User:Geo Swan/Three Gorges Dam boat lift

The Three Gorges Dam ship lift is the largest mechanism of its kind in the world. The Three Gorges Dam, is one of the largest dams in the world, on one rivers with the most cargo and passenger traffic in the world. The dam was designed to have two separate mechanisms for transporting cargo past the dam barrier: a pair of short canals that each had five conventional canal locks, on them, and a large boat lift, called a shiplift in China.

Delayed opening
The conventional canal locks were ready, when the dam was complete, in 2006, but Chinese authorities failed to meet a series of announced completion dates for the shiplift, for over a decade. Operational testing began in September 2016. The mechanism wasn't fully ready for commercial use until November 2016.

Specifications
In preliminary designs the shiplift was envisioned as being able to carry vessels the same size as those passing through the conventional canal locks. But, as built, the maximum size of vessel the mechanism carries is 3,000 tonnes.

Accounts vary as to how long it takes for the shiplift to carry a vessel, from twenty minutes, to an hour. It takes four to five hours for the conventional lock system.

Like all mechanisms of its kind, the shiplift has a large water-tight basin, sometimes called a caisson, for transporting vessels. When the basin is at the top or bottom of its traverse, water-tight doors open at one end. A vessel or vessels to be transported enter the basin, the water-tight doors are closed; the basin is moved to the other end of its traverse, where a second set of water-tight doors open, allowing the vessel(s) to proceed on their way.

While 160 cables carry counterweights that perfectly balance the basin, it is moved by a set of helical gears, one at each corner. There is a motor, at each corner, to rotate the helical gear, but a mechanical transmission connects the four gears, so that they will all rotate at the exact same rate, even if some of the motors fail.

A complicating factor for the Three Gorges shiplift, not shared by most other shiplifts, is that the water level at both the top and bottom of the mechanism can vary by dozens of metres.

The maximum size of vessel that can pass through the conventional canal locks displaces about 10,000 tonnes. Initi

Although Chinese authorities asserted that the lift was functional in July 2016, it was not operational until September 18, 2016, when operational testing began.

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