dortmund-Ems Canal. One variant is the twin lock, in which part of the lock water of one lock chamber is used to fill the other lock chamber of a double lock; Example: Herne-Ost lock on the Rhine-Herne Canal.

Slides such as plate contactors or segment contactors are used to fill and empty the chamber. In older locks, these are located directly in the lock gates or in the gate circumferences. In ship locks in the 21st century, the slides are built into longitudinal channels. In order to minimize turbulence when filling the lock chamber, the water is supplied through longitudinal channels in the chamber walls or in the chamber floor (base courses), which are distributed over the entire length of the chamber. The slides were previously moved by hand with winches, but now the slides are moved hydraulically or with electric lifting cylinders.

A special form of locks, in which both the displacement of the doors and the carried the slide without additional energy by are Louis Hotopp developed locks in which all movements of gates by pneumatic done. The compressed air required to operate the locks is generated by the difference in water level between above and below water by means of falling water columns. The locks of the Hotopp system made it possible to build modern locks in regions that were not yet electrified. Hotopp locks are still in operation on the Elbe-Lübeck Canal today.

Locks are generally used for heights of up to about 25 meters; boat lifts are usually required for greater heights. For economic reasons, as few steps as possible are provided, which have a greater drop height. Ship locks with a great fall height, the lock chambers of which are closed off with a transverse wall (mask) above the passage opening to the underwater, are called shaft locks ; Example: Anderten double-shaft lock on the Mittelland Canal. Locks that have to overcome great heights of fall can also be implemented as lock stairs with several locks in direct succession, including their outer locks. Examples of this are the Fonserannes lock staircase in France, the Niederfinow lock staircase on the Havel-Oder waterway in Germany (36 m drop, replaced by a boat lift in 1934), the lock staircase on the Drei-Schluchten-Damm in China or the Wytegra lock staircase in the Volga. Baltic Sea Canal (80 m head) in Russia. Several lock chambers lying directly behind one another, in which the lower gate of one of them is also the upper gate of the next lower lock chamber, are called coupling locks .

Locks in flowing waters damming the water when the lock gates are closed and therefore need a parallel weir through which the dammed water can flow off if it is not needed for the lock.

With sea ​​locks at the entrance to harbor basins or sea canals with a connection to tidal waters, the sea is tide-dependent sometimes upstream and sometimes downstream, while the water level of the harbor or canal is kept constant. Such barriers or protective sluices are also used in the inland area at the confluences of shipping channels in rivers with expected floods; Example: Hanekenfähr lock on the Dortmund-Ems Canal. With this construction, a weir is not necessary.

A dock lock consists of only one main lock (like a dry dock , hence the name). This type of lock was built many times in the 19th century. Since it does not require a lock chamber, space and money are saved. The lock only takes place when the water level in front of and behind the main lock (in the case of tide-dependent seaports), the time window for this is around 1 hour, a serious disadvantage of this type of lock. Dock locks can also be carried out in the case of chamber locks; this is necessary if the length of the ship's hull exceeds that of the lock chamber.

In some particularly narrow locks, the sides of the lock are lined with a sturdy wooden structure that acts as a tail unit for the ships' entry.


Fulda lock in Rotenburg from the 16th century (out of order)

The word lock derives from the medieval Latin sclusa ( military ab), which originated in Latin excludere (rule) has.

The Greek historian Diodorus reports that during the restoration of the Bubastis Canal between the Nile and the Red Sea around 280 BC ( begun under Pharaoh Necho II , but probably not completed until 498 BC under the Persian King Darius I ) . The Greek King Ptolemy II Philadelphos (284 to 246 BC) had a double (?) Lock built in at the east end of the building. This canal fell into disrepair in the 1st century BC. BC, but was restored under the Roman Emperor Trajan in the 2nd century AD. The canal was in use with restrictions until the late 8th century AD.

In China, the canal lock for ships was invented in 984 by Qiao Weiyue, deputy commissioner for transportation in Huainan . Until then, vertical gradients in the canals there were overcome by slides or ramps, which repeatedly damaged the ships and led to the cargo being stolen. In addition, when it was dry, the operation of the slides was very limited. Qiao Weiyue had two "hanging gates" built at a distance of 50 paces (76 m), roofing over the space in between, and fortifying the bank, thus building a lock. From then on, height differences of 1.2 to 1.5 m per lock were no longer a problem.

Poppenbüttler lock and lock master's house in 1856

In 1325, the first ship lock was built in Germany as a chamber lock . Technical forerunners were water locks and weirs with boat slides . Locks were weirs that were opened after damming; the boats then swam downhill on the tidal wave.

In order to create a navigable connection between Hamburg and Lübeck , the Alster-Beste Canal was built in the 15th and 16th centuries . For this purpose, nine Alster locks were built in the Alster (to compensate for the 17 m gradient), four locks (8 m gradient) in the Alster Canal and eight locks (15 m gradient ) in the Beste . The Hamburg - Lübeck route was 91 kilometers long. In the course of this construction work, the Wulksfelder, Wohldorfer and Fuhlsbütteler locks were built around 1448 . After four years of construction, the project was interrupted for lack of money. The shipping route along the Alster from Stegen to Hamburg was completed in 1465. Between 1527 and 1529 the sand fields, Rader, Heidkruger, Mellingburger and Poppenbüttler locks were rebuilt and old locks were replaced.

At weirs with boat slides, the boat was lowered or raised on a ramp; such boat slides were in use on small commercial watercourses until the 19th century. On the Upper Rhine between Eglisau and Rheinfelden, several boat slides (officially: slippage systems) and trolleys for motor boats up to 20 m or 30 m in length have been preserved. At the locks of other waters, fish ladders or boat lanes are built as a firing channel for pleasure boats for the passage of ships or small pleasure boats.


The largest lock in Germany is the sea lock of the IVth entrance in Wilhelmshaven , which belongs to the outer port of the Navy . It has two lock chambers with a length of 390 m, a width of 60 m and a jamb depth of 14.75 m under the mean harbor water level (volume around 320,000 m³). A lock gate (sliding gate) with a passage width of 60 m weighs approximately 1,700 tons. For comparison with an inland lock: The Main lock in Ottendorf is 301 m long and 12 m wide (volume around 27,500 m³).

The three savings locks Hilpoltstein , Eckersmühlen and Leerstetten on the Main-Danube Canal have the highest drop of all locks built in Germany at 24.67 meters. The new lock Uelzen II is considered to be the largest economy lock in the world.

The second largest lock in the world is the Berendrecht lock , which opened in 1989 on the right bank of the Scheldt, to the port of Antwerp in Belgium . It is 500 m long, 68 m wide and 17.7 m deep (volume around 600,000 m³). With one lock, up to four ocean-going vessels with a maximum draft of 11.85 m and several inland vessels can be locked. The mean tidal range in front of the lock is 4.94 m.

In the immediate vicinity on the left bank of the Scheldt, originated to a new area of the port of Antwerp Kieldrechtsluis with equal width and length, but with 4 m of greater depth, in order from June 2016 postpanamax ships, of up to 12,000 TEU record to -Containern can. This makes it the largest lock in the world.

The Panama Canal was expanded from 2007 to 2016; new locks with a length of 427 m and a width of 55 m and a depth of 18.3 m were built, corresponding to a volume of around 430,000 m³ (details here ).


Large ships can collide with a closed or partially open lock gate and damage it and the ship. Another danger arises if, for example, a road bridge runs over a lock and the superstructures of a ship are so high that they only fit below the clear height of the bridge when they are folded down or when the water level is lowered. To prevent such collisions, a type of crane arm in some locks in front of the sluice gate, which is at risk of collision, places a strong rope with a rope brake across the waterway and locks it into place on the other bank, so that even a large ship is slowed down when the brakes fail Rope can be held back by gate or bridge.

If a ship travels very close (parallel) to a lock wall , it is hydrodynamically attracted by the Bernoulli effect and it can come into unwanted rubbing. However, the effect can also be used to lay on one side. Ships are usually moored / leashed in the lock chamber so that they do not drift away uncontrollably when they are filled, for which purpose bollards embedded in vertical rows are used. If a watercraft is moored, it has to be loosened repeatedly and fastened again to one of the bollards above or below. If this adjustment of the height of the leash is neglected, there is a risk that especially narrow, i.e. small boats, will be caused to tip over by the vertical line pull.

When filling a lock, water eddies that become immediately dangerous, at least for very small boats, can arise. Drifting to a large ship is also dangerous, as its propellers and possible bow thrusters cause strong currents on the surface of the water when maneuvering in the lock or starting to extend it. Large ships usually have priority and go faster than a small paddle boat. A small ship is better off going into the lock only after the big one, waiting at the far end of the lock chamber until the big ship has gone out again and the vortices left behind have subsided again.

Even without leashing, the edge of a boat, such as a skirting board , with recessed hook in the lock wall means, while the water level rises or falls. The one-sided vertical force can cause the boat to tip over and capsize.


Kleinmachnow coat of arms on the Teltow Canal

The lock in the coat of arms of Kleinmachnow represents an extraordinary common figure .

See also


  • on the terms: DIN 4054 hydraulic engineering, Sept. 1977

Web links

Commons : locks  - collection of images, videos and audio files
Wiktionary: Schleuse  - explanations of meanings, word origins, synonyms, translations

Individual evidence

  1. HOAI Section 3
  2. ^ Detlef Kaack: Hotopp locks. Retrieved September 29, 2018 .
  3. Artificial shipping canals in antiquity: The so-called ancient Suez Canal. (PDF; 3.3 MB). In: SKYLLIS - Journal of Underwater Archeology. 3rd year, issue 1, 2000, pp. 28ff.
  4. ^ Canals for Shiping in Ancient Egypt
  5. ^ Wilhelm Melhop : The Alster. Described in terms of history, local knowledge and river engineering. Hartung, Hamburg 1932, DNB 361213794 .
  6. ISTER hiking trip from Vohburg to Vilshofen. Linzer Ruderverein Ister from July 24th, 2014 (picture of a double-4-person rowing boat in a boat lane at a Danube power plant)
  7. Main-Danube Canal - Ships drive over the mountain . As of October 10, 2009.
  8. www.wsa-uelzen.wsv.de .
  9. ^ Website of the MSC shipping company for the Benderecht lock
  10. Port of Antwerp starts building the largest lock in the world ( Memento of December 15, 2013 in the Internet Archive ), www.portofantwerp.com
  11. Antwerp is building the mega-lock / steel of the Eiffel Tower times three , ORF.at May 20, 2013.
  12. Cruise ship becomes lifeboat orf.at, August 22, 2015, accessed on July 24, 2017. - Small boat capsized while being locked.