Opened July 9, 1904, this lift lock is the highest of its type in the world, transferring boats between two water levels in a single 19.8 m (65 ft.) lift. Designed in place of conventional locks, which would have lengthed the time considerably to transverse a gradual drop, this lift lock was a unique solution made feasible. It operates on a balance principle. Each boat chamber is supported by a ram, 2.28 m (7.5 ft.) In diameter. These move up and down inside water-filled cylinders connected by a pipe. A valve, located in its centre, controls the flow of water between the two cylinders.In operation, the upper boat chamber is filled with an extra 30 cm (1 ft.) of water which weighs 130.6 t (144 tons). When the valve is opened, this added weight causes the upper chamber to descend and the lower to rise.
353 Hunter St East
world's highest operating hydraulic lift lock, operating on the balance principle
Courtesy Flickr/Mac Armstrong (CC BY-SA 2.0)