Water wedge lift
The water wedge lift is a special form of the ship lift , namely an inclined lift with wet conveyance in the longitudinal direction, without a trough. Instead of a trough, a wedge-shaped body of water, together with the ships floating on it, is pushed diagonally upwards or moved downwards in a controlled manner in an inclined channel.
history
As early as 1885, Julius Greve published his designs for water wedge lifts in German specialist magazines. These were further developed by the French Jean Aubert in the 1950s and 1960s.
So far only two water wedge lifts have been built worldwide. The first in 1973 was the Montech water wedge lift in the Canal latéral à la Garonne (German: Garonne Lateral Canal ) in southern France. The Fonserannes water wedge lift followed in 1983 - also in southern France - in the Canal du Midi parallel to the Fonserannes lock staircase near Béziers .
Today (2017) both plants are out of operation. The two lifting vehicles that have fallen into disrepair are to be viewed as technical monuments from a certain distance.
Plant components
A water wedge lift consists of
- stationary parts, namely
- concreted channel with a constant cross-section that leads straight up an even slope,
- Barrier gate at the bottom of the gutter
- Barrier gate at the top of the channel (sluice gate)
- and the lifting vehicle with
- Drive unit, e.g. B. (in Montech) two rigidly connected traction vehicles,
- a slide with which the water wedge can be shut off in the channel downhill, as well as
- a horizontal transom - a little uphill in front of the gate - to moor the ship.
The slide forms a movable seal against the bottom and side walls of the concrete channel. This seal is one of the most critical components of the water wedge elevator. It must be sufficiently tight, must not have too great a frictional resistance and its wear must be tolerable.
Working principle
The functional principle using the example of a ship to be transported ("lifted") upwards:
- The concrete channel, which is closed off from the upper water by the fixed upper barrier gate, is mostly dry, but extends below into the lower water, so that there is a water wedge that is initially still connected to the lower water, limited at the bottom and at the sides by the bottom and inner walls of the channel .
- The lifting vehicle is in the lower end position. Its portal-shaped construction allows ships to enter the water wedge from underwater underneath.
- After the ships have entered the water wedge, the lifting vehicle lowers the crossbeam attached to its front part. The ships to be transported are moored to it.
- Now the slide on the lifting vehicle behind the crossbeam is lowered, isolating the water wedge from the rest of the underwater. The crossbar avoids collisions between the slide and the ships.
- Now the fixed lower shut-off gate to the underwater is closed, just like with a lock .
- Then the lifting vehicle begins its upward journey. Its driven wheels run on both sides of the concrete channel. As a result of the closed slide acting as a movable seal, the lifting vehicle pushes the water wedge together with the ships floating on it up the channel. At the beginning of the journey, while the slide moves away from the lower shut-off gate, the remaining water in between expands a little way into the channel, whereby its level sinks.
- When the lift truck and water wedge have reached the top, i. H. when the water level of the water wedge has reached that of the headwater, the journey ends.
- Now the fixed upper shut-off gate is opened so that the water wedge is connected to the upper water.
- Finally, the ships are untied from the transom and can sail out into the upper water.
The following applies to ships to be transported downwards:
- Entry of the ships through the fixed upper gate in the water wedge, which is held by the lifting vehicle above.
- Securing the ships to the transom.
- Closing the upper barrier.
- Downward travel of the lifting vehicle and thus downward transport of the water wedge with the ships. Before the end of the journey, the slide meets the lower residual water in the channel, which is then raised again to the level of the underwater when the journey continues to the lower end point.
- Open the fixed lower locking gate.
- Lifting the slide.
- Loosing the crossbeam and lifting it.
- Exit of the ships through the portal of the lifting vehicle into the underwater.
The purpose of the lower fixed barrier gate is to
- to prevent that when the water wedge is pushed upwards, the entire still horizontal part of the channel is filled by water flowing in from underwater,
- To facilitate the entry of the lifting vehicle with a water wedge from above: it then only has to approach against residual water (see above), but not against large amounts of water at the lower end of the channel.
As a result of inevitable leaks, water always trickles through the vehicle's gate valve when the water wedge is transported. These losses can be compensated for by a regulated post-flow from the headwater.
energy
Due to the Archimedes' principle , the mass of the water wedge including the ship is independent of the mass of the ship. Potential energy must be used when driving uphill. This is provided by the engines of the lifting vehicle. When driving downhill, potential energy is gained, which is burned by braking.
In principle, the energy consumption can be reduced if only a smaller wedge of water is transported for the transport of smaller ships. This requires that the top and bottom end positions of the lift truck be variable; this is not implemented in the existing water wedge lifts. Empty trips of the lifting vehicle with the slide open are possible with very little energy expenditure and are useful if only ships are to be transported in one direction at a time. When going downhill, however, the entire volume of the water wedge is removed from the upper water and no longer returned.